The degradation of strength and lengths of isotonic twitch contractions of rat gastrocnemius muscle under ischemiareperfusion conditions was described in the article. Was demonstrated that strength and lengths recession directly dependent on ischemia and subsequent reperfusion duration. It was found that in the selected conditions detectable muscle contraction reaches zero level after 90-100 minutes of the ischemia. In the reperfusion phase partial contraction restoration was detected. Recovery level depended on preliminary ischemia duration. Maximum recovery level was observed after 4 (2+2) hours of ischemia-reperfusion, strengths restored up to 72±3,2% and lengths reached 7±1,3% of nonischemic control. In the case of 3+3 and 4+4 hours of ischemia-reperfusion function regenerated up to 42±4,1% and 12±2,3% of strengths control accordingly, lengths stayed on zero level in both situations. Contraction properties in reperfusion period recovered to some steady state level that probably allows us to determine muscle damage in ischemia stage. Simples, utility and possibility of noninvasive use of this method of muscle function evaluation can be useful in clinical practice.