Determination of preferred walking speed on treadmill may lead to high oxygen cost on treadmill walking

The energy consumption of walking relates to the intensity of physical effort and can be affected by the alterations in walking speed. Therefore, walking speed can be accepted as a crucial, determinant of energy consumption measurement for a walking test. We aimed to investigate the differences in preferred walking speed (PWS) determined both on overground and on a treadmill and, to measure walking energy expenditure and spatio-temporal parameters of gait on a treadmill at both, speeds. Participants (n = 26) walked on a treadmill at two pre-determined speeds for 7 min while, indirect calorimetry measurements were being performed. Spatio-temporal parameters were collected, by video-taping during each walking session on a treadmill. The average overground preferred walking speed (O-PWS) was 85.96 ± 12.82 m/min and the average treadmill preferred walking speed (T-PWS), was 71.15 ± 13.85 m/min. Although T-PWS was lower, oxygen cost was statistically higher when, treadmill walking at T-PWS (0.158 ± 0.02 ml/kg/m) than when the treadmill walking at O-PWS, (0.1480 ± 0.02 ml/kg/m). Cadence (127 ± 9.13 steps/min), stride (134.02 ± 14.09 cm) and step length (67.02 ± 6.90 cm) on the treadmill walking at O-PWS were significantly higher than cadence (119 ± 10 steps/min), stride (117.96 ± 14.38 cm) and step length (59.13 ± 7.02 cm) on the treadmill walking at TPWS. In conclusion, walking on treadmill using O-PWS is more efficient than walking on treadmill using TPWS, in walking tests. Since using T-PWS for treadmill walking tests overestimates the oxygen cost of walking, O-PWS should be used for oxygen consumption measurement during treadmill walking tests.