Analysis of vastus lateralis and vastus medialis oblique muscle activation during squat exercise with and without a variety of tools in normal adults

Impact of Starting Knee Flexion Angle on Muscle Activity and Performance during Plyometrics without Jumping

Most of the existing research has focused on jump plyometrics, where landing reaction forces must be dissipated among lower limb articulations. In contrast, the investigation of resisted plyometrics without jumping, devoid of such landing forces, remains relatively limited. This study aimed to (i) investigate the impact of resisted plyometrics without jumping at two knee flexion angles (60 and 90 degrees) on vastus muscle activity relative to limb dominance and (ii) assess strength, power, and work during the concentric-eccentric phases of these exercises. Thirty-one healthy participants underwent quantification of lower limb muscle amplitude, strength, power, and work during resisted plyometrics without jumping from both 60° and 90° knee flexion positions. After anthropometric evaluations, participants used a dynamometer with a load equal to 80% of body weight while wireless surface electromyography electrodes recorded data. Statistical analyses utilized paired t-tests or nonparametric equivalents and set significance at p ≤ 0.05. Results showed significantly higher muscle activity in the vastus medialis (VM) (dominant: 47.4%, p = 0.0008, rs = 0.90; nondominant: 54.8%, p = 0.047, rs = 0.88) and vastus lateralis (VL) (dominant: 46.9%, p = 0.0004, rs = 0.86; nondominant: 48.1%, p = 0.021, rs = 0.67) muscles when exercises started at 90° knee flexion, regardless of limb dominance. Substantial intermuscle differences occurred at both 60° (50.4%, p = 0.003, rs = 0.56) and 90° (54.8%, p = 0.005, rs = 0.62) knee flexion, favoring VM in the nondominant leg. Concentric and eccentric strength, power, and work metrics significantly increased when initiating exercises from a 90° position. In conclusion, commencing resisted plyometrics without jumping at a 90° knee flexion position increases VM and VL muscle activity, regardless of limb dominance. Furthermore, it enhances strength, power, and work, emphasizing the importance of knee flexion position customization for optimizing muscle engagement and functional performance.

Pattern Strabismus in a Tertiary Hospital in Southern China: A Retrospective Review

Background and objectives: To analyze demographic and clinical features of pattern strabismus patients and assess the relationship among these clinical variables and risk factors. Materials and Methods: Medical records of pattern strabismus patients who had undergone strabismus surgery at our center between 2014 and 2019 were retrospectively reviewed. Data collected included gender, age at onset, age at surgery, refraction, Cobb angle, pre- and post-operative deviations in the primary position, up- and downgaze, angle of ocular torsion, type/amount of pattern, grade of oblique muscle function and presence/grade of binocular function. To verify the clinical significance of the Cobb angle, 666 patients who had undergone surgery within one week after ocular trauma between 2015 and 2021 were enrolled as controls. Results: Of the 8738 patients with horizontal strabismus, 905 (507 males and 398 females) had pattern strabismus, accounting for 10.36%. Among these 905 patients, 313 showed an A-pattern and 592 showed a V-pattern. The predominant subtype was V-exotropia, followed by A-exotropia, V-esotropia and A-esotropia. Over half of these patients (54.6%) manifested an A- or V-pattern in childhood. The overall mean ± SD Cobb angle was 5.03 ± 4.06° and the prevalence of thoracic scoliosis was 12.4%, both of which were higher than that observed in normal controls (4.26 ± 3.36° and 7.8%). Within A-pattern patients, 80.2% had SOOA and 81.5% an intorsion, while in V-pattern patients, 81.5% had IOOA and 73.4% an extorsion. Patients with binocular function showed decreases in all of these percent values. Only 126 (13.9%) had binocular function, while 11.8% of A-pattern and 15.1% of V-pattern patients still maintained binocular function. Pre-operative horizontal deviation was negatively correlated with binocular function (r = −0.223, p < 0.0001), while the grade of oblique muscle overaction was positively correlated with the amount of pattern (r = 0.768, p < 0.0001) and ocular torsion (r = 0.794, p < 0.0001). There were no significant correlations between the Cobb angle and any of the other clinical variables. There were 724 patients (80.0%) who had received an oblique muscle procedure and 181 (20.0%) who received horizontal rectus muscle surgery. The most commonly used procedure consisted of horizontal rectus surgery plus inferior oblique myectomy (n = 293, 32.4%), followed by isolated horizontal rectus surgery (n = 122, 13.4%). Reductions of pattern were 14.67 ± 6.93 PD in response to horizontal rectus surgery and 18.26 ± 7.49 PD following oblique muscle surgery. Post-operative deviations were less in V- versus A-pattern strabismus. Post-operative binocular function was obtained in 276 of these patients (30.5%), which represented a 16.6% increase over that of pre-operative levels. The number of patients with binocular function in V-pattern strabismus was greater than that of A-pattern strabismus (p = 0.048). Conclusions: Of patients receiving horizontal strabismus surgery, 10.36% showed pattern strabismus. In these patients, 54.6% manifested an A- or V-pattern in childhood, and V-exotropia was the most frequent subtype. Pattern strabismus patients showed a high risk for developing scoliosis. Cyclovertical muscle surgery was performed in 724 of these patients (80.0%), and horizontal rectus surgery was effective in correcting relatively small levels of patterns. Binocular function represented an important factor as being involved with affecting the occurrence and development of pattern strabismus.

How effective is an evidence-based exercise intervention in individuals with patellofemoral pain?

OBJECTIVES

Guidelines for a comprehensive rehabilitation programme for patellofemoral pain (PFP) have been developed by international experts. The aim of this study was to analyse the effect of such a rehabilitative exercise programme on pain, function, kinesiophobia, running biomechanics, quadriceps strength and quadriceps muscle inhibition in individuals with PFP.

DESIGN

Observational study.

SETTING

Clinical environment.

PARTICIPANTS

Twenty-seven participants with PFP.

MAIN OUTCOME MEASURES

Symptoms [numeric pain rating scale (NPRS)and the pain subscale of the Knee Injury and Osteoarthritis Outcome Score (KOOS)], function measured by using the KUJALA scale and KOOS, kinesiophobia measured by using the Tampa scale, three-dimensional biomechanical running data, quadriceps isometric, concentric and eccentric strength and arthrogenic muscle inhibition (AMI) were acquired before and after the six-week exercise programme.

RESULTS

Although pain did not significantly improve all patients were pain-free after the six-week exercise programme (NPRS: p = 0.074). Function, kinesiophobia and quadriceps AMI improved significantly after the six-week exercise programme (KUJALA: p = 0.001, KOOS: p = 0.0001, Tampa: p = 0.017, AMI: p = 0.018). Running biomechanics during stance phase did not change after the exercise intervention. Quadriceps strength was not different after the six-week exercise programme (isometric: p = 0.992, concentric: p = 0.075, eccentric: p = 0.351).

CONCLUSION

The results of this study demonstrate that the current exercise recommendations can improve function and kinesiophobia and reduce pain and AMI in individuals with PFP. There is a need for reconsideration of the current exercise guidelines in stronger individuals with PFP.

Correlation between timed up and go test and skeletal muscle tensiomyography in female nursing home residents

OBJECTIVES

Tensiomyography (TMG) derived contraction time (Tc) and amplitude (Dm) are related to muscle fibre composition and to muscle atrophy/tone, respectively. However, the link between mobility and TMG-derived skeletal muscle contractile properties in older persons is unknown. The aim of the study was to correlate lower limb skeletal muscle contractile properties with balance and mobility measures in senior female residents of retirement homes in Austria.

METHODS

Twenty-eight female participants (aged from 67-99 years) were included in measurements of contractile properties (TMG) of four skeletal muscles: vastus lateralis, vastus medialis, biceps femoris and gastrocnemius medialis. Their balance and mobility performance was measured using a timed up and go test (TUG).

RESULTS

Time needed to complete TUG is negatively correlated to biceps femoris (r= -0.490; p= 0.008), vastus lateralis (r= -0.414; p=0.028) and vastus medialis (r= -0.353; p=0.066) Dm and positively correlated to vastus lateralis Tc (r=0.456; p=0.015). Overall, vastus lateralis Tc and vastus medialis Dm explained 37% of TUG time variance.

CONCLUSIONS

Our study demonstrates that TMG-derived quadriceps muscle contractile parameters are correlated with the balance and mobility function in female nursing home residents.

Activation of back and lower limb muscles during squat exercises with different trunk flexion

[Purpose] The purpose of this study was to investigate the activation of back and lower limb muscles in subjects who were performing a squat exercise at different angles of trunk flexion. [Subjects and Methods] Twenty healthy subjects (age 21.1± 1.8 years, height 168.7 ± 8.2 cm, weight 66.1 ± 12.3 kg) volunteered. The activation of the erector spinae muscle, rectus femoris muscle, gluteus maximus muscle and biceps femoris muscle was observed while the subjects performed squat exercises with a trunk flexion of 0°, 15°, and 30°. [Results] The erector spinae muscle, gluteus maximus muscle, and biceps femoris muscle were activated more during the squat exercise with the trunk flexion at 30° than the exercise with the trunk flexion at 0°. The rectus femoris muscle showed a tendency to decrease as the truck flexion increased. [Conclusion] Squat exercise be executed while maintaining an erect trunk posture if one wishes to strengthen the quadriceps muscle while reducing the load on the lower back.