The Effects of Interval Respiratory Muscle Training on Athletic Performance

The purpose of this randomized, controlled trial was to compare the physiological and athletic performance adaptations induced by constant versus progressive-load inspiratory muscle training (IMT) in competitive athletes.

Inspiratory muscle fatigue can trigger the respiratory metaboreflex, causing sympathetic vasoconstriction in locomotor muscles and compromising exercise tolerance. Strengthening the inspiratory muscles is hypothesized to attenuate this reflex and improve limb muscular endurance and aerobic capacity.

Participants completed a 4-week intervention with a threshold inspiratory device (PowerBreathe).

* Constant IMT Group: Performed 2 daily sessions (morning and evening) of 30 breaths at a fixed intensity of 40% MIP, 5 days per week.
* Incremental IMT Group: Performed 2 daily sessions of 30 breaths, 5 days per week, starting at 50% MIP in Week 1, and progressing weekly to 60%, 70%, and 80% MIP in Weeks 2, 3, and 4, respectively.

Initial sessions were supervised in the exercise physiology laboratory, with remaining sessions performed under remote video monitoring. Outcomes were evaluated across multiple laboratory visits before and 48 hours following the 4-week protocol.

• IMT %40 MIP (Device), also known as The Constant IMT group trained with a fixed resistance of 40% MIP throughout the intervention.: This study examined two inspiratory muscle training (IMT) protocols using the PowerBreathe device. Participants in both groups performed IMT twice daily, five days a week, for four weeks. Each session included 30 inspiratory breaths, totaling 60 breaths per day. The Constant IMT group trained with a fixed resistance of 40% MIP throughout the intervention. All participants received supervised instruction during the initial session. Subsequent sessions were home-based, monitored weekly through video submissions and participant check-ins. This design enables a structured comparison between progressive and constant loading in IMT for improving respiratory strength and endurance in trained athletes.
• IMT %50-60-70-80 (Device), also known as The Incremental IMT group began training at 50% of Maximal Inspiratory Pressure (MIP), with resistance increased weekly to 60%, 70%, and 80%.: This study examined two inspiratory muscle training (IMT) protocols using the PowerBreathe device. Participants in both groups performed IMT twice daily, five days a week, for four weeks. Each session included 30 inspiratory breaths, totaling 60 breaths per day. The Incremental IMT group began training at 50% of Maximal Inspiratory Pressure (MIP), with resistance increased weekly to 60%, 70%, and 80%. All participants received supervised instruction during the initial session. Subsequent sessions were home-based, monitored weekly through video submissions and participant check-ins. This design enables a structured comparison between progressive and constant loading in IMT for improving respiratory strength and endurance in trained athletes.

Primary outcomes

• Change in maximal inspiratory pressure (MIP) [Baseline and Week 4 (end of the intervention).]: Maximal inspiratory pressure (MIP) will be measured using a device with a respiratory pressure measurement function and expressed in cmH2O. Change will be calculated as the Week 4 value minus the baseline value.
• Change in Maximal Expiratory Pressure (MEP) [Baseline and Week 4 (end of the intervention).]: Maximal expiratory pressure was measured from total lung capacity against an occluded airway using a digital respiratory pressure meter (MicroRPM) and expressed in cmH2O. Change was calculated as Week 4 minus baseline.

Secondary outcomes

• Change in forced vital capacity (FVC) [Baseline and Week 4 (end of the intervention).]: Forced vital capacity (FVC) will be measured by spirometry and expressed in liters. Change will be calculated as the Week 4 value minus the baseline value.
• Change in Forced Expiratory Volume in 1 Second (FEV1) [Baseline and Week 4 (end of the intervention).]: Volume exhaled in the first second of a forced exhalation maneuver was measured using spirometry, expressed in liters (L).
• Change in FEV1/FVC Ratio [Baseline and Week 4 (end of the intervention).]: The ratio of forced expiratory volume in 1 second to forced vital capacity was assessed using spirometry, expressed as a percentage (%).
• Change in Slow Vital Capacity (SVC) [Baseline and Week 4 (end of the intervention).]: Vital capacity measured during relaxed, unforced breathing using spirometry, expressed in liters (L).
• Change in Maximal Voluntary Ventilation (MVV) [Baseline and Week 4 (end of the intervention).]: Maximal volume of air ventilated over a 12-second sprint breathing protocol was extrapolated to liters per minute (L/min).
• Change in Seated Medicine Ball Throw Distance [Baseline and Week 4 (end of the intervention).]: Upper body explosive power was measured by throwing a 3 kg medicine ball overhead from a seated position with the back supported against a wall. The maximum distance achieved across three trials was recorded in centimeters (cm).
• Change in 30-Second Modified Push-Up Repetitions [Baseline and Week 4 (end of the intervention).]: Upper body muscular endurance was evaluated by counting the maximum number of correctly executed push-up repetitions performed within 30 seconds.
• Change in 1-Minute Sit-Up Repetitions [Baseline and Week 4 (end of the intervention).]: Abdominal muscular endurance was evaluated by recording the maximum number of correctly executed sit-up repetitions completed in 60 seconds.
• Change in 1-Repetition Maximum (1RM) Bench Press Strength [Baseline and Week 4 (end of the intervention).]: Maximal upper body dynamic strength was assessed via 1RM barbell bench press test protocol, expressed in kilograms (kg).
• Change in 1-Repetition Maximum (1RM) Back Squat Strength [Baseline and Week 4 (end of the intervention).]: Maximal lower body dynamic strength was determined using a standard 1RM barbell back squat protocol, expressed in kilograms (kg).
• Change in Isometric Hand Grip Strength [Baseline and Week 4 (end of the intervention).]: Isometric hand grip strength was assessed using a Takei hand dynamometer for dominant and non-dominant hands, recorded in kilograms (kg).
• Change in Isometric Back and Leg Strength [Baseline and Week 4 (end of the intervention).]: Isometric back and leg strength were evaluated using a Takei digital back-and-leg dynamometer, recorded in kilograms (kg).
• Change in Vertical Jump Height [Baseline and Week 4 (end of the intervention).]: Explosive lower extremity power was evaluated via vertical jump test using a jump meter (KK 5406 Jumpmeter). The best attempt was recorded in centimeters (cm).
• Change in Single Leg Hop Performance and Limb Symmetry Index [Baseline and Week 4 (end of the intervention).]: Functional lower extremity performance was measured using single-leg hop test protocols (single hop, triple hop, crossover hop, and side hop). Maximum distance was recorded in cm, and the Limb Symmetry Index (LSI, %) was calculated.
• Change in Anaerobic Peak and Mean Power (Wingate Test) [Baseline and Week 4 (end of the intervention).]: Anaerobic power was evaluated using a 30-second all-out Wingate test on a Monark 894E cycle ergometer against a resistance of 7.5% body weight, expressed in Watts (W).
• Change in Estimated Maximal Oxygen Consumption (VO2max) [Baseline and Week 4 (end of the intervention) .]: Aerobic capacity was evaluated using the Bruce Treadmill Test protocol. The test began on a motorized treadmill at 2.74 km/h and a 10% incline, with speed and incline increasing every 3 minutes until volitional exhaustion. Total test duration (T, in minutes) was recorded, and VO2max was estimated using the standardized regression equation: VO2max = 14.8 - (1.379 * T) + (0.451 * T\^2) - (0.012 * T\^3), expressed in mL/kg/min. Change was calculated as Week 4 minus baseline.

Sex: Male, ages: 18 Years to 30 Years, accepts healthy volunteers

Inclusion Criteria:

* Between the ages of 18 and 30,
* Having at least 5 years of active training experience,
* Having a regular training frequency of at least 4 days per week

Exclusion Criteria:

* Having a history of lung dysfunction and cardiovascular disease,
* Having had a lower or upper respiratory tract infection within the last four weeks,
* Having a history of smoking,
* Having any ongoing disability

• Results publication: Gomes Neto M, Ferrari F, Helal L, Lopes AA, Carvalho VO, Stein R. The impact of high-intensity inspiratory muscle training on exercise capacity and inspiratory muscle strength in heart failure with reduced ejection fraction: a systematic review and meta-analysis. Clin Rehabil. 2018 Nov;32(11):1482-1492. doi: 10.1177/0269215518784345. Epub 2018 Jul 9. PMID 29984598
• Results publication: Gething AD, Williams M, Davies B. Inspiratory resistive loading improves cycling capacity: a placebo controlled trial. Br J Sports Med. 2004 Dec;38(6):730-6. doi: 10.1136/bjsm.2003.007518. PMID 15562168
• Results publication: Fernandez-Lazaro D, Gallego-Gallego D, Corchete LA, Fernandez Zoppino D, Gonzalez-Bernal JJ, Garcia Gomez B, Mielgo-Ayuso J. Inspiratory Muscle Training Program Using the PowerBreath(R): Does It Have Ergogenic Potential for Respiratory and/or Athletic Performance? A Systematic Review with Meta-Analysis. Int J Environ Res Public Health. 2021 Jun 22;18(13):6703. doi: 10.3390/ijerph18136703. PMID 34206354
• Results publication: Cunha M, Mendes F, Paciencia I, Rodolfo A, Carneiro-Leao L, Rama T, Rufo J, Delgado L, Moreira A. The effect of inspiratory muscle training on swimming performance, inspiratory muscle strength, lung function, and perceived breathlessness in elite swimmers: a randomized controlled trial. Porto Biomed J. 2019 Oct 24;4(6):e49. doi: 10.1097/j.pbj.0000000000000049. eCollection 2019 Nov-Dec. PMID 33501396
• Results publication: Charususin N, Dacha S, Gosselink R, Decramer M, Von Leupoldt A, Reijnders T, Louvaris Z, Langer D. Respiratory muscle function and exercise limitation in patients with chronic obstructive pulmonary disease: a review. Expert Rev Respir Med. 2018 Jan;12(1):67-79. doi: 10.1080/17476348.2018.1398084. Epub 2017 Nov 6. PMID 29072087
• Results publication: Chang YC, Chang HY, Ho CC, Lee PF, Chou YC, Tsai MW, Chou LW. Effects of 4-Week Inspiratory Muscle Training on Sport Performance in College 800-Meter Track Runners. Medicina (Kaunas). 2021 Jan 15;57(1):72. doi: 10.3390/medicina57010072. PMID 33467421
• Results publication: Piskin NE, Aktug ZB, Kara M, Yavuz G, Ozturk GT, Ibis S, Aka H. The Effect of Blood Flow Restriction Training on Isokinetic Strength Muscle Thickness and Athletic Performance. J Musculoskelet Neuronal Interact. 2025 Jun 1;25(2):208-218. doi: 10.22540/JMNI-25-208. PMID 40452197
• Results publication: Bostanci O, Mayda H, Yilmaz C, Kabadayi M, Yilmaz AK, Ozdal M. Inspiratory muscle training improves pulmonary functions and respiratory muscle strength in healthy male smokers. Respir Physiol Neurobiol. 2019 Jun;264:28-32. doi: 10.1016/j.resp.2019.04.001. Epub 2019 Apr 3. PMID 30953791

• Study Protocol and Informed Consent Form: Ethics Committee (PDF, 2024-07-31)
• Informed Consent Form: Ethics Committee Turkish (PDF, 2024-07-31)