The efficacy of respiratory muscle training in raising the ventilatory threshold: a pilot study

Oxygen uptake (V ̇O2) at the ventilatory threshold (Tvent) is an effective submaximal indicator of cardiorespiratory function. V ̇O2 at Tvent is a potent indicator of the ability of an individual to withstand physical exertion, such as exercise training, activities of daily living or the physiological insult during recovery from surgery. PURPOSE: Therefore the purpose of this pilot study was to determine whether 6 weeks of RMT could be used to delay the steep increase in ventilation rate, thereby increasing Tvent and reducing the work of breathing and in sedentary adults.

METHODS: 7 sedentary adults volunteered. Mean±SD for age, stature and body mass were 22.6±3.4 years, 1.72±0.11 m, and 74.4±17.8 kg, respectively. Following a pulmonary function and cycle exercise test familiarisation session participants undertook two graded cycle exercise tests, ending when the respiratory exchange ratio exceeded 1.0. Each test was separated by 6 weeks of RMT: 2 sets of 30 breaths twice daily, 7 days a week, at 50% of pre RMT maximal inspiratory and expiratory mouth pressures (PImax and PEmax, respectively). TVent was calculated using the V slope method and V ̇O2, percentage of predicted V ̇O2 max (%pred V ̇O2 max), power output (W) and heart rate compared pre and post RMT at TVent. PImax and PEmax were assessed pre and post RMT. Data were assessed for normality and analysed using either Dependent t-tests or Wilcoxon-Signed Rank tests. Cohen’s d (parametric) and r (non-parametric) were used to calculate small (≥0.2), moderate (≥0.5) and large (≥0.8) effect sizes.

RESULTS: PImax and PEmax increased from 88±32 cmH2O to 106±29 cmH2O (p<0.01, d = 0.59) and 85±34 cmH2O to 125±56 cmH2O (p<0.05, d=0.86), respectively, pre to post RMT. V ̇O2 at TVent increased from 2.06±0.72 l.min-1 (26.2±6.4 ml.kg-1.min-1) pre RMT to 2.22±0.66 l.min-1 (28.3±5.9 ml.kg-1.min-1) post RMT (p<0.05, r=-0.64) and %pred V ̇O2 max increased from 78±17% pre RMT to 85±17% post RMT (p<0.05, r=-0.42). Power output at TVent increased from 95±37 W pre RMT to 113±25 W post RMT (p<0.05, d=0.57) with heart rate remaining unchanged.

CONCLUSION: These preliminary data suggest a potential role for RMT in raising TVent in sedentary adults, which allowed a greater power output at Tvent without a greater cardiac response.