The effect of a six-week whole body vibration training protocol on the physical capacities and fatigability of overweight young female adults

Abstract

Whole body vibration (WBV) training is a relatively new training technique and is considered low intensity as it elicits non-voluntary muscle contractions generated by mechanical vibrations. The aim of this study was to examine the effects of a 6-week WBV training paradigm on the physical capacities and fatigability of overweight young female adults. We hypothesized that WBV would increase fat free mass as well as leg power and strength, decrease the fatigue index of the lower limbs during the Wingate test, increase fatigue resistance, improve neuromuscular efficiency and decrease fatigue perception in overweight young female adults. Participants (n=24) were overweight young female adults (body fat percentage 30-35) between the ages of 20 and 40 and were randomized into 2 groups; control group (CON; n=10) or whole body vibration group (VIB; n=14). This study consisted of six weeks of training and four testing sessions: 2 before (sessions 1 & 2) and 2 following (sessions 3 & 4) the training regimen. During testing sessions 1 and 3, the basal metabolic rate, body composition, leg power (Wingate), elasticity index (EI), squat and countermovement jumps and fatigue perception (questionnaires) were assessed for all subjects. Isokinetic tests to measure strength and muscle fatigue tests were performed during testing sessions 2 and 4. The training protocol lasted 6 weeks and exercises were performed 3 times a week. Sessions lasted 30 minutes and entailed 15 sets of 1-minute exercises followed by 1-minute rest intervals. One set consisted of 15 controlled and timed squats (15 flexion and extension per minute). The VIB group performed their exercises on the power Plate® pro 6. Vertical vibration amplitude settings were kept on low (2mm) throughout the entire 6 weeks and set at a frequency of 30Hz for weeks 1-3 and increased to 35Hz for weeks 4-6. The CON group performed the same exercises without vibration. iv The results revealed that a 6-week WBV training regimen had no effect on body composition or basal metabolic rate. WBV training did not affect EI as evidenced by similar squat jump and countermovement jump measures for both the CON and VIB groups. WBV training had no effect on leg power as measured using the Wingate ergocycle. The Wingate test did show a decrease in the fatigue index for both groups (p˂0.05). Unexpectedly, a decrease in strength was found in extension phase during the eccentric contractions (120°/s) and flexion phase during concentric contractions (120°/s and 180°/s). As there were no changes in fat free mass, it seems that the reduction in strength was due to central changes. The fatigue rate represented by regression slopes showed that the VIB group was more fatigue resistant post training compared to the CON group. Fatigue perception as measured using a multidimensional approach with questionnaires (FSS, MFI and SHARP) revealed no changes in fatigability for either group. To conclude, this study demonstrated that WBV training in overweight young female adults had minimal effects on the physical capacities and fatigability of our subjects. Higher intensity vibration parameters, a longer training regimen or individualized vibration parameters may have greater benefits for overweight subjects and should be considered in future studies.