Reliability and Within Subject Variability of V̇E, V̇O₂, Heart Rate and Blood Pressure During Submaximum Cycle Ergometry

Abstract

To assess the reliability and within subject variability of steady-rate ventilation (V̇E), oxygen uptake (V̇O₂), heart rate, systolic and diastolic blood pressure, 4 subjects exercised for 10 minutes at 3 work rates on a bicycle ergometer: 50 W, 125 W and 55% of maximum work rate (55% max). Each testing session included two work rates and only 2 testing sessions were scheduled per week. The order of the work rates was counterbalanced. In 8 to 10 weeks, 3 of the subjects completed 20 trials at 50 W while the fourth subject completed 11 trials, and all the subjects completed 10 trials at 125 W and 55% max. The within subject variability (S² _W) was expressed as a percent of the mean steady-rate response. V̇O₂ ranged from 21.2% to 27.5% of V̇O₂max at 50 W, from 37.7% to 49.7% at 125 W and from 42.9% to 63.7% at 55% max. The S² _W averaged 6.8% for VE, 4.3% for V̇O₂, 3.2% for heart rate, 7.3% for systolic blood pressure and 10.5% for diastolic blood pressure. Reliability coefficients were calculated for the steady-rate scores by dividing the between subject variation by the total variation. The reliability was similar for V̇E, V̇O₂ and heart rate and ranged from r = 0.69 to r = 0.97. Systolic and diastolic blood pressure reliabilities were lower and ranged from r = 0.27 and r = 0.80. In summary, the steady-rate ventilation, oxygen uptake and heart rate responses were reliable and consistent. The reliability of blood pressure was low. It is possible that this low reliability may result from variability in stroke volume or total peripheral resistance.

Key words

Exertion - exercise - ergometry - oxygen uptake - ventilation - heart rate - blood pressure - variability - error variance