The influence of pedaling frequency and crank load on the sensitivity of the soleus short latency stretch reflex (SLR) was examined in nine healthy subjects during pedaling by the use of a custom-built robotic actuator. The SLR decreased successively in downstroke when pedaling frequency increased from 20 to 40 and 60 revolutions per minute at a constant crank load (p = .005). The SLR was unchanged at crank load increases of 2.6 or 5.1 Nm at a constant pedaling frequency (p > .05). Accordingly, it was shown that increased muscle activation level as a consequence of added crank load and increased movement speed does not increase the sensitivity of the soleus SLR.
Birgit Larsen, Michael Voigt and Michael J. Grey
Ernst A. Hansen, Michael Voigt, Uwe G. Kersting and Pascal Madeleine
In the current study we investigated changes in voluntary rhythmic leg movement frequency (freely chosen cycling cadence) and rhythmic movement pattern (tangential pedal force profile) after fatiguing hip flexion and hip extension exercises. Nine healthy individuals performed ergometer cycling at freely chosen cadence and at a cadence of 1 Hz before and after fatiguing hip flexion and hip extension exercises. The freely chosen cadence was not affected after fatiguing exercises. An alteration of key characteristics of the tangential pedal force profile was found during cycling at a cadence of 1 Hz after hip flexion exercise. Thus, minimum tangential pedal force decreased by 12.0 ± 11.3% (p = .006), while maximum tangential pedal force increased by 4.6 ± 4.2% (p = .011), and the phase with negative tangential pedal force increased by 2.6 ± 3.2% (p = .040). In conclusion, novel information was obtained on aspects of rhythmic leg movement behavior in form of pedaling after fatiguing exercise.