Ray, A. D., Pendergast, D. R., Simpson, A., & Lundgren, C. E. (2008). Respiratory muscle training against a resistance improves respiratory and underwater swimming performance. ACSM 55th Annual Meeting Indianapolis, Presentation Number, 2110.

"The purpose of this study was to use underwater swimming, where the work of breathing (WB) is greater due to increased gas density and breathing gear resistance, to test the hypothesis that there is a pulmonary limitation to endurance performance and that respiratory muscle training against resistance (RRMT) would eliminate this limitation". Experienced male divers (N = 9) completed a four-week fin-swimming protocol (three one-hour sessions per week) followed by four weeks of resistive respiratory muscle training (five 30-minute sessions per week) During resistive respiratory muscle training, Ss performed a swim maintenance protocol (two one-hour sessions per week). A swimming endurance test (70% VO2max) was performed before and after resistive respiratory muscle training in a hyperbaric chamber compressed to 120 feet (4.64 ATA). Maximal inspiratory and maximal expiratory pressures as well as a respiratory endurance were also measured at depth.

Four Ss completed the protocol with no significant change in VO2max or pulmonary function. The increased work of breathing at depth decreased respiratory performance. At depth following resistive respiratory muscle training, maximal inspiratory pressure and maximal expiratory pressure were significantly increased. After resistive respiratory muscle training, swimming endurance increased an average of 34%, while maximal inspiratory pressure and maximal expiratory pressure were all significantly higher when measured in a separate dive that was terminated at the same time as the pre-resistive respiratory muscle training swim.

Implication. Increased work of breathing at depth decreased respiratory performance. Resistive respiratory muscle training significantly improved both respiratory and swimming performance.

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