Physical fitness in aging men

Of 56 middle-aged male joggers (mean age 43.3 yr), 38 were measured for maximal oxygen uptake (VO2max) and 18 for cardiac output at a heart rate of 170 bpm (Q170). Each Q170 was divided by subject body surface area to yield cardiac index (CI170). A treadmill protocol was used to elicit maximal exercise during measurement of VO2max. The bicycle ergometer was employed when measuring Q170. For maximal exercise, termination was upon subject-declared fatigue. In subjects measured for VO2max, heart rate at 3.5 miles/h and 5% treadmill grade (HRsubmax) as well as heart rate at maximal exercise (HRmax) were noted. Heart rates were monitored electrocardiographically. A modified Douglas bag technique was applied when sampling expired air for determination of VO2max. Carbon dioxide rebreathing was used to estimate Q170. Data were grouped according to age (43 yr and older; 42 yr and younger). There were significant (P less than 0.05) positive relationships between VO2max and HRmax and between HRsubmax and age. Significant negative relationships existed between HRmax and HRsubmax, and between CI170 and 10 km running time. There were no significant differences (P greater than 0.05) between means achieved by the age groups. The overall mean for VO2max was 43.36 ml/kg per min and for Q170 33.53 1/min. Findings suggest that men who remain physically active retain youthful characteristics of cardiorespiratory function.