Reliability of treadmill measures and criteria to determine VO2max in prepubertal girls

Purpose: The main objective of this study was to determine the reliability of measuring treadmill exercise economy ((V) over dotO(2submax)) and the maximal oxygen uptake ((V) over dotO(2max)) 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 (V) over dotO(2max) and to describe methods that would allow a high proportion of young children to achieve criteria for reaching a true (V) over dot(2max). 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). (V) over dotO(2submax) was determined while walking for 4 min at 2.5 mph with 0% grade. (V) over dotO(2max) 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 (V) over dotO(2) were measured using a Sensormedics metabolic monitor. Results: There were no significant differences between visits 1 and 2 in mean HR, RR, RER, V, (V) over dot(2submax) (421 vs 422 mL.min(-1), respectively), and (V) over dot(2max) (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 (V) over dotO(2) = 12.4%. Intra-individual CVs for the maximum tests were: HRmax = 2.1%, RRmax = 10.8%, RERmax = 5.3%, V-max = 11.7%, and (V) over dotO(2max) = 7.5%. A high proportion of the girls reached criteria for (V) over dotO(2max) [RER>1.00, HR>85% of age predicted maximum, and plateauing of (V) over dotO(2max)] 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 (V) over dotO(2max) 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 (V) over dotO(2max).