ABSTRACT
Objective To observe the surface electromyography (sEMG) characteristics of upper limbs during one-finger pushing manipulation under different operating forces, so as to find out the muscle coordination movement pattern for key operating technology. Methods sEMG data of performing one-finger pushing manipulation by the expert, skilled and novice groups were collected. The manipulation force was divided into three different types, namely mild, moderate and severe. The continuous, stable data were adopted for analysis on Myo-Research software. Results Significant differences were found in the upper limb muscle integrated electromyography (iEMG) values (P0.05), with the flexor carpi ulnaris, deltoid, wrist flexors and extensors ranking the top three of iEMG ratio. The expert and skilled groups had the same core muscles in the same movement pattern during their manipulation operation, while the novice group had different core muscles under different forces. There were significant differences in co-contraction ratio among the expert, skilled and novice groups (P<0.01). The novice and expert groups had the highest and lowest co-contraction ratio, respectively, and the co-contraction ratio was gradually decreased with force increasing. During 6-minute manipulation operation, deltoid median frequency(MF) slope of the expert group was declined more slowly than that in the other two groups (P<0.05), which indicated that the expert group were better at resisting to fatigue. Conclusions The expert and skilled groups have the same sEMG characteristics during one-finger pushing manipulation operation with the same core muscles. The movement pattern of upper limb muscles is of regularity. The iEMG ratio, MF slope and co-contraction ratio can be used as reference standard for evaluating the durability, and homogeneity of the manipulation operation and normalization of force application.
ABSTRACT
Objective To evaluate the recovery effect of postural control by electrical stimulation acupoint massage after local muscle fatigue by investigating joint torque, surface electromyography (EMG) signal, balance ability and foot pressure distributions. Methods Six subjects (12 person-times) accepted isokinetic, SEMG and foot pressure test under the condition of normal rest or electrical stimulation acupoint massage after ankle fatigue. Results After electrical stimulation acupoint massage, ①the forward and backward displacement of COF (center of force) was significantly reduced and the contact area of T1, T2 and T4,5 was increased to (11.64±2.12), (6.57±0.97), (3.72±1.33) cm2, respectively. ② In ankle isokinetic test (90°/s), the total work of ankle plantar flexion and dorsiflexion was significantly increased to (56.71±13.26) and (19.75±3.79) J. ③ In right leg stance, RMS (root mean square) of the tibialis anterior and lateral gastrocnemius was decreased significantly; the ankle isokinetic test (90°/s) showed that the RMS of the medial and lateral gastrocnemius was increased from (48.95±13.50) and (33.67±6.41) μV to (59.87±11.46) and (43.73±4.65) μV, respectively. Conclusions Electrical stimulation acupoint massage can optimize the force strategy and improve the stability of the ankle, further improve the postural control ability, promote the recovery of sports ability and avoid sports injuries.
ABSTRACT
Objective To investigate the effect of a novel hip flexor training machine on muscle activation and range of motion (ROM) in lower limb under the condition of different resistances. Methods Six volunteers performed consecutive rightly hip flexion and extension for 30 times under light or heavy resistance randomly on the training machine, and the muscle activity and ROM in lower limb during the movement were measured at the same time. Results The muscle activation of rectus abdominal, hip flexor muscles, gluteus maximum, rectus femoris and biceps femoris under heavy resistance was significantly higher than that under light resistance (P<0.05); the muscle activation of rectus abdominis, hip flexor muscles and rectus femoris at during the last 3 times were significantly higher than that at of the first 3 times under heavy resistance (P<0.05); under light resistance, only the muscle activation of erector spinae and rectus femoris during the last 3 times were significantly higher than that of the first 3 times. The ROM and angle of hip extension under heavy resistance were significantly smaller than those under light resistance. Conclusions Under the rational ROM of hip joint, this new hip flexor training machine can stimulate the hip flexion and extension muscles and other co-contraction muscles to accomplish the movement, especially under the condition of heavy resistance.
ABSTRACT
Objective To explore the influence of basketball shoes on impact force and corresponding muscle activation in the lower limb during the active and passive landing. Methods Twelve male ball players wearing two types of shoes (basketball shoes with cushioning insole vs. control shoes) performed the jump drop and passive landing from three different height on the tiltable platform. The dynamometric platform and electromyography (EMG) measurement system were used to collect the impact forces and EMG data from 5 major muscles in the lower limb simultaneously. Results As for the active drop jump, wearing basketball shoes didn’t have any effect on the amplitude/frequency of impact forces and muscle activation in the lower limb. However, during the passive landing, wearing basketball shoes could significantly decrease the amplitude of impact forces, the peak loading rate and the input frequency (P<0.05), and the post-activation of major muscles in the lower limb were also significantly decreased (P<0.05). Conclusions During the active landing, the intervention of footwear shows no significantly influence on characteristics of impact forces and muscle activation. However, when the human body does not under the full control of landing, wearing basketball shoes can change the input frequency, decrease the muscle post-activation, and play a positive role in preventing the sports injuries and enhancing the metabolic efficiency during the landing.