Karol Skup

Background/Objectives: Optimal activation of the quadriceps femoris, particularly the vastus medialis, while minimizing excessive activation of the vastus lateralis, is crucial for treating knee injuries like ACL ruptures and patellofemoral pain syndrome. Restoring proper muscle balance may enhance rehabilitation outcomes, but effective strategies for modulating muscle activity remain unclear. High-velocity low-amplitude hip manipulation has shown potential to influence neuromuscular function, yet its impact on quadriceps activation during knee extension has not been well studied. Therefore, the main aim of this study is to examine the effects of a single session of high-velocity low-amplitude hip manipulation on quadriceps femoris muscle activation and maximum voluntary contraction during knee extension. Methods: This study utilizes a randomized controlled design. Thirty physically active men and women (mean age: 21.9 ± 1.7 years) were randomly assigned to either an experimental group (n = 15; receiving hip joint manipulation) or a control group (n = 15; undergoing a sham intervention). Participants in the intervention group received a treatment involving hip manipulation and short-duration traction. Muscle activity of the rectus femoris, vastus lateralis, and vastus medialis was assessed using surface electromyography before and after the intervention, while muscle performance was measured by evaluating isometric knee extension strength in the lower limb. The isometric strength test was conducted in a seated position with the knee flexed at 60 degrees in Biodex System 4. Results: This study finds that the experimental group had significantly higher vastus lateralis mean amplitude (p = 0.020; effect size = 0.186) and vastus medialis mean amplitude (p < 0.001; effect size = 0.577) of electromyography root mean square electromyography compared to the control group. The experimental group also showed greater vastus medialis max amplitude (p < 0.001; effect size = 0.435). No significant differences were noted for rectus femoris mean amplitude (p = 0.078; effect size = 0.110), vastus lateralis max amplitude (p = 0.363; effect size = 0.031), rectus femoris max amplitude (p = 0.069; effect size = 0.117), or median frequency of the raw electromyography signal across muscle groups. Conclusions: In conclusion, high-velocity low-amplitude hip manipulation significantly enhances vastus medialis activation, highlighting its potential to improve quadriceps balance. These findings support the incorporation of hip manipulation into rehabilitation protocols.

(1) Background: Activation of the gluteus medius (GM) muscle while minimizing the involvement of the tensor fascia latae (TFL) is crucial in treating many lower limb and lumbar spine injuries. Previous studies have demonstrated the effectiveness of joint manipulations in regulating muscle activity. The main objective of this study was to evaluate the effects of hip joint manipulation (HJM) on the muscle strength and activity (GM and TFL) of hip abductors in asymptomatic young participants. (2) Methods: The study followed a double-blind randomized controlled design. Thirty healthy, physically active women and men, free from spinal and lower limb injuries, voluntarily participated. The participants were allocated to two groups: those allocated to the HJM intervention and those in the control group receiving a sham intervention. They were assessed before and after the intervention using surface electromyography to measure muscle activation (EMG_RMS) of the GM and TFL during maximal voluntary isometric hip abduction. (3) Results: HJM resulted in a significant increase in EMG_RMS amplitude solely within the GM muscle (p < 0.01); (4) Conclusions: This study suggests that HJM may increase EMGRMS amplitude in the GM muscle; however, the effects are neither statistically nor clinically significant when compared to the control group for most of the muscles analyzed.