The Effect of Body Weight Support on Kinetics and Kinematics of a Repetitive Plyometric Task

Abstract

Though essential to athletic performance, the ability to land from a jump often remains limited following injury. While recommended, jump training is difficult to include in rehabilitation programs due to high impact forces. Body weight support (BWS) is frequently used in rehabilitation of gait following neurological and orthopedic injury, and may also allow improved rehabilitation of high-impact tasks. There is a differential effect of BWS on walking and running gaits, and the effect of BWS on movements with relatively large vertical displacement is unknown. The current study evaluates the effect of BWS on a replicable single-leg hopping task. We posited that progressive BWS would decrease limb loading while maintaining the joint kinematics of the task. Twenty-eight participants repetitively hopped on and off a box at each of four BWS levels. Peak vertical ground reaction forces decreased by 22.5% between 0% and 30% BWS (P < .001). Average hip, knee, and ankle internal moments decreased by 0.5 N·m/kg each. Slight kinematic changes across BWS levels were clinically insignificant. The high level of task specificity evidenced by consistent kinematics coupled with a similar reduction of internal moment at each joint suggests that BWS may be a useful strategy for rehabilitation of jumping tasks.

Clinical Efficacy of Jump Training Augmented With Body Weight Support After ACL Reconstruction: A Randomized Controlled Trial

“…For the first 6 weeks, the JTBWS group performed jump training in a custom BWS system described fully in previous work. 13,14 Training was initiated at a BWS level of 30%, wherein a near-constant vertical force equal to 30% of the patient’s body weight was exerted at the center of mass. The level of BWS was decreased by 10% every 2 weeks per tolerance to activity, with associated changes in repetition according to the kinetic effects of BWS on the knee moment in landing.…”

“…The level of BWS was decreased by 10% every 2 weeks per tolerance to activity, with associated changes in repetition according to the kinetic effects of BWS on the knee moment in landing. 13 The final 2 weeks of training were performed without BWS and were essentially the same as the final 2 weeks of training in the JTBW group in terms of both exercises performed and number of repetitions. All other training parameters, such as feedback, reinforcement, attentional focus, practice patterning, and introduction of sport-specificity (eg, dribbling a basketball), progressed over time and similarly between groups, as detailed in previous work.…”

“…8 Through use of body weight support (BWS), the intensity of jump landing tasks can be decreased with minimal effect on normal kinematic and kinetic behaviors, thereby allowing increased repetition of training. 13…”

Kinematics of assisted and unassisted plyometric training of vertical jumping and rebounding in youth male football players – A six-week training study

“…Compensation can also be achieved using buoyancy during water-based plyometrics [31] or from the elastic recoil of a trampoline surface [32], however, these modalities appear to be less commonly utilised. There are multiple potential rationales for incorporating assisted plyometric training into a strength and conditioning programme including to reduce ground reaction force for load-compromised rehabilitating athletes [33], as a potentiating stimulus for bodyweight jumping [34], or to increase movement velocity to serve as a supramaximal 'over-speed' training stimulus [7]. A number of researchers have compared the effects of a period of assisted and unassisted plyometric training on numerous performance measures.…”

“…Despite evidence for the performance adaptations associated with assisted plyometric training, there is a paucity of research on how it may chronically impact on plyometric technique, specifically ankle kinematics. Acutely, body-weight support during a repetitive unilateral hopping task has not been shown to alter lower limb kinematics relative to an unassisted control in a clinically meaningful way [33], however, it is unclear whether this would be the case over a longer period of time where altering kinematics may be desirable. Therefore, the purpose of this study is to compare the kinematics of assisted and unassisted plyometric training of vertical jumping and rebounding activities in youth academy football players following a six-week training intervention.…”