Characterising the influence of pre-drive lung volume on force and power production during rowing

Abstract

Purpose: This study evaluated the effect of lung volume at the catch position to force and power outputs during single maximal effort strokes in rowing. Responses were compared when the participants were ‘fresh’ and following specific inspiratory muscle fatigue (IMF). In addition, a single subject pilot study was performed to characterise the changes in intra-thoracic (ITP), intra-abdominal (IAP) and trans-diaphragmatic (Pdi) pressures during a 30 second maximal effort piece on a rowing ergometer. Methods: Nine male rowers of international standard participated in the research. Static force, as well as the power produced during a single stroke were assessed at residual volume (RV), 25%TLC, 50%TLC, 75%TLC, total lung capacity (TLC), and a self-selected lung volume (S-S). Lung volumes were derived from maximal flow-volume loops (MFVLs) and achieved using online real-time feedback. Inspiratory muscle fatigue (IMF) was induced by breathing against an inspiratory load equivalent to 80% baseline maximal inspiratory pressure (MIP), at a breathing frequency (fB) of 15 breaths per minute, and a duty cycle of 0.6. Expiration was unimpeded. The single subject pilot study was undertaken using balloon catheters to measure ITP, IAP, and Pdi during a 30 second maximal effort free-rating piece on the ergometer. Results: There was no significant effect of lung volume upon either force or power production. The RMF protocol induced a significant reduction in MIP (159.9 ± 70.8 vs. 106.8 ± 58.7 cmH2O; p = 0.000), but not maximal expiratory pressure (MEP; 159.9 ± 79.2 vs. 166.6 ± 53.0 cmH2O; p = 0.376). RMF induced a significant reduction in force output with increasing lung volume, across all lung volumes (mean force 1313.4 ± 31.9 vs. 1209.6 ± 45.0N; p < 0.008), but not power (mean power 598.6 ± 31.9 vs. 592.7 ± 45.0W; p > 0.05). Self-selected lung volumes were consistent across all tests for force and power (mean 38.1 ± 6.9% [Force] vs. 28.2 ± 0.6% [Power]; p > 0.017). The pilot study indicated that internal pressures fluctuate markedly during maximal effort rowing (pressure, [max, min, average] cmH2O; IAP [144.69, 7.46, 73.59], ITP [75, -22.65, 15.34], Pdi [111.84, 7.09, 58.83]), suggesting that the trunk muscles play an active role in power production during rowing. Conclusion: The present study suggests that there is no significant effect of lung volume on force or power when athletes are in a fresh condition. However, a decrement in force production is present with inspiratory muscle fatigue. Combined with evidence of high internal pressures during maximal effort rowing, these data may indicate a role for the inspiratory muscles in force production during rowing.