Plasma osmolality, volume, and renin activity at the "anaerobic threshold"

Abstract

Plasma renin activity (PRA), volume (PV), osmolality, and hemodynamic parameters were examined in relation to the anaerobic threshold (AT) during progressive cycle ergometry (PE) and repetitive bouts of unilateral isokinetic knee extension-flexion (LE) at 50% maximum voluntary contractions in eight normotensive males. During PE, the observed rise in PRA paralleled that of lactate with abrupt increases occurring at the AT. Correlation of % delta lactate (La), % delta osmolality, and % delta PV with % delta PRA were r = 0.65, 0.36, and -0.51, respectively (all P less than 0.01). In addition, when mean arterial pressure was plotted as a function of VO2, the rate of rise was greater below the AT than above the AT (11.5 vs. -2.4 mmHg X l-1 X min, P less than 0.001). A time control study (TC) exercising subjects for the same duration but at work rates maintained below the AT resulted in significantly lower values for both PRA and La (7.18 vs. 11.27 mg angiotensin I (ANG I) X ml-1 X min and 3.16 vs. 9.93 mM, P less than 0.05 for TC vs. PE) while producing a similar fall in % delta PV and rise in osmolality. During LE, a high correlation was obtained for % delta PRA and % delta La (r = 0.86, P less than 0.01) but not for % delta PRA with % delta PV or % delta osmolality. The data demonstrate that PRA parallels lactate during exercise and that mean arterial pressure rises more slowly beyond the AT despite a more rapid rise in PRA.

Measurement of anaerobic threshold during dynamic exercise in healthy subjects: comparison among visual analysis and mathematical models

“…This condition, associated with other processes already underway during exercise, such as aerobic metabolism, permits the progressive formation of chemical energy which is stored as adenosine triphosphate (ATP), so as to permit the conversion of ATP to mechanical energy by the muscles and the continuation of effort until physical exhaustion [1]. Activation of the anaerobic mechanism induces several metabolic changes such as the formation of lactic acid which triggers modifications of many variables related to the cardiorespiratory, nervous and hormonal systems, among others [1][2][3][4][5][6].…”

Trace elements and electrolytes in human resting mixed saliva after exercise.

“…13 It is well documented that sympathetic adrenal activity increases during submaximal incremental exercise. [14][15][16] Increased sympathetic activity (estimated by plasma levels of catecholamines) during exercise has been previously associated with an increase in saliva concentrations of Na + and Cl − . 17 These findings were later confirmed by a field test.…”