Reduced muscle strength can affect daily activities, so monitoring is essential. Methods such as isokinetic dynamometers assess maximum muscle force, while hand dynamometers measure hand grip strength. Research has investigated hand grip strength as a predictor of upper, lower and total strength, but the results remain unsystematic. The aim of this study was to systematize the current state of knowledge to test whether hand grip strength can be used as an indicator of overall strength and functional performance. A review of studies from 2000 to 2023 was conducted using: ScienceDirect, PubMed and GoogleScholar. The focus was on articles that examined the relationship between hand grip strength and muscle torque. The following keywords, entered in different configurations, were used in the search: ’hand grip’, ’muscle strength’, ’correlation’ and ’association’. A total of 22 studies were selected for analysis, involving 752 healthy adults, 30 physically active people, 120 ill adults, 2965 older people and 112 ill older people. The analysis looked at associations between hand grip strength and muscle moments of the trunk, limbs and knee joint. The results from the literature indicate that the value of the correlation between hand grip strength and muscle torque varies (from low to high) depending on the test method or group. Therefore, caution should be exercised when using hand grip strength as the sole measure of overall strength and functional performance.

The work aimed to assess the functioning of the musculoskeletal system within the lumbar spine in relation to everyday postures of sitting and standing. The comparative analysis was based both on experimental tests and computer simulations performed in the AnyBody Modeling System environment. Input data used to prepare models were based on the information obtained in experimental tests. The test participants were tasked with adopting two postures: 1) standing position and 2) sitting position. Kinematics measurements were performed using the Zebris ultrasonic system. During sitting position, the tests additionally involved the use of a dynamometric platform measuring reaction forces occurring between buttocks and the seat. The comparative analysis included measurements of the trunk inclination angle and the pelvic inclination angle as well as results of computer simulations. The sitting posture is responsible for increased trunk inclination and a change in the position of the pelvis. In terms of the sitting position, it was possible to observe an increase in the loads affecting individual intervertebral joints of the lumbar spine by 155-184% in comparison with the standing posture (100%). Simulations revealed an increased muscle activity of the erector spinae, abdominal internal oblique muscles and abdominal external oblique muscles. Adopting a sitting position increases the loads on the lumbar spine and increases the activity of the erector spinae and abdominal muscles compared to the standing position, which is caused by change in the position of the pelvis and the curvature of the lumbar region.

Background/Objectives: Sarcopenia is the progressive loss of muscle mass, strength, and/or function, leading to reduced physical performance, independence, and social participation. This study aimed to analyze the effects of age-related muscle strength loss and sarcopenia on muscle function during standing in older females. Methods: This study included experimental and modeling analyses using the AnyBody Modeling System in 20 older females. Based on DEXA results, participants were divided into older females without sarcopenia (OF) and with sarcopenia (OFS). Body posture while standing was assessed using the Zebris APGMS Pointer system. A model of muscular strength changes due to natural aging and progressive sarcopenia was developed based on literature data. The experimental results informed model studies in the AnyBody Modeling System, which incorporated changes in body posture and loss of muscle strength. Results: Total muscle activity during standing increases with age; however, this increase is significantly more pronounced in individuals with sarcopenia, especially after the age of 65. At 65, total muscle activity was 15% higher in the OFS model than in the OF model, while the difference was 44% at 80. After age 65, muscle fatigue increased considerably with progressive sarcopenia. At age 80, muscle fatigue while standing with sarcopenia can be more than three times higher than in those without sarcopenia. Conclusions: Aging leads to increased muscle activity while standing, and sarcopenia further amplifies this effect, particularly in individuals over 65. Modeling results highlight the pronounced impact of sarcopenia on muscle fatigue, demonstrating its significant functional consequences in older females.

The increasing prevalence of adult obesity is a major global health problem. Causes include sedentary lifestyles and physical inactivity, as well as the place and style of work. This work aimed to assess the impact of an increase in BMI, resulting from a sedentary lifestyle, on the functioning of the human musculoskeletal system during daily activities. Standing and sitting down were analyzed using numerical simulations in the AnyBody Modeling System. The results showed that by 2050, an increase in body weight will lead to an 11% increase in lumbar spine loads and up to 14% increase in knee and hip joint loads compared to 2015. Increased body weight will also increase muscle fatigue, requiring the body to exert more force to perform the same activities. The BMI change prediction model shows that the average man will be overweight or obese in the coming years, which will likely increase musculoskeletal loads.

BACKGROUND: Correct body weight is one of the factors that allows you to maintain a properly functioning body. Abnormal body weight can cause muscle tissue remodelling, affecting activity and muscle fatigue. Changes in the muscular system can cause occurrence of functional limitations. OBJECTIVE: To determine the effect of weight change on fatigue and activity of the muscular system during daily activities. METHODS: The evaluation of musculoskeletal functioning was based on the results of computer simulations conducted in the AnyBody Modeling System. The following activities were analysed: standing, sitting down and getting up from a chair, holding and lifting an object, and walking. The simulations of the activities were carried out using averaged kinematic data, and by changing body mass in the range of 50 kg to 100 kg by increments of 2 kg, to map different nutritional status from excessive thinness to extreme obesity. Identification of loads in the musculoskeletal system was based on solving an inverse dynamics problem and then the estimation of muscle force values using static optimization. The simulation results allowed to determine the value of muscle fatigue and the level of muscle activity. RESULTS: For activities (i.e., standing, walking, sitting down and getting up from a chair) it was observed that the value of muscle fatigue increases with increasing body mass. However, for activities that cause more load on the musculoskeletal system, i.e. lifting and holding an object, the highest value of muscle fatigue was observed in underweight individuals. CONCLUSION: The change in body weight alters the functioning of the muscular system and thus the ability to perform activities. It was shown that in case of underweight, overweight or obese people, abnormal body weight can be the reason for occurrence of difficulties in performing the activities of lifting and holding a 20 kg object, as well as walking.

Pregnancy induces numerous modifications in the musculoskeletal system of the female body. Since one of the essential roles of the lumbopelvic structure is to support mechanical loads in the upright position, this study was designed to simulate the response of this complex to the growing foetus in pregnant women. The authors hypothesized that posture (i.e., lordosis and muscle involvement) under pregnancy conditions might be adjusted to minimize the demands of the obstetrical load. The analysis of the load on the musculoskeletal system during gestation was made based on numerical simulations carried out in the AnyBody Modeling System. The pregnancy-related adjustments such as increased pelvic anteversion and increased lumbar lordosis enhance the reduction of muscle activation (e.g., erector spinae, transversus abdominis or iliopsoas), muscle fatigue and spinal load (reaction force). The results may help develop antenatal exercise programs targeting core strength and pelvic stability.