INSPIRATORY MUSCLE FATIGUE FOLLOWING RUNNING TO VOLITIONAL FATIGUE - THE INFLUENCE OF BASE-LINE STRENGTH

Respiratory muscle fatigue has been demonstrated following short-term exercise to volitional fatigue, as well as following prolonged submaxi mal exercise. There is some suggestion that the respiratory muscles of 'athletic' individuals have superior strength and greater fatigue res istance but it is not known whether inspiratory muscle strength influe nces fatigueability of the inspiratory muscles. The present study exam ined this question in 24 moderately trained young men. Inspiratory mus cle strength was measured at residual volume using a hand held Mouth P ressure Meter before and after an incremental, multistage shuttle run to volitional fatigue. Following the run, there was a significant fall in inspiratory mouth pressures (- 10.5 +/- SD 8.2%; p < 0.001 Pre- vs Post P-lpeak). The subjects with the weakest inspiratory muscles exhi bited significantly greater fatigue than those with the strongest (- 1 7.0 +/- SD 7.8% c.f. 6.8 +/- SD 4.4% for the 25th and 75th percentiles respectively p < 0.01). These data support existing evidence that the respiratory muscles fatigue following high intensity exercise. In add ition, they provide new evidence that this phenomenon occurs in modera tely trained young men and that the severity of the fatigue is related to the baseline strength of the inspiratory muscles.