Interaction between muscle temperature and contraction velocity affects mechanical efficiency during moderate-intensity cycling exercise in young and older women

Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom Submitted 29 December 2008 ; accepted in final form 8 July 2009 The effect of elevated muscle temperature on mechanical efficiency was investigated during exercise at different pedal frequencies in young and older women. Eight young (24 ± 3 yr) and eight older (70 ± 4 yr) women performed 6-min periods of cycling at 75% ventilatory threshold at pedal frequencies of 45, 60, 75, and 90 rpm under control and passively elevated local muscle temperature conditions. Mechanical efficiency was calculated from the ratio of energy turnover (pulmonary O 2 uptake) and mechanical power output. Overall, elevating muscle temperature increased ( P < 0.05) mechanical efficiency in young (32.0 ± 3.1 to 34.0 ± 5.5%) and decreased ( P < 0.05) efficiency in older women (30.2 ± 5.6 to 27.9 ± 4.1%). The different effect of elevated muscle temperature in young and older women reflects a shift in the efficiency-velocity relationship of skeletal muscle. These effects may be due to differences in recruitment patterns, as well as sarcopenic and fiber-type changes with age. energy turnover; efficiency/velocity relationship; elderly; pedal frequency Address for reprint requests and other correspondence: R. A. Ferguson, School of Sport and Exercise Sciences, Loughborough Univ., Leicestershire LE11 3TU, United Kingdom (e-mail: R.Ferguson{at}lboro.ac.uk )