Albuterol and exercise effects on ankle extensor strength during 40 days of unloading

In-flight ankle extensor (AEXT) strength losses are an impediment to long-term space travel. The current study examines if albuterol helps resistance exercise (RE) abate AEXT strength loss incurred over a 40-d unloading period.

All subjects (21 men, M; 15 women, W) performed unilateral limb suspension (ULLS) and exercised on a flywheel ergometer (FERG) with their otherwise unloaded AEXT. With a double-blind randomization assignment, subjects either received placebo (PLA, lactose) or albuterol (ALB, 16 mg x d(-1)) via four daily capsule doses with no crossover. FERG calf press workouts done 3 d x wk(-1) provided concentric and eccentric total work (CTW, ETW) and average power (CAP, EAP) measures. Workout data from the 40-d period were averaged and partitioned into four consecutive 10-d periods. Data were compared with a 2 (gender) x 2 (treatment) x 4 (time) MANCOVA, with day 0 AEXT strength measurements and a drug/body mass ratio as covariates.

CTW and ETW days 11-20, 21-30, and 31-40, as well as CAP and EAP days 11-20 and 21-30 showed the following significant results: ALB-W > ALB-M, PLA-M > PLA-W. CAP and EAP days 31-40 showed the following significant results: ALB-W, ALB-M, PLA-M > PLA-W.

The combined RE-albuterol treatment most likely evoked unloaded AEXT strength gains in women due to heightened myofibril sensitivity for Ca+2. Despite a drug/body mass covariate, gender-related differences should be interpreted with caution. Future work should compare absolute and relative beta2 agonist dosages on gender-related muscle mass and strength changes.