Abstract
Whole-body vibration (WBV) training may improve the strength of lower extremity muscles in patients with knee osteoarthritis (KOA), but the inconsistency in vibration parameters leads to differences in findings. This cross-sectional study is aimed at observing the effects of different vibration frequencies and knee flexion angles on the activation of lower extremity muscles in patients with KOA. Enrolled participants received WBV training at 0, 30, and 60° knee flexion angles with vibration frequencies of 0, 5, 10, and 20 Hz. Activation rates for vastus medialis, vastus lateralis, rectus femoris, biceps femoris, and semitendinosus in different combinations were collected through surface electromyography. The effects of frequency and angle on muscle activation rate were quantified by repeated measures ANOVA. Individual and synergistic effects of frequency and angle were also analysed. Twenty-six participants with KOA were included. Muscle activation increased with the vibration frequency in 0–20 Hz range and with knee flexion angle in 0–60° range. WBV training at 20 Hz was the most effective for knee muscle activation, and static squatting at 60° was the most suitable for WBV training. Therefore, WBV training can increase the activation rate of knee flexor and extensor muscles in patients with KOA, and the most efficient combination was 20 Hz vibration frequency and 60° knee flexion. When applying WBV to patients with KOA, individual differences and rehabilitation purposes should be considered in selecting vibration parameters and knee angle to effectively increase neuromuscular activity.
Highlights
Knee osteoarthritis (KOA) is a chronic degenerative disease characterised by the inflammation of the knee joint and surrounding soft tissues [1,2,3]
The primary hypotheses were as follows: (1) in the Whole-body vibration (WBV) low-frequency group (0–20 Hz), the neuromuscular activity in the lower extremities of patients with KOA is progressively induced by the increasing frequency, and (2) a synergistic relationship occurs between the effects of knee angle and vibration frequency on muscle activation
At 0 and 30° knee angles, the vibration frequency induced a significant difference on vastus medialis (VM) activation, and the muscle activation rate (EMG%maximal voluntary contraction (MVC)) increased with the frequency
Summary
Knee osteoarthritis (KOA) is a chronic degenerative disease characterised by the inflammation of the knee joint and surrounding soft tissues [1,2,3]. Pamukoff et al [21] found that WBV and local muscle vibration enhance the quadricep strength in healthy adults, but Segal et al [22] reported that a 12-week WBV exercise does not remarkably improve the muscle strength of lower extremities for patients with KOA. The present work is aimed at exploring the effects of different low vibration frequencies and knee flexion angles on the muscle activation of patients with KOA who received WBV. The primary hypotheses were as follows: (1) in the WBV low-frequency group (0–20 Hz), the neuromuscular activity in the lower extremities of patients with KOA is progressively induced by the increasing frequency, and (2) a synergistic relationship occurs between the effects of knee angle and vibration frequency on muscle activation
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