Net caloric cost and electromyographic responses to seated leg presses performed against inertial resistance

Abstract

An inertia-based ergometer is among the latest devices suggested to abate space flight-induced muscle deconditioning. The current study uses separate sets of subjects to assess net caloric cost (n = 14) and electromyography (EMG) (n = 46) responses to leg presses done on the ergometer. All subjects performed the eight-repetition protocol three times over a two-week period. Net caloric cost measurements entailed indirect calorimetry from O 2 uptakes resulting from exercise on the ergometer. EMG subjects provided first and eighth repetition work, root mean square (RMS) and mean power frequency (MPF) data. Work output was more correlated to net caloric cost (r = 0.83, p < 0.05) than were anthropometric variables. EMG subject data showed work had gender-by-muscle-action and repetition-by-muscle-action effects, with male concentric and first repetition concentric data responsible the respective interactions. From the first to the eighth repetition, eccentric work incurred insignificant changes. RMS had a repetition-by-muscle-action effect, with eighth eccentric repetition data the source of the interaction. MPF showed an effect for repetition (eighth < first). In lieu of significant eighth-repetition RMS and MPF changes, high-threshold lengthening motor unit recruitment and/or greater series elastic element activity may explain the lack of eccentric work losses.