Respiratory Muscle Training Against a Resistance Improves Respiratory and Underwater Swimming Performance

Recent studies have shown that respiratory failure limits maximal and sustained submaximal (endurance) performance and that respiratory muscle training improves respiratory performance as well as cycling, rowing, running and swimming performance. PURPOSE: 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. METHODS: Nine experienced male divers were recruited from the local diving community (29±6 yrs, 160.4±57 cm, 74.3±29 kg). Divers completed a four wk. fin swimming protocol (3 times/wk for 1 hr) followed by 4 wks of RRMT 5 times/wk for 30 min. During RRMT subjects performed a swim maintenance protocol (2 times/wk for 1 hr). A swimming endurance test (70% VO2max) was performed pre-and post-RRMT in a hyperbaric chamber compressed to 120 feet (4.64 ATA). Maximal inspiratory (Pins) and maximal expiratory (Pexp) pressures as well as a respiratory endurance were also measured at depth. RESULTS: Currently, four subjects completed the protocol with no significant change in VO2max or pulmonary function. At depth RET was significantly reduced from the surface (3.7 ± 2.2 min vs. 23.7±23.1 min., respectively). Following RRMT, Pins (170±12 cmH2O,+56%) and Pexp (225±86 cmH2O,+33%) were significantly increased (1 ATA). After RRMT, swimming endurance increased from 26.3±13.4 min to 35.2±14.6 min (+34%), while Pins (301±164 cmH2O,+8.3%), Pexp (167±98 cmH2O,+14.3%), RET (5.5±6 min,+49%) were all significantly higher when measured in a separate dive that was terminated at the same time as the pre-RRMT swim. CONCLUSIONS: As hypothesized, the increased WB at depth decreased respiratory performance (RET). RRMT significantly improved both respiratory and swimming performance. These data suggest that the respiratory muscles fatigue when the WB is increased and that this fatigue was delayed by RRMT.