ABSTRACT
PURPOSE/BACKGROUND: A reduction in the maximal force output of muscles following pre-performance stretching has been reported. Several studies have suggested that localized vibration may enhance or replace stretching for gaining flexibility. It is important to know if localized vibration may also compromise muscle output. The purpose of this investigation was to determine the immediate effects of localized hamstring vibration on hamstrings (HAM) and quadriceps (QUAD) performance. METHODS: Thirty asymptomatic participants, 19 female and 11 male, mean age 25.4 years (±SD 2.7) received either five minutes of localized vibration to the right hamstrings at 30 Hz and 6 mm amplitude, or sham. One week later, each participant received the alternate treatment. Following treatments, right (R) and left (L) isometric HAM and QUAD strength was measured twice by handheld dynamometer and maximal horizontal hop distance of each lower extremity was measured by single leg hop test (SLH). Treatment outcomes were compared using paired t-tests. Treatment order effect was measured by independent T-test. Pre-study intrarater reliability for dynamometry was established using ICC((3,2)). RESULTS: Mean (±SD) values for strength following vibration were 58.7 kg (15.7), 60.4 kg (14.0), 45.5 kg (14.2), 45.8 kg (13.2) for R QUAD, L QUAD, R HAM, L HAM respectively. SLH mean values were R SLH 153.8 cm (35 cm) and L SLH 155.4 cm (36 cm). There were no significant differences in means between vibration and sham treatment for any outcomes on either leg (p-values ranged .412-.971); p<.001 for all comparisons. Order had no significant effect (p-values .370-1.0). Intrarater ICCs were .888, .762, .884, .960 for R HAM, L HAM, R QUAD, L QUAD. CONCLUSIONS: Unilateral application of localized vibration to the hamstrings at a duration previously reported to increase flexibility did not diminish the isometric performance of the hamstrings or quadriceps of either leg. LEVEL OF EVIDENCE: 1b.
