Eccentric exercise training as a countermeasure to non-weight-bearing soleus muscle atrophy.

Although various exercise paradigms have been tested, none has completely prevented muscle atrophy during non-weight bearing. Because loaded eccentric contractions occur during normal daily activity but are absent during non-weight bearing, this investigation tested whether eccentric resistance training could prevent soleus muscle atrophy during non-weight bearing. Adult female rats were randomly assigned to either weight bearing +/- intramuscular electrodes or non-weight bearing +/- intramuscular electrodes groups. Electrically stimulated maximal eccentric contractions (4 sets of 6 repetitions at approximately 0.2 fiber lengths/s, 128 degrees range of motion) were performed on anesthetized animals at 48-h intervals during the 10-day experiment. Non-weight bearing significantly reduced soleus muscle wet weight (28-31%) and noncollagenous protein content (30-31%) compared with controls. Eccentric exercise training during non-weight bearing attenuated but did not prevent the loss of soleus muscle wet weight and noncollagenous protein by 77 and 44%, respectively. The potential of eccentric exercise training as an effective and highly efficient counter-measure to non-weight-bearing atrophy is demonstrated in the 44% attenuation of soleus muscle noncollagenous protein loss by eccentric exercise during only 0.035% of the total non-weight-bearing time period.