The elevated metabolic cost of walking at preferred speeds of healthy elderly on treadmills compared to overground is not related to increased self-reported anxiety

Purpose To investigate whether the elevation in metabolic cost of walking on treadmills compared to overground for healthy elderly is related to self-reported anxiety and if changes in self-reported anxiety are related to changes in heart rate. Methods We measured overground preferred walking speed, oxygen consumption rate and heart rates during rest and walking, and self-reported anxiety in 10 elderly (mean age 69.5 ± 3.1 years, 8 males and 2 females). At their preferred speed, the participants first walked overground, then on a high treadmill, and then on a low treadmill. Gross and Net metabolic costs of walking were calculated from the rates of oxygen consumption. Results Gross and net metabolic cost of walking were higher ( p < 0.05) on high treadmill (net cost: 2.64 J kg −1 m −1 ) and low treadmill (net cost: 2.68 J kg −1 m −1 ) compared to overground (net cost: 2.44 J kg −1 m −1 ), and the same was true for heart rate. There were no significant differences ( p > 0.05) in metabolic costs and heart rates between the two treadmill conditions. Self-reported anxiety was higher on the high treadmill compared to overground ( p = 0.004) and compared to low treadmill ( p = 0.02). We found no significant difference ( p > 0.05) for self-reported anxiety between overground and the low treadmill. Conclusion These results show that treadmill walking cannot be adequately generalized to overground walking. The differences found in metabolic cost on treadmills compared to overground were not related to differences in self-reported anxiety. Furthermore, the changes in heart rate are not related to changes in self-reported anxiety.