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. 2023 Apr 6;18(4):e0280231. doi: 10.1371/journal.pone.0280231

The effects of ischemia during rest intervals on strength endurance performance

Robert Trybulski 1,2,#, Marta Bichowska 3,#, Rafal Piwowar 4,#, Anna Pisz 5,#, Michal Krzysztofik 6,#, Aleksandra Filip-Stachnik 6,#, Krzysztof Fostiak 3,#, Piotr Makar 3,#, Michal Wilk 5,6,*,#
Editor: Daniel Boullosa7
PMCID: PMC10079082  PMID: 37023019

Abstract

Background

The study aimed to evaluate the effects of ischemia used during the rest periods between successive sets on maximal number of performed repetitions, time under tension and bar velocity during the bench press exercise.

Methods and materials

Thirteen healthy resistance trained men volunteered for the study (age = 28.5 ± 7.1 years; body mass = 87.2 ± 8.6 kg; bench press 1RM = 143.1 ± 20.7 kg; training experience = 11.0 ± 6.9 years). In experimental protocol the subjects performed 5 sets of bench press exercise at 70%1RM with maximal number of repetitions in each and with 5 minutes rest periods between each set. During the ischemia condition occlusion with 80% arterial occlusion pressure (AOP) was applied using a 10 cm wide cuff, before the first set of the bench press exercise and during all rest periods between sets (for 4.5 minute). During the control condition no ischemia was applied.

Results

The two-way repeated measures ANOVA showed a statistically significant interaction effect for time under tension (p = 0.022; η2 = 0.20). However, the results did not show a statistically significant interaction effect for peak bar velocity (p = 0.28; η2 = 0.10) mean bar velocity (p = 0.38; η2 = 0.08), and for number of performed repetitions (p = 0.28; η2 = 0.09). The post hoc analysis for interaction showed significantly shorter time under tension for ischemia condition compared to control in set 1 (p < 0.01). The post hoc analysis for main effect of condition revealed that time under tension was significantly shorter for ischemia compared to control condition (p = 0.04).

Conclusion

The results of this study indicate that ischemia intra-conditioning does not increase strength-endurance performance as well as bar velocity during bench press exercise performed to muscle failure.

Introduction

Ischemia is a method of restricting blood flow through the special cuffs which can be used in the limbs and can be applied during the rest as well during the different types of physical activity [1]. So far, much attention has been devoted to the use of ischemia during resistance exercise. Ischemia induced before or during effort increase exercise physical performance as well as stimulates physiological responses such as improvement of metabolic efficiency (attenuating ATP depletion), also glycogen depletion and the lactate production [2–11]. Further ischemia causes changes in systemic VO2, in the deoxygenation of muscular Hb/Mb, and the opening of the ATP-dependent K+ channels which can enhance the level of performance [3–5,8,9,12]. There are many different methods related to the point, timing of application and the duration of ischemia as part of physical exercise: pre-conditioning (ischemia induced only before a training session), continuous (ischemia induced during the exercise and rest periods), and intermittent (ischemia induced during exercise, not during rest periods) [13–15] The main differences between those methods are related to the point when ischemia is induced [16]. Recently, another method of using ischemia as part of resistance exercises has been introduced called ischemic intra-conditioning [14]. During ischemic intra-conditioning, the cuffs are applied only during each rest period between sets of resistance exercise and released before start effort [14]. Wilk et al. [14] showed an increase in bar velocity and power output during the bench press exercise (5 sets, 3 repetitions, 60%1RM; 5-minute rest periods) when ischemia (80% full arterial occlusion pressure (AOP) of the upper limb at rest) was applied before each set of resistance exercise. Since the ischemia used only during the rest periods increase explosive performance [17] it is possible that the positive effect may also apply to maximal strength as well as strength-endurance performance. Previous study showed that ischemic pre-conditioning increases maximal number of performed repetitions during resistance exercise for the lower and upper limbs [16,18–20]. Novaes et al. [20] showed that ischemic pre-conditioning applied 40 min before warm-up (4 cycles of 5-minute ischemia at 220mmHg) and completed 5 min before warm-up increased total training volume (sum of a total number of performed repetitions x load in bench press, leg press, lateral pulldown, hack machine squat, shoulder press, and Smith back squat) compared to control condition. Similar Marocolo et al. [19] showed that ischemic pre-conditioning (4 cycles of 5 minutes ischemia at 220mmHg) increased the maximal number of performed repetitions during leg extension in the first set and second set, but not in the third. Therefore generally, the ischemia used before resistance exercise increases the maximal number of performed repetitions, however currently, there are no studies assessing the impact of ischemic intra-conditioning on strength-endurance performance.

Since the ischemic pre-conditioning increase strength-endurance performance, it can be assumed that ischemic intra-conditioning could also cause positive effect on strength-endurance performance. Therefore, the present study aimed to evaluate the effects of ischemia used before the first set as well as during all rest periods between successive sets on maximal number of performed repetitions, time under tension and bar velocity during the bench press exercise. It was hypothesized that the ischemic intra-conditioning would increase strength-endurance performance during the bench press exercise.

Materials & methods

Experimental approach to the problem

During the experimental protocols each participant performed two experimental sessions (one week apart) in a random order: a) when ischemia were used before each of exercise sets (ischemia condition); b) control, when ischemia were not used. In experimental protocol the subjects performed bench press exercise, 5 sets, at load 70%1RM and maximal number of repetitions in each. A 5-min rest-interval was used between each set. For ischemic session the cuffs pressures (10 cm wide cuff) was set to 80% AOP. Pneumatic cuffs were used on both arms: a) after warm-up before initial set; b) over all four brake interval between sets (for 4.5 minute). During the control sessions the cuffs were no used. The Bioethics Committee approved the experimental (number 02/2019).

Subjects

Thirteen men (resistance trained) participated in the experimental (body mass = 87.2 ± 8.6 kg; age = 28.5 ± 7.1 years; bench press 1RM = 143.1 ± 20.7 kg; training experience = 11.0 ± 6.9 years; ratio strength = 1.60 ± 0.2 (1RM / body weight)). The following inclusion criteria were used: a) absence of muscular injuries b) bench press maximal strength (1RM) more than 150% body mass. Participants signed written informed consent to participate in the study and were allowed to withdraw from participation at any time.

Procedures

Familiarization session and one repetition maximum test (1RM)

The familiarization session was performed 2-weeks before the main experimental sessions. During the familiarization session each participant performed a warm-up close to their standard training habits. After warm-up, each participant performed bench press exercise (3 sets, around 60%1RM, maximal number of performed repetitions) with ischemia used only during rest periods. The ischemia was used for 4.5 minute and released thirty second before starting each set. A week before the main experimental sessions, the maximal strength test (1RM) in bench press was performed [14,21]. The 1RM test started with the standard warm-up (upper body). Next, was performed bench press at load 20%1RM (8 reps), 40%1RM (6 reps), and 60%1RM (3 reps). The first control load in bench press was set to presumed 70–80%1RM. Then the load increased by 5 to 10kg for each performed attempt. During each set one repetition was performed. The load increased until the maximum results were obtained.

Main experimental trials

In counterbalanced and randomized order the participants performed two experimental sessions: (a) ischemia session, where the cuffs was used before each set of bench press (b) control session, where the subjects performed bench press exercise without ischemia. In both conditions the bench press exercise were performed (5 sets; load 70%1RM). In each set, the participant performed maximal possibility number of repetitions, with maximal speed movement in both phases of movement [22]. A 5-minutes rest periods between each sets was used. Velocity of the bar was recorded by Tendo Analyzer (Slovakia) [23]. The bar peak velocity (PV) values was received from the best repetition in each separately set. The bar mean velocity values was received from the all repetitions performed in each separately set [24]. The number of performed repetitions as well as time under tension was obtained from the recorded videos. In order to ensure the reliability of manual video data collection, three persons made the data analysis.

Ischemia

The cuffs used to induce ischemia (Smart Tools, USA; 10 cm wide) were applied in the most proximal area of both arms. The cuffs was applied 5 minutes before every performed set. The ischemia was induced for 4.5 minutes and additional 30s was intended to put on or take off the cuffs (inflate the cuffs—20s.; deflate the cuffs– 10s.). The cuffs have been completely removed when performing the bench press. The cuff pressure was approximately 80% AOP (114.0 ± 10.7 mmHg). To determine the individual pressure value, we used a standardized procedure described elsewhere [13,14].

Statistical analysis

For statistical analyses was used Statistica 9.1. The Shapiro-Wilk test was used to verify normality, homogeneity of sample group. Statistical differences between ischemic and control conditions independently for mean velocity (MV), peak velocity (PV), time under tension and for number of performed repetitions were analyzed by two-way repeated ANOVA [(ischemic session vs. control session) × 5-sets bench press]. The partial eta squared were used to determined effect sizes (ES). Partial eta squared values were classified 0.01–0.059 as small, 0.06–0.137 as moderate, and >0.137 as large. Post hoc comparisons using the Tukey’s test were conducted to locate the differences between mean values, when a main effect or an interaction was found. For pairwise comparisons, ESs were determined by Cohen’s d which was characterized d<0.2 as trivial; d between 0.49 and 0.20 as small; d between 0.8 and 0.5 as moderate; d > 0.8 as large. The p < 0.05 was determined as statistical significance.

Results

The results showed significant statistically interaction effect in time under tension (p = 0.022; η2 = 0.20). Further, there was lack of significant statistically interaction effect for PV (p = 0.28; η2 = 0.10) MV (p = 0.38; η2 = 0.08), and for number of performed repetitions (p = 0.28; η2 = 0.09).

The ANOVA also showed a statistically significant main effect of condition for time under tension (p = 0.04; η2 = 0.31; 22.3 s vs. 23.7 s, respectively for ischemia and control conditions). Further there was no main effect of condition for number of performed repetitions (p = 0.55; η2 = 0.03), for PV (p = 0.90; η2 < 0.01) and for MV (p = 0.26; η2 = 0.10).

The test Tukeya analysis for interaction showed significantly shorter time under tension for condition under ischemia compared to control group in first set (p < 0.01; 28.0 s vs. 31.4 s; Table 1). The test Tukeya analysis for main effect showed significant shorter time under tension for ischemia compared with the control condition (p = 0.04; 22.3 s vs. 23.7 s).

Table 1. Differences in performance variables during control and ischemia conditions.

Condition Set 1
(95%CI)		 Set 2
(95%CI)		 Set 3
(95%CI)		 Set 4
(95%CI)		 Set 5
(95%CI)
Peak Bar Velocity [m/s]
Control 0.73 ± 0.07
(0.69 to 0.78)		 0.69 ± 0.08
(0.64 to 0.74)		 0.66 ± 0.09
(0.61 to 0.71)		 0.64 ± 0.10
(0.58 to 0.70)		 0.61 ± 0.10
(0.55 to 0.67)
Ischemia 0.70 ± 0.07
(0.66 to 0.75)		 0.68 ± 0.09
(0.63 to 0.74)		 0.66 ± 0.10
(0.60 to 0.72)		 0.65 ± 0.12
(0.58 to 0.72)		 0.63 ± 0.11
(0.56 to 0.70)
ES 0.43 0.12 0.00 0.09 0.19
Mean Bar Velocity [m/s]
Control 0.56 ± 0.05
(0.53 to 0.59)		 0.52 ± 0.04
(0.50 to 0.55)		 0.52 ± 0.06
(0.48 to 0.56)		 0.46 ± 0.07
(0.42 to 0.50)		 0.47 ± 0.06
(0.44 to 0.51)
Ischemia 0.54 ± 0.05
(0.51 to 0.58)		 0.54 ± 0.07
(0.50 to 0.58)		 0.51 ± 0.08
(0.46 to 0.56)		 0.44 ± 0.10
(0.38 to 0.50)		 0.43 ± 0.05
(0.40 to 0.46)
ES 0.40 0.35 0.14 0.09 0.72
Number of performed repetitions [n]
Control 16.8 ± 3.4
(14.8 to 18.9)		 13.7 ± 1.4
(12.8 to 14.6)		 11.9 ± 1.0
(11.3 to 12.6)		 9.8 ± 1.2
(9.1 to 10.5)		 9.4 ± 1.3
(8.6 to 10.1)
Ischemia 16.5 ± 2.0
(15.3 to 17.8)		 14.3 ± 2.3
(12.9 to 15.7)		 12.2 ± 1.6
(11.2 to 13.2)		 10.3 ± 1.3
(9.6 to 11.1)		 9.3 ± 1.4
(8.4 to 10.2)
ES 0.11 0.32 0.22 0.40 0.07
Time Under Tension [s]
Control 31.4 ± 2.9
(29.7 to 33.2)		 24.8 ± 2.8
(23.1 to 26.4)		 23.4 ± 2.3
(22.0 to 24.8)		 20.4 ± 3.3
(18.5 to 22.4)		 18.6 ± 2.3
(17.2 to 20.0)
Ischemia *28.0 ± 4.0
(25.6 to 30.5)		 24.4 ± 3.8
(22.2 to 26.7)		 21.6 ± 2.9
(19.9 to 23.3)		 19.2 ± 2.5
(17.7 ± 20.7)		 18.3 ± 2.8
(16.6 to 20.0)
ES 0.97 0.12 0.69 0.41 0.12
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All data are presented as mean with standard deviation [SD]; CI = confidence interval; ES = Cohen’s d;

*Statistically significant differences in comparison with the corresponding value in control condition p < 0.05.

Discussion

The result of this study showed that ischemic intra-conditioning did not increase the strength-endurance capabilities when the bench press at 70%1RM was performed. The result of the presented study shows lack of significant differences in a maximal number of performed repetitions, as well as a lack of differences in bar velocity between ischemia and control condition, when bench press exercise was performed to muscle failure. However, what is particularly important despite that was not observed differences in a maximal number of performed repetitions between conditions, the result of the presented study shows a decrease in time under tension for ischemia compared to control condition.

Currently, there is only one available study that investigated the impact of ischemic intra-conditioning (restriction used only during the rest periods between sets) in resistance exercise [14]. These authors showed that ischemic intra-conditioning increased bar velocity and power output during the bench press performed with a load of 60% of 1RM (5 sets of 3 repetitions with 5-minute rest between sets). However, this is the first study that investigated the effects of ischemic intra-conditioning in strength-endurance performance. The result of present study did not show differences in number of performed repetitions, and in bar velocity (both PV and MV) between ischemia and control condition during the five sets of bench press exercise performed to failure. In the study by Wilk et al. [14] the experimental procedure contains a lower number of repetitions (only 3 reps in each set) lasting approximately 3–5 s per set while in present study each set was performed to muscle failure and lasted 18–32 s. It seems that the duration of exercise or fact that the successive sets to failure are performed may determine the acute ischemic intra-conditioning effect, hence the differences in outcomes between our result and study Wilk et al. [14]. Therefore, the lack of changes in strength- endurance performance for ischemic condition compared to study Wilk et al. [14] may be related to the longer duration of the effort. Ischemia before effort increase exercise physical performance as well as stimulates physiological responses such as improvement of metabolic efficiency (attenuating ATP depletion), also glycogen depletion and the lactate production [2–11]. Further ischemia causes changes in systemic VO2, in the deoxygenation of muscular Hb/Mb, and the opening of the ATP-dependent K+ channels which can enhance the level of performance [3–5,8,9,12]. However, these physiological responses may have a positive effect on physical performance, but when the effort after the ischemia is not performed several times to failure. It seems that the duration of exercise or fact that the successive sets to failure are performed may determine the acute ischemic intra-conditioning effect, hence the differences in outcomes between our result and study Wilk et al. [14].

Nonetheless, it should be noted that although the present study did not show differences in maximal number of performed repetitions between conditions, there was observed decrease in time under tension for ischemia condition. The shorter time under tension without changes in the number of performed repetitions can be related with the increase of velocity in eccentric movement as it was recoded in study Wilk et al. [24]. However, in presented study the eccentric velocity was not measured. Therefore, based on result of time under tension it can be concluded that ischemic intra-conditioning decrease maximal time of effort during resistance exercise. However, performing repetitions to exhaustion in each set with additional ischemia applied in rest periods would be expected to cause significant reductions in exercise capacity [25] not only in time under tension but also reductions of explosive performance however such reductions were not observed. The effect of maintaining a certain amount of power output during progressive fatigue following ischemic intra-conditioning was previously observed also in a study by Trybulski et al. [26] showed that ischemia applied during the rest period between sets of Kaiser Squats prevented progressive fatigue compared to the control condition which could also take place in the our study. Maintaining peak and mean concentric velocity during ischemia condition, may be related to the fact that ischemic intra-conditioning compensates or limits the negative effects of arising fatigue. The muscles blood flow previously subjected to ischemic pre-conditioning, become more resistant to arising acute effort fatigue and its potential adverse effects on performance [27], therefore it can be assumed that a similar effect will occur for both ischemic pre and intra-conditioning used during one training protocol. The previous studies showed that the ischemia used only as pre-conditioning increased the strength-endurance performance [16,18–20,28]. Novaes et al. [20] showed that total training volume (the number of performed repetitions) increased following the ischemic pre-conditioning. A similar result was observed in a study by Marocolo et al. [19]. Ischemic pre-conditioning increase physical performance and stimulates acute responses such as improvement of metabolic efficiency by attenuating ATP depletion, as well as glycogen depletion and post exercise lactate production [2–11]. Furthermore, ischemic as pre-conditioning improve blood flow in skeletal muscles, by inducing vasodilation [29], improving functional sympatholysis [18] and preserving microvascular endothelium function during stress [30–33]. The similar effect can be observed when ischemic intra-conditioning is used. Although some studies have showed positive effects of pre-conditioning ischemia on physiological responses and performance, not all studies such report beneficial effects. Marocolo et al. [34] did not observe changes in performance following ischemic pre-condition, while Paixao et al. [35] showed negative effect of ischemic pre-condition. Therefore the effect of ischemia on performance are highly contentious [15] and its effectiveness may depend on the methodology of using ischemia (time when ischemia is applied, duration of ischemia, number of cycles, pressure of cuffs). However, even if the ischemia used during rest periods doesn’t increase performance it should be noted that this ischemic intra-conditioning does not decrease a maximal number of performed repetitions, as well as peak and mean bar velocity.

An important factor influencing the efficiency of different schemes of ischemia are number of ischemic cycles during training sessions and the duration of a single ischemia cycle as well as pressure of cuffs. Marocolo et al. [19] showed that ischemic pre-conditioning (4 cycles of 5 minutes ischemia at 220mmHg) increased the maximal number of performed repetitions during leg extension in the first set and second set, but not in the third. Contrary, Cocking et al. [36] showed that five cycles of pre-conditioning ischemia cycles (5 cycles for 5 min, cuffs pressure 220mm/Hg) have not promoted enhancements in exercise performance, similar to our study where five ischemic intra-conditioning cycles (5 cycles for 4.5 min, cuffs pressure 114mmHg) do not induce enhancements in strength-endurance performance. Therefore, its seems that such ischemia protocols is insufficient or too burdensome to induce positive responses in physical performance. Furthermore, in the presented study also single pre-conditioning ischemia before first set of bench press exercise did not increase strength-endurance performance and explosive performance for first set. Therefore, both the repetitive 4.5-min ischemia did not cause any changes in the number of performed repetitions, but also single 4.5-min pre-conditioning ischemia was not optimal to cause positive change in the 1st set of exercise.

Although the results of the present study expands knowledge and training clues, there are some study limitations that should be addressed. In presented study the physiological or metabolic responses was not determined what is main limitation which should be addressed. Furthermore, the variations of pressure of ischemia as well as different time of ischemia may also have a significant impact on endurance-performance, which require further studies.

Conclusions

This study indicate that ischemic intra-conditioning does not increase strength-endurance performance as well as bar velocity in bench press exercise performed to muscle failure. Therefore, ischemic intra-conditioning is not effective method to increase strength-endurance performance of upper body. However, even if the ischemia used during rest periods do not increase performance it should be noted that this ischemic intra-conditioning does not decrease maximal number of performed repetitions, as well as peak and mean bar velocity. Therefore, the maintaining volume of effort and peak and mean concentric velocity during ischemia condition, while possibly increasing physiological responses, may increase acute responses which may indirectly affect chronic muscle adaptation.

Supporting information

S1 Raw data

(XLSX)

Click here for additional data file. (25.7KB, xlsx)

Data Availability

All relevant data are within the manuscript and its Supporting information files.

Funding Statement

The study was supported by the statutory research of the Jerzy Kukuczka Academy of Physical Education in Katowice, Poland. The study was also funded by the Grant Agency of Charles University through a grant awarded to MK and MW (PRIMUS/22/HUM/019). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Decision Letter 0

Daniel Boullosa

30 Mar 2022

PONE-D-21-36446The effects of ischemia during rest intervals on strength endurance performancePLOS ONE

Dear Dr. Wilk,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Sorry for the delay but it was very hard to find reviewers for this manuscript. As we have only one review report, I would like to invite you to respond it and suggesting me other potential reviewers during the next round of revisions to achieve the minimum number of reviewers required for peer review (2).

Please submit your revised manuscript by May 13 2022 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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We look forward to receiving your revised manuscript.

Kind regards,

Daniel Boullosa

Academic Editor

PLOS ONE

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- https://www.frontiersin.org/articles/10.3389/fphys.2021.715096/full

We would like to make you aware that copying extracts from previous publications, especially outside the methods section, word-for-word is unacceptable. In addition, the reproduction of text from published reports has implications for the copyright that may apply to the publications.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This is an interesting study where authors investigate the effects of ischemia applied before the first set and between sets of resistance exercise (bench press) performed to failure on number of repetitions, time under tension and bar velocity. The authors conclude that ischemia applied between-sets does not increase strength-endurance nor bar velocity during bench press exercise performed to muscle failure.

I hope that my comments be helpful to improve the readability of the manuscript.

General comments

The manuscript is well written and easy to follow. Although I am not a native English speaker, I suggest some minor adjustments in writing. The objective is clear and the results are important to the practitioner. Some caution must be exercised when trying to speculate the results from acute study to long term adaptations. I believe the discussion section needs some work to improve the interpretation of the results.

Specific comments.

Introduction

I would not say that ischemia is the same as blood flow restriction, as ischemia may result from the external compression, but it is not the method.

L 64-65 - What do the authors mean by “The differences between those methods are related to the point when ischemia is applied”. This sentence refers to using restriction continuous, intermittent or pre-conditioning.

Also, when BFR is used during resistance training, the aim is to partially blood inflow and fully restrict blood outflow in the exercising muscles. This is not the aim of the ischemic pre-conditioning. So I suggest that this paragraph be rewritten.

L62- replace combine with combined

L67 – I suggest that “ischemic pre-conditioning” be used instead of “ischemia pre-conditioning”

L68 – please use the same term – ischemia intra-conditioning (or ischemic, if you choose to replace), but do not use “intra-conditioning ischemia”. The same comment applies to other places in the manuscript where “intra-conditioning ischemia” is used.

L75 – I suggest that “… it can be assumed…” be replaced with “… it is possible that…”.

L77 – performed

L79 – ischemic pre-conditioning. I suggest that the authors include when the ischemic pre-conditioning was applied. It is possible that some readers are not familiar with this strategy.

L83 -replace “a” with “the”

L86 -replace “a” with “the”

L89 – Please include what was assessed as physical performance?

L91-93 – In this study, ischemia was applied not only between sets, but also previous to the beginning of the training sets.

L94-95 – Please rewrite the sentence starting with “It was hypothesized…”

Methods

This section is easy to follow.

I wonder why bar velocity and time under tension were assessed if the objective was to investigate the effects of ischemic intra-conditioning in strength endurance performance. It is not in the introduction; they are not markers of strength endurance and is briefly discussed in the discussion section.

L 158- coefficient

L182-184 – please, rewrite. It is confusing. What tests were used?

Results

Table 1 – specify what is present in parentheses. I believe it is the CI. Specify that the ES presented is Cohen’s d.

Discussion

For me, this is the critical part of this manuscript, and authors need to rewrite some of the information to improve flow and readability. For example, in the 2nd paragraph, authors mention the results of bar velocity and power and contrast them to the findings of strength endurance. These variables are very different.

Also, I suggest that authors organize the discussion according to the variables they investigate, and then try to make a final statement gathering all the discussion presented.

L228 - replace author’s with authors’

L 239 – 241 – There is a comparison with the study by Wilk who observed that ischemic intra-conditioning improved bar velocity is a training session consisting of 5 sets with 3 reps at 60% 1RM (maximal number of repetitions was not assessed). Why authors try to discuss the different set durations if the first study did not assess strength endurance?

The important question that has to discussed is why was not there difference between experimental and control condition in the present study?

When authors bring the study of Wilk I imagined they would discuss the lack of effects in bar velocity. This is an interesting discussion. The highest peak velocity and mean velocity should have presented the same pattern in this study and Wilk’s, why it did not happen?

Time under tension decreased and number of repetitions was not affected, how do you explain that?

L47-L251 – This is important information and should be discussed further

L252- I am not sure that physiological responses should be discussed here, as you did not assess them. But Why would physiological responses increase during ischemia condition?

L257 – it is not just intra-conditioning that can have affected the results, but also the pre-conditioning.

L277 – replace do with does

L280- Please discuss the pressure applied

L285 – delete was

L286- delete the

L310 – Present the limitation in a different paragraph.

L324 – 327 – This is speculation and the authors have no results to support it. It should not be in the conclusion.

References

Please correct the references as there are no journal names.

**********

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Reviewer #1: Yes: Renato Barroso

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PLoS One. 2023 Apr 6;18(4):e0280231. doi: 10.1371/journal.pone.0280231.r002

Author response to Decision Letter 0

7 Aug 2022

Reviewer #1: This is an interesting study where authors investigate the effects of ischemia applied before the first set and between sets of resistance exercise (bench press) performed to failure on number of repetitions, time under tension and bar velocity. The authors conclude that ischemia applied between-sets does not increase strength-endurance nor bar velocity during bench press exercise performed to muscle failure.

I hope that my comments be helpful to improve the readability of the manuscript.

Reply - We are grateful for the commitment and very valuable comments that helped us to improve the quality of the manuscript. We hope that the revised manuscript adequately addresses all the raised issues.

General comments

The manuscript is well written and easy to follow. Although I am not a native English speaker, I suggest some minor adjustments in writing. The objective is clear and the results are important to the practitioner. Some caution must be exercised when trying to speculate the results from acute study to long term adaptations. I believe the discussion section needs some work to improve the interpretation of the results.

Specific comments.

Introduction

I would not say that ischemia is the same as blood flow restriction, as ischemia may result from the external compression, but it is not the method.

Reply – yes we agree with the reviewer that ischemia may result from external compression, that's why we made such a change to: “The ischemia-induced by the external compression or by the BFR cuffs”

L 57-58

L 64-65 - What do the authors mean by “The differences between those methods are related to the point when ischemia is applied”. This sentence refers to using restriction continuous, intermittent or pre-conditioning.

Also, when BFR is used during resistance training, the aim is to partially blood inflow and fully restrict blood outflow in the exercising muscles. This is not the aim of the ischemic pre-conditioning. So I suggest that this paragraph be rewritten.

Reply - I have corrected the indicated sentence L60-64

L62- replace combine with combined

Reply – the change has been made

L67 – I suggest that “ischemic pre-conditioning” be used instead of “ischemia pre-conditioning”

Reply – the change has been mad

L68 – please use the same term – ischemia intra-conditioning (or ischemic, if you choose to replace), but do not use “intra-conditioning ischemia”. The same comment applies to other places in the manuscript where “intra-conditioning ischemia” is used.

Reply - Thank you, I have standardized the term throughout

L75 – I suggest that “… it can be assumed…” be replaced with “… it is possible that…”.

Reply – the change has been made

L77 – performed

Reply – the change has been made

L79 – ischemic pre-conditioning. I suggest that the authors include when the ischemic pre-conditioning was applied. It is possible that some readers are not familiar with this strategy.

Reply – we added such information about when the ischemia was applied L77- 78

L83 -replace “a” with “the”

Reply – the change has been made

L86 -replace “a” with “the”

Reply – the change has been made

L89 – Please include what was assessed as physical performance?

Reply – the change has been made L79-81

L91-93 – In this study, ischemia was applied not only between sets, but also previous to the beginning of the training sets.

Reply - I added information on application of ischemia also before the first set L91

L94-95 – Please rewrite the sentence starting with “It was hypothesized…”

Reply – the sentence was rewritten L 93-95

Methods

This section is easy to follow.

I wonder why bar velocity and time under tension were assessed if the objective was to investigate the effects of ischemic intra-conditioning in strength endurance performance. It is not in the introduction; they are not markers of strength endurance and is briefly discussed in the discussion section.

Reply – time under tension is increasingly used as an indicator of exercise volume, more reliable than the number of repetitions, and the value of the maximal exercise volume performed is an important aspect in assessing strength-endurance performance. Further also changes in bar velocity may indicate the level of increasing fatigue. Therefore, both parameters can be important parameters in the assessment of the impact of BFR on the level of strength-endurance performance.

L 158- coefficient

Reply - word was corrected

L182-184 – please, rewrite. It is confusing. What tests were used?

Reply – sentence was corrected

Results

Table 1 – specify what is present in parentheses. I believe it is the CI. Specify that the ES presented is Cohen’s d.

Reply – yes it is CI. The table was corrected

Discussion

For me, this is the critical part of this manuscript, and authors need to rewrite some of the information to improve flow and readability. For example, in the 2nd paragraph, authors mention the results of bar velocity and power and contrast them to the findings of strength endurance. These variables are very different.

Also, I suggest that authors organize the discussion according to the variables they investigate, and then try to make a final statement gathering all the discussion presented.

Reply – The main problem with preparing the discussion is that there are no other studies about intra-conditioning and strength-endurance performance to which we could compare our results, so we used the results from other ischemia methods (ischemic pre-conditioning) or other measuring and other variables. However, as suggested by the reviewer, we have made changes to the discussion structure

L228 - replace author’s with authors’

Reply – done

L 239 – 241 – There is a comparison with the study by Wilk who observed that ischemic intra-conditioning improved bar velocity is a training session consisting of 5 sets with 3 reps at 60% 1RM (maximal number of repetitions was not assessed). Why authors try to discuss the different set durations if the first study did not assess strength endurance?

Reply - we decided to make this comparison because there are no other studies that have used ischemia only during rest intervals

The important question that has to discussed is why was not there difference between experimental and control condition in the present study?

When authors bring the study of Wilk I imagined they would discuss the lack of effects in bar velocity. This is an interesting discussion. The highest peak velocity and mean velocity should have presented the same pattern in this study and Wilk’s, why it did not happen?

Time under tension decreased and number of repetitions was not affected, how do you explain that?

Reply - as suggested by the reviewer, we have added appropriate explanations L242-251

L47-L251 – This is important information and should be discussed further

Reply - the discussion in this regard has been expanded L255-259

L252- I am not sure that physiological responses should be discussed here, as you did not assess them. But Why would physiological responses increase during ischemia condition?

Reply - yes, the reviewer is right, so we have removed the term potential increases of physiological responses during ischemia condition.

L257 – it is not just intra-conditioning that can have affected the results, but also the pre-conditioning.

Reply – yes, we made appropriate changes

L277 – replace do with does

Reply – done

L280- Please discuss the pressure applied

Reply - Ghosh et al. does not provide such information therefore we decide to delete this ref. In other refs. we added relevant information L287-303

L285 – delete was

Reply – done

L286- delete the

Reply – done

L310 – Present the limitation in a different paragraph.

Reply – done

L324 – 327 – This is speculation and the authors have no results to support it. It should not be in the conclusion.

Reply - I agree with the reviewer's opinion, therefore I deleted the indicated sentence

References

Please correct the references as there are no journal names.

Reply - In fact, I haven't noticed such a big mistake. Thank you for paying attention

Attachment

Submitted filename: Responses to Review.docx

Click here for additional data file. (17.3KB, docx)

Decision Letter 1

Daniel Boullosa

27 Sep 2022

PONE-D-21-36446R1The effects of ischemia during rest intervals on strength endurance performancePLOS ONE

Dear Dr. Wilk,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Nov 11 2022 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Daniel Boullosa

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: No

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: No

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Thanks for the opportunity to review the revised version of the manuscript.

As I mentioned in the previous review, Ischemia is not the same as blood flow restriction.

The first sentence of the introduction states that. “Ischemia also referred blood flow restriction (BFR)…”. Ischemia is the “deficient supply of blood to a body part (such as the heart or brain) that is due to obstruction of the inflow of arterial blood” (Merriam-Webster dictionary. Thus, I suggest the term BFR be used with caution and not as synonymous of ischemia.

Methods, Results and Discussion sections are difficult to understand.

In L59-60 – It is stated that there are different methods of applying BFR. I would expect that authors mentioned “how” the restriction was applied and not “when”. In this part of the manuscript, I believe that the main point should be on the ischemia and “when” it is induced, which brings the problem that was investigated: Intra-conditioning ischemia.

Maybe some adjustment in the terminology used is necessary. The use of ischemia before the exercise or before transplantation (as it was originally used) has been called Ischemic pre-conditioning. I suggest that authors use ischemic intra-conditioning, instead of ischemia intra-conditioning. Ischemia is a noun while ischemic is an adjective, which is the case as “ischemic” is characterizing the “pre-conditioning”.

However, if I had to hypothesize something, I would say that ischemic intra-conditioning would impair strength and endurance performance, as it reduces the supply of oxygen to the working muscles, which is necessary to the recovery of substrates and removal of metabolites.

L73 – replace “Previously” with “previous”

L87 – conditioning instead of condition

L88 – delete but

L90 – “…before THE first set…”. Delete “the” before “… all rest…”

L102 – A 5-min rest-interval was used between each set.

L103 – ischemic instead of ischemia.

L104 – Pneumatic cuffs were used on both arms…

L105 – replace brake with interval. “Brake” refers to something used to slow down or stop movement.

L109 – replace take part with participated

L112 – replace “lack” with “absence”.

Avoid starting a sentence with a number.

Please rewrite “Procedures” section

How time under tension was calculated?

L152 – delete “To” (last word in this line)

L154-155 – please rewrite the sentence starting with . The statistical differences…

What variables were analyzed? And how?

L162 – What does li mean?

If there was an effect, please present what was the direction of the effect. For example, PV was higher in Condition I compared to condition II (p….).

L170 – Tukeya?

L172 – Tukeya?

In the table – How ES was calculated? It seems that it refers to Cohen’s d, but in the statistical analysis section, ES refers to eta squared.

Discussion section

L185-186 – I would leave the last sentence of this paragraph to the conclusion.

I suggest that discussion section be rewritten to improve the understanding. I have made a suggestion in the second paragraph of the discussion.

Currently, there is only one available study that investigated the impact of ischemic intra-conditioning (restriction used only during the rest periods between sets) in resistance exercise (3). These authors showed that ischemic intra-conditioning increased bar velocity and power output during the bench press performed with a load of 60% of 1RM (5 sets of 3 repetitions with 5-minute rest between sets). However, this is the first study that investigated the effects of ischemic intra-conditioning in strength-endurance performance. The result of present study did not show differences in number of performed repetitions, and in bar velocity (both PV and MV) between ischemia and control condition during the five sets of bench press exercise performed to failure. In the study by Wilk et al. (3) the experimental procedure contains a lower number of repetitions (only 3 reps in each set) lasting approximately 3–5 s per set while in present study each set was performed to muscle failure and lasted 18-32 s. It seems that the duration of exercise or fact that the successive sets to failure are performed may determine the acute ischemia intra-conditioning effect, hence the differences in outcomes between our result and study Wilk et al. (3). Therefore, the lack of changes in strength- endurance performance for ischemic condition compared to study Wilk et al. (3) may be related to the longer duration of the effort.

I am not sure how the physiological mechanisms can help in the discussion. For the mechanisms presents. Number of repetitions should have been improved, which was not observed. I wonder if there were other mechanisms involved.

L215- present instead of presented. Did not instead of didn’t

L218 – IN THE number of repetitions….

L220 – present. Replace measurement with measured.

L220-224 – what is the rationale of suggesting that time under tension is a better indicator of training volume than repetition, and why is it being mentioned here? Are the authors suggesting that training without ischemic intra-conditioning would result in smaller changes in strength and muscle size even with the same number of repetitions performed? What is the rationale? Be careful when extrapolating results from acute studies to long term adaptations. Maybe the following reference can help: Carvalho L, Concon V, Meloni M, De Souza EO, Barroso R. Effects of resistance training combined with ischemic preconditioning on muscle size and strength in resistance-trained individuals. The Journal of sports medicine and physical fitness. 2020 Nov;60(11):1431-6.

As I mentioned before, if I had to guess, I would say that ischemic condition would impair strength and endurance performance. I enjoyed the discussion in L230-259.

I am not sure that the discussion L260-281 is necessary. Also, it seems contradictory as Wilk showed that 4 bouts of 5min of ischemia induced important changes in power and bar velocity.

Discussion starting in L282 is speculative. It is not even known if acute “physiological, metabolite and hormonal responses” after ischemic condition are different.

**********

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PLoS One. 2023 Apr 6;18(4):e0280231. doi: 10.1371/journal.pone.0280231.r004

Author response to Decision Letter 1

6 Nov 2022

Reviewer #1: Thanks for the opportunity to review the revised version of the manuscript.

Reply – Dear Reviewer.

Once again thank you very much for your great commitment in reviewing the article and valuable comments. I made all necessary corrections and I believe that the article gained a lot of scientific value

As I mentioned in the previous review, Ischemia is not the same as blood flow restriction.

The first sentence of the introduction states that. “Ischemia also referred blood flow restriction (BFR)…”. Ischemia is the “deficient supply of blood to a body part (such as the heart or brain) that is due to obstruction of the inflow of arterial blood” (Merriam-Webster dictionary. Thus, I suggest the term BFR be used with caution and not as synonymous of ischemia.

Reply - Thank you for pointing out the differences in BFR and ischemia. In order to make the content of the article clearer, we have limited the use of the term BFR (L56-58; 65-69)

Methods, Results and Discussion sections are difficult to understand.

Reply - in line with the comments, I have revised these sections for the better of clarity

In L59-60 – It is stated that there are different methods of applying BFR. I would expect that authors mentioned “how” the restriction was applied and not “when”. In this part of the manuscript, I believe that the main point should be on the ischemia and “when” it is induced, which brings the problem that was investigated: Intra-conditioning ischemia.

Reply – I made the appropriate corrections (L59-65)

Maybe some adjustment in the terminology used is necessary. The use of ischemia before the exercise or before transplantation (as it was originally used) has been called Ischemic pre-conditioning. I suggest that authors use ischemic intra-conditioning, instead of ischemia intra-conditioning. Ischemia is a noun while ischemic is an adjective, which is the case as “ischemic” is characterizing the “pre-conditioning”.

Reply – I made the appropriate corrections

However, if I had to hypothesize something, I would say that ischemic intra-conditioning would impair strength and endurance performance, as it reduces the supply of oxygen to the working muscles, which is necessary to the recovery of substrates and removal of metabolites.

Reply - Initially, when I started researching the impact of ischemic intra-conditioning on strength performance, I also assumed that theoretically, it should decrease strength capabilities. However, several previous studies especially in the field of power output showed on the contrary that ischemic intra-conditioning caused an improvement in power performance. Therefore this topic seems to be very interesting

L73 – replace “Previously” with “previous”

Reply – Change has been made L80

L87 – conditioning instead of condition

Reply – done L93

L88 – delete but

Reply - done

L90 – “…before THE first set…”. Delete “the” before “… all rest…”

Reply – done

L102 – A 5-min rest-interval was used between each set.

Reply – the sentence was changed L108

L103 – ischemic instead of ischemia.

Reply – done L109

L104 – Pneumatic cuffs were used on both arms…

Reply – change has been made L110

L105 – replace brake with interval. “Brake” refers to something used to slow down or stop movement.

Reply – this sentence was rewritten L111

L109 – replace take part with participated

Reply – done L115

L112 – replace “lack” with “absence”.

Reply – done L118

Avoid starting a sentence with a number.

Reply - I changed the number to the word L129

Please rewrite “Procedures” section

Reply - I have made corrections in procedure section

How time under tension was calculated?

Reply – I have added information on how the TUT data was collected L149-151

L152 – delete “To” (last word in this line)

Reply – done

L154-155 – please rewrite the sentence starting with . The statistical differences…

What variables were analyzed? And how?

Reply - I have made the appropriate corrections and added the information about which variables were analyzed L165-175

L162 – What does li mean?

Reply - I corrected this error

If there was an effect, please present what was the direction of the effect. For example, PV was higher in Condition I compared to condition II (p….).

Reply - in the case of significant differences, I added information about the conditions between which L165-175

L170 – Tukeya?

Reply – yes, test Tukeya

L172 – Tukeya?

Reply - yes, test Tukeya

In the table – How ES was calculated? It seems that it refers to Cohen’s d, but in the statistical analysis section, ES refers to eta squared.

Reply - I made the appropriate correction in the statistics section L165-175

Discussion section

L185-186 – I would leave the last sentence of this paragraph to the conclusion.

Reply - As suggested, I moved this sentence to conclusion

I suggest that discussion section be rewritten to improve the understanding. I have made a suggestion in the second paragraph of the discussion.

Currently, there is only one available study that investigated the impact of ischemic intra-conditioning (restriction used only during the rest periods between sets) in resistance exercise (3). These authors showed that ischemic intra-conditioning increased bar velocity and power output during the bench press performed with a load of 60% of 1RM (5 sets of 3 repetitions with 5-minute rest between sets). However, this is the first study that investigated the effects of ischemic intra-conditioning in strength-endurance performance. The result of present study did not show differences in number of performed repetitions, and in bar velocity (both PV and MV) between ischemia and control condition during the five sets of bench press exercise performed to failure. In the study by Wilk et al. (3) the experimental procedure contains a lower number of repetitions (only 3 reps in each set) lasting approximately 3–5 s per set while in present study each set was performed to muscle failure and lasted 18-32 s. It seems that the duration of exercise or fact that the successive sets to failure are performed may determine the acute ischemia intra-conditioning effect, hence the differences in outcomes between our result and study Wilk et al. (3). Therefore, the lack of changes in strength- endurance performance for ischemic condition compared to study Wilk et al. (3) may be related to the longer duration of the effort.

Reply - thank you very much for the huge contribution to the proofreading, I agree that the current form of this paragraph is much better and clear. L204-220

I am not sure how the physiological mechanisms can help in the discussion. For the mechanisms presents. Number of repetitions should have been improved, which was not observed. I wonder if there were other mechanisms involved.

Reply - In line with my earlier comment, I have moved the potential physiological mechanisms to the introduction. In line with previous studies, pre-conditioning ischemia increased number of performed repetitions during leg extension, however our study did not show such effect. Therefore, what I pointed out in the introduction, the methodology of applying ischemia (when is used) may play a key role in assessing its impact ischemia on acute performance changes. (L270-272)

L215- present instead of presented. Did not instead of didn’t

Reply – done L232

L218 – IN THE number of repetitions….

Reply – done L235

L220 – present. Replace measurement with measured.

Reply – done L237

L220-224 – what is the rationale of suggesting that time under tension is a better indicator of training volume than repetition, and why is it being mentioned here? Are the authors suggesting that training without ischemic intra-conditioning would result in smaller changes in strength and muscle size even with the same number of repetitions performed? What is the rationale? Be careful when extrapolating results from acute studies to long term adaptations. Maybe the following reference can help: Carvalho L, Concon V, Meloni M, De Souza EO, Barroso R. Effects of resistance training combined with ischemic preconditioning on muscle size and strength in resistance-trained individuals. The Journal of sports medicine and physical fitness. 2020 Nov;60(11):1431-6.

Reply – yes, I agree that this paragraph was to speculative. Therefore I decide to delete this sentence.

As I mentioned before, if I had to guess, I would say that ischemic condition would impair strength and endurance performance. I enjoyed the discussion in L230-259.

Reply - Initially, when I started researching the impact of ischemic intra-conditioning on strength performance, I also assumed that theoretically, it should decrease strength capabilities. However, several previous studies especially in the field of power output showed on the contrary that ischemic intra-conditioning caused an improvement in power performance.

I am not sure that the discussion L260-281 is necessary. Also, it seems contradictory as Wilk showed that 4 bouts of 5min of ischemia induced important changes in power and bar velocity.

Reply - there are studies that indicate that the number of cycles of ischemia are important, also from a practical point of view it also seems to be useful information. I have kept the length of this section to a minimum

Discussion starting in L282 is speculative. It is not even known if acute “physiological, metabolite and hormonal responses” after ischemic condition are different.

Reply - I agree with the reviewer opinion and this paragraph has been removed

Thank you.

Best regards

Michal Wilk

Decision Letter 2

Daniel Boullosa

1 Dec 2022

PONE-D-21-36446R2The effects of ischemia during rest intervals on strength endurance performancePLOS ONE

Dear Dr. Wilk,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please, address the best you can the expert reviewers's concerns to avoid another round of revisions before acceptance. I agree with the reviewer that you should be precise with the language used. Please, communicate exactly what you did observe avoiding extrapolations. Personally, I don't like the concept of "strength endurance performance" as it is an oxymoron (i.e. nor it is strength nor it is endurance) but may accept it as it is your paradigm. However, I should alert you that this concept may confound the readers.

Please submit your revised manuscript by Jan 15 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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PLOS ONE

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Reviewer #1: All comments have been addressed

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Reviewer #1: Partly

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Reviewer #1: Yes

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Reviewer #1: Yes

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Reviewer #1: Dear authors

I commend you for the the study and the manuscript, and thank you for the changes made.

I just have two further comments:

1) In the first two paragraph of the introduction, the definition of ischemia and blood flow restriction is still confusing.

2) In line 239-240: I am not sure I agree with the conclusion that strength-endurance is decreased based on the shorter time under tension in ischemic intra-conditioning condition. The number of repetitions did not change. I like the discussion that ischemia may have increased eccentric velocity. Is time under tension a better marker of strength endurance compared to number of repetitions?

**********

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Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

**********

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PLoS One. 2023 Apr 6;18(4):e0280231. doi: 10.1371/journal.pone.0280231.r006

Author response to Decision Letter 2

5 Dec 2022

Reviewer #1: Dear authors

I commend you for the the study and the manuscript, and thank you for the changes made.

Reply -Thank you again for your valuable comments. Personally, the process of reviewing this article has taught me a lot and allowed me to look a bit differently at the colloquial or misleading terms I often use in my manuscripts.

Thank you!

I just have two further comments:

1) In the first two paragraph of the introduction, the definition of ischemia and blood flow restriction is still confusing.

Reply - in order to avoid any confusion, I have decided to completely remove the term blood flow restriction. Additionally, the first two sentences were re-written. (L55-57)

2) In line 239-240: I am not sure I agree with the conclusion that strength-endurance is decreased based on the shorter time under tension in ischemic intra-conditioning condition. The number of repetitions did not change.

Reply - yes, I have to admit that it may be too speculative to determine the decline in strength- endurance based on TUT alone. Thank you for this comment and I made the appropriate change by introducing time of effort instead strength-endurance performance. (L239)

I like the discussion that ischemia may have increased eccentric velocity. Is time under tension a better marker of strength endurance compared to number of repetitions?

Reply - For several years, in each of my experimental protocols, I independently analyzed the number of performed repetitions and TUT. There are indications that the TUT is a more reliable indicator of volume compared to the number of repetitions (PMID: 34043184; 32735429; 29922395; 32269656; 31817252). The main aspect that may affect differences between TUT and REPS is the fact that the repetition is considered completed only when the full movement, full repetition is perform (eccentric and concentric phases), while the TUT determines the duration of the effort and even if the effort is stopped in the middle of the entire repetition, this time is counted to the value of TUT, but this effort (not full repetition) is not counted to the number of repetitions. Therefore, it is worth analyzing both parameters.

Best Regards

Michal Wilk

Decision Letter 3

Daniel Boullosa

26 Dec 2022

The effects of ischemia during rest intervals on strength endurance performance

PONE-D-21-36446R3

Dear Dr. Wilk,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Daniel Boullosa

Academic Editor

PLOS ONE

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Reviewers' comments:

Acceptance letter

Daniel Boullosa

28 Mar 2023

PONE-D-21-36446R3

The effects of ischemia during rest intervals on strength endurance performance

Dear Dr. Wilk:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

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