Several studies have described "Alternate activity", in which individual muscles of the synergistic muscle group alternate between high activity and silent periods, and rotate in a complementary pattern to maintain constant torque, during sustained low-level contractions. The purpose of this study was to investigate the physiological property of alternate activity among the synergists. Eight human subjects performed static contractions at an ankle joint angle of 110° plantar flexion at 10% maximal voluntary contraction (MVC) for 120 min. Simultaneously, a surface electromyogram (EMG) was recorded of the triceps surae muscles. Doppler ultrasound techniques were used to measure blood velocity and the arterial diameter of the popliteal artery during exercise. Maximal torque at MVC and mean EMG (mEMG) level decreased significantly after sustained isometric low-level contractions, but there was no significant difference in the mEMG/maximal force ratio of triceps surae muscles, which is thought to indicate peripheral fatigue between pre- and post-exercise. Throughout the "Alternate activity", arterial diameter and pulse rate did not change, but blood flow significantly increased (p<0.001) depending on an increase in blood velocity. These results suggest that "Alternate activity" among the triceps surae muscles may be one mechanism that functions either to decrease or to postpone peripheral fatigue during sustained low-level contraction.

Background : The effects of rehabilitation on hemodialysis patients are unknown. We assessed the effects and investigated the association between rehabilitation treatment effects and all-cause mortality. Methods : This prospective cohort study included 120 patients on maintenance hemodialysis. ADL was assessed using the Functional Independence Measure (FIM) score (total points, 126), which comprises 13 motor items (total points, 91) and five cognitive items (total points, 35). A survival curve was constructed using the Kaplan-Meier analysis and stratified into an increase or no-increase of the FIM score. Multivariable logistic regression analysis was used to determine factors associated with the effects of rehabilitation. Discriminative sensitivity of FIM cognitive items for an increase in total FIM was estimated using the area under the receiver operating characteristic (AuROC) curve. Results : The average total FIM score increased from 64.2±3.6 to 75.8±3.0, and the increase in FIM motor and cognitive items was 11.0±1.3 and 0.5±0.6, respectively. The cumulative survival rate within 2.5 years was significantly higher in the FIM increase group than that in the FIM no-increase group. FIM cognitive items and anemia were significantly associated with rehabilitation effects, and AuROC showed that a cutoff of 34 points in cognitive FIM had moderate discriminative sensitivity for a total FIM increase (AuC, 0.719 ; p<0.0008). Conclusions : Rehabilitating hemodialysis patients improved their FIM score (particularly the motor items), and a higher FIM score resulted in a better prognosis. The effectiveness of rehabilitation depends on maintaining a perfect FIM cognitive score.