There is strong evidence that breathing muscles may become exhausted during both short term high intensity exercise (MMA, Boxing) and endurance exercise (marathon running, triathlons).
Respiratory system limitations can impact exercise performance in highly trained individuals (Boutellier et al. 1992), especially at high intensities, where the increased work of breathing results in compromised exercise performance (Harms et al. 2000).
Furthermore, respiratory muscle fatigue not only decreases the ability to ventilate adequately (Lomax and McConnell 2003), but also increases limb muscle sympathetic nerve activity (MSNA) (St Croix et al. 2000), which has been shown to reduce blood flow to the peripheral muscles (Sheel et al. 2001).
Further, the dyspnoea experienced may limit an individual’s ability to continue to exercise at the required intensity (Altose et al. 1985). Eur J Appl Physiol (2005) 94: 527–540
Restricting air intake during physical exercise provides the respiratory muscles with an extra load, which in turn works the breathing muscles more intensely to strengthen them.
Effects of hypercapnic-hypoxic training on respiratory muscle strength:
The aim of the present study was to determine the effects of an 8-week hypercapnic-hypoxic (H-H or breath holding) training program on respiratory muscles strength and 100 meter crawl swimming performance.
The study was conducted on a sample of 26 elite Croatian swimmers (experimental group [EG] n=12, control group [CG] n=14). Both groups were subjected to the same swimming training programs and training sessions on a treadmill.
The experimental group was additionally subjected to hypercapnic-hypoxic training program with increased muscular activity.
The group of swimmers, who were subjected to the hypercapnic-hypoxic regimen, has significantly improved strength of their inspiratory and expiratory muscles in comparison to swimmers in the control group. The swimmers from the experimental group have improved the inspiratory muscle strength values (MIP) for 14.9% and the expiratory muscle strength values (MEP) for 1.9% in relation to the control group.
Based on the results of this study it can be assumed that the hypercapnic-hypoxic practice has significantly increased the respiratory muscle strength. Statistically significant differences can be attributed to the eight-week exposure to hypercapnia and hypoxia combined with increased muscle activity.
Such practice may have enlarged the diaphragm thickness which plays an important role in respiratory system and sports performance. Voluntary holding of breath may have resulted in involuntary contractions of intercostal muscles during the hypercapnic-hypoxic practice.
It is also assumed that above mentioned contraction occurrence has resulted in hypertrophy of intercostal muscles. According to the available literature, mobility of breastbone and costal joints and changes in lung and breast muscle elasticity are also possible changes that occur during voluntary breath holding.
Dajana KARAULA, Jan HOMOLAK, Goran LEKO. Effects of hypercapnic-hypoxic training on respiratory muscle strength and front crawl stroke performance among elite swimmers. Turkish Journal of Sport and Exercise. Year: 2016 – Volume: 18 – Issue: 1 – Pages: 17-24