Continuous muscle stretch prevents disuse muscle atrophy and deterioration of its oxidative capacity in rat tail-suspension models.
OBJECTIVE
The purpose of this study was to evaluate the effect of continuous muscle stretch on disuse-atrophied muscles.


METHODS
Sprague-Dawley rats were used and divided into five groups: control group, hind limb suspended for 3 and 7 days, and hind-limb suspension plus strenuous continuous muscle stretch for 3 and 7 days. In the hind-limb suspension plus strenuous continuous muscle stretch groups, the gastrocnemius-plantaris-soleus muscles were stretched using a plastic plate that immobilized the ankle joint at the maximum dorsal flexed position during the hind-limb suspension period. The intracellular energy metabolism of the working muscle during electric stimulation was evaluated by phosphorus-31 magnetic resonance spectroscopy in vivo. Changes in phosphocreatine, inorganic phosphate, and the intracellular pH were monitored to evaluate intramuscular oxidative capacity. Maximum tension and muscle wet mass were also measured.


RESULTS
The oxidative capacity, muscle wet weight, and maximum tension decreased after hind-limb suspension. The muscle oxidative capacity at control levels was maintained during the first 3 days in muscles subjected to continuous strenuous stretch. It was also effective to prevent the decrease in muscle mass and maximum twitch tension during the initial 3 days. However, the effects did not persist.


CONCLUSIONS
Continuous strenuous stretch was effective to prevent disuse muscle atrophy and its functional deterioration; however, its effects did not last long.
Sasa
Takahiro
T
Department of Orthopedics, School of Medicine, The University of Tokushima, Tokushima, Japan.
Sairyo
Koichi
K
Yoshida
Naoyuki
N
Fukunaga
Mari
M
Koga
Keiko
K
Ishikawa
Makoto
M
Yasui
Natsuo
N
D000818:Animals; D004195:Disease Models, Animal; D004734:Energy Metabolism / Q000502:physiology*; D019417:Hindlimb Suspension / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020966:Muscular Disorders, Atrophic / Q000503:physiopathology* / Q000517:prevention & control*; D009929:Organ Size / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values