Single-dose effects of whole body vibration on quadriceps strength in individuals with motor-incomplete spinal cord injury.

CONTEXT

Paresis associated with motor-incomplete spinal cord injury (SCI) impairs function. Whole body vibration (WBV) may increase strength by activating neuromuscular circuits.

OBJECTIVE

We assessed effects of a single session of WBV on lower extremity strength in individuals with motor-incomplete SCI.

DESIGN

A single-session blinded randomized controlled trial.

SETTING

Rehabilitation research laboratory.

PARTICIPANTS

Subjects (n = 25; age 49.7 ± 12.5 years) had chronic SCI (>1 year) and were able to stand for at least 45 seconds. Interventions Subjects were randomized either to WBV (n = 13) consisting of four 45-second bouts with 1-minute intervening rest periods (frequency: 50 Hz, amplitude: 2 mm) or to sham electrical stimulation (n = 12).

OUTCOME MEASURES

Maximal voluntary isometric quadriceps force was measured with a fixed dynamometer. A modified Five-Time-Sit-To-Stand (FTSTS) test was used to assess functional lower extremity strength. Measures were made at pre-test, immediate post-test, and delayed post-test 20 minutes later.

RESULTS

At immediate post-test, change in voluntary isometric force in the WBV group was 1.12 kg greater than in the sham group. The within-group change for the WBV group was significant with a moderate effect size (P = 0.05; ES = 0.60). No force-related changes were observed in the sham group. The modified FTSTS scores improved in both groups, suggesting that this measure was subject to practice effects.

CONCLUSION

Evidence from the present study suggests that even a single session of WBV is associated with a meaningful short-term increase in quadriceps force-generating capacity in persons with motor-incomplete SCI. The multi-session use of WBV as part of a strengthening program deserves exploration.