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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Caruso
John F
JF
Exercise and Sports Science Program, The University of Tulsa, Tulsa OK, USA. johncaruso@utulsa.edu
Hamill
John L
JL
Yamauchi
Miki
M
Cook
Tim D
TD
Mercado
Dean R
DR
Wickel
Eric E
EE
D000318:Adrenergic beta-Agonists / Q000627:therapeutic use*; D000420:Albuterol / Q000627:therapeutic use*; D000842:Ankle / Q000502:physiology; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000187:drug effects*; D018908:Muscle Weakness / Q000517:prevention & control*; D018482:Muscle, Skeletal / Q000187:drug effects; D012737:Sex Factors; D018544:Weightlessness Countermeasures
D000318:Adrenergic beta-Agonists; D000420:Albuterol