The influence of seat height on the mechanical function of the triceps surae muscles during steady-rate cycling.

The purpose of this study was to manipulate bicycle seat height in order to perturbate muscle length, contraction velocity and excitation of soleus and medial gastrocnemius muscles. One group of female riders (n=13) rode a stationary ergometer at 200 W and a cadence of 80 rpm. Individuals rode at a self-selected seat height, a 10% lowered and 5% raised seat position. It was hypothesized that because the two muscles would operate at decreased contraction velocities at the low seat, the integrated EMG would be less for the lowest seat position. The soleus and medial gastrocnemius muscles showed a significant decrease in integrated EMG value with decreased seat height (soleus F(2,24)=5.4, p<0.01, gastrocnemius F(2,24)=51.6, p<0.0001). The combined effect of the movement at the ankle and knee joints resulted in increased length of gastrocnemius rather than shortening at the lowered seat-height position as anticipated. This suggested that there was a greater role of knee-joint angle in determining the muscle excitation for medial gastrocnemius. The original hypothesis was accepted, confirming the importance of setting proper seat height.

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