ABSTRACT
Objective To compare the pedaling force and lower extremity electromyography (EMG) with different cadences (60, 75, 90 r/min) and diverse cycling intensities (50%, 65%, 80% POV) and study the different influence on exerciser's pedaling force and lower extremity EMG. Methods Twelve healthy males participated in this study, and underwent two stages. In stage 1 the power output test at VO2max (POV) was got by cycle ergometer. In stage 2, nine conditions (3 kinds of intensities × 3 kinds of cadences) were completed respectively by using counter-balance design to record the changes for their pedaling force and lower extremity EMG. Results The negative pedaling work was significantly increased with the cadence increasing, and the appearing time of the peak pedaling force was significantly shifted forward in the cycle. When the crank angle was at 270°, the average increase of the pedaling force with the cadence increasing could obtain 1.84 times higher. In general, the firing rate of lower extremity muscular activation would be increased with the cadence increasing. Conclusions The cadence has greater effect on the pedaling force and lower extremity EMG. The tendency of pedaling force was shifted forward and the pattern of pedaling force became smoother with the cadence increasing. There are no significant differences among the diverse intensities. Based on the pedaling efficiency in this study, the optimal cadence for untrained people should be 60 r/min.
ABSTRACT
Objective To investigate the effects of Tai Chi Chuan combined with vibration training on the excitability of α-motorneuron pool and γ-reflex arc. Methods 55 healthy college students were divided into Tai Chi Chuan + vibration training (TAV) group, Tai Chi Chuan training (TAI) group, vibration training (VB) group, and control group (CON) for 8 weeks with 3 times training per week. Each time at pre-and post-training, H-reflex and M-wave were recorded by electrical stimulus induced on soleus muscle. T-reflex was also collected by knocking on the Achill tendon. Results After 8-week training, the ratios of Hmax/Mmax and T-reflex/Mmax in VB group were significantly decreased (P<0.05), while the ratio of T-reflex/Mmax in TAV group was significantly increased (P<0.05), and the change percentage of T-reflex/Mmax was significantly higher than that in VB group (P<0.05). Conclusions Although the vibration training could decrease the resting excitability of α-motorneuron pool, the Tai Chi Chuan combined with vibration training could give the muscle spindle stronger excitement so as to further induce the high excitability of γ-reflex arc. It indicated that the Tai Chi Chuan combined with vibration training is feasible since the neural adaptation around peripheral neuron system could be induced after such kind of training.
ABSTRACT
Objective To investigate the acute effect of local vibration stimulus with low frequency on hand control ability, flexibility, grip strength, and muscle EMG activity. Methods 10 subjects in this study held a vibrator for 20 seconds with isometric contraction at the vibration frequency of 12.5 Hz (vibration group, VIB) or with only isometric contraction (control group, CON). The same procedure measurement, including control ability, flexibility, grip strength, and muscle activity, were recorded both at pre-stimulus (pre-test) and 60-second after stimulus (post-test), respectively. Paired-t test was used to compare the values between pre-test and post-test and the changing rate between groups. Results The control ability and flexibility in pre-post test showed significant improvement after VIB intervention in VIB (P＜0.05). The changing rate of grip strength and EMG in VIB was significantly higher than those in CON (P＜0.05). Conclusions Acute local vibration stimulus with low frequency can be used to improve the hand control ability and flexibility for those who need better hand functional ability in the future.