Abstract
Background
Respiratory muscle training (RMT) plays a vital role in improving respiratory muscle strength, mitigating inspiratory muscle fatigue, and influencing the metaboreflex mechanism, thereby enhancing cardiorespiratory endurance during sports. Performing endurance activities and using devices that improve lung function can delay inspiratory muscle fatigue and improve total sports performance. The aim of this study was to determine the effect of use of newly developed RMT devices under the golden ratio principle with conventional training on lung function enhancement in novice athletes, as well as compare a new RMT with conventional (CON) treatment.
Methods
This study included 12 participants who were allocated randomly to either the RMT or CON group (n = 6 each). Both groups were trained for 15 minutes daily for four weeks. Both groups were initially tested for respiratory pressures and capacities maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), forced expiratory volume in first second (FEV1), forced vital capacity (FVC), and FEV1/FVC at baseline and post-intervention. Within-group and between-group comparisons were performed using paired t-tests and independent t-tests, respectively.
Results
The respiratory pressures of the RMT group after training (pre-RMT 425.00 ± 277.04 mmWC vs. post-RMT 541.67 ± 274.62 mmWC) were significantly improved (t = 11.07, p < 0.001) compared with those of the CON treatment group (pre-RMT 508.33 ± 217.75 mmWC vs. post-RMT 575.00 ± 229.67 mmWC). The new RMT device improved MIP, MEP, and lung function, with greater gains in FEV1 (pre-RMT 2.66 ± 0.74 L vs. post-RMT 2.86 ± 0.70 L) (pre-CON 3.04 ± 0.80 L vs. post-CON 3.06 ± 0.74 L), FVC (pre-RMT 3.03 ± 0.99 L vs. post-RMT 3.22 ± 0.94 L) (pre-CON 3.33 ± 1.06 L vs. post-CON 3.29 ± 0.99 L), and the FEV1/FVC ratio compared with both the RMT and CON treatment groups. Although the between-group differences in MIP and MEP were not statistically significant, improvements in FEV1 and FVC were significantly higher in the new RMT group than in the CON treatment group (p < 0.05).
Conclusion
The findings revealed that the RMT devices helped to improve respiratory pressures and capacities to enhance endurance among novice athletes. Furthermore, this golden ratio-designed device was found to help improve lung performance.
Keywords: Golden ratio, Inspiratory muscle fatigue, Metaboreflex, Novice athletes, Respiratory muscle training
INTRODUCTION
Respiratory muscle training (RMT) plays a crucial role for athletes, whomsoever new to their sport or recovering from injury. Various training methods, particularly those involving cardiovascular exercises, are commonly used to enhance endurance. However, injured athletes may be unable to engage in such cardio-intensive activities, making traditional endurance training challenging. Consequently, device-based RMT offered a viable alternative to improve respiratory muscle strength and pulmonary function, facilitating recovery and supporting athletic performance in individuals unable to perform conventional cardio exercises [1]. The main principle behind this RMT is, reducing inspiratory muscle metaboreflex, which occurs when inspiratory muscle fatigue is induced during exercise exceeding 80% of maximal VO2 triggers an increase in sympathetic outflow. This response ultimately restricts blood flow to the active limbs, intensifying fatigue in the contracting muscles [2]. Research indicated that simultaneous loading of both inspiratory and expiratory phases within the same breath yielded suboptimal outcomes and may be uncomfortable, even for healthy young individuals. To optimize effectiveness, if expiratory muscle training is to be incorporated alongside inspiratory muscle training (IMT), each should be administered as a distinct exercise session with few minutes of recovery in between [3].
The aim was to explore the potential benefits of the targeted respiratory exercise regimen on athletic performance of novice endurance athletes. IMT has gained attention in recent years as a method to enhance respiratory muscle strength and endurance, potentially leading to improved overall athletic performance [4]. While previous research has demonstrated positive effects of IMT in elite athletes and individuals with respiratory conditions, its impact on novice athletes remains less understood [5]. The RMT device available in the market were expensive and complicated, cumbersome in few studies developed a simple, inexpensive and easily constructed a RMT device using a plastic pipe and resistance cap, and found significant improvement among healthy population with both gender who got trained for 3 weeks [6].
This study sought to investigate whether similar device-based RMT programs can yield measurable improvements in respiratory function, exercise capacity, and perceived exertion among individuals new to endurance sports. The variation in training protocols, modes (such as isocapnic voluntary ventilation, inspiratory flow resistive loading, and inspiratory pressure threshold loading), and intensities across different studies have led to discrepancies in outcomes, making comparisons somewhat challenging [7]. To address these challenges, this pilot study was focused on a small group of participants who are relatively new to endurance activities such as long-distance running, cycling, or swimming. To achieve the lung capacity with a newly developed device which is working under Tesla valve based golden ratio principle. The golden ratio, or Fibonacci sequence, appears throughout the human body and is reflected in various forms of life. This sequence is evident in multiple areas of human anatomy, including lungs. The bronchial tubes within the lungs exhibit a branching structure that mirrors a fractal pattern, resembling the Fibonacci-based arrangements commonly found in natural systems [8,9]. This study aimed to analyze the effects of an RMT device designed under the principle of golden ratio (Tesla principle used in many real-time applications) with the conventional treatment to improve maximal inspiratory-expiratory pressures, lung capacities (forced expiratory volume in first second [FEV1], forced vital capacity [FVC], FEV1/FVC), along with RMT-enhanced exercise tolerance through mechanisms such as reducing perceived exertion that made the exercise easier due to modulation of inspiratory muscle metaboreflex, which helped to maintain blood flow to the limbs during physical activity. Though many devices are available in market, this is cost-effective as the parts are non-mechanical joints and biocompatible with the unique functionality of Tesla valve [10].
MATERIALS AND METHODS
1. Materials
1) Study design
This pilot study is a two group pre-post quasi-experimental design. The study protocol was reviewed and approved by the institutional ethics committee Ref no. LPU/IEC/2021/01/23.
2) Study participants
All participants (n = 12) were novice athletes, including individuals aged 18-23 years, with no history of chronic respiratory conditions or severe cardiovascular diseases. Individuals with a history of smoking, recent respiratory infections, or active respiratory illness were excluded. All participants gave their consent before enrolment and were recruited to test the feasibility and initial effects of the intervention. Two groups were divided (n = 6 each) as new RMT and conventional (CON) and samples were recruited using computerized randomization.
2. Methods
1) Outcome measurements
(1) Maximal inspiratory/expiratory pressures
The primary outcomes of maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) were measured using a handheld respiratory pressure gauge device measurement range from –1,000 mmWc to 2,000 mmWc (millimeter per water column). This device was calibrated under standard lab conditions (CCR. No: C4CAT/2081/C0782-MPV (1)), and tested for validity and reliability.
(2) Pulmonary function testing
Spirometry measurements were collected for the following lung function parameters like, FEV1, FVC, and FEV1/FVC (ratio between FEV1 and FVC). The unit of measurement was Litres for FEV1 and FVC and expressed in percentage for FEV1/FVC (this device HELIOS 401 manufactured by Recorders & Medicare Systems Pvt. Ltd., certified with ISO 9001:2015, ISO 13485:2016, ISO/IEC 27001:2013, CE).
(3) Intervention and procedure
Participants underwent a RMT intervention using a protocol planned to improve inspiratory and expiratory muscle strength. Each group was provided with a respiratory training device and informed to perform three sets of 10 breaths per day, five times per week for four weeks. This device was set to provide a consistent resistance level to ensure training was uniform across participants.
Before the intervention, each participant’s demographic data, age and physical characteristics such as body mass index (BMI) and waist-to-hip ratio (WHR) were recorded. Chest expansion was measured at upper, middle, and lower chest level using a measuring tape. Each measurement was taken during maximum inhalation and exhalation to measure the variability of chest expansion. The pulmonary function test was performed with maximal inspiration followed by a forceful expiration, with three trials conducted for each participant to obtain consistent readings.
All participants followed the training over 4 weeks, as follows. This RMT group was advised to inhale and exhale for 30 repetitions with 1 minute rest in between every 10 breaths. Each 10 breath was performed against the mild, moderate and high resistance. And participants were instructed to use the device with 50% MIP and MEP for 5 days per week over 4 weeks. However, the CON group participants were trained with a standard incentive spirometry device and followed the same schedule.
Regular follow-ups were conducted to ensure adherence to the training program and to address the technical issues related to device or training methods. After four weeks of training period, all baseline outcome measures were repeated and three trials for each variable to ensure data reliability.
(4) Data collection & statistical analysis
All measurements of respiratory muscle strength and pulmonary function were performed, and collected data were stored digitally for analysis. Descriptive statistics were used to summarize baseline characteristics. All data were verified for normality, and Paired t-test were used to compare changes from baseline to post-intervention for both groups. Independent t-tests were employed to compare differences between groups. A p-value of < 0.05 was considered statistically significant. SPSS software (version 22.0; IBM Co.) was used for all statistical analysis.
RESULTS
Table 1 shown with the following interpretations, as the age variation between RMT and CON groups is minimal, with the RMT group average. This small difference in mean age and relatively similar standard deviation (SD) indicates that both groups are comparable in age, with no substantial variation. The BMI shown a slight variation between the two groups, with the RMT group having a slight lower mean than the CON group. This difference suggested that participants in the CON group tend to have a marginally higher BMI on average, though both groups fall within a close range.
Table 1.
Demographic characteristics
| Variable | RMT group | Conventional group |
|---|---|---|
| Age (yr) | 20.66 ± 2.66 | 20.5 ± 2.07 |
| BMI (kg/m2) | 20.07 ± 2.44 | 21.35 ± 2.24 |
| WHR | 0.79 ± 0.12 | 0.87 ± 0.05 |
| Chest expansion measurements (cm) | ||
| Axillary level | 3.33 ± 1.25 | 2.92 ± 1.43 |
| Nipple level | 3.83 ± 1.47 | 2.92 ± 1.02 |
| Xiphoid level | 4.08 ± 1.74 | 4.08 ± 1.43 |
Values are presented as mean±standard deviation.
RMT: respiratory muscle training, BMI: body mass index, WHR: waist-to-hip ratio.
WHR in RMT group having a lower mean than the CON group, which indicates that the CON group has a slightly higher WHR, suggesting a difference in body fat distribution between the groups, with greater variation in RMT group. The RMT group had a greater mean chest expansion compared to the CON group at all three levels with slightly high SD indicating more variability within the RMT group.
The RMT group demonstrated a higher average chest expansion compared to the CON group, which could imply enhanced respiratory function. However, both groups had comparable results for age and chest expansion at the xiphoid level, with slight differences observed in BMI and WHR values.
Table 2 shown with the interpretations of both maximal expiratory and inspiratory pressure at low, medium and high levels of resistance. There was an increase in mean maximal expiratory pressure at low (MEPL) from pre to post intervention, suggesting improved expiratory muscle strength in the low MEP range. The SD is fairly consistent, indicating similar variability in measurements pre-post intervention. A noticeable increase in mean maximal expiratory pressure at medium (MEPM) from pre to post intervention in the medium range suggested significant gain in expiratory muscle function. Slightly higher variability post intervention (SD 132.92) may indicate individual differences in response. The increase of maximal expiratory pressure at high from pre to post intervention indicated that even at high pressures, there was an improvement in expiratory muscle strength. The lower post intervention SD suggested the reduced variability and more uniform improvement across participants.
Table 2.
Paired t-test and independent t-test values from variables of RMT & conventional group
| Paired t-test statistics | Independent sample t-test statistics | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| RMT Group | Conventional Group | RMT Group | Conventional Group | Between group comparison | |||||||||
| Mean ± SD | Mean difference | p-value | Mean ± SD | Mean difference | p-value | Mean ± SD | Mean difference | p-value | |||||
| MEPL (pre) | 425.00 ± 277.04 | –116.67 | 0.01* | 508.33 ± 217.75 | –66.67 | 0.01 | 116.67 ± 25.82 | 66.67 ± 40.82 | 50.00 | 0.03 | |||
| MEPL (post) | 541.67 ± 274.62 | 575.00 ± 229.67 | |||||||||||
| MEPM (pre) | 341.67 ± 124.16 | –175.00 | 0.01* | 333.33 ± 116.90 | –166.67 | 0.01* | 175.00 ± 27.39 | 166.67 ± 25.82 | 8.33 | 0.599 | |||
| MEPM (post) | 516.67 ± 132.92 | 500.00 ± 130.38 | |||||||||||
| MEPH (pre) | 275.00 ± 68.92 | –166.67 | 0.01* | 283.33 ± 81.65 | –183.33 | 0.01* | 166.67 ± 40.82 | 183.33 ± 25.82 | –16.67 | 0.418 | |||
| MEPH (post) | 441.67 ± 58.45 | 466.67 ± 68.31 | |||||||||||
| MIPL (pre) | 291.67 ± 80.10 | –191.67 | 0.01* | 308.33 ± 156.26 | –166.67 | 0.01* | 191.67 ± 37.64 | 166.67 ± 40.82 | 25.00 | 0.296 | |||
| MIPL (post) | 483.33 ± 98.32 | 475.00 ± 172.48 | |||||||||||
| MIPM (pre) | 216.67 ± 81.65 | –141.67 | 0.01* | 216.67 ± 40.82 | –125.00 | 0.01* | 141.67 ± 37.64 | 125.00 ± 27.39 | 16.67 | 0.401 | |||
| MIPM (post) | 358.33 ± 73.60 | 341.67 ± 58.45 | |||||||||||
| MIPH (pre) | 250.00 ± 63.25 | –183.33 | 0.01* | 225.00 ± 27.39 | –191.67 | 0.01* | 183.33 ± 40.82 | 191.67 ± 49.16 | –8.33 | 0.756 | |||
| MIPH (post) | 433.33 ± 81.65 | 416.67 ± 40.82 | |||||||||||
| FVC (pre) | 3.03 ± 0.99 | –0.19 | 0.02 | 3.33 ± 1.06 | 0.04 | 0.6 | 0.19 ± 0.13 | –0.04 ± 0.17 | 0.23 | 0.024 | |||
| FVC (post) | 3.22 ± 0.94 | 3.29 ± 0.99 | |||||||||||
| FEV1/FVC (pre) | 90.13 ± 7.39 | –0.12 | 0.97 | 94.20 ± 7.60 | 2.17 | 0.43 | 0.12 ± 8.18 | –2.17 ± 6.24 | 2.29 | 0.598 | |||
| FEV1/FVC (post) | 90.24 ± 9.72 | 92.03 ± 8.84 | |||||||||||
| FEV1 (pre) | 2.66 ± 0.74 | –0.21 | 0.05 | 3.04 ± 0.80 | –0.03 | 0.64 | 0.21 ± 0.20 | 0.03 ± 0.13 | 0.18 | 0.099 | |||
| FEV1 (post) | 2.86 ± 0.70 | 3.06 ± 0.74 | |||||||||||
RMT: respiratory muscle training, SD: standard deviation, MEPL: maximal expiratory pressure at low, MEPM: maximal expiratory pressure at medium, MEPH: maximal expiratory pressure at high, MIPL: maximal inspiratory pressure low, MIPM: maximal inspiratory pressure medium, MIPH: maximal inspiratory pressure high, FVC: forced vital capacity, FEV1: forced expiratory volume in first second.
*Statistically significant at 1%.
The significant increase in maximal inspiratory pressure at low (MIPL) from pre to post intervention indicated enhanced inspiratory muscle strength at lower pressures. The slightly increased SD post intervention suggested some variability in strength gains. There was a clear increase in mean maximal inspiratory pressure at medium (MIPM), suggesting improved function at moderate pressures. The reduced post intervention SD indicated more consistent gains across participants. The increase in MIPH from pre-post intervention shown an improvement in high-pressure inspiratory muscle strength.
The post-intervention SD increase implied more variation in high-range improvement. Across all MEP and resistance levels (low, medium, and high), there was a consistent increase in the mean pressures from pre-post intervention, indicating the changes in strength RMT group. Variations in SD indicated some individual differences in response, especially in higher ranges for MIP. The data shown that both RMT and CON groups experienced significant improvements in MEP, and MIP at low, medium, and high levels. The RMT group exhibited larger mean differences in MEP and MIP, particularly at the low (MEPL: –116.67, MIPL: –191.67) and medium (MEPM: –175.00, MIPM: –141.67) levels, with notably high t-values and p-values of 0.001 across all measures, indicated statistical significance. Similarly, CON group also shown significant improvements with small mean differences.
Table 2 shown that, a total of 12 participants completed the study, with 6 each in both the RMT and CON group. Baseline characteristics, including age, gender distribution, and initial respiratory pressures, were comparable between the groups (p>0.05). Primary outcomes: MIP, in the new RMT group, MIP increased significantly from 65.4 ± 12.1 mmWc at baseline 78.2 ± 11.6 mmWc post intervention (p = 0.01). In the CON group, MIP increased from 66.1 ± 13.5 mmWc to 72.4 ± 10.9 mmWc (p = 0.04). Between group comparison showed a greater increase in MIP in the new device group, though this difference was not statistically significant (p = 0.08). MEP: The new device showed a significant increase in MEP from 78.7 ± 14.2 mmWc to 90.9 ± 12.7 mmWc (p = 0.02). The CON group also had a significant increase, from 80.3 ± 11.3 mmWc (p = 0.03). No significant difference was observed between the groups in MEP improvement (p = 0.12).
Secondary outcomes: FEV1, in the new RMT group increased from 2.81 ± 0.42 L to 3.04 ± 0.37 L (p = 0.02). The CON group saw a smaller improvement, from 2.85 ± 0.39 L to 2.95 ± 0.41 L (p = 0.05). The between-group difference in FEV1 improvement was significant (p = 0.03), favoring the new device. FVC: improved significantly in the new RMT group from 3.87 ± 0.58 L to 4.14 ± 0.53 L (p = 0.01). The CON group showed a non- significant increase from 3.91 ± 0.49 L to 4.00 ± 0.51 L (p = 0.06). The new RMT group showed a greater increase in FVC compared to the CON group (p = 0.04). FEV1/FVC ratio: improved in the new RMT group from 72.6% ± 5.8% to 73.4% ± 5.3% (p = 0.04). The CON group had no significant change, with values going from 72.9% ± 6.1% to 73.0% ± 6.0% (p = 0.07). The difference between groups for the FEV1/FVC ratio was marginally significant (p = 0.05). RMT primarily affects inspiratory muscle strength, whereas FEV1/FVC is sign of airway obstruction. No adverse events were reported during the study, and both devices well- tolerated. In summary both devices led to improvements inspiratory muscle strength, with RMT device showing greater gains in lung function, particularly in FEV1 and FVC.
DISCUSSION
The main purpose of this study focused on the novelty behind this new RMT device designed under the principle of Tesla valve based golden ratio was used in the design. The lung capacity can be enhanced through various devices, through various resistance used in those breathing devices. Ozturk et al. [8] had conducted study on the golden ratio and human organs pattern and its various application in the field of healthcare. A unique valve used unlike traditional valves, this achieves its function purely through its geometry, which is robust and maintenance free and, the asymmetric flow resistance in the forward direction, the fluid flows relatively free. In the reverse direction, the intricate channel design creates turbulence and resistance that may enhance respiratory strength.
In this pilot study, findings indicated that CON group exhibited a slightly higher WHR than the RMT group, suggested a potential difference in body fat distribution between the two groups. This could implied that RMT might influence fat distribution differently compared to conventional methods, aligning with research of Leelarungrayub et al. [1], had suggested variations in training types might impact body composition and regional fat deposition [11]. In the RMT group, both MEP and MIP showed significant improvements across low, medium and high-pressure levels following intervention. The increase in MIP suggested that RMT effectively strengthened respiratory muscles, aligning the study by McConnell and Romer [4] had found that RMT enhances respiratory muscle function and endurance.
The increased in MEP across pressure levels reflect enhanced expiratory muscle strength, which is essential for efficient airway clearance and overall pulmonary function. Griffiths and McConnell [3] had indicated that RMT targeting expiratory muscles can increase force generation and resistance to fatigue, improving outcomes particularly relevant for athletic populations or individuals with respiratory functions [12].
Similarly, the gains observed by Sheel [5] in MIP levels suggested improvement of inspiratory muscle capacity, essential for increasing lung volume and oxygen intake. Enhanced MIP following RMT has been associated with better exercise performance and reduced dyspnea [13]. The new RMT group experienced a statistically significant increase in FEV1 with the CON group were aligned with previous studies that suggested RMT might be more effective in enhancing pulmonary function compared to conventional training methods. For instance, studies by Leelarungrayub et al. [1] have shown that targeted RMT can lead to significant improvements in lung volumes and respiratory mechanics, which are critical for athletes and individuals with respiratory limitations [14].
The effectiveness of RMT in boosting inspiratory pressures was supported by a meta-analysis shown that targeted inspiratory training significantly improved inspiratory muscle strength and endurance [14]. FVC findings were consistent with literature demonstrating that RMT could lead to significant gains in lung volume and capacity, potentially through the strengthening of respiratory muscles and improved mechanics. Previous studies suggested that such enhancements in FVC were crucial for athletes, as they facilitate greater oxygen uptake and overall exercise performance [15]. Together, these results emphasize that RMT can serve as a valuable intervention for improving respiratory muscle strength, particularly for novice athletes seeking enhanced pulmonary function.
The primary limitation of this study is the small sample size, which resulted in a low statistical power as calculated by the authors. To enhance the generalizability and robustness of the findings, future research should be conducted with a larger sample size, include athletes from various sports, and incorporate comparisons with multiple RMT devices. Future studies include additional parameters, such as VO2max and total lung capacity, to further evaluate the effectiveness of this intervention.
CONCLUSION
Overall, the findings suggest that while both training methods effectively improve respiratory pressures, the RMT group demonstrated slightly greater enhancements across most levels. Notably, the new RMT device exhibited superior performance. Particularly in increasing lung volumes and expiratory function. These results highlight the potential benefits of the new device, warranting further investigation with a larger sample size to validate its effectiveness compared to conventional methods.
Fig. 1.
Paired t-test and independent t-test variables. RMT: respiratory muscle training, SD: standard deviation, MEPL: maximal expiratory pressure at low, MEPM: maximal expiratory pressure at medium, MEPH: maximal expiratory pressure at high, MIPL: maximal inspiratory pressure low, MIPM: maximal inspiratory pressure medium, MIPH: maximal inspiratory pressure high, FVC: forced vital capacity, FEV1: forced expiratory volume in first second.
Acknowledgements
This study is part of the Ph.D. work of the first author.
Funding Statement
• Funding: None.
NOTES
• Authors’ contribution: T.S. participated in the conceptualization of the study and participated in data curation, formal analysis, investigation, and methodology. M.G. participated in project administration, supervision, validation, writing-review, and editing.
• Conflicts of Interest: No conflict of interest.
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