Research On The Characteristics Of Lower Limb Muscles During The First Stance Phase In Sprinting Based On OpenSim

The sprint competition is one of the most entertaining competitions in track and field competitions.Humans constantly surpass themselves and create history on the 100-meter runway.The sprint acceleration phase is one of the important factors influencing the 100-meter performance.And the first stance phase after the start is a key step,which is related to the follow-up performance of the entire 100-meter run.Most previous studies on sprint acceleration used traditional kinematics and dynamics methods to measure and analyze the effects of body posture and external force on athletic performance.Nowadays,the development and maturity of dynamic simulation can contribute to deeply study the relationship between muscle function and sport performance,and provide a new opportunity for studying the characteristics of motion of human musculoskeletal system.Therefore,this study aims to applying dynamic simulation to explore the muscle function of the lower limbs during the first stance phase to understand the relationship between muscle function and sport performance,and to provide the theoretical support for determining the technical points during the first stance phase.The kinematics,ground reaction forces and surface electromyography data of two Chinese well-trained sprinters(subject A and B)were collected during the first stance in sprinting.The kinematics and ground reaction forces were filtered using a 4th-order Butterworth low-pass filter with cutoff frequencies of 12 Hz and 60 Hz,respectively.The surface electromyography data was filtered(10-400 Hz)using a 4th-order Butterworth bandpass filter followed by rectification.The dynamic simulation software OpenSim3.3 was used to establish a three-dimensional musculoskeletal model with 22 segments.Muscle forces of lower limbs were calculated by static optimization method,and muscle length,muscle contraction rate,muscle power and muscle work were calculated.In the first stance phase,the hip and knee joints of the stance leg continue to extend throughout the stance period.The ankle joint is dorsiflexion at the initial stage,and remained stable in the middle stage,and rapidly changed from dorsiflexion to plantar flexion at the end of stance.The hip joint of the swing leg mainly performs the flexion motion.The knee joint performs flexion at the initial stage and remains stable in the middle stage.The ankle joint performs a slower dorsiflexion.The gluteus maximus continue to generate great centripetal force and maintains a stable power output,producing energy.The quadriceps contract centripetally throughout the whole phase,producing tremendous muscle strength and energy.The triceps surae continue to generate centrifugal force in the early stage of stance,doing negative work and absorbing energy.The iliopsoas of the swing leg continue to generate centripetal force and energy.The gluteus maximus and hamstring muscles mainly do negative work,absorbing energy.The ankle joint flexor and extensor muscles do less work.For the first stance phase,the gluteus maximus,quadriceps and triceps surae of the stance leg are the main muscle groups that support and propel the body.The iliopsoas muscle of the swing leg is the main muscle group that drives the lower limbs forward.In the pre-and early-stance phases,the hip joints are affected by not only the hip muscles but also the knee muscles.Since the hamstring muscle of the swing leg generates great centrifugal force,there is a high risk of injury.In the early stance,the ankle joint relies mainly on the triceps surae to produce powerful muscle strength to support the body.Athletes should pay attention to develop muscle strength of the gluteus maximus,quadriceps femoris and triceps surae in training.Meanwhile,athletes should control their body postures to prevent the center of mass being lifted earlier.Researchers could give insight to the relationship of exercise performance and motion technique and muscle function by establishing dynamic simulations,furthermore,proposing a more scientific training program to improve the athlete's movement skills and athletic performance.