The extent of individual differences in relative endurance and physiological response was examined in adolescent boys (n=22) and compared to data of prepubescent boys (n = 21) and adult men (n = 21). Subjects performed two (test and retest) relative endurance cycle ergometer tests at an initial rate of 105% V̇O2 max, which they attempted to maintain for 8 minutes. Relative endurance performance was defined as the revolutions for each minute of the test (RPM). There were no differences among groups for the total revolutions turned or the total percent dropoff from the initial rate. All groups had similar patterns for consistency of RPM except for Minute 3. The prepubescent boys exhibited the greatest within-individual variation (Si) for HR, especially after Minute 4 (p<.05). On the average, a greater proportion of the total variability in HR was due to Si in comparison to true individual differences (St) for the prepubescents (47%) than either the adolescents (13%) or the adults (11%). The adolescents had the lowest proportion of total variability in V̇O2 due to Si (adolescents 9%, adults 16%, prepubescents 26%). The data support an earlier hypothesis of a threshold age effect on the stability of individual differences for physiological response during relative endurance exercise. A change may occur during adolescence.
Stanley P. Sady is with the Dept. of Medicine, Miriam Hospital, and the Brown University Program in Medicine, Providence, RI02906. Victor L. Katch is with the Dept. of Kinesiology, Div. of P.E. and Section of Pediatric Cardiology, Sch. of Medicine, University of Michigan, Ann Arbor, MI 48109. Kris Berg is with the School of HPER, University of Nebraska at Omaha, Omaha, NE 68182. John Villanacci was with the University of Michigan at the time of the study and is now in Austin, TX.