Abstract: BACKGROUND: Aging is becoming increasingly serious. The elderly with skeletal muscle degeneration do not tolerate high intensity exercise, and are easy to fall, resulting in disability or death. How to improve the lower limb muscle strength of the elderly has become a hot research issue.
OBJECTIVE: To provide guidance for daily activities through analyzing the influence of walking step length on lower limb muscle strength of the elderly (> 60 years old), and exploring the appropriate walking style. 
METHODS: Thirty healthy male elderly subjects aged 65-75 years old were randomly selected and their morphological parameters were measured. The skeletal muscle model was established by importing the simulation software Opensim 4.0. Vicon 2.3 three-dimensional motion capture system was used to record the movement track of the subjects’ normal step and large step walking in real time, and the plantar three-dimensional force platform was used to record the ground reaction force on the plantar during walking. The motion data of the subjects were imported into Opensim 4.0 software to establish the movement model, and the dynamic simulation was carried out. The effectiveness of the method was verified by the data of plantar dynamometer. Muscle strength changes of ilium, rectus femoris, psoas major, gluteus maximus, gluteus medius, biceps femoris, adductor magnus and medial femoral muscle were analyzed during walking with different step lengths in the elderly. The muscle strength data of two different pace walks of each subject were imported into SPSS 20.0 for statistical analysis, and paired t-test was performed.  
RESULTS AND CONCLUSION: (1) By establishing the skeletal muscle model of the subjects and the movement model of walking with different steps, the muscle strength curves of the important muscles of the lower limbs in the process of walking with different steps were derived. (2) Through statistical analysis, there were significant differences in the muscle strength of walking with different paces (P > 0.05). (3) The change rules of step length and lower limb muscle strength were summarized: within a certain range, with the increase of step length, the muscle strength of rectus femoris, medial femoris and semitendinosus increased significantly, while the muscle strength of ilium, psoas maximus, gluteus maximus, gluteus medius and adductor magnus increased slightly. (4) It is shown that walking with increased step length can improve lower limb muscle strength and can provide a theoretical basis for the elderly to choose correct walking style, rehabilitation training and exercise prescription development.  

Key words: step length, muscle strength, motion capture, simulation, daily exercise