Respiratory muscle training and the performance of a simulated anti-G straining maneuver.

INTRODUCTION: Prolonged +G,-exposure eventually decreases a pilot's ability to maintain an effective anti-G straining maneuver (AGSM). Previous studies have implicated the respiratory muscles (RMs) as main contributors to this AGSM-induced fatigue. Thus, this study aimed to investigate if respiratory muscle training (RMT) may be of benefit to improve RM strength, endurance, and performance of the AGSM.

METHODS: Subjects (N=14; 27 +/- 5.3 yrs) trained with a commercially available RM trainer for 6 wk, 4 times/wk 20 min per session. Data collection consisted of pulmonary function tests (PFTs) and a RM testing protocol simulating the AGSM. Testing occurred every 2 wk for the duration of RMT, and similarly during the 6-wk control (CON) phase where subjects did not train. The simulated AGSM performance was evaluated through measures of peak respiratory pressures, peak systolic arterial pressure (SAP), mean arterial pressure (MAP), and tidal volumes.

RESULTS: Training significantly improved (P < 0.05) RM strength after 6 wk of RMT measured in maximal expiratory pressures (RMT = 207.8 +/- 15.8 cmH2O; CON = 181.3 +/- 13.7 cmH2O) and maximal inspiratory pressures (RMT = -154.7 +/- 8.9 cmH2O; CON = -141.9 +/- 8.5 cmH2O). All other PFTs were unchanged. During performance of the AGSM, only peak expiratory pressure demonstrated an increased performance benefit (RMT = 91.5 +/- 5.9 cmH2O; CON = 82.8 +/- 4.3 cmH2O). Peak inspiratory pressure, SAP, MAP, and tidal volumes remained unchanged.

CONCLUSION: Without evident translation of the increased RM strength to performance of the AGSM at +1 Gz, the benefits of RMT for ameliorating AGSM-induced fatigue within the high +G, environment are limited.