Inspiratory resistive loading improves cycling capacity: a placebo controlled trial

Abstract

Background: Respiratory muscle training has been shown to improve both its strength and endurance. The effect of these improvements on whole-body exercise performance remains controversial. Objective: To assess the effect of a 10 week inspiratory resistive loading (IRL) intervention on respiratory muscle performance and whole-body exercise endurance. Methods: Fifteen apparently healthy subjects (10 men, 5 women) were randomly allocated to one of three groups. One group underwent IRL set at 80% of maximum inspiratory pressure with ever decreasing work/rest ratios until task failure, for three days a week for 10 weeks (IRL group). A second placebo group performed the same training procedure but with a minimal resistance (PLA group). IRL and placebo training were performed at rest. The remaining five control subjects performed no IRL during the 10 week study period (CON group). Cycling endurance capacity at 75% V O 2 peak was measured before and after the intervention. Results: After the 10 week IRL intervention, respiratory muscle strength (maximum inspiratory pressure) and endurance (sum of sustained maximum inspiratory pressure) had significantly improved (by 34% and 38% respectively). An increase in diaphragm thickness was also observed. These improvements translated into a 36% increase in cycling time to exhaustion at 75% V O 2 peak. During cycling trials, heart rate, ventilation, and rating of perceived exertion were attenuated in the IRL group. No changes were observed for the PLA or CON group either in the time to exhaustion or cardiorespiratory response to the same intensity of exercise. Conclusion: Ten weeks of IRL attenuated the heart rate, ventilatory, and perceptual response to constant workload exercise, and improved the cycling time to exhaustion. Familiarisation was not a factor and the placebo effect was minimal.

Effects of high-intensity interval training on pulmonary function

“…Using IMT, one study observed an increase in inspiratory muscle strength of ~41% in healthy subjects (Enright et al, 2006). Other studies using healthy subjects found smaller increases in inspiratory muscle strength of ~7-17% (Downey et al, 2007;Gething et al, 2004;Holm et al, 2004;Witt et al, 2007). The difference in these studies appears to be the intensity at which the IMT was performed, varying from 50-80%, with the largest increases observed at 80% (Downey et al, 2007;Enright et al, 2006;Gething et al, 2004;Witt et al, 2007).…”

“…Other studies using healthy subjects found smaller increases in inspiratory muscle strength of ~7-17% (Downey et al, 2007;Gething et al, 2004;Holm et al, 2004;Witt et al, 2007). The difference in these studies appears to be the intensity at which the IMT was performed, varying from 50-80%, with the largest increases observed at 80% (Downey et al, 2007;Enright et al, 2006;Gething et al, 2004;Witt et al, 2007). Effects observed with high intensity IMT are consistent with those observed in this study, suggesting that the greater inspiratory muscle strength we observed with HIT compared to ET, was due to greater demand placed on the respiratory muscle with HIT.…”

Pulmonary adaptations to swim and inspiratory muscle training

“…However, this seems doubtful since the RT2 inspiratory muscle trainer used in the present study, which utilizes inspiratory flow resistive loading and the TIRE protocol, has previously been shown to improve both the strength and endurance of the inspiratory muscles. Improved cycling capacity in healthy subjects (Gething et al 2003;Gething et al 2004b) has been reported. Increased strength and endurance of the inspiratory muscles, enhanced lung volume (VC), increased diaphragm thickness and greater exercise capacity in healthy subjects (Enright et al 2006) has also been shown with similar equipment and protocols.…”

“…The device used was the RT2 trainer and associated software (DeVilbiss Sunrise Medical Ltd, Wollaston, UK). The RT2 training device is a pressure manometer with a 2mm leak, which utilises an infra-red link to a computer containing the software of the "Test of Incremental Respiratory Endurance" (TIRE) regimen, as previously described (Chatham et al 1999;Chatham et al 2004;Enright et al 2004;Gething et al 2004a;Gething et al 2004b). The 2mm leak provides a set resistance to inspiratory flow.…”

Special training of inspiratory muscles in fitness activities and exercise capacity in young women

“…However, there is no consensus about an optimal protocol to induce and assess the fatigability of the inspiratory muscles [3]. Although the ergogenic effect of respiratory muscle training (rMT) remains controversial [4][5][6], several recent well-controlled studies have shown that threshold inspiratory muscle training (IMT) [7][8][9][10], as well as voluntary normocapnic hyperpnoea training [10,11] can improve exercise performance in healthy subjects. In general, the functional capacity of the healthy human respiratory system, including the lung, chest wall, and neural control systems, exceeds the demands placed upon it during heavy exercise.…”