Electromechanical Changes in Rat Gastrocnemius Following Exercise Training and Steroid Administration

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Abstract
An experiment was conducted to determine the combined effects of exercise and anabolic steroid treatment on muscle contractile and electromechanical properties in male and female rats. The exercised animals were trained to perform a 16-cm vertical jump with an increasing load over an 8-week period. Steroid-treated animals were given nandrolone phenpropionate (Durabolin; 0.2 mg/day) over the last 3 weeks. Contractile properties and electromechanical delay (interval between electrical activation and mechanical onset, [EMD]) were measured in the gastrocnemius muscle after 8 weeks. The steroid treatment produced a greater effect in the female animals as indicated by increases in body weight and twitch force and a decrease in EMD. The exercise protocol produced increases in tetanic tension. Faster EMD scores occurred following both exercise and steroid treatments which were independent of muscle mass. These results demonstrate that 1) exercise and anabolic steroid administration produce distinct gender-related differences, and 2) some mechanism other than that responsible for gains in muscle mass must be operative to account for the decreases observed in EMD.