Medial-lateral Ground Reaction Force Research Articles

Consideration of Gender Differences in Ankle Stabilizer Selection for Half-Squat Parachute Landing

Chinese paratroopers have traditionally performed the half-squat parachute landing (HSPL), which was different from the well-known parachute landing fall. During HSPL, ankle biomechanics have been shown to vary greatly between genders. Therefore, it is necessary to consider gender with regard to the design of ankle stabilizers for paratroopers. Eight male and eight female healthy participants landed from platforms under three ankle conditions based on different stabilizer rigidity levels (barefoot control, elastic tape, and semi-rigid brace). Multivariate analysis of variance was used to analyze the effects and interactions of ankle stabilizer, gender, and dropping height on the ground reaction forces (GRF), ankle kinematics, and the shank surface electromyogram (EMG). Compared to men, women had significantly higher peak medial-lateral GRF when they were equipped with stabilizers (tape: men 0.521 vs. women 0.856 bodyweight; brace: men 0.531 vs. 0.935 bodyweight), except when barefoot. Both stabilizers significantly decreased all peak angular displacements, but no significant interaction was detected between gender and stabilizer rigidity in ankle kinematics. Compared to barefoot, the semi-rigid brace significantly increased male pre-landing EMG amplitude of the tibialis anterior from 218 to 525 microV and post-landing EMG amplitude of the lateral gastrocnemius from 323 to 910 microV, but no corresponding change took place in women. The semi-rigid stabilizer was helpful for men in increasing shank muscle activities. Increased stabilizer rigidity had little influence on the muscle activities of women and this could contribute to greater injury risk in women during HSPL.

Ground reaction forces and kinematics of plant leg position during instep kicking in male and female collegiate soccer players

The players' ability to achieve the greatest distance in kicking is determined by their efficiency in transferring kinetic energy from the body to the ball. The purpose of this study was to compare the kinetics and kinematics of the plant leg position between male and female collegiate soccer players during instep kicking. Twenty-three soccer players (11 males and 12 females) were filmed in both the sagittal and posterior views while performing a maximal instep kick. Plant leg kinetic data were also collected using an AMTI 1000 force platform. There were no significant differences between the sexes in plant leg position, but females had significantly greater trunk lean, plant leg angle, and medial-lateral ground reaction force than the males. Males showed higher vertical ground reaction forces at ball contact, but there were no significant differences in ball speed at take-off between the sexes. Ball speed at take-off was inversely related to peak anterior–posterior ground reaction force ( − 0.65). The anatomical differences between the sexes were reflected in greater trunk lean and lower leg angle in the females.

태권도 주춤 서 몸통지르기 유형별 생체역학적 변인 비교 분석

The purpose of this study is to compare 4 different body punch types(type 1: a punch using a shoulder, type 2: a punch using a waist, type 3: a punch using lower extremities, and type 4: a punch with elbows by your side at chest level) in horseback-riding stance and establish suitable teaching theory and method, which would be a useful reference to Taekwondo instructors on the spot(in Taekwondo dojangs all around Korea). Five exhibition players from Korean national Taekwondo exhibition team participated in this study. Each participant was asked to perform the four different types of punches and their kinematic and kinetic data were recorded with 7 vicon cameras(125Hz) and two force plates(AMTI, 1200Hz). We analyzed displacement, time, resultant center of body mass trajectory, velocity, trunk angular velocity, and ground reaction force(GRF) from each body segment in body punch and the result. I performed 1-way ANOVA(RM) for average values of each player after standardization and statistical significance was set as p<.05. was as the following ; First, they showed a tendency to take the body punch posture with the biggest motion at a shoulder and on descending order a waist and a knee. Second, a mean time for each body punch on ascending order 0.46sec. for type 2, 0.49sec for type 3, 0.50sec. for type 4, and 0.56sec. for type 1. Third, a mean resultant center of body mass trajectory for each body punch the longest 4.07cm for type 3 and the shortest 2.458cm for type 1. Fourth, a mean of maximal velocity of a fist strike was the fastest 5.99m/s for type 3, 5.93m/s for type 4, 5.67m/s for type 2, and 5.01m/s for type 1 on the descending order. Fifth, a mean of maximal trunk angular velocity of the fastest 495.6deg./sec. for type 4 and 337.7deg./sec. for type 1 on the descending order. Sixth, strongest value was type 3, 2 for anterior-posterior ground reaction force(left -54.89N, right 60.58N), type 4 for medial-lateral GRF(left 83.59N, right -80.12N), and type 3 for vertical GRF(left 341.79N, right 426.11N).

The effect of an inclined landing surface on biomechanical variables during a jumping task

Professional dancers sustain a high number of injuries. Epidemiological studies have suggested that performing on inclined "raked" stages increases the likelihood of injury. However, no studies have examined if biomechanical differences exist between inclined and flat surfaces during functional tasks, such as landing from a jump. Such differences may provide a biomechanical rationale for differences in injury risk for raked stages. Eight professional dancers performed drop jumps from a 40cm platform on flat and inclined surfaces while forces, lower extremity kinematics, and electromyographic activity were collected in a controlled laboratory environment. Dancers landed on the laterally inclined surface with significantly higher knee valgus (4 degrees ), peak knee flexion (9 degrees ), and medial-lateral ground reaction force (GRF) (13.4% body weight) compared to the flat condition. The posterior GRF was higher in the anterior inclined condition compared to the flat condition. In the anterior inclined condition, subjects landed with 1.4 degrees higher knee valgus, 4 degrees more plantarflexion at initial contact, and 3 degrees less dorsiflexion at the end of landing. Biomechanical variables that have been suggested to contribute to injury in previous studies are increased in the inclined floor conditions. These findings provide a preliminary biomechanical rationale for differences in injury rates found in observational studies of raked stages.

Simulation models of human vertical jumping: case settled?

Professional dancers sustain a high number of injuries. Epidemiological studies have suggested that performing on inclined “raked” stages increases the likelihood of injury. However, no studies have examined if biomechanical differences exist between inclined and flat surfaces during functional tasks, such as landing from a jump. Such differences may provide a biomechanical rationale for differences in injury risk for raked stages.Eight professional dancers performed drop jumps from a 40 cm platform on flat and inclined surfaces while forces, lower extremity kinematics, and electromyographic activity were collected in a controlled laboratory environment.Dancers landed on the laterally inclined surface with significantly higher knee valgus (4°), peak knee flexion (9°), and medial–lateral ground reaction force (GRF) (13.4% body weight) compared to the flat condition. The posterior GRF was higher in the anterior inclined condition compared to the flat condition. In the anterior inclined condition, subjects landed with 1.4° higher knee valgus, 4° more plantarflexion at initial contact, and 3° less dorsiflexion at the end of landing.Biomechanical variables that have been suggested to contribute to injury in previous studies are increased in the inclined floor conditions. These findings provide a preliminary biomechanical rationale for differences in injury rates found in observational studies of raked stages.