Proceedings of The Physiological Society

University College London December 2005 (2006) Proc Physiol Soc 1, PC29

Poster Communications

Interactions between muscle performance and blood pressure

Fitzpatrick, Richard; Luu, Billy; Wright, Julie;

1. Prince of Wales Medical Research Institute, Randwick, NSW, Australia.

This study investigates the relationship between systemic blood pressure, force output and fatigue in the human adductor pollicis muscle, a hand muscle in which fatigue-resistant oxidative fibres predominate, and the tibialis anterior muscle, which contains predominantly fatigue-prone gylcolytic fibres. Previously, we showed that as the local perfusion pressure of the contracting adductor pollicis declines within the physiological range, its force output is reduced [1] and it fatigues faster [2]. Systemic blood pressure (BP) increases when a muscle is voluntarily contracted and continues to increase as the muscle fatigues [2]. Here we investigate how that increase in systemic BP affects muscle performance. Subjects (N=6, 27-55 years) sat with the hand at heart level while supramaximal stimulation of the ulnar nerve produced repeated (1 Hz) tetanic contractions (5 at 40 ms) of adductor pollicis. Isometric force output gradually declined indicating a progressive muscle fatigue. After 2 min of these contractions force had declined by an average of 15%. We then raised BP by having subjects make a sustained isometric voluntary contraction of a thigh muscle. As systemic BP rose (29

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