• Marybeth Brown and Jennifer Taylor.
• Program in Physical Therapy, Washington University School of Medicine, St. Louis, MO, USA. brownmb@health.missouri.edu
• Arch Phys Med Rehabil. 2005 Dec 1; 86 (12): 2261-9.

ObjectiveTo compare the effectiveness of no exercise with prehabilitation (exercise before hindlimb unweighting [HLU]) versus rehabilitation (exercise given after HLU) on gait function and skeletal muscle mass and force.DesignRandomized controlled trial.SettingAnimal laboratory.AnimalsMale-specific, pathogen-free Fisher344/Brown Norway rats (N=149). Groups consisted of adult and old controls, HLU, prehabilitation, rehabilitation, natural cage recovery (reloading), and exercise without HLU.InterventionsTen days of general conditioning exercise were given to 6-month-old adult and 30-month-old old rats before or after a week of HLU.Main Outcome MeasuresGait stride length and width; soleus, plantaris, extensor digitorum longus, and peroneus longus mass and peak contractile force; whole gastrocnemius mass; and total protein concentration for the soleus and gastrocnemius.ResultsMuscle mass (approximately 30%) and force (24%-36%) declined with age in all muscles studied. In adult rats declines in muscle mass occurred with HLU in the soleus, plantaris, and gastrocnemius. Prehabilitation did not prevent the loss of muscle mass in adult rats. Rehabilitation and natural recovery effectively restored soleus and gastrocnemius muscle mass in adult rats but not soleus peak force. Old rats had a significant 23% HLU effect only on gastrocnemius mass (control, 1670+/-129 mg; HLU, 1274+/-184 mg). Prehabilitation did not prevent the decline in gastrocnemius mass. Rehabilitation in old rats restored gastrocnemius mass to within 13% of control levels. Prehabilitation was effective for preventing and rehabilitation was effective for restoring soleus contractile force in old rats (control, 114+/-9 mg; HLU, 67+/-22 mg; prehabilitation, 106+/-31 mg; rehabilitation, 120+/-26 mg) compared with recovery without exercise (86+/-29 g). A significant reduction in stride length was observed with aging (136+/-18 mm vs 98+/-10 mm), which decreased further with HLU (78+/-14 mm). Prehabilitation attenuated HLU-related reductions in stride length, and rehabilitation was effective for stride length restoration in old rats.ConclusionsExercise, particularly rehabilitation, was more effective for old than young rats. Prehabilitation and rehabilitation diminished some of the detrimental effects of HLU on skeletal muscle mass and force and gait function in old rats.

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