REINALDO FIGUEROA-COLON, GARY R. HUNTER, MATTHEW S. MAYO, RUBY A. ALDRIDGE, MICHAEL I. GORAN, and ROLAND L. WEINSIER. Reliability of treadmill measures and criteria to determine V̇O2max in prepubertal girls. Med. Sci. Sports Exerc., Vol. 32, No. 4, pp. 865–869, 2000.
Purpose: The main objective of this study was to determine the reliability of measuring treadmill exercise economy (V̇O2submax) and the maximal oxygen uptake (V̇O2max) in prepubertal girls tested twice, 6 wk apart. We also wanted to examine the percentage of young girls who were able to reach the criteria for achieving V̇O2max and to describe methods that would allow a high proportion of young children to achieve criteria for reaching a true V̇O2max.
Methods: We studied 61 normal-weight, prepubertal girls with a mean (± SD) age 7.3 ± 1.3 yr (range 4.8 to 10.3 yr). V̇O2submax was determined while walking for 4 min at 2.5 mph with 0% grade. V̇O2max was measured during a progressive, all-out, continuous treadmill test using standardized procedures and criteria. Heart rate (HR) was measured using a Polar monitor. Respiratory rate (RR), respiratory exchange ratio (RER), ventilation (V), and V̇O2 were measured using a Sensormedics metabolic monitor.
Results: There were no significant differences between visits 1 and 2 in mean HR, RR, RER, V, V̇O2submax (421 vs 422 mL·min−1, respectively), and V̇O2max (1036 vs 1049 mL·min−1, respectively). Intra-individual coefficients of variation (CV) between visits 1 and 2 for submaximal tests were: HR = 5.1%, RR = 12.4%, RER = 7.2%, V = 12.5%, and V̇O2=12.4%. Intra-individual CVs for the maximum tests were: HRmax = 2.1%, RRmax = 10.8%, RERmax = 5.3%, Vmax = 11.7%, and V̇O2max = 7.5%. A high proportion of the girls reached criteria for V̇O2max [RER>1.00, HR>85% of age predicted maximum, and plateauing of V̇O2max] in both visits: 99% reached one of three criteria, 92% reached two of three criteria, and 70% reached all three criteria. Twenty girls [mean age 7.2 ± 1.2 yr] reached at least two criteria in both visits, whereas 32 girls [mean (± SD) age 8.6 ± 1.0 yr] reached three criteria in both visits.
Conclusion: Exercise measurements using treadmill testing were reliable in healthy, normal-weight, prepubertal girls. Older girls when compared to the younger girls were able to reach criteria for V̇O2max more often. Thus, we recommend that one testing should give researchers an accurate measure of walking economy and aerobic capacity, and that two criteria are enough for determining V̇O2max.
Maximal oxygen uptake or aerobic power (V̇O2max) is the gold standard for determining aerobic fitness (4). V̇O2max is used to evaluate the change that occurs after training, to help assess functional capacity, and to compare with values in healthy individuals (1). Although V̇O2max can be reliably measured in adults, there has been some discussion as to whether it is reliable in young children (2,5,16,17,19). One study (5) reported poorer coefficients of reliability in 10-yr-old boys who did not reach a plateau (increase in workload with no corresponding increase in V̇O2max) during V̇O2max testing than in those boys who did reach a plateau. The boys in the plateauing group had greater variability in V̇O2max than the boys in the nonplateauing group (5). Calculation of standard errors of prediction of the two groups from published data indicates that the nonplateauing group actually had lower standard errors of prediction than the plateauing group (5). Other studies (2,16–18) have shown that plateauing is not necessary for obtaining reliable measures of V̇O2max. However, none of the above studies have included subjects younger than 8 yr of age. To our knowledge no one has determined what test criteria are necessary for obtaining reliable measures in children younger than 8 yr.
Employing a treadmill, we used the following physiological criteria for reaching V̇O2max: a respiratory exchange ratio (RER) > 1.00, a heart rate (HR) > 85% of age predicted maximum, and a defined plateau of V̇O2 [i.e., a change with workload that is < 2 SD below that observed in the mean values between the submaximal workloads or < 150 mL·min−1 (16)]. The main objective of this study was to determine the reliability of measuring treadmill exercise economy (V̇O2submax) and the maximal oxygen uptake (V̇O2max) in 61 girls tested twice, 6 wk apart. We also wanted to examine what percentage of young girls were able to reach criteria for achievement of V̇O2max and to describe methods that allow a high proportion of young children to achieve criteria for reaching a true V̇O2max.