Aim: To analyze the most force rising ratio (+ dF/dt(max)) and the most force descending ratio (- dF/dt(max)) for more sensitive index of skeletal contractility.
Methods: Mouse model of swimming training was used, most force (f(max)), + dF/dt(max) and - dF/ dt(max) of gastrocnemius contracting were measured and changes of gastrocnemius supermicro-structure was observed.
Results: Mitochondria increased and myoneme was regular in general training load, gastrocnemius F(max) - dF/dt(max) significantly increased than in control (P < 0.05), + dF/dt(max) increased more significantly (P < 0.01). Mitochondria was rare and myoneme was unusual in overtraining load, gastrocnemius F(max), - dF/dt(max) reduced significantly than in control (P < 0.05), + dF/dt(max) reduced more significantly (P < 0.01).
Conclusion: + dF/dt(max) is better index than F(max) in judging skeletal contractility.