A KNEE EXTENSOR COUNTERMEASURE TO UNWEIGHTING

Abstract

1158 The study combines resistance exercise with albuterol administration as a countermeasure to unweighting-induced knee extensor losses as part of a double blind design. Two healthy nonasthmatic males underwent 40 days of unilateral limb suspension (ULLS), a space flight analog for muscular deconditioning. Ambulatory activities were performed on crutches, with the left leg excluded from weight-bearing. During ULLS, subjects concurrently exercised on an inertial resistance ergometer and consumed the maximal therapeutic albuterol dosage (16mg/day) via four capsule administrations. With the unweighted knee extensors, subjects performed four sets of eight repetitions of unilateral leg presses three times per week to volitional fatigue. Subjects were encouraged to apply maximal tension throughout the range of motion. Per training session subjects were examined for compliance. Pre (Day 0), mid (Day 21), and posttesting (Day 40) of the unweighted knee extensors consisted of: one maximal strength test set, surface electromyography (EMG) of the vastus medialis (VM), and cross-sectional area (CSA) calculation. Strength testing examined concentric and eccentric measures. EMG examined three trials each involving maximal and submaximal (100 Nm) torque. Data were treated using one-way ANOVAs with an alpha of 0.05. The countermeasure caused a nonsignificant posttest knee extensor CSA decrement (-0.71%) following 40 days of ULLS. Nonsignificant changes in concentric (-1.71%) and eccentric (+13.34%) peak torque occurred after 40 days of ULLS. Max and submax EMG, associated with losses in neural drive and intrinsic muscle function respectively, were unchanged following 40 days of ULLS. The nonsignificant changes in eccentric peak torque and CSA suggest the countermeasure may augment gains in specific tension during 40 days of ULLS. Results suggest combining treatments may help ameliorate knee extensor losses during ULLS.