Respiratory Muscle Fatigue Limits Upper‐Body Exercise Tolerance in Collegiate Cross‐Country Skiers

Abstract

The development of respiratory muscle fatigue compromises lower‐body exercise performed to the limit of tolerance, especially in endurance athletes. It is unclear if respiratory muscle fatigue has a similar effect on upper‐body exercise tolerance where respiratory muscles have important respiratory, postural, and locomotor roles. The purpose of this study was to evaluate the effects of inspiratory muscle fatigue on upper‐body exercise tolerance. I hypothesized that high‐intensity arm cranking performed by upper‐body endurance trained athletes would induce considerable ventilator stress and reduce upper‐body exercise tolerance. Seven male Division I collegiate cross‐country skiers (20 ± 2 yrs, 183 ± 6 cm, 76 ± 6 kg, upper‐body VO2peak and Wpeak 50 ± 5 mL/kg/min, 197 ± 24 W, respectively) performed two upper‐body exercise trials. For the control exercise trial (CON‐EX), athletes performed arm‐cranking at ~85% of Wpeak (170 ± 20 W) until their limit of tolerance. For the inspiratory muscle fatigue exercise trial (IMF‐EX), athletes performed the same task while having pre‐existing fatigue in their inspiratory muscles (~20% reduction in maximal inspiratory pressure) induced through a threshold resistance breathing device. Physiological responses and the limit of tolerance were compared between trials. During CON‐EX, ventilatory demand was high as indicated by the high ventilation rates (137 ± 17 L/min). After CON‐EX, MIP decreased by 10 ± 8% (158 ± 30 vs. 136 ± 26 cm H2O) and remained reduced by 7 ± 7% for 11 min (P < 0.05). Compared to CON‐EX, IMF‐EX limit of tolerance decreased by 33 ± 14% (14.2 ± 2.4 vs. 9.6 ± 2.7 min, P < 0.01). During IMF‐EX, ventilation, breathing frequency, perceived exertion, and dyspnea increased whereas tidal volume decreased (all P < 0.05). For these collegiate cross‐country skiers, high‐intensity arm‐cranking taxed their respiratory muscles and impaired their inspiratory muscle function. Further, artificial induction of inspiratory muscle fatigue decreased limit of tolerance and increased perceptual stress. Collectively, our results demonstrate the functional consequences of inspiratory muscle fatigue on upper‐body performances. Our findings of increased ventilatory stress and reduced upper‐body exercise tolerance in athletes who regularly performed upper‐body endurance exercise contrasts previous upper‐body research using untrained individuals. Thus, further research is needed to explore the impact of respiratory muscle fatigue has on upper‐body performance and the mechanisms behind it. These findings have implications for athletes performing upper‐body exercise, researchers, and clinicians who use arm‐cranking as an exercise and/or rehabilitation modality.Support or Funding InformationThis study was supported by the Portage Health Foundation, Michigan Space Grant Consortium, and American Physiology Society.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.