Cardiac Frequency During Submaximal Exercise in Young Adults; Relation to Lean Body Mass, Total Body Potassium and Amount of Leg Muscle

The cardiac frequency and consumption of oxygen during submaximal exercise, lean body mass, total body potassium, thigh muscle width and an index of thigh muscle volume have been obtained for seventy‐nine healthy men and women, ages 18 to 38 yrs, who were not in athletic training but accustomed to taking some exercise. For these subjects, at any specified submaximal rate of consumption of oxygen, the cardiac frequency is negatively correlated with the indices of body muscle which are themselves inter‐correlated ( r 〉 0·89). The latter relationships provide a basis for prediction of total body potassium (coefficient of variation 6·1 %). The relationship of exercise cardiac frequency to body muscle is similar in both men and women; it provides a better description of frequency than one based on consumption of oxygen alone (coefficient of variation respectively 12% and 18%). Cardiac frequency is independently related to the level of habitual activity of the subjects. The implications of these findings are discussed.