P 097—Metabolic cost of transport in over-ground and treadmill walking of healthy elderly and effects of a treadmill familiarization protocol

Abstract Background Previous research has shown that the mechanics of walking on a treadmill is similar to walking overground. However it might be true that the energetics of walking is not similar between overground and treadmill, especially for older adults. We hypothesized that a lack of or inadequate familiarization on a treadmill would increase the Metabolic Cost of Transport (MCoT) in older adults due to increased levels of anxiety and the novelty of the locomotor task. Methods 10 healthy elderly (5 males and 5 females, mean age of 75.3 SD(6.3) years) were recruited and they walked first at their overground Preferred Walking Speed (PWS) for 8 min to reach a steady state of oxygen consumption in the morning. After that the same speed was imposed on a dual-belt treadmill and they walked for 15 min to properly familiarize themselves with the treadmill. This was called the familiarization session (Session 1). In the afternoon they repeated both the overground and treadmill walking again in the same order and with the same protocol. This session was called the post-familiarization session (Session 2). Results The group average of the overground PWS was 1.28 SD(0.11) m/s (4.61 SD(0.40) km/hr). During the familiarization session, the group average of the Gross Cost of Transport (GCoT) was 3.47 SD(0.35) J/kg/m while walking overground and 4 SD(0.65) J/kg/m while walking on a treadmill. The Net Cost of Transport (NCoT) was 2.64 SD(0.37) J/kg/m while walking overground and 3.14 SD(0.64) J/kg/m while walking on a treadmill. During the post-familiarization session, the group average of the GCoT was 3.84 SD(0.35) J/kg/m while walking overground and 3.94 SD(0.67) J/kg/m while walking on a treadmill. The NCoT was 2.76 SD(0.39) J/kg/m while walking overground and 2.90 SD(0.68) J/kg/m while walking on a treadmill. Both the GCoT and NCoT were statistically significantly higher on a treadmill than overground during the familiarization session. This elevation was not present during the post-familiarization session. There were also no statistically significant differences in the Resting Metabolic Rate (RMR) between before walking overground and before walking on a treadmill in either the familiarization or the post-familiarization session. Discussion and Conclusion This shows that the energetics of walking can be different for even healthy elderly on a treadmill if they are not or inadequately familiarized to it. This underlines the importance of adequate familiarization to treadmill walking for elderly in trying to understand the MCoT in this population.