Differences in the muscle activities of the quadriceps femoris and hamstrings while performing various squat exercises

Hamstring-to-quadriceps activation ratio during lower-limb strengthening exercises

Multiple exercises included in strength training involve greater activation of the quadriceps compared to hamstring muscles, which may lead to knee joint imbalances. The aim of this study was to examine the ratio of surface electromyography (sEMG) activity hamstring and quadriceps muscle groups (hamstring-to-quadriceps activation ratio; H:Q EMG), as well as lateral to medial hamstring activation ratio (LH:MH) in parallel squat, Romanian deadlift, hip thrust, lying leg curl and seated knee extension. The H:Q EMG was greater during lying leg curl compared to other exercises during both the concentric and eccentric phase, however the Romanian deadlift and hip thrust also resulted in relatively high H:Q EMG. Pairwise comparisons revealed that LH:MH was greater in the parallel squat compared to the Romanian deadlift and hip thrust in the concentric phase, and compared to the Romanian deadlift and hip thrust during the eccentric phase. Our data suggests that the lying leg curl promotes the greatest hamstring activation and H:Q EMG, amongst the exercises investigated, while also providing relatively homogenous LH:MH. The lying leg curl should be considered as a primary exercise in rehabilitation and training programmes, aiming to proportionally activate LH:MH and increase H:Q EMG, which may improve knee muscle balance.

Effects of rehabilitation treatments jointly considered by physiatrists and rehabilitation therapists in patients with severe burn injury

Rehabilitation treatments for patients with severe burn injury (SBI) are difficult owing to the lack of knowledge, skills, and experience among clinicians and physical and occupational therapists, resulting in serious patient disability. This study retrospectively evaluated the effectiveness of rehabilitation treatments jointly considered by physiatrists and rehabilitation therapists (Physiatrist and Registered therapist Operating rehabilitation: PROr) for patients with SBI admitted to our hospital's burn intensive care unit (BICU). Eligible patients were classified into the PROr and standard rehabilitation (SR) groups. Contents of the rehabilitation program in the BICU, the functional ambulation categories (FAC), and the Barthel index at the first rehabilitation, BICU discharge, and hospital discharge were collected. Of the 184 patients with severe burns admitted to the BICU, 29 (PROr group, n = 16; SR group, n = 13) met the eligibility criteria. The PROr group received more types of exercise interventions for a longer time than the SR group. No significant differences in the FAC and Barthel index scores at the first time of rehabilitation were found between the two groups; however, the scores of FAC and Barthel index at BICU and hospital discharges were higher in the PROr group than in the SR group. The PROr program may help in the functional improvement of patients with SBI.

Modified Squat Test for Predicting Knee Muscle Strength in Older Adults

BACKGROUND

Methods for evaluating the strength of the knee extensor muscles play a vital role in determining the functionality of the lower limbs and monitoring any alterations that occur over time in older individuals. This study assessed the validity of the Modified Squat Test (MST) in predicting knee extensor muscle strength in older adults.

METHODS

This study included a total of 110 older adults. We collected demographic information such as sex, age, body weight, height, and thigh circumference. Muscle strength was assessed by measuring the maximum voluntary isometric contraction of the knee extensors, and by performing the MST (5 and 10 repetitions) and single-leg standing balance test. Stepwise multiple linear regression analysis was used to investigate multiple factors impacting the prediction of knee extensor strength.

RESULTS

Factors such as age, sex, thigh circumference, performance on the single-leg standing eye-open (SSEO) task, and the time required to complete the 10 MST repetitions together explained 77.8% of the variation in knee extensor muscle strength among older adults. We further developed a predictive equation to calculate strength as follows: strength = 36.78 - 0.24 (age) + 6.16 (sex) + 0.19 (thigh circumference) + 0.05 (SSEO) - 0.54 (time required to complete 10 MST repetitions) ± 5.51 kg.

CONCLUSION

The 10-repetition MST is an invaluable instrument for establishing an equation to accurately predict lower limb muscle strength.

Female Lower Body Muscle Forces: A Musculoskeletal Modeling Comparison of Back Squats, Split Squats and Good Mornings

The aim of this study was to analyze lower leg muscle forces during strength exercises such as back squats, good mornings and split squats, with a particular emphasis on females. By focusing on females, who are more vulnerable to anterior cruciate ligament injuries, we aimed to better understand muscle engagement and its role in injury prevention. Eight participants were monitored during exercises with a barbell load of 25% of body weight and, during the back squat, an additional 50% load. The analysis was conducted using personalized musculoskeletal models, electromyography (EMG) and Vicon motion capture systems to assess various muscle groups, including the m. gluteus maximus and m. gluteus medius, as well as the hamstring and quadriceps muscles. The back squat produced the highest forces for the quadriceps muscles, particularly the rectus femoris (>25 N/kg), as well as in the back leg during the split squat (>15 N/kg). The gluteal muscles were most active during good mornings and in the front leg of the split squat, especially the m. gluteus maximus medial part (>20 N/kg). The hamstrings generated the highest muscle forces in the front leg of the split squat, with the greatest forces observed in the m. semimembranosus. Our research highlights how musculoskeletal modeling helps us to understand the relationship among muscles, joint angles and anterior cruciate ligament injury risks, especially in strength training females. The results emphasize the need for personalized exercise guidance and customized models to make strength training safer and more effective.

Effects of progressive body-weight versus barbell back squat training on strength, hypertrophy and body fat among sedentary young women

The objective of this study was to compare the effects of progressive bodyweight training and barbell back squat on muscle strength, muscluar hypertrophy, and body fat percentage in sedentary young women. Thirteen sedentary young women (aged 19.77 ± 0.83 years, height 164.91 ± 6.01) were randomly assigned to either the progressive bodyweight group (n = 6, consisting of 10 levels of movements progressing from bilateral to unilateral) or the barbell squat group (n = 7, 60-80% 1RM). Both groups underwent two training sessions per week for 6 weeks. Measurements of muscle strength (isokinetic knee extensor and flexor muscle peak torque of each leg), muscle thickness (gluteus maximus, rectus femoris, and gastrocnemius muscles), and body fat percentage were taken at baseline and post-testing. Both groups showed a significant increase in isometric peak torque of the knee extensor and flexor (p < 0.05), but there were no significant between-group differences in isometric peak torque of the knee extensor and flexor (p > 0.05) or in the mean concentric peak torque of the knee H/Q ratio (p > 0.05). Both groups also showed significant increases in muscle thickness (p < 0.05), with no significant differences in Gastrocnemius, Rectus femoris and Gluteus maximus (p > 0.05). The percentage of body fat significantly decreased in the barbell group (pre: 28.66 ± 4.58% vs post: 24.96 ± 5.91%, p = 0.044), but not in the bodyweight group (pre: 24.18 ± 4.63% vs post: 24.02 ± 4.48%, p = 0.679). Our findings indicate that while both training methods increased maximum strength and muscle mass, barbell back squat training may be more effective in reducing body fat percentage.

A Sustainable Swedish School Intervention with Extra Aerobic Exercise—Its Organization and Effects on Physical Fitness and Academic Achievement

A large majority of Swedish children do not reach the recommended daily activity level. Some, but not all, studies show that extra physical activity may have positive effects on children’s school performance, physical fitness and health. The present purpose was to offer pupils from the 7th to the 8th grade extra aerobic exercise led by physical education teachers and to evaluate the effects on aerobic fitness, muscle strength, school grades and health. The hypothesis was that extra aerobic exercise would improve physical fitness, school grades and health. In the two-year project, 122 pupils aged 13–14 years from three schools constituted an aerobic group with 30 min extra exercise sessions (≥70% maximal heart rate) twice weekly. A control group of 26 pupils was included. All 148 pupils also had regular 60 min physical education lessons (2/week). A moderate to large significant effect size (via partial eta-squared) of the interaction effect for the aerobic group compared to the control group over time was generally seen for aerobic fitness, the muscle strength test with push-ups, school grades in Swedish, English and physical education, and in average school grade for four school subjects combined, thus also including mathematics. Within the aerobic group, significant improvements were also shown for aerobic fitness, endurance and strength of abdominal and leg muscles, and the total physical test index during the two-year project. The control group showed no corresponding improvement in these parameters. Improvements in school grades were generally seen among both sexes in the aerobic group, whereas improvements in physical capacity were distinctly more pronounced among boys and seldom among girls. A similar pattern with significant improvement in several school grades was noted in all three intervention schools, although one of the schools had a distinctly larger proportion of children who immigrated to Sweden. The aerobic group showed significantly higher ratings (with a small to moderate effect size) on several questions about physical self-perception than the control group at the end of the 8th grade. This teacher-led school intervention generated a sustainable project with improvements in physical fitness and school grades. The project might act as an inspiration for other schools to increase physical activity to improve physical fitness and possibly school grades.