This study examined lower extremity joint kinematics in individuals with chronic ankle instability (CAI) and controls during unanticipated and anticipated single-leg drop landings onto a laterally inclined platform. Physically active adults with CAI 15 (n = 15) and controls (n = 15) performed an unanticipated and anticipated 30 cm single-leg drop landing onto a 20° laterally inclined platform. Three-dimensional ankle, knee and hip-joint kinematics were recorded 200 ms pre- to 200 post-landing and analysed with a 2 (group) × 2 (landing condition) SPM ANOVA (p < 0.05). Results revealed individuals with CAI displayed significantly greater ankle internal rotation post-landing across both landing conditions. Anticipated landings elicited significantly greater pre-landing ankle inversion and external rotation, knee abduction and hip adduction. Additionally, significantly less ankle inversion, knee and hip flexion, and knee adduction and hip abduction were present during post-landing of the anticipated landing. Greater ankle internal rotation during landing may contribute to the ankle ‘giving way’ in individuals with CAI. However, preparatory and reactive proximal-joint kinematics were similar in both groups during landing. This highlights the possible role of the knee and hip joints in assisting with ankle-joint stability during anticipated inversion perturbations.

Background: An induced loss of balance resulting from a postural perturbation has been reported as the primary source for postural instability leading to falls. Hence; early detection of postural instability with novel wearable sensor-based measures may aid in reducing falls and fall-related injuries. The purpose of the study was to validate the use of a stretchable soft robotic sensor (SRS) to detect ankle joint kinematics during both unexpected and expected slip and trip perturbations. Methods: Ten participants (age: 23.7 ± 3.13 years; height: 170.47 ± 8.21 cm; mass: 82.86 ± 23.4 kg) experienced a counterbalanced exposure of an unexpected slip, an unexpected trip, an expected slip, and an expected trip using treadmill perturbations. Ankle joint kinematics for dorsiflexion and plantarflexion were quantified using three-dimensional (3D) motion capture through changes in ankle joint range of motion and using the SRS through changes in capacitance when stretched due to ankle movements during the perturbations. Results: A greater R-squared and lower root mean square error in the linear regression model was observed in comparing ankle joint kinematics data from motion capture with stretch sensors. Conclusions: Results from the study demonstrated that 71.25% of the trials exhibited a minimal error of less than 4.0 degrees difference from the motion capture system and a greater than 0.60 R-squared value in the linear model; suggesting a moderate to high accuracy and minimal errors in comparing SRS to a motion capture system. Findings indicate that the stretch sensors could be a feasible option in detecting ankle joint kinematics during slips and trips.

In order to successfully hit a baseball, hitters must utilize a series of preparatory movements (swing phases) which include shifting their body weight, stepping, landing, and swinging. The purpose of this study was to examine the differences between start times for swing phases (shifting, stepping, landing, and swinging)for currently active baseball players. Participants ( n = 12) were all current collegiate baseball athletes. Retroreflective markers, surface electromyography (EMG) and two force platforms were utilized to complete a swing analysis. Each participant completed five swinging trials off a tee. All dependent variables were compared using a repeated measures 1×4 ANOVA with LSD post hoc comparison ( p < 0.05) if necessary. The results demonstrated that the participants started the swing phases in a statistically significant sequence of shifting, stepping, landing, and swinging. The ability of the athletes to start the swing phases in this sequential order may be advantageous to regulate spatial parameters of their swing and provide more time to generate power. These results allow for coaches to better understand how to instruct their athletes to be successful at the plate.

BACKGROUND: This study quantified the peak vertical ground reaction force (VGRF), impulse, and average and instantaneous loading rates developed during bilateral plyometric exercises. METHODS: Fourteen collegiate male athletes performed 4 different bilateral plyometric exercises within a single testing session. Depth jumps from thirty, 60 and 90 centimeter heights (DJ30, DJ60, and DJ90, respectively), and a 2 consecutive jump exercise (2CJ), were randomly performed. The subjects landed on and propelled themselves off two force platforms embedded into the floor. The stance phase of each plyometric movement was analyzed for vertical force characteristics. The dependent variables were normalized to body weight. One-way repeated-measures ANOVA revealed significant differences between exercises (P <= 0.05). RESULTS: For VGRF, only the DJ60 and 2CJ exercises were not different from each other. The impulses between DJ60 and DJ90, and DJ30 and 2CJ, were not different. All exercises were different from each other in regards to average and instantaneous loading rate except for DJ30 vs. DJ60, and DJ90 vs. 2CJ. The DJ90 condition reported the highest peak VGRF by approaching five times body weight. The 2CJ condition had similar impulse and loading rates as the DJ90 condition. CONCLUSIONS: A proper progression and detailed program planning should be utilized when implementing plyometric exercises due to their different impact kinetics and how they might influence the body upon ground contact.