Exploring the impact of body mass change on fatigue and activity of the muscular system during daily routine.

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.

Effect of strengthening and weakening of abdominal and dorsal muscles on lumbar spine loads in parents of disabled children.

Pain in the lower part of the back is one of the most common chronic illnesses globally. This work aimed to determine the impact of the reinforcement of particular groups of abdominal and dorsal muscles on the loads exerted on the lumbar section of the spine in 30 mothers of children with motor disabilities. An optical Ariel Performance Analysis System recorded and processed the kinematics data of everyday activities. Tests investigating the effects of the strengthening or weakening of abdominal and dorsal muscles on loading in the lumbar section of the spine utilized the AnyBody Modelling System. Input data for the simulations included mean values of body positions, while the effects of strengthening or weakening of muscles were simulated in the muscle forces model by introducing different values for muscle physiological cross-sectional area (PCSA). Simulations used decreasing or increasing PCSA values of abdominal muscles and the erector spinae. The analysis involved component and resultant force values on the lumbosacral joint (L5-S1) of the spine and intra-abdominal pressure values. The highest reduction of the resultant reaction value in L5-S1 was observed in the simulations that increased the PCSA of the transverse abdominal (TrA). Indeed, a double increase in the TrA cross-section caused a reduction of the resultant reaction in L5-S1 by 30% and the anterior-posterior and proximal-distal forces by approximately 20-30%. Increased PCSA of the erector spinae exerted higher loads on the spine. These results indicate that strengthening weakened abdominal muscles, particularly TrA, in parents of children with motor disabilities reduces lower spinal loads during daily activities.

A sitting or standing position - which one exerts more loads on the musculoskeletal system of the lumbar spine? Comparative tests based on the methods of mathematical modelling.

PURPOSE: The work aimed to assess the functioning of the musculoskeletal system within the lumbar spine in relation to everyday postures of sitting and standing. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Gait Kinematics Index, Global Symmetry Index and Gait Deviations Profile: Concept of a new comprehensive method of gait pathology evaluation.

PURPOSE: The objective of the work was to define a new comprehensive method of evaluating gait pathology (Gait Kinematics Index, Global Symmetry Index and Gait Deviations Profile). METHODS: The article presents in detail a mathematical algorithm of a new comprehensive method of evaluating gait pathology. Input data for the algorithm are the kinematic parameters of gait. The method is based on the determination of the following parameters: standardized angular variables (Wji), kinematic indicators of gait (KIj), gait cycle indicators (GCIi), Gait Kinematic Index (GKI), Gait Deviations Profile (GDP, GDPj), Global Symmetry Index (GSI) and Symmetry Indices (SIj) for kinematic gait values. The algorithm is based on the determination of the difference between results obtained in relation to the kinematics of movement of a given patient and the average value obtained in relation to the standard in each percentage of a gait cycle. The proposed method was tested using results obtained for 59 healthy persons and one patient with locomotor function disorder. RESULTS: The GKI values for the reference group amounted to 0.89 ± 0.23. Information which can be obtained using the proposed gait assessment method was presented using an example of a patient with the disorder of locomotor functions. Areas of gait deviations, which were identified on the basis of the determined indicators, were presented in a graphic form using GDP. CONCLUSIONS: The new gait assessment method makes it possible to identify gait using a single numerical value, evaluate movements in individual joints and in subsequent moments as well as to assess the symmetry of gait.

The effect of the pelvis position in the sagittal plane on loads in the human musculoskeletal system.

PURPOSE: The research work aimed to perform the mathematical modelling-based assessment concerning the effect of the position of the pelvis in the sagittal plane on loads present in the musculoskeletal system in the standing position. METHODS: The analysis of the effect of various positions of the pelvis was performed using the Free Posture Model in the AnyBody Modeling System software. Simulated positions involving various values of pelvis inclination ranged from the extreme pelvic retroposition (-7°) through normative values (0-23°) to the extreme pelvic anteversion (33°). RESULTS: The lowest resultant reaction forces in the intervertebral joints recorded for an angle of inclination restricted within the range of 9-27° and segment L5-S1 amounted to less than 0.7 BW. A change in the pelvic inclination from the normative values towards retroposition or anteversion resulted in the increased muscular activity of the erector spinae, transverse abdominal muscles as well as internal and external oblique muscles. Regarding the lower limbs, changes in the activity were observed in the biceps femoris muscle, iliac muscle, gluteus minimus, gluteus medius and the gluteus maximus. CONCLUSION: The results obtained in the research-related tests confirmed that the pelvic inclination affects loads present in the musculoskeletal system. The abovenamed results will be used to develop therapeutic exercises aimed to reduce loads present in the musculoskeletal system. The aforesaid exercises will be used to teach participants how to properly position their pelvis and how to activate individual groups of muscles.