Resistance training preserves skeletal muscle function during unloading in humans.
OBJECTIVE
The intent of this investigation was to design and evaluate a low-volume, high-intensity resistance-training program to preserve knee extensor (KE) and plantar flexor (PF) size as measured by cross-sectional area (CSA), strength, and neuromuscular function (IEMG) with unloading.


METHODS
Thirty-two men (age = 30 +/- 3 yr; weight = 80 +/- 4 kg; height = 181 +/- 2 cm) participated. Sixteen men underwent 21 d of unilateral lower-limb suspension (ULLS) and were assigned to control (ULLS-CON, N = 8) or countermeasures (ULLS-CM, N = 8). The remaining subjects were ambulatory for 21 d and were assigned to control (AMB-CON, N = 8) or countermeasures (AMB-CM, N = 8). Countermeasure subjects performed resistance training every third day during the 21-d period.


RESULTS
KE and PF CSA decreased (P < 0.05) 7% in the ULLS-CON, whereas no changes occurred in ULLS-CM, AMB-CON, and AMB-CM. ULLS-CON maximal voluntary contraction (MVC) decreased 17% (P < 0.05) in the KE and PF. ULLS-CON torque-velocity characteristics (concentric and eccentric) decreased (P < 0.05), 22% to 12% and 20% to 14% (slow to fast) in the KE and PF, respectively. ULLS-CM PF increased (P < 0.05) in MVC and eccentric contractions, whereas no other changes occurred in MVC or torque-velocity characteristics in the KE or PF of the ULLS-CM, AMB-CON, and AMB-CM subjects. Submaximal IEMG increased (P < 0.05) whereas maximal IEMG decreased (P < 0.05) in the KE and PF of the ULLS-CON group. However, no change or slight improvements in IEMG activity were found in the KE and PF of the ULLS-CM, AMB-CON, and AMB-CM.


CONCLUSIONS
These results indicate that a resistance-training paradigm employed every third day during 21 d of unloading was effective in maintaining skeletal muscle strength (static and dynamic) and size of the KE and PF.
Schulze
Kimberley
K
Human Performance Laboratory, Ball State University, Muncie IN 47306, USA.
Gallagher
Philip
P
Trappe
Scott
S
D000328:Adult; D000886:Anthropometry; D004576:Electromyography; D002149:Energy Intake / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D019417:Hindlimb Suspension / Q000502:physiology*; D006801:Humans; D007717:Knee / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010806:Physical Education and Training / Q000379:methods*; D019415:Torque