The effects of whole-body vibration on the cross-transfer of strength

Abstract

This study investigated whether the use of superimposed whole-body vibration (WBV) during cross-education strength training would optimise strength transfer compared to conventional cross-education strength training. Twenty-one healthy, dominant right leg volunteers (21 ± 3 years) were allocated to a strength training (ST, m = 3, f = 4), a strength training with WBV (ST + V, m = 3, f = 4), or a control group (no training, m = 3, f = 4). Training groups performed 9 sessions over 3 weeks, involving unilateral squats for the right leg, with or without WBV (35 Hz; 2.5 mm amplitude). All groups underwent dynamic single leg maximum strength testing (1RM) and single and paired pulse transcranial magnetic stimulation (TMS) prior to and following training. Strength increased in the trained limb for the ST (41%; ES = 1.14) and ST + V (55%; ES = 1.03) groups, which resulted in a 35% (ES = 0.99) strength transfer to the untrained left leg for the ST group and a 52% (ES = 0.97) strength transfer to the untrained leg for the ST + V group, when compared to the control group. No differences in strength transfer between training groups were observed (P = 0.15). For the untrained leg, no differences in the peak height of recruitment curves or SICI were observed between ST and ST + V groups (P = 1.00). Strength training with WBV does not appear to modulate the cross-transfer of strength to a greater magnitude when compared to conventional cross-education strength training.

Figure 1

Mean ± SE 1RM strength (expressed as a percentage change) for all groups before (light bars) and after training (dark bars). *denotes an increase in strength following training (P < 0.016). There were no differences in strength between the ST and ST + V groups following training (P = 0.15).

Figure 2

Mean strength (expressed as a percentage change) of the trained right and untrained left leg post training, for ST (a) and ST + V (b) groups.

Figure 3

Mean ± SE MEP amplitudes (expressed as a percentage of M_MAX) obtained from the left untrained rectus femoris for the control (a), ST (b), and ST + V (c) groups before (light curve) and after (dark curve) training. Each recruitment curve is characterised by AMT, estimated slope and peak height (plateau), and the stimulus intensity at which the MEP amplitude is 50% of the maximum MEP (V ₅₀). ^†identifies AMT. *denotes significant increases in peak height post training (P < 0.016). There were no differences in peak height between the ST and ST + V groups following training (P = 1.00).

Figure 4

Mean ± SE SICI (expressed as a percentage change) for all groups before (light bars) and after training (dark bars). *denotes a significant reduction in SICI following training for the ST and ST + V groups (P < 0.016); however, no differences in SICI following training were observed between the ST and ST + V groups (P = 1.00).