Received July 9, 2004
Revised July 28, 2004
Accepted after revision August 24, 2004

¹ University of Birmingham

^* To whom correspondence should be addressed. E-mail: j.p.fisher{at}bham.ac.uk.

	Abstract

The cardiovascular response to isometric exercise is governed by both central and peripheral mechanisms. Both metabolic and mechanical stresses on the exercising skeletal muscle produce cardiovascular change, yet it is often over looked that the afferent signal arising from the muscle can be modified, by factors other than exercise intensity. This review discusses research revealing that muscle fibre type, muscle mass and training status are important factors in modifying this peripheral feedback from the active muscles. Studies in both animals and humans have shown that the pressor response resulting from exercise of muscle with a faster contractile character and isomyosin content is greater than that from a muscle of slower contractile character. Athletic groups participating in training programs that place a high anaerobic load on skeletal muscle groups, show attenuated muscle afferent feedback. Similarly, longitudinal studies have shown that specific local muscle training also blunts the pressor response to isometric exercise. Thus it appears that training may decrease the metabolic stimulation of muscle afferents and in some instances chronic exposure to the products of anaerobic metabolism may blunt the sensitivity of the muscle metaboreflex. There may be surprising parallels between the local muscle conditions induced in athletes training for longer sprint events (i.e. 400 m) and by the low-flow conditions in, for example, the muscles of chronic heart failure (CHF) patients. Whether their similar attenuations in muscle afferent feedback during exercise are due to decreased metabolite accumulation or a desensitisation of the muscle afferents is not yet known.

Key Words: Cardiovascular, Exercise, Skeletal muscle