| Objective:The decline in lower limb motor function and the dramatic increase in the incidence of falls in postmenopausal women not only affect their quality of life,but also place a huge burden on the state and society.The aim of this paper is to design a more optimal exercise intervention programme to develop lower limb motor function in post-menopausal women.A comparative study of the effects of whole-body vibration resistance training on lower limb muscle activation in post-menopausal women in different positions and intensities was conducted in Study 1 to design a more rational whole-body vibration resistance training programme.An empirical study was conducted in Study 2 to validate the effectiveness of whole-body vibration resistance training in improving lower limb motor function in postmenopausal women by applying the whole-body vibration resistance training programme.Methods:Study 1 Fifteen healthy post-menopausal women were recruited and subjected to 15 different modes of whole-body vibration resistance training in 3 positions(static half-squat,static half-squat with elastic band and half-squat up)×5 vibration intensities(0Hz,0mm;30Hz,2mm;40Hz,2mm;30Hz,4mm and 40Hz,4mm).Surface EMG signals were recorded from the rectus femoris,lateral femoris,medial femoris,gluteus maximus,biceps femoris and medial head of gastrocnemius muscles bilaterally,and a two-factor repeated measures ANOVA was used to compare the effect of different combinations of lower limb muscle activation and to select a more reasonable whole-body vibration resistance training protocol for the empirical study.In Study 2,80 healthy postmenopausal women were recruited and randomly divided into 3 groups:(ⅰ)whole-body vibration+resistance training group(WBV+RTG,n=27),which performed whole-body vibration+resistance training for 30 min three times a week for 12 weeks;(ⅱ)resistance training group(RTG,n=26),which performed the same movement pattern as the whole-body vibration+resistance training group,but without vibration application;(ⅲ)blank control group(CG,n=27),maintaining the same lifestyle habits.The subjects in the three groups were tested for lower limb isometric strength,walking mobility,squatting mobility,static and dynamic balance before and after the intervention,and the differences between the three groups were compared using paired samples t-test and analysis of covariance.Results:Study 1 Results showed that:(1)The main effect of body position on EMGrms of rectus femoris,gluteus maximus and gastrocnemius was significant(P<0.05);the main effect of intensity on EMGrms of lateral femoris,medial femoris,biceps femoris and gastrocnemius was significant(P<0.05).(2)Whole-body vibration resistance training from dynamic semisquat resulted in significantly higher EMGrms for the rectus femoris than for static semisquat and static semi-squat with elastic band loading(P<0.05).Static semi-squat with elastic band loading and dynamic semi-squat with significantly higher EMGrms for gluteus maximus than static semi-squat(P<0.05).Dynamic semi-squats raised gastrocnemius EMGrms significantly higher than static semi-squat with elastic band loading(P<0.05).(3)Strength 4 and Strength 5 lateral femoral EMGrms were significantly higher than Strength 1,Strength 4 was significantly higher than Strength 2 and Strength 5 was significantly higher than Strength 3;Strength 4 medial femoral EMGrms were significantly higher than Strength 1 and Strength 3;Strength 2,Strength 3,Strength 4 and Strength 5 biceps EMGrms were significantly higher than Strength 1,Strength 4 and Strength 5 were significantly higher than Strength 2;Strength 2,Strength 3,strength 4 and strength 5 gastrocnemius EMGrms were significantly higher than strength 1(P<0.05)and strength 5 was significantly higher than strength 2(P<0.05).Study 2 Results of the study:(1)Lower limb muscle strength and its related indexes:the strength of the left and right ankle dorsiflexors and the right ankle plantarflexors were significantly higher in the WBV+RTG and RTG groups than in the CG group after the intervention(P<0.05),and the strength of the left ankle plantarflexors was significantly higher in the WBV+RTG group than in the CG group(P<0.05);the duration of the five sitto-stand experiments was significantly lower in the two training groups than in the CG group after the intervention(P<0.05).(2)Walking mobility function:the gait cycle,double support phase,step width and COP Path width were significantly lower in the WBV+RTG group than in the other two groups after the intervention(P<0.05);their step speed,step frequency and stride length were significantly higher than in the other two groups(P<0.05);the step length symmetry was significantly lower in the WBV+RTG group than in the RTG group(P<0.05),and the gait variability was significantly lower than in the CG group(P<0.05).The ankle range of motion in the WBV+RTG group was significantly higher than that in the CG group(P<0.05);the 4m walking speed in the two training groups was significantly higher than that in the CG group after the intervention(P<0.05).(3)Squatting movement function:the mean speed and maximum knee flexion angle in the centripetal phase were significantly higher in the WBV+RTG group than in the CG group after the intervention(P<0.05);the maximum vertical ground reaction force was significantly higher in both training groups than in the CG group(P<0.05).(4)Balance function:static balance:the combined velocity of Romberg’s center of pressure swing,combined center of pressure displacement and mean swaying velocity of standing open with one foot closed on the left side were significantly lower in both intervention groups than in the CG group after the intervention(P<0.05),and the test time of standing open with one foot closed on the left side was significantly higher than in the CG group(P<0.05);knee flexion 60° Body weight shifted to the left side in the WBV+RTG group after the intervention,while the RTG group shifted to the right side(P<0.05).Dynamic balance:The combined speed of movement and combined maximum deflection of the center of pressure at the limit of stability were significantly higher in the two training groups than in the CG group after the intervention(P<0.05);the time taken for timed up-and-go was significantly lower in the two training groups than in the CG group(P<0.05).(5)Responsiveness:The whole-body reaction time in the WBV+RTG group was significantly lower than that in the RTG and CG groups after the intervention(P<0.05).Conclusions:(1)WBV+RTG is effective in increasing the activation of lower limb muscles in postmenopausal women compared to no vibration.The body position and intensity of wholebody vibration training had a site-specific activation effect on the lower-limb muscles.Static semi-squats with elastic bands were effective in improving the activation of the gluteus maximus,while dynamic semi-squats with resistance with self-weight improved the activation of the rectus femoris,gluteus maximus and gastrocnemius muscles simultaneously.The higher vibration frequency(40Hz)did not lead to a significant increase in activation of the lower-limb muscles compared to the lower frequency(30Hz).(2)Simple resistance training can effectively improve lower limb muscle strength,walking mobility function,and can effectively improve static balance function and dynamic balance function in postmenopausal women.(3)Whole-body vibration resistance training can effectively improve lower limb muscle strength,walking mobility and squatting mobility in postmenopausal women,and can effectively improve static balance function and dynamic balance function,and enhance the responsiveness of postmenopausal women.(4)Compared with resistance training alone,whole-body vibration resistance training is more comprehensive in improving the lower limb function of postmenopausal women,and is more advantageous in walking mobility and static balance function. |
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