Human movement science
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Human movement science · Aug 2017
Local dynamic stability of the spine and its coordinated lower joints during repetitive Lifting: Effects of fatigue and chronic low back pain.
The nonlinear Lyapunov exponent (LyE) has been proven effective for evaluating the local stability of human movement and exploring the effects of load, speed and direction of individuals with and without nonspecific chronic low back pain (CLBP). The purpose of this study was to examine spinal and lower joint stability and response to fatigue of individuals with and without CLBP while performing lifting-lowering movements. Fourteen healthy individuals and 14 patients with nonspecific CLBP were recruited to perform lifting movement repeatedly while holding two equally-sized dumbbells in their hands. ⋯ Patients with CLBP showed more stable hip movement on the frontal and transverse planes (p<0.05). These results suggested that lifting/progressive fatigue could increase the risk of injury to the spine and hip. These findings indicate that patients with CLBP applied different control strategies for the hip; thus, spinal control stability should be evaluated together with the stability of the lower joints.
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Human movement science · Aug 2017
Asymmetrical stabilization and mobilization exploited during static single leg stance and goal directed kicking.
The motor control properties of the right and left legs are dependent on the stabilization and mobilization features of the motor tasks. The current investigation examined the right and left leg control differences - interlateral asymmetries - during static single leg stance and dynamic goal directed kicking with an emphasis of the asymmetrical stabilization and mobilization components of movements. Ten young, healthy, right-leg preferred individuals with minimal kicking experience completed both tests on each limb. ⋯ For mobilization control, the left kicking leg showed greater JROM displacements at the distal (knee and ankle) joints and reduced JROM primarily with hip frontal plane movements compared to the right kicking leg. The reported interlateral asymmetries during kicking may reflect a behavioral adaptation that results in differential stabilization between the right and left legs. Overall, the findings suggest that novel tasks, such as dynamic goal directed kicking, appear to be more sensitive than static balance in identifying interlateral asymmetries.
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Human movement science · Aug 2017
Effects of gait speed on the body's center of mass motion relative to the center of pressure during over-ground walking.
Preferred walking speed (PWS) reflects the integrated performance of the relevant physiological sub-systems, including energy expenditure. It remains unclear whether the PWS during over-ground walking is chosen to optimize one's balance control because studies on the effects of speed on the body's balance control have been limited. The current study aimed to bridge the gap by quantifying the effects of the walking speed on the body's center of mass (COM) motion relative to the center of pressure (COP) in terms of the changes and directness of the COM-COP inclination angle (IA) and its rate of change (RCIA). ⋯ Significant quadratic trends (p<0.05) with highest directness at PWS were found in IA during single-limb support, and in RCIA during single-limb and double-limb support. The results suggest that walking at PWS corresponded to the COM-COP control maximizing the directness of the RCIAs over the gait cycle, a compromise between the effects of walking speed and the speed of weight transfer. The data of IA and RCIA at PWS may be used in future assessment of balance control ability in people with different levels of balance impairments.