Albuterol aids resistance exercise in reducing unloading-induced ankle extensor strength losses

Abstract

While resistance exercise (REX) reduces ankle extensor (AE) mass and strength deficits during short-term unloading; additional treatments, concurrently administered with REX, are required to attenuate the greater losses seen with longer unloading periods. Subjects performed left leg REX, which otherwise refrained from ambulatory and weight-bearing activity for 40 days, while randomized to a capsule (placebo, albuterol) dosing regimen with no crossover to note whether albuterol helps REX mitigate unloading-induced AE losses. A third group of subjects served as unloaded controls. On days 0, 20, and 40, the following data were collected from the left leg: calf cross-sectional area and AE strength measures. Cross-sectional area was estimated using anthropometric methodology, whereas AE strength data were obtained from eight unilateral calf-press repetitions on an inertial-based REX device. Repeated-measures mixed-factorial 3 x 3 analyses of covariance, with day 0 values as a covariate, revealed group x time interactions for the strength variables eccentric total work (ETW) and average power (EAP). Tukey's honestly significant difference shows REX-placebo subjects incurred significant ETW and EAP losses by day 40, whereas the REX-albuterol treatment evoked strength gains to those same variables without concurrent muscle accretion. Corresponding concentric variables did not display similar changes. Day 40 control data significantly declined for many variables; relative to the REX-albuterol treatment, some losses were significant after 20 days. ETW and EAP gains to unloaded AE may be due to one or more mechanisms. Continued research identifying mechanisms responsible for such changes, as well as the safety of REX-albuterol administration in other models, is warranted.

Blood Lactate and Hormonal Responses to Prototype Flywheel Ergometer Workouts

“…T he knee extensors are a muscle group prone to space flight-induced mass and strength losses (8,16). Greater losses generally occur with longer flights, with the rate of strength loss exceeding that for muscle atrophy (7,16).…”

“…The device in Figure 1, which operates without gravity, offers more eccentric resistance than standard free weight equipment (5). The merits of the flywheel ergometer (FERG) to reduce strength losses in a 40-day ground-based microgravity analog were assessed and showed that the device offered a substantial mechanical load stimulus to the unloaded knee extensors (8).…”

“…The merits of FERG workouts were assessed in ambulatory and ground-based microgravity simulation models (7)(8)(9)(10). In addition, the FERG was examined for its utility in Earthbound applications, such as to abate musculoskeletal losses in the elderly (6).…”

Temporal Strength Changes From Resistance Exercise and Albuterol on Unloaded Muscle

“…When therapeutic oral b 2 agonist and REX treatments were combined in a disuse atrophy model, they increased bone mineral content and muscle strength to an unloaded limb (8,9). The treatments may cause greater relative strength gains in disuse models than in healthy humans due to higher b 2 receptor density or sensitivity (2,15,27).…”

“…The impact of oral b 2 agonist and REX treatments upon KE strength changes over 40 days of ULLS were recently examined (9). Two groups performed unloaded KE REX 3 days per week.…”