Background: The wall squat is considered an effective exercise because it can reduce the knee load and prevent excessive lumbar movement. However, the relationship between wall squat performance and strength of knee extensors and hip extensors remained unclear. Objects: The purpose of this study was to compare the strengths of the knee extensors and hip extensors between groups with low and high wall squat performance. Method: Nineteen males (low performance group: 9 subjects, high performance group: 10 subjects) participated in this study and performed wall squats. The subjects who were performing less than 30% of the average wall squat count were classified into the low wall squat performance group (less than or equal to 4 times) and the subjects who performed more than 30% of the average wall squat count were classified into the high wall squat performance group (greater than or equal to 8 times). Knee extensor and hip extensor strength were measured with a strength measurement system. An independent t-test was used to compare the strengths of the knee extensors and hip extensors between the groups with low and high wall squat performance. Results: The ratios of knee extensor and hip extensor strength to bodyweight were greater in the high wall squat performance group than in the low wall squat performance group (knee extensors: p<.001; hip extensors: p=.03). In the high- and low-performance groups, the ratios of knee extensor strength to bodyweight were 42.74±5.72 and 30.76±8.54, respectively, and the ratios of hip extensor strength to bodyweight were 31.95±10.61 and 20.66±11.25, respectively. Conclusion: Our findings suggest that knee extensor and hip extensor strength are needed for high wall squat performance. Thus, exercise to increase the knee and hip extensors strength can be recommended to improve squat performance.

The purpose of this study was to determine the muscle activities of the erector spinae (ES), gluteus maximus (Gmax), gluteus medius (Gmed), and the hamstring (HAM) and the ratios of Gmax/ES, Gmax/HAM, and Gmed/HAM during the prone heel squeeze (PHS) with different knee flexion angles (45˚, 90˚, and 135˚). Fifteen young and healthy subjects (8 men, 7 women) were recruited for the study. Surface electromyography signals were collected on ES, Gmax, Gmed, and HAM during PHS. A separate one-way analysis of variance with repeated measures was used to determine the significance of the muscle activities of ES, Gmax, Gmed, and HAM and the ratios of Gmax/ES, Gmax/HAM, and Gmed/HAM with different knee flexion angles during PHS. There was a significant increase in the Gmax activity at the knee flexion of 90˚ in comparison with that of the 45˚ (p=.016). There were significant increases in the Gmed activity at the knee flexion of 90˚ (p=.008) and 135˚ (p=.006) in comparison with that of the 45˚. There were significant decreases in the HAM activity at the knee flexion of 90˚ (p=.009) and 135˚ (p=.004) in comparison with that of the 45˚. There were significant increases in the Gmax/HAM muscle activity ratio at the knee flexion of 90˚ (p=.007) and 135˚ (p=.012) in comparison with that of the 45˚. There were significant increase in the Gmed/HAM muscle activity ratio at the knee flexion of 135˚ in comparison with that of the 45˚ (p=.008). The knee flexion of 90˚ during PHS can induce decreasing activity of HAM and increasing activity of Gmax, and the knee flexion of 135˚ during PHS can induce decreasing activity of HAM and increasing activity of Gmed. Hence, PHS with different knee flexion positions could be considered for the different target muscle.

The purpose of this study was to determine the effect of sciatic nerve mobilization technique on perceived pain, straight leg raise test (SLR), and strength of knee extensor, location of symptoms (LOS) in patients with chronic low back pain. 22 patients with chronic low back pain were recruited for this study. The subjects were randomly assigned to either the experimental group (EG) or the control group (CG), with 11 patients in each group. All patients received a routine physical therapy (hot pack and transcutaneous electrical nerve stimulation). The mobilization technique of the sciatic nerve was performed for 10 min in the case of the EG subjects. Outcome measurements included the level of the perceived pain, SLR, and strength of the knee extensor, LOS. The measurements were recorded 3 times: before the intervention, after the intervention, and at 1 hour of follow up. The two groups did not significantly differ with regard to the level of perceived pain, SLR, and strength of the knee extensor, LOS before the test (p>.05). In the case of the EG subjects, all the variables measured after the intervention significantly differed from those measured before the intervention (p<.05). However, in the case of the CG subjects, a significant difference was noted only with regard to the level of perceived pain (p<.05). The findings indicate that sciatic nerve mobilization technique exerts a positive effect on the control of subjective symptoms and knee strength in patients with chronic low back pain. Further studies are required to generalize the result of this study.

In dancers, intact muscular coordination is a well balanced antagonist, which could be a decisive factor in protection against injury as dancers often have hypermobile joints and their ankle joints often bear their full body weight in extreme positions. The purposes of this study were to identify the isokinetic strength to the knee and ankle and the isometric strength of the trunk in female collegiate dancers and controls. Furthermore, the study aimed to investigate the peak torque ratio of knee extension to flexion, ankle plantarflexion (PF) to dorsiflexion (DF), and dominant legs to nondominant. Twenty-one female collegiate dancers (20.0 years of age) and twenty-one female collegiate students (19.3 years of age) performed isokinetic maximum efforts of the knee extensors and flexors at and , the ankle plantarflexors and dorsiflexors at and and isometric maximum efforts of the lumbar extensors at 0˚, 12˚, 24˚, 36˚, 48˚, 60˚, and 72˚. The results were as follows: The isokinetic peak torque of the knee extensors and the ratio of knee extensors to flexors of dancers were significantly higher than those of controls (p<.01). However, the isometric peak torque of the back extensors (p<.01) and isokinetic peak torque of the ankle plantarflexors and dorsiflexors (p<.05) of dancers were significantly lower than those of controls. Further studies are needed to identify the difference in proprioception of the joints between dancers and controls.

The purpose of this study was to examine the effect of the hip internal rotation on knee extensor and hip abductor electromyographic (EMG) activity during stair up and stair down mobility. Eighteen healthy subjects were recruited. All subjects performed stair up and down movements on a step of 30cm height while maintaining the hip in neutral (condition 1) and hip in internal rotation (condition 2). Surface EMG activity was recorded from five muscles (gluteus maximus, vastus lateralis (VL), vastus medialis oblique (VMO), posterior gluteus medius (Gmed), and tensor fascia latae (TFU)) and hip internal rotation angle was measured using a three dimensional motion analysis system The time period for stair up and down was normalized using the MatLab 6.5 program, and EMG activity was normalized to the value of maximal voluntary isometric contraction (%MVIC). The EMG activities according to the hip rotation (neutral or internal rotation) during the entire time period of stair up and down in each phase were compared using a paired t-test. During the entire period of stair up, the EMG activities of VL and TFL in condition 2 were significantly greater than in condition 1 (p<.05). During the entire period of stair down, the EMG activities of VL and TFL in condition 2 were significantly greater than in condition 1 (p<.05). However, the EMG activities of the other muscles were not significantly different between the conditions (p>.05). These results suggest that the stair up and down maintaining hip internal rotation was could be a contributing factor on patellar lateral tracking.