Magnitude and Time Course of Cardiovascular and Metabolic Adaptations to Exercise.

Abstract

Twenty-five males under the age of 35 years (9 high fit--VO(,2)(' )max. (GREATERTHEQ) 12 METS; 9 low fit--VO(,2)(' )max. < 12 METS; and 7 control) participated in ten weeks of submaximal bicycle ergometer conditioning at a heart rate equal to 70 percent of peak oxygen consumption to assess the time course of alterations in peak oxygen consumption; the appropriateness of utilizing the rate constant (k) of an oxygen uptake kinetics curve as a meaningful measure of integrated cardiovascular and metabolic function; and the conditioning regimen's effect on initial measures of cardiovascular and metabolic function. Oxygen consumption was assessed at peak levels as well as absolute (300 kilogram meter/min) and relative (40 percent of peak load) work levels. M-mode echocardiographic evaluation of left ventricle function (unidimensional) was assessed, at rest, in a subsample of participants, during initial and final evaluations. The time course of alterations in peak oxygen consumption appeared linear in the high fit group, though a slight decrement was noted in the last stage of the conditioning regimen. The decrease in peak oxygen uptake appeared to be related to attendance and motivational difficulties. The low fit group showed gains in peak oxygen consumption from weeks zero to three and a decrement thereafter. This response appeared to be related to insufficient training intensity. The rate constant (k) of an oxygen uptake kinetics curve does not favorably correlate with peak oxygen uptake and cannot be utilized as a meaningful indicator of overall cardiovascular and metabolic function. Additionally, ten weeks of submaximal conditioning resulted in statistically significant reductions, in the high fit group, in measures of VO(,2)(' )at 300 kilogram/meter/minute (absolute) and peak heart rate and an increase in systolic blood pressure. The low fit group exhibited statistically significant decrements in the rate constant (k) at a work load equal to 40 percent of peak(' )VO(,2) (relative) and peak diastolic blood pressure and an increase in half time-relative. No control variables or other measures in the low and high fit groups exhibited any statistically significant alterations.