ABSTRACT
Physical working capacity, the workload at a heart rate of 170 bpm (PWC170), has been utilized as a marker of maximal oxygen uptake. The precision of PWC170 in predicting VO2max in children has not been fully evaluated. In this study, 35 children (18 boys and 17 girls, mean ages 10.5 and 9.9 years, respectively) underwent maximal cycle testing to assess the relationship between VO2max and PWC170. These measures correlated closely in absolute terms (r = 0.71 and 0.70 for girls and boys, respectively), but the relationship was weaker when both were expressed per kg body weight (r = 0.65 and 0.48, respectively). When VO2max was calculated from the regression equation of VO2max versus PWC170, the mean error from measured VO2max was 3.4 ml.kg-1.min-1 (SD 2.5) for the girls and 2.8 ml.kg-1.min-1 (SD 2.6) for the boys. These findings indicate that although mean predictability of VO2max from PWC170 is good, the variability is wide, with a 10-15% error at one standard deviation. PWC170 provides only a crude estimate of VO2max and should not be used to predict individual maximal aerobic power.
Subject(s)
Oxygen Consumption/physiology , Physical Endurance/physiology , Physical Fitness/physiology , Anaerobic Threshold/physiology , Body Surface Area , Body Weight , Child , Electrocardiography , Exercise , Exercise Test , Female , Heart Rate/physiology , Humans , Male , Pulmonary Gas Exchange/physiologyABSTRACT
Previous studies have indicated that values for mechanical efficiency during cycle exercise in prepubertal subjects are similar to those in adults. Few studies have directly compared these groups, however, and earlier reports did not consider the importance of assessing efficiency at similar relative exercise intensities. Nineteen prepubertal boys and 21 college men underwent cycle exercise testing for determination of delta efficiency (the energy required to increase workload), related to both absolute work load and relative work intensity (percent VO2max). No significant differences in either of these measures were observed between the two groups. Mean delta efficiency between workloads of similar relative intensity was 23.2% for the prepubertal subjects and 22.5% for the adults (p greater than .05). Between equal absolute workloads the values were 23.2 and 26.5%, respectively (p greater than .05). These findings support earlier contentions that the efficiency of muscular contraction during exercise is comparable in pre- and post-pubertal subjects.