Skip to main content
NCBI home page
International Journal of Exercise Science logoLink to International Journal of Exercise Science
. 2023 Nov 1;16(2):1398–1412. doi: 10.70252/NLME4834

The Effects of Pre-Exercise Ice-Slurry Ingestion on Thermoregulation and Exercise Performance of Highly Trained Athletes: A Scoping Review

PRANITHA GOPATHI 1,†, KEREN HARISH TIWARI 2,‡, KOMMI KALPANA 3,‡
PMCID: PMC10824289  PMID: 38288403

Abstract

Ice-slurry prepared from plain ice, crushed ice, or sports drink has been used as a cooling strategy before exercise to regulate body temperature and improve exercise performance. However, consensus regarding the benefit is unclear. Therefore, the present review aimed to study the effects of pre-exercise ice-slurry ingestion on thermoregulation and exercise performance of highly trained athletes. The Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) checklist was used. The data extraction was done using the search engine Google Scholar, and digital repositories such as Cochrane, Scopus, Medline, Ebsco, Proquest and Pubmed. The keywords ‘Pre-cooling’, ‘Ice-slurry’, ‘Ice Slush’ ‘Thermoregulation’ ‘Heat Loss’ ‘Heat Stress’ ‘Body Temperature’ ‘Athletes’, ‘Sports Persons’ ‘Exercise Performance’ were used. Among the identified records (n = 151), 11 articles which met the inclusion criteria were examined. Out of the eleven studies, six studies reported a significant decrease in core/rectal/GI/skin/body temperature, and six studies reported a significant increase, or positive influence on exercise performance, and three studies both on thermoregulation and exercise performance. Ingestion of pre-exercise ice-slurry (30 min BE; −1°C to +1°C) in the dosage range of 7–14g/kg/BM has a significant beneficial effect on thermoregulation and exercise performance. Ice-slurry prepared from plain crushed ice, or sports drink, or carbohydrate and electrolyte drinks may have a similar effect on thermoregulation and exercise performance.

Keywords: Pre-cooling Strategies, ice-slurry, thermoregulation, exercise performance, athletes

INTRODUCTION

Exercising in hot and humid environments for long durations can increase the skin and core temperature of the athletes; this can result in the early onset of fatigue and impair athletic performance (28). To compete with metabolic heat production coupled with environmental heat stress (air temperature, humidity, wind speed, and solar radiation), intensity and duration of exercise; the parallel need for heat transfer from the body is essential to maintain thermal equilibrium. An increase in the blood flow to the peripheral skin, and the concomitant sweating responses are progressively, and proportionally amplified to achieve thermal equilibrium (3).

Dehydration compromises the thermoregulation during exercise, thus resulting in heat accumulation and thermoregulatory strain/stress in the body which further can lead to hyperthermia-induced fatigue (3, 28). Loss of > 2% of body mass from total body water can impair the nervous system and cardiovascular system functioning, physiological adaptations, thermoregulation, and thereby, fitness and athletic performance (14). Total body water with a minimal variation of +1% to −1% can optimally thermoregulate the athlete’s body (37.5°C) during training and competition (14, 16). To maintain euhydration and thermoregulation during training, or competition, athletes use different strategies to reduce the thermal strain. One among them is the use of pre-cooling strategies to reduce body temperature before exercise, thereby reducing the metabolic heat production and increasing the maximum exercise time, or performance (13, 21).

Athletes use pre-cooling strategies such as cold air exposure, cold water immersion (2–20°C) (whole-body immersion, part-body immersion), exposure to ice, or ice products (iced towels, iced garments like ice vests and/or neck cooling collars), and air inhalation. But these are not convenient to use all the time in the field. The most convenient alternative ways are internal pre-cooling strategies like consumption of cool beverage/slush. Ice-slurry is used to lower the core temperature before exercise, and to increase the heat storage capacity during exercise to delay, or prevent the attainment of critical core temperature (12, 13, 21, 24, 25).

Ice-slurry ingestion acts as an ergogenic aid for endurance athletes in improving aerobic performance in hot environments (18). However, the attainment of benefits by athletes from ice-slurry is not always consistent as this depends on the temperature, amount, and duration of consumption of ice-slurry and acclimatisation. The previous systematic reviews focused on different pre-cooling strategies (12, 19), pre and per-cooling across different exercise and environmental conditions (8, 20), with inclusion studies conducted on untrained athletes (20), or comparison with other cooling techniques (7). Keeping the above factors in view, the present review is aimed to collate the information from various studies on strategies and effects of pre-exercise ice-slurry ingestion on thermoregulatory responses and exercise performance of highly trained athletes (many hours of sports training regularly and competition as the major professional activity) in heat stress conditions.

METHODS

The Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) checklist was used for the present review. The following inclusion and exclusion criteria were used in the selection of research articles.

Inclusion Criteria

  1. Studies that include the details related to pre-exercise ice-slurry ingestion, thermoregulation and exercise performance of athletes

  2. Studies that were conducted in concern of age group 20–35 yrs

  3. Peer reviewed Journals

  4. Studies published in the English language

  5. Free full text intervention studies.

Exclusion Criteria

  1. Studies related to moderately, or untrained, or recreational, or diseased, or disordered, or injured, or para-athletes

  2. Non peer reviewed research journals

  3. Conference papers, white papers, dissertations, or other research documents that include review-based analysis.

  4. non-availability of full-text articles

Data Extraction

The data extraction was done between April 2020 to July 2020 and June to November 2022 by using the search engine Google Scholar, and digital repositories such as Cochrane Library, Scopus, Medline, Ebsco, Proquest and Pubmed. The following steps were involved in the extraction of the research journals. The first step of the strategy was to enter the keywords such as ‘Pre-cooling’, ‘Ice-slurry’, ‘Ice Slush’, ‘Thermoregulation’, ‘Heat Loss’, ‘Heat Stress’, ‘Body Temperature’, ‘Athletes’, ‘Sports Persons’ and ‘Exercise Performance’ in the digital repositories and Boolean terms such as ‘AND’ or ‘OR’ were used to extract the number of research journals. The second step of the search strategy was to apply the filter to choose the type of journal because conference papers are not used in this analysis. The third step was the screening of research journals based on the title and then abstract to satisfy all the inclusion criteria such as age and other factors. Finally, the articles that satisfy all the eligibility criteria are selected to answer the research questions. A Microsoft Excel spreadsheet was used to extract the following information: title of the article, author, country, year of publication, gender, age, number of subjects, environmental conditions, experimental design, type, timing, and dosage, effect on thermoregulation, and effect on performance (Table 1).

Table 1.

Study Characteristics

S. No Author Country Type of Sport Gender No. of Subjects Age (yrs) Experimental Design Environmental Conditions Type of Exercise Intervention Groups Dosage of Ice-Slurry Time of Ingestion Type of Ice-Slurry Effect on Core/Rectal Temperature Effect on Performance
01 Mejuto et al., 2018 Spain Road Cycling Male 07 34.7 RCD
PP		 32°C
50% RH,		 10km time trial on cycle ergometer TN: No cooling - - - Significant decrease in RT in PRE, PRE+MID No significant differences between the three conditions
Slight positive effect in PRE intervention
PRE: Ice-slurry 14g/kg/BM 30 min BE 7.4% CHO electrolyte drink (−1°C)
PRE+MID : Ice-slurry + iced towels 14g/kg/BM 30 min BE 7.4% CHO electrolyte drink (−1°C)
02 Stevens et al., 2016 Australia Runners Male 11 29 RCD 33°C
46% RH		 5-km running on non-motorized tread mill ICE: Ice-slurry 7.5 g/kg/BM 30 min BE Sports drink (−1 °C) Significant decrease in RT in ICE than CON and MEN Significantly improved in MEN than ICE and CON
No difference between CON and ICE
MEN: Mid-cooling by a menthol mouth rinse - - -
CON: No Intervention - - -
CON: Water before and during exercise DE: 100 ml of water every 200 kJ - -
03 Beaven et al., 2018 New Zealand Rugby Male 07 21.5 RCD -- 5X40 m maximal running sprints Control:15 min passive rest - After 15 min passive rest - Decreased RT
COLD> H+C>Control> Heat		 H+C significantly improved sprint performance
H+C>Control> COLD> Heat
Heat: Wearing a lower-body survival garment - After 15 min passive rest -
Cold: Ice-slushy 500ml After 15 min passive rest -
H+C: Wearing the survival garment and ice-slushy 500ml After 15 min passive rest -
04 Saldaris et al., 2019 Australia Endurance athletes Male 09 24 RCD 34.2°C
52.9 RH		 800 kJ cycle time trial CON: Water - - Crushed Ice (−0.3±0.1° C) Reduced CT in ICE Power output improved by 7.8% in ICE
ICE: Crushed Ice 7g/kg BM 30 min BE -
05 Zimmerman et al., 2017 Australia Cycling & Triathletes Female 10 28 RCD 34.9°C
49.8% RH		 800 kJ cycle time-trial ICE: Crushed Ice BE: 7g/kg BM of ice-slurry + DE: 100 mL of water every 200 kJ 30 min BE Crushed ice (0.5°C) Decreased CT in ICE No significant difference in performance time
CON: Water before and during exercise DE: 100 mL of water every 200 kJ - -
06 Gerrett et al., 2017 Japan Trained Athletes Male 12 30.4 RCD 30.2°C
42.5% RH		 Intermittent exercise protocol of walk, jog, run, sprint Control: CHO solution - - 0.23% of CHO (23.4 ± 0.9 °C) CT was lower in ICE No Significant difference in distance covered
ICE: Ice-slurry 7.5 g/kg BM 30 min BE 0.23% of CHO (0.1 ± 0.1 °C)
07 Zimmermann et al., 2018 Australia Cyclists/triathletes Male 15 24 RCT 35°C
50% RH		 800 kJ cycle time trial PRE: No precooling + water after every 200kJ - - 100 ml of water (27.0±2.0° C) No Change in CT Both improved cycle time trial
83% Positive benefit for with POST CTT
POST: Ice-slurry + Heat acclimation 7g/kg BM 30 min BE Crushed ice (1°C)
08 Brade et al., 2014 Australia Team Sports Male 12 21.8 RCD 35.2°C
57.8 RH		 70 min of repeat sprint cycling (30 sprint-10 recovery period-30 sprint) CON: No Intervention - - - No significant difference in CT Mean power (Watts) and total work was increased J +Ice Slushy > J > CON > Ice Slushy
J: Cooling jacket - - -
Ice Slushy: Ice slushy 7 g/kg BM (2.3 g/kg/B M every 10 min) and 2.1 g/kg BM during half time 30 min BE and during half time recovery period. Plain ice (0.6°C)
J+Ice Slushy: Jacket + Ice slushy 7 g/kg BM (2.3 g/kg/B M every 10 min) and 2.1 g/kg BM during half time 30 min BE and during half time recovery period. Plain ice (0.6°C)
09 Ross et al., 2011 Australia Cyclists Male 11 33 RCD 32°C – 35°C
50% – 60% RH		 46.4 km cycling on a cycle ergometer Con: ad libitum consumption of cold water - - Cold water (4°C) No significant difference in RT 1.3 % increase in performance
3.0% increase in power output with New Cool
Std Cool: Whole-body immersion in cold (10°C) water for 10 min followed by wearing a cooling jacket - - -
New Cool: Combination of ice-slurry + iced towels 14 g/kg BM 30 min BE Sports drink (Gatorade)
10 Stevens et al., 2015 Australia Runners Male 08 27 RCD 33°C
46% RH		 Self-paced 5 km running time trial on a non motorized treadmill Control - - Tepid fluid (22°C) No significant difference in RT No significant difference between control and ice-slurry
Ice-Slurry: Ice-slurry ingestion in six equal boluses over a30 min 7.5 mL/kg BM 30 min BE Sports drink (−1°C)
11 Thomas et al., 2019 UK Trained Athletes Male 10 30.5 RCD 34.4°C
36.3% RH		 46 min self-paced intermittent exercise INT: Ice-slurry 7.5 g/kg (3 equal aliquots of 2.5 g/kg/BM every 10 min) 30 min BE 0.75 g/kg/BM of CHO Solution (−0.5 ± 0.4°C) No significant difference in GI, body and Skin temperature No significant difference in sprint or submaximal performance
CON: Water 7.5 g/kg of water 30 min BE 0.75 g/kg/BM of CHO Solution (−0.5 ± 0.4°C)
EXT: Cooling garment + water 7.5 g/kg of water 30 min BE 0.75 g/kg/BM of CHO Solution (−0.5 ± 0.4°C)
MIX: Cooling garment + ice-slurry 7.5 g/kg of ice-slurry (3 equal aliquots of 2.5 g/kg/BM every 10min) 30 min BE 0.75 g/kg of body mass of CHO Solution (−0.5 ± 0.4°C)
Open in a new tab

BM: Body Mass; BE: Before Exercise; RH: Relative Humidity; RCD: Randomised Crossover Design; RCT: Randomised Control Trial; CHO: Carbohydrate; RT: Rectal Temperature; CT: Core Temperature: GI: Gastrointestinal

RESULTS

After the primary search, 159 records related to the keywords were identified. Based on the title search, duplicate (n = 81), and irrelevant records (n = 78) were removed. Following this, abstract and full-text screening was carried out, and 11 articles were included based on the eligibility criteria (Fig. 1).

Fig 1.

Fig 1

Open in a new tab

Article Selection Methodology

Study Characteristics

The characteristics and details of the included studies are presented in Table 1. Most of the studies were done in Australia (n = 7) followed by Japan (n = 1), Spain (n = 1), UK (n = 1), and New Zealand (n = 1). The studies were conducted on cyclists (n = 2), runners (n = 2), cyclists and triathletes (n = 2), well-trained athletes (n = 2), endurance athletes (n = 1), team sports (n = 1), and rugby (n = 1). Studies were randomized counterbalance, (n = 10), or randomized control trials (n = 1) and the number of participants ranged from 7 to 15. Most of the studies (n = 10) were conducted on male athletes and only one study was on female athletes The studies were conducted in controlled conditions in laboratories (Temperature ranged from 30.2°C to 35.2°C and Relative humidity ranged from 42.5 to 60%) either on a treadmill (n = 3), or on a cycle ergometer (n = 6), or an intermittent protocol (n = 1), or indoor sprinting (n = 1).

Intervention with Ice-Slurry

Among the studies (n = 11), four studies studied the effect of ice-slurry with the control group (9, 23, 26, 31), six studies combined the ice-slurry intervention with an iced towel (15, 22), cool jackets (6, 29), survival garment (2), heat acclimatization (30), and one study with menthol mouth rinse (27). Ten out of 11studies selected for the present review supplemented ice-slurry in the range of 7–14g/kg BM before 30 min of warm-up i.e, during the pre-cooling period. One study provided 500ml of ice slushy after warm-up for 10 min and 15 min passive rest period (2).

Ice-Slurry Intervention on Thermoregulation: In Comparison with Other Study Groups

Rectal and core temperature were studied to understand the thermoregulation (Table 1&2).

Table 2.

Summary of Results

S.No Author Intervention Groups Dosage of Ice-Slurry Pre-Exercise Ice-Slurry Intervention
Effect on Temperature Effect on Performance
01 Mejuto et al., 2018

  1. No cooling

  2. Ice-slurry

  3. Ice-slurry + mid cooling with Iced towels

 14g/kg BM Decreased RT in ice-slurry, ice-slurry + mid cooling with iced towels Positive effect on 10km cycling time trial in ice-slurry
02 Stevens et.al., 2016

  1. Control

  2. Ice-slurry

  3. Mid-cooling by a menthol mouth rinse

 7.5g/kg BM Decreased RT in ice-slurry No effect with Ice-slurry Increased running performance with menthol mouth wash
03 Beaven et al., 2018

  1. 15-min passive rest

  2. Wearing a lower-body survival garment

  3. Ice-slushy

  4. H+C: Wearing a survival garment & ice slushy

 500ml Decreased RT in ice slushy, H+C Significantly increased sprinting performance in H+C and ice slushy
04 Saldaris et al., 2019

  1. Water

  2. Ice-slurry

 7g/kg BM Decreased CT Significantly power output in 800KJ cycling time trial
05 Zimmermann, et.al., 2017

  1. Water

  2. Crushed ice

 7g/kg BM Decreased CT No effect on 800 kJ cycle time-trial
06 Gerrett et al., 2017

  1. CHO Solution

  2. Ice-slurry

 7.5g/kg BM Decreased CT No effect on Intermittent exercise performance
07 Zimmermann, et al., 2018

  1. Water

  2. Ice-slurry+Heat Acclimatisation

 7g/kg BM No significant difference in CT Significantly Increased 800KJ cycling time trial
08 Brade et al., 2014

  1. Control

  2. Cooling jacket

  3. Ice-slurry

  4. Ice-slurry + Jacket

 7g/kg BM and 2.1g/kg BM half time No significant difference in CT Positive effect in Ice-slurry + Jacket
09 Ross, et al., 2011

  1. Whole-body immersion in cold (10°C) water

  2. Wearing a cooling jacket

  3. Ice-slurry + Iced towels

 14 g/kg BM No significant difference in RT Significantly increased 46.4 km cycling
10 Stevens et al., 2015

  1. Tepid fluid

  2. Ice-slurry

 7.5g/kg BM No significant difference in RT No effect on running Time trial
11 Thomas et al., 2019

  1. Water

  2. Ice-slurry

  3. Cooling garment + water

  4. Cooling garment + ice-slurry

 7.5g/kg/BM No significant difference in GI, body and skin temperature No significant difference in sprint or submaximal performance
Open in a new tab

BM: Body Mass; BE: Before Exercise; CHO: Carbohydrate; RT: Rectal Temperature; CT: Core Temperature: GI: Gastrointestinal; Bolded text denotes findings were significant

At the Start of Exercise

Immediately following ice-slurry ingestion during the pre-cooling period, there was a significant reduction in temperature. Five studies reported a decrease in rectal temperature (2, 15, 22, 26, 27), and five studies focused on core temperature showed a decrease in core temperature within 15–20 min of ice-slurry ingestion (6, 9, 23, 30, 31), and another study showed decreased gastro-intestinal, body and skin temperature (29).

After Exercise

Among the studies, only six studies reported a reduction in core/rectal/body/skin/temperature post exercise with ice-slurry intervention. Of these, a significant decrease in rectal temperature was found in three studies (2, 15, 27). The other three studies (9, 23, 31) reported a decrease in mean core temperature. The other studies reported that there was no significant effect either on rectal temperature (22, 26), or on core temperature (6, 30), and gastrointestinal, body and skin temperature (29).

Ice-Slurry Intervention on Thermoregulation: In comparison with Other Interventions

Ice-slurry supplementation (ICE) was compared with other cooling interventions to see their effect on thermoregulation (n = 7). A combination of ice-slurry ingestion with other cooling strategy-iced towel at torso (15), and wearing the survival garment, and consuming the ice slushy showed a significantly positive effect on rectal temperature after exercise (2). Menthol mouth rise (MEN) showed higher rectal temperature over ice-slurry (ICE: 36.9 ± 0.3°C vs MEN 37.2 ± 0.4°C) [25]. On the contrary, a few studies showed no significant effect on thermoregulation (6, 22, 29, 30).

Ice-Slurry Intervention on Exercise Performance: In Comparison with Other Study Groups

Of all studies (n = 11), six studies reported a significant increase, or improvement in exercise performance with pre-exercise ice-slurry ingestion (2, 6, 15, 22, 23, 30). The studies reported a positive effect (15), an increase in running sprint performance (2), mean power output of 7.8% in a cycle time trial (CTT) (23), cycling time trial performance (CTT) (30), power output (6), mean power output of 3.0% (8W), and increased performance time of 1.3% (1.06 min) in a CTT (22). In contrast, five studies showed no difference in performance with ice-slurry (9, 26, 27, 29, 31) (Table 1 & 2).

Ice-Slurry Intervention on Exercise Performance: In Comparison with Other Interventions

Ice-slurry intervention was also compared with ice-slurry along with other cooling strategies, (n = 6) and in comparison with mid cooling by mouth wash (n = 1). Ice-slurry and a mid-cooling ice towel intervention improved 46.4 km cycling performance, and power output than whole body immersion in cold water followed by wearing a cooling jacket (22). Similarly, wearing a survival garment and ice-slushy/slurry, (2, 6) and heat acclimatisation plus ice-slurry showed significantly improved performance (30). Menthol mouth rinse (MEN) has shown a significant positive improvement in treadmill performance time than ice-slurry (MEN:25.3 ± 3.5 min vs ICE: 26.3 ± 3.2 min) (27). On the contrary, no greater benefits with ice-slurry plus mid cooling with ice towel/cooling garment intervention (15, 29) over ice-slurry (Table 1&2).

Dosage and Timing of Ice-Slurry on Thermoregulation and Exercise Performance

The dosage and timing of supplementation of ice-slurry have an effect on thermoregulation and exercise performance. Supplementation of 7–14 g/kg BM of ice-slurry reported a positive effect (8 out of 11) either on thermoregulation, and exercise performance, or both.

Ice-slurry intervention of 7 g/kg BM (23), and 14g/kg BM (15), and 500ml of ice slushy plus wearing a survival garment after a 10 min warm-up and 15 min passive rest (2) showed an improvement in thermoregulation, and a positive effect on exercise performance.

On the contrary, supplementation of 7g/kg BM (15, 24), 7.5 g/kg BM (17, 22, 25), and 14g/kg BM (22) of ice-slurry showed mixed results showing positive effect on thermoregulation not showing its positive effect on exercise performance, or vice versa. 7.5g/kg BM (26, 29) showed no improvement in thermoregulation, and performance (Table 1&2).

Type of Ice-Slurry

Ice-slurry was prepared using different types of sports drinks, or plain ice, and the temperature ranged from −1°C to +1°C. Observation done on the results reported showed that the influence of ice-slurry on thermoregulation and performance were different even on the consumption of the same amount of dosage and type of ice-slurry (Table 1&2).

DISCUSSION

Exercise capacity and performance is impaired due to thermal strain in hot and humid conditions. To overcome this, athletes use different strategies; one of the most popular is cooling methods, either internal or external. Internal cooling methods are those which are ingested in and act from inside the body like ice-slurry, menthol, etc., and external cooling methods are those that are not ingested and act external on the body, like wearing cooling jackets, whole-body immersion in cold water, or cold air flow (20). Either internal and external cooling methods, or a combination of both, can benefit athletes but have controversial results (6). Ice-slurry intervention is one of the recently used strategies by athletes to thermo-regulate and benefit athletes by helping them perform to their maximum. Ice-slurry intervention can be done at any point of time from before 30 min of exercise (which is called a pre-cooling period) to the recovery period in split doses or at once (26). The present study aimed to collate the information from various studies on strategies, and effects of pre-exercise ice-slurry ingestion on thermoregulatory responses and exercise performance of highly trained athletes in heat stress conditions.

In the precooling phase, temperature (core/rectal/skin/body/GI) was reduced with ice slurry. Ice-slurry is considered the most effective pre-cooling strategy over cool water ingestion (12, 24). The mechanism behind the ingestion of ice slurry is the enthalpy of the fusion of ice. Ice-slurry ingestion acts as an additional heat sink, and lowers sweating rates, increases internal heat loss, reduces end-exercise core temperatures, increases body heat storage, delays the onset of hyperthermia-induced fatigue, and decreases thermal sensation and improves performance (10). It can also result in core temperature afferent signaling to the brain (17). Though we have observed varied results post-exercise, the thermoregulation was better with ice-slurry intervention (2, 9, 15, 23, 27). Body heat storage on ice-slurry ingestion is highly dependent on sufficient reductions in sweating efficiency. Decrements in sweating efficiency depend on environmental conditions (ambient temperature and humidity) for a given metabolic or physiologic heat production, and rate of airflow across the skin (1). Due to this limitation, the benefit may not be able to sustain the same results per and post-exercise.

Our study found improved exercise performance, i.e., increased cycling time trial (CTT), sprint, power output, or submaximal performance (2, 6, 15, 22, 23, 30) with ice-slurry intervention. Among these studies, five provided intervention with ice-slurry and mid-cooling with iced towels or jackets, wearing the survival garment, or heat acclimatization. Ice-slurry intervention during pre-cooling can help athletes improve repeat sprint cycling performance only for a limited time while doing exercise (6). Pre along with per/mid-exercise cooling (1, 4, 5, 11) and heat acclimatization (1) may be effective in improving exercise performance in hot environments.

A menthol mouth rinse, a new intervention to benefit athletes is becoming popular nowadays. Stevens et al. (27) compared ice-slurry intervention with menthol mouth rinse in runners, results showed that ice-slurry intervention can thermoregulate better than menthol, but the 5km running performance was improved in menthol mouth rinse than with ice-slurry. L-menthol and ice-slurry ingestion can expand the overall time of exercise and this extension was witnessed to be around 1% more than baseline performance (11). This shows menthol can improve or sustain running performance in hot and humid conditions.

A majority of the studies provided the intervention 30 min before the exercise. Ice-slurry ingestion of 7.5 g/kg BM in two equal boluses resulted in lower core temperature with no performance benefit in well-trained male athletes (9), similar results were observed in male runners on consumption of same quantity of ice-slurry made from sports drink served in two equal boluses (−1°C) (27). 14 g/kg BM of ice-slurry also resulted in positive thermoregulation (15), and performance in cyclists (15, 22). On the other hand, no benefit on thermoregulation and sprint performance from 3 equal aliquots of 7.5 g/kg/BM of CHO-based ice-slurry intervention (29), or ingestion of 6 equal aliquots 7.5 ml/kg/BM in male runners (26). These contrasting results may be because of differences in serving compared with other interventions i.e., splitting the same dosage into three, or six equal portions whereas others served in two equal portions. The influence of ice-slurry on thermoregulation was from 15 min after ingestion to the rest of the exercise period (9, 29, 31). Zimmermann et al (31) also reported that the ice-slurry effect was only for a short duration up to 20 min after the consumption in a CTT. Similarly, the thermoregulatory effect was up to 2km only in a 5km time trial when consumed in the pre-cooling period (27). These results encourage further exploration of appropriate timing and dosage of ice-slurry ingestion for its ergogenic effect.

Without considering other interventions of the study, and considering only pre-exercise ice-slurry ingestion to identify the role of ice-slurry made from plain crushed ice, sports drinks, carbohydrate and electrolyte solutions showed varied results. Ingestion of 7 g/kg BM of plain ice-slurry (23, 31), or 7.5 g/kg BM (9, 27), or 14 g/kg/BM (15) ice-slurry made from sports drinks or carbohydrate solutions showed improved thermoregulation. But 7.5g/kg BM of ice-slurry made from CHO solution showed no improvement in thermoregulation (26).

Ingestion of 7 g/kg BM of plain ice-slurry showed improved 800 kJ CTT performance (23). But Zimmerman et al. (30) showed no performance benefit during 800kJ CTT performance. Similarly, 14g/kg BM of ice-slurry made from 7.4% carbohydrate-electrolyte sports beverage showed a positive effect 10km CTT performance (15), and 7.5 g/kg/BM sports drink and CHO solutions-based ice-slurry showed no improvement (9, 26, 27). This shows that the dosage from 7–14g/kg/BM may help to maintain thermoregulation and increase exercise performance, and the type of ice-slurry may not influence the effect.

We have found thermoregulatory and exercise performance benefits with ice-slurry alone, or along with other interventions, but need more research evidence as few reported a positive thermoregulatory with no performance benefit, a few vice versa, and some no difference in thermoregulation and performance irrespective of dosage and timing. Nevertheless, ice-slurry ingestion can be most helpful for endurance athletes like runners, cyclists and triathletes. Future research can focus on gender-specific, a combination of cooling methods, type, timing, and dosage of ice-slurry on thermoregulation and exercise performance.

Limitations

The study followed a subjective approach rather than a quantitative analysis. There is a lack of numerical investigation, and the use of real-time analysis. The restricted amount of data that is used in the study can affect the generalizability of the research outcome. Quantitative analysis can be done for exploring the research question. The lack of research in female athletes would be a limitation to apply the practical aspects of ice-slurry in exercise.

Conclusion

Ingestion of pre-exercise ice-slurry (30 min BE; −1°C to +1°C) in the dosage range of 7–14g/kg/BM has a significant beneficial effect on thermoregulation and exercise performance of highly trained athletes. Pre-exercise ice-slurry ingestion along with per/mid-cooling with iced towels/jackets/ice-slurry, or heat acclimatization, or menthol mouth rinse may be beneficial for maintaining thermoregulation and performance. Ice-slurry prepared from plain crushed ice, or sports drink, or carbohydrate and electrolyte drinks have a similar effect on thermoregulation, and exercise performance. Athletes are encouraged to experiment with a range of ice-slurry strategies during their mock competition settings to determine the performance benefits.

REFERENCES

  • 1.Alhadad SB, Tan PMS, Lee JKW. Efficacy of heat mitigation strategies on core temperature and endurance exercise: A meta-analysis. Front Physiol. 2019;10:71. doi: 10.3389/fphys.2019.00071. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Beaven CM, Kilduff LP, Cook CJ. Lower-limb passive heat maintenance combined with pre-cooling improves repeated sprint ability. Front Physio. 2018;9:1064. doi: 10.3389/fphys.2018.01064. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Bergeron MF. Heat stress and thermal strain challenges in running. J Ortho Sports Phy Therapy. 2014;44(10):831–838. doi: 10.2519/jospt.2014.5500. [DOI] [PubMed] [Google Scholar]
  • 4.Bongers CC, Hopman M, Eijsvogels TM. Cooling interventions for athletes: an overview of effectiveness, physiological mechanisms, and practical considerations. Temperature. 2017;4:60–78. doi: 10.1080/23328940.2016.1277003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Bongers CCWG, Thijssen DHJ, Veltmeijer MTW, Hopman MTE, Eijsvogels TMH. Precooling and percooling (cooling during exercise) both improve performance in the heat: a meta-analytical review. Br J Sports Med. 2015;49:377–384. doi: 10.1136/bjsports-2013-092928. [DOI] [PubMed] [Google Scholar]
  • 6.Brade C, Dawson B, Wallman K. Effects of different precooling techniques on repeat sprint ability in team sport athletes. Eur J Sport Sci. 2014;14(Suppl 1):S84–91. doi: 10.1080/17461391.2011.651491. [DOI] [PubMed] [Google Scholar]
  • 7.Choo HC, Nosaka K, Peiffer JJ, Ihsan M, Abbiss CR. Ergogenic effects of precooling with cold water immersion and ice ingestion: A meta-analysis. Eur J Sport Sci. 2018;18(2):170–181. doi: 10.1080/17461391.2017.1405077. [DOI] [PubMed] [Google Scholar]
  • 8.Douzi W, Dugué B, Vinches L, Al Sayed C, Hallé S, Bosquet L, Dupuy O. Cooling during exercise enhances performances, but the cooled body areas matter: A systematic review with meta-analyses. Scan J Med & Sci Sports. 2019;29(11):1660–1676. doi: 10.1111/sms.13521. [DOI] [PubMed] [Google Scholar]
  • 9.Gerrett N, Jackson S, Yates J, Thomas G. Ice slurry ingestion does not enhance self-paced intermittent exercise in the heat. Scan J Med & Sci Sports. 2017;27(11):1202–1212. doi: 10.1111/sms.12744. [DOI] [PubMed] [Google Scholar]
  • 10.González-Alonso J, Teller C, Andersen SL, Jensen FB, Hyldig T, Nielsen B. Influence of body temperature on the development of fatigue during prolonged exercise in the heat. J Appl Physio. 1999;86(3):1032–1039. doi: 10.1152/jappl.1999.86.3.1032. [DOI] [PubMed] [Google Scholar]
  • 11.Jeffries O, Goldsmith M, Waldron M. L-Menthol mouth rinse or ice slurry ingestion during the latter stages of exercise in the heat provide a novel stimulus to enhance performance despite elevation in mean body temperature. Euro J Appl Physio. 2018;118(11):2435–2442. doi: 10.1007/s00421-018-3970-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12.Jones PR, Barton C, Morrissey D, Maffulli N, Hemmings S. Pre-cooling for endurance exercise performance in the heat: A systematic review. BMC Medicine. 2012;10:166. doi: 10.1186/1741-7015-10-166. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13.Marino F. Methods, advantages, and limitations of body cooling for exercise performance. Br J Sports Med. 2002;36(2):89–94. doi: 10.1136/bjsm.36.2.89. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.McDermott BP, Anderson SA, Armstrong LE, Casa DJ, Cheuvront SN, Cooper L, Kenney WL, O’Connor FG, Roberts WO. National athletic trainers’ association position statement: fluid replacement for the physically active. J Athletic Training. 2017;52(9):877–895. doi: 10.4085/1062-6050-52.9.02. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15.Mejuto G, Chalmers S, Gilbert S, Bentley D. The effect of ice slurry ingestion on body temperature and cycling performance in competitive athletes. J Thermal Biol. 2018;72:143–147. doi: 10.1016/j.jtherbio.2018.01.012. [DOI] [PubMed] [Google Scholar]
  • 16.Naghii MR. The significance of water in sport and weight control. Nutr Health. 2000;14(2):127–132. doi: 10.1177/026010600001400205. [DOI] [PubMed] [Google Scholar]
  • 17.Onitsuka S, Nakamura D, Onishi T, Arimitsu T, Takahashi H, Hasegawa H. Ice slurry ingestion reduces human brain temperature measured using non-invasive magnetic resonance spectroscopy. Sci Reports. 2018;8(1) doi: 10.1038/s41598-018-21086-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Quod MJ, Martin DT, Laursen PB. Cooling athletes before competition in the heat: Comparison of techniques and practical considerations. Sports Med. 2006;36(8):671–682. doi: 10.2165/00007256-200636080-00004. [DOI] [PubMed] [Google Scholar]
  • 19.Rodríguez MÁ Piedra JV, Sánchez-Fernández M, Del Valle M, Crespo I, Olmedillas H. A matter of degrees: a systematic review of the ergogenic effect of pre-cooling in highly trained athletes. Int J Envi Res Public Health. 2020;17(8):2952. doi: 10.3390/ijerph17082952. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Roriz M, Brito P, Teixeira FJ, Brito J, Teixeira VH. Performance effects of internal pre- and per-cooling across different exercise and environmental conditions: A systematic review. Front Nutrition. 2022;9:959516. doi: 10.3389/fnut.2022.959516. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21.Ross M, Abbiss C, Laursen P, Martin D, Burke L. Precooling methods and their effects on athletic performance: a systematic review and practical applications. Sports Med. 2013;43 doi: 10.1007/s40279-012-0014-9. [DOI] [PubMed] [Google Scholar]
  • 22.Ross M, Garvican L, Jeacocke N, Laursen P, Abbiss C, Martin D, Burke L. Novel precooling strategy enhances time trial cycling in the heat. Med Sci Sports & Exer. 2011;43(1):123–133. doi: 10.1249/mss.0b013e3181e93210. [DOI] [PubMed] [Google Scholar]
  • 23.Saldaris J, Landers G, Lay B. The effect of crushed ice ingestion on endurance performance and decision-making in hot and humid conditions. Int J Perform Anal Sport. 2019;19(3):393–401. doi: 10.1080/24748668.2019.1613588. [DOI] [Google Scholar]
  • 24.Siegel R, Maté J, Brearley MB, Watson G, Nosaka K, Laursen PB. Ice slurry ingestion increases core temperature capacity and running time in the heat. Med Sci Sports Exer. 2010;42(4):717–725. doi: 10.1249/MSS.0b013e3181bf257a. [DOI] [PubMed] [Google Scholar]
  • 25.Siegel R, Maté J, Watson G, Nosaka K, Laursen PB. Pre-cooling with ice slurry ingestion leads to similar run times to exhaustion in the heat as cold water immersion. J Sports Sci. 2012;30(2):155–165. doi: 10.1080/02640414.2011.625968. [DOI] [PubMed] [Google Scholar]
  • 26.Stevens C, Dascombe B. Changes in intragastric temperature reflect changes in heat stress following tepid fluid ingestion but not ice slurry ingestion. J Human Perform Extreme Envi. 2015;12(1) doi: 10.7771/2327-2937.1067. [DOI] [Google Scholar]
  • 27.Stevens CJ, Thoseby B, Sculley DV, Callister R, Taylor L, Dascombe BJ. Running performance and thermal sensation in the heat are improved with menthol mouth rinse but not ice-slurry ingestion. Scan J Med Sci Sports. 2016;26(10):1209–1216. doi: 10.1111/sms.12555. [DOI] [PubMed] [Google Scholar]
  • 28.Tatterson AJ, Hahn AG, Martin DT, Febbraio MA. Effects of heat stress on physiological responses and exercise performance in elite cyclists. J Sci Med Sport. 2000;3(2):186–193. doi: 10.1016/s1440-2440(00)80080-8. [DOI] [PubMed] [Google Scholar]
  • 29.Thomas G, Cullen T, Davies M, Hetherton C, Duncan B, Gerrett Independent or simultaneous lowering of core and skin temperature has no impact on self-paced intermittent running performance in hot conditions. Euro J Appl Physiol. 2019;119(8):1841–1853. doi: 10.1007/s00421-019-04173-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 30.Zimmermann M, Landers GJ, Wallman KE. Precooling with crushed ice: as effective as heat acclimation at improving cycling time-trial performance in the heat. Int J Sports Physiol Perfor. 2018;13(2):228–234. doi: 10.1123/ijspp.2016-0766. [DOI] [PubMed] [Google Scholar]
  • 31.Zimmermann M, Landers GJ, Wallman KE. Crushed ice ingestion does not improve female cycling time trial performance in the heat. Int J Sport Nutr Exer Metab. 2017;27(1):67–75. doi: 10.1123/ijsnem.2016-0028. [DOI] [PubMed] [Google Scholar]

Articles from International Journal of Exercise Science are provided here courtesy of Western Kentucky University

RESOURCES