Isometric Mid-thigh Pull Kinetics: Sex Differences and Response to Whole-Body Vibration

Merrigan, JJ, Dabbs, NC, and Jones, MT. Isometric mid-thigh pull kinetics: Sex differences and response to whole-body vibration. J Strength Cond Res 34(9): 2407-2411, 2020-The purpose was to investigate whether whole-body vibration's (WBV's) effect on force-time characteristics is dependent on time and sex. Subjects (men, n = 18; women, n = 18) performed a static quarter squat with WBV (frequency: 30 Hz; amplitude: 2-4 mm) and without for 5 × 30 seconds repetitions (1:1, WBV:rest). Next, they performed 2 sets of 3 repetitions of the isometric mid-thigh pull (IMTP) with 3 minutes of intraset rest and 5 minutes of interset rest. Peak force (PF) and rate of force development (RFD) from 0 to 50, 0 to 150, and 0 to 250 milliseconds (RFD50, RFD150, and RFD250) were analyzed (p < 0.05). A significant effect of condition existed for PF (p = 0.019) and RFD from 0 to 250 seconds (p = 0.031). In women, RFD was moderately affected immediately post-WBV (p = 0.070; d = 0.49). Yet in men, the effect of WBV on RFD existed 15 minutes after exposure (p = 0.017; d = 0.36). In absolute terms men produced more PF than women (1,008.6 ± 289.7 N; p < 0.001). All RFD bands were greater in men than those of women (RFD50, 5,519.3 ± 2,927.2 N·s; RFD150, 3,361.4 ± 1,385.3 N·s; RFD250, 2,505.7 ± 867.1 N·s; p < 0.05). However, relative to fat-free mass, PF in men (40.1 ± 7.2 N·kg) was not different from women (37.7 ± 6.4 N·kg; p = 0.284). The same was true for RFD150 (21.1 ± 24.1 N·kg·s; p = 0.084) and RFD250 (10.9 ± 14.1 N·kg·s; p = 0.128). Yet, RFD50 remained greater in men (139.1 ± 33.6 N·kg·s) than that of women (86.8 ± 34.5 N·kg·s; p = 0.034). Current WBV protocols resulted in trivial to moderate effects on IMTP forces, which may be dependent on sex and time. Finally, it is recommended that women complete movements with the intent to move weight quickly to improve early RFD.

Effect of Whole Body Horizontal Vibration Exercise in Chronic Low Back Pain Patients: Vertical Versus Horizontal Vibration Exercise

OBJECTIVE

To elucidate the effect of a 12-week horizontal vibration exercise (HVE) in chronic low back pain (CLBP) patients as compared to vertical vibration exercise (VVE).

METHODS

Twenty-eight CLBP patients were randomly assigned to either the HVE or VVE group. All participants performed the exercise for 30 minutes each day, three times a week, for a total of 12 weeks. Altered pain and functional ability were evaluated using the visual analog scale (VAS) and Oswestry Disability Index (ODI), respectively. Changes in lumbar muscle strength, transverse abdominis (TrA) and multifidus muscle thicknesses, and standing balance were measured using an isokinetic dynamometer, ultrasonography, and balance parameters, respectively. These assessments were evaluated prior to treatment, 6 weeks and 12 weeks after the first treatment, and 4 weeks after the end of treatment (that is, 16 weeks after the first treatment).

RESULTS

According to the repeated-measures analysis of variance, there were significant improvements with time on VAS, ODI, standing balance score, lumbar flexor, and extensor muscle strength (all p<0.001 in both groups) without any significant changes in TrA (p=0.153 in HVE, p=0.561 in VVE group) or multifidus (p=0.737 in HVE, p=0.380 in VVE group) muscle thickness. Further, there were no significant differences between groups according to time in any of the assessments. No adverse events were noticed during treatment in either group.

CONCLUSION

HVE is as effective as VVE in reducing pain, strengthening the lumbar muscle, and improving the balance and functional abilities of CLBP patients. Vibrational exercise increases muscle strength without inducing muscle hypertrophy.

Whole body vibration to attenuate reduction of explosive force in chronic kidney disease patients: a randomized controlled trial

To investigate whether whole body vibration (WBV) training increases the explosive force of the knee extensors in chronic kidney disease (CKD) patients. Fourteen CKD patients undergoing hemodialysis were randomly allocated in WBV training or Sham group. Explosive force parameters (contractile impulse [CImp] and relative rate of force development [RFDr]) obtained in early (30 and 50 msec) and late phases (100 and 200 msec) of the knee extensors force/time curve. CImp and RFDr obtained at the early phase of force/time curve reduced after the intervention period, with a smaller decline for WBV (CImp at 50 msec [~-15% and -51%, P=0.038], RFDr at 30 msec [~-22% and -52%, P=0.044] and RFDr at 50 msec [~-11% and -54%; P=0.008]). In the late phase there was a lower decline for WBV group compared to Sham group, respectively: CImp: 100 msec (~-8% and -55%, P=0.025), 200 msec (~-3% and -46%, P= 0.025); RFDr 100 msec (~0.01% and -56%, P=0.033), 200 msec (~-5% and -36%, P=0.004). Three months of WBV training may attenuate the explosive force reduction in CKD patients.

Immediate effect of vibratory stimuli on quadriceps function in healthy adults

INTRODUCTION

The purpose of this study was to compare the effect of whole body vibration (WBV) and local muscle vibration (LMV) on quadriceps function.

METHODS

Sixty adults were randomized to WBV, LMV, or control groups. Quadriceps function [Hoffmann (H)-reflex, active motor threshold (AMT), motor evoked potential (MEP) and electromyographic amplitude, peak torque (PT), rate of torque development (RTD), and central activation ratio (CAR)] was assessed before and immediately after and 10 and 20 minutes after interventions.

RESULTS

WBV improved PT, CAR, AMT, EMG, and MEP amplitude, and EMG amplitude and CAR were greater than control after application. LMV improved EMG amplitude and AMT, and EMG amplitude was greater than control after application. AMT remained lower 10 and 20 minutes after WBV and LMV. No differences were noted between LMV and WBV. Vibration did not influence H-reflex or RTD.

CONCLUSIONS

WBV and LMV increased quadriceps function and may be used to enhance the efficacy of strengthening protocols. Muscle Nerve 54: 469-478, 2016.

Acute effects of unilateral whole body vibration training on single leg vertical jump height and symmetry in healthy men

[Purpose] The aim of the present study was to investigate the acute effects of unilateral whole body vibration training on height and symmetry of the single leg vertical jump in healthy men. [Subjects] Thirty males with no history of lower limb dysfunction participated in this study. [Methods] The participants were randomly allocated to one of three groups: the unilateral vibratory stimulation group (n=10), bilateral vibratory stimulation group (n=10), and, no vibratory stimulation group (n=10). The subjects in the unilateral and bilateral stimulation groups participated in one session of whole body vibration training at 26 Hz for 3 min. The no vibratory stimulation group subjects underwent the same training for 3 min without whole body vibration. All participants performed the single leg vertical jump for each lower limb, to account for the strong and weak sides. The single leg vertical jump height and symmetry were measured before and after the intervention. [Results] The single leg vertical jump height of the weak lower limb significantly improved in the unilateral vibratory stimulation group, but not in the other groups. The single leg vertical jump height of the strong lower limb significantly improved in the bilateral vibratory stimulation group, but not in the other groups. The single leg vertical jump symmetry significantly improved in the unilateral vibratory stimulation group, but not in the other groups. [Conclusion] Therefore, the present study found that the effects of whole body vibration training were different depending on the type of application. To improve the single leg vertical jump height in the weak lower limbs as well as limb symmetry, unilateral vibratory stimulation might be more desirable.