Effects of weight gaining to lower limb joint moments: a gender-specific sit-to-stand analysis.

The prevalence of obesity, a worldwide health problem, is increasing. Obesity or overweight has significant effects, especially on lower limb biomechanics. Previous studies have investigated the biomechanical effects of weight gain on the knee and hip joints. These studies have been conducted on different individuals with normal weight and overweight. However, no investigation has been carried out between women and men in terms of weight gain. Females usually gain weight in the gluteal-femoral region, whereas males gain weight in the abdominal region. Due to this difference, it is thought that the effects of weight gain should be examined in a gender-specific manner. In this study, a link-segment model of the lower limb was created. Then the sit-to-stand movement was simulated according to female and male-specific weight gain scenarios. According to these results, weight gain in the abdominal region (men-specific) increases the ankle and knee joint moments more than weight gain in the gluteal-femoral region (women-specific). In obese scenarios for males and females, while the ankle and knee joint moment increases, the hip joint moment decreases. These results would be beneficial for considering biomechanical differences caused by gender-specific weight gain in rehabilitation processes and orthotic and prosthetic designs.

Analysis of maximum joint moment during infant lifting-up motion.

BACKGROUND: Infant care activities can induce musculoskeletal disease. However, little is known about the biomechanical joint load during lifting-up of an infant. OBJECTIVE: The aim of this study was to investigate normalized maximum moment during lifting-up of infant dummies weighing 4.6 kg, 7.6 kg, and 9.8 kg. METHODS: Six healthy young subjects participated in our study. All subjects performed lifting-up activities of dummies to shoulder height with their feet apart and natural postures in their comfortable speed. Three-dimensional reflective marker trajectories and ground reaction forces were used as input to calculate joint moments using a full body musculoskeletal model. Joint moments were normalized by each subject's body mass. Friedman's test was performed to compare mean differences of normalized joint moments for lifting up three dummy weights. RESULTS: Lumbar joint had the greatest normalized joint moment. Lumbar and hip extension moments were significantly increased with dummy weight (P< 0.05). In contrast, knee extension and ankle plantarflexion moment were not significantly affected by dummy weight (P> 0.05). CONCLUSIONS: These results indicate that the lumbar joint plays the most important role in infant lifting-up motion and that the load of lumbar and hip joint should be reduced when lifting a heavier infant. These results could contribute to the development of an effective lifting strategy and an assisting device for lifting an infant.

Inverse dynamics simulation on lower limb responses of badminton athlete under impact loads / 医用生物力学

Objective To analyze the badminton athletes’dynamic responses in their lower limbs under impact loads. Methods A human musculoskeletal model was established based on AnyBody Modeling System software and verified by measuring surface electromyography (EMG). The muscle force, joint force, joint torque of lower limbs during right Front-Court Lunge Step in badminton were studied by inverse dynamic simulation and analysis through Vicon motion capture system and force platform. Results The musculoskeletal model was validated to be effective by EMG. During right Front-Court Lunge Step in badminton，the force peak of the hip and ankle joint in Z direction was larger than that in X and Y direction, and the force peak of the knee joint in X direction was larger than that in Y and Z direction. During buffer period, the hip joint in X, Y, Z direction showed adduction, extension and internal rotation torque, respectively, the knee joint in X, Y, Z direction showed abduction, flexion and external rotation torque, respectively, and the ankle joint in X, Y direction showed varus and plantar flexion torque, respectively. The peak torque of the hip, knee and ankle joint in X direction was significantly larger than that in Y and Z direction. Vastus lateralis, biceps femoris, anterior tibial and medial gastrocnemius played a larger role against the ground reaction, while rectus femoris, semitendinosus, soleus played a relatively smaller role against the ground reaction. Conclusions The established musculoskeletal model in the study can provide a technical platform to analyze athletes’biomechanical properties of lower limbs under impact loads. To avoid sport injuries, more attention should be paid to the effect from ground reaction force load at touchdown instant on hip, knee and ankle joints in anteroposterior and mediolateral direction during footwork similar to Front-Court Lunge Step in badminton, and at the same time, the strength training of vastus lateralis, biceps femoris, anterior tibial and medial gastrocnemius of badminton players should not be ignored during specialized training.