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1983 Publications

Indices Of Sympathetic Nervous System Function During Isokinetic G.W. Gleim, P.M. Zabetakis, M.F. Michelis*, J.A. Nicholas.Institute of Sports Medicine and Section Nephrology, Lenox Hill Hospital, New York, New York 10021 - last modified 2013-02-09 21:49
Med. Sci. Sports Exerc., Vol. 15:94, 1983.


We examined the effects of isokinetic knee extension/flexion on plasma renin activity (PRA), lactate (La), and plasma volume (PV) and their relation to the hemodynamic parameters of heart rate (HR) and blood pressure (BP). Eight normotensive male subjects aged 25-30 were initially tested for maximum knee extension/flexion strength on a cybex at 60(/sec. On two separate days each subject returned and exercised one leg at 50% of their max value for 5 repetitive cycles of 1 min. exercise and 30 sec. rest. Blood samples and hemodynamic measures were obtained immediately before and after the five sets. This isokinetic exercise caused significant increases in all variables except diastolic BP (paired t-test, p < .01). Correlation analysis revealed the following significant relations between variables:

No significant correlations were found for BP with any other variable. Notably, %(PV did not correlate with (PRA. Since all subjects exercised at the same percent of maximum (50%) and for the same time, the amount of external work performed is not the primary mediator of changes in HR and PRA.

These data demonstrate that non-osmotic factors regulate PRA during isokinetic exercise. The significant correlation of La with PRA and with HR suggests that the amount of muscle working anaerobically dictates renin release via the sympathetic nervous system.