Chronic elbow injuries from tumbling in female gymnastics present a serious problem for performers. This research examined how the biomechanical characteristics of impact loading and elbow kinematics and kinetics change as a function of technique selection. Seven international-level female gymnasts performed 10 trials of the round-off from a hurdle step to flic-flac with 'parallel' and 'T-shape' hand positions. Synchronized kinematic (3D-automated motion analysis system; 247 Hz) and kinetic (two force plates; 1,235 Hz) data were collected for each trial. Wilcoxon non-parametric test and effect-size statistics determined differences between the hand positions examined in this study. Significant differences (p < 0.05) and large effect sizes (ES > 0.8) were observed for peak vertical ground reaction force (GRF), anterior-posterior GRF, resultant GRF, loading rates of these forces and elbow joint angles, and internal moments of force in sagittal, transverse, and frontal planes. In conclusion, the T-shape hand position reduces vertical, anterior-posterior, and resultant contact forces and has a decreased loading rate indicating a safer technique for the round-off. Significant differences observed in joint elbow moments highlighted that the T-shape position may prevent overloading of the joint complex and consequently reduce the potential for elbow injury.

BackgroundOver the past thirty years, there has been dramatic increase in incidence of Achilles tendon rupture in the athletic population. The purpose of this study was to compare the lower extremity mechanics of Achilles tendon ruptured runners with healthy controls.MethodsThe participants with a past history of an Achilles tendon repair (n = 11) and healthy control (n = 11) subgroups were matched on sex, age, type of regular physical activity, mass, height, footfall pattern and lateral dominancy. Running kinetics and kinematics of the ankle, knee and hip were recorded using a high-speed motion capture system interfaced with a force platform. Achilles tendon length was measured using ultrasonography. Main outcome measures were lower extremity joint angles and moments during stance phase of running and Achilles tendon lengths.ResultsAthletes from Achilles tendon group had an affected gastro-soleus complex. Athletes with history of Achilles tendon rupture had reduced ankle range of motion during second half of the stance phase of running (Δ7.6°), an overextended knee during initial contact (Δ5.2°) and increased affected knee range of motion (Δ4.4°) during the first half of stance phase on their affected limb compared to the healthy control group. There was a 22% increase in the maximal hip joint moment on contralateral side of the Achilles tendon group compared to the healthy controls.ConclusionThese results suggest a compensation mechanism, relatively extended knee at initial ground contact against the deficit in the muscle-tendon complex of the triceps surae. Overextension during sporting activities may place the knee at risk for further injury. Avoidance of AT lengthening and plantarflexion strength deficit after surgery and during rehabilitation might help to manage AT rupture since these factors may be responsible for altered running kinematics.

The aim of this study was to examine the biomechanical injury risk factors at the wrist, including joint kinetics, kinematics and stiffness in the first and second contact limb for parallel and T-shape round-off (RO) techniques. Seven international-level female gymnasts performed 10 trials of the RO to back-handspring with parallel and T-shape hand positions.Synchronized kinematic (3D motion analysis system; 247 Hz) and kinetic (two force plates; 1235 Hz) data were collected for each trial. A two-way repeated measure ANOVA assessed differences in the kinematic and kinetic parameters between the techniques for each contact limb. The main findings highlighted that in the both RO techniques the second contact limb wrist joint is exposes to higher mechanical loads than the first contact limb demonstrated by increased axial compression force and loading rate. In the parallel technique the second contact limb wrist joint is exposing to higher axial compression load. Differences between wrist joint kinetics highlight that the T-shape technique may potentially lead to reducing these bio-physical loads and consequently protect the second contact limb wrist joint from overload and biological failure. Highlighting the biomechanical risk factors facilitates the process of technique selection making more objective and safe.

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The aim of this study was to determine how elite volleyball players employed the arm swing (AS) to enhance their jump performance. The study assessed how the AS influenced the duration and magnitude of the vertical ground reaction force (VGRF) during the main phases (preparatory, braking and accelerating) of the countermovement vertical jump (CMVJ), the starting position of the body at the beginning of the accelerating phase and the moment when the AS began contributing to increasing the jump height. Eighteen elite volleyball players performed three CMVJs with and without an AS. Kinetics and kinematics data were collected using two Kistler force plates and the C-motion system. The time and force variables were evaluated based on the VGRF, and the position of the body and the trajectory of the arm movement were determined using kinematic analysis. The AS improved the CMVJ by increasing the jump height by 38% relative to jumping without an AS. The AS significantly shortened the braking phase and prolonged the accelerating phase, however, it did not influence the preparatory phase or the overall jump duration. The AS also significantly increased the average force during the accelerating phase as well as the accelerating impulse. The AS upward began at 76% into the overall jump duration. The AS did not influence the body position at the beginning of the accelerating phase. These findings can be used to improve performance of the CMVJ with the AS and in teaching beginning volleyball players proper jumping technique.