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This study quantified vertical ground reaction forces (vGRFs) and lower limb stiffness for both sexes walking and running with body-borne load over 2 surfaces. Nine males and 9 females had lower limb biomechanics quantified during a walk (1.3 m/s) and run (4.5 m/s) with (15 kg) and without (0 kg) body-borne load over a firm and soft foam surface. vGRF measures, and leg and lower limb joint stiffness were submitted to a linear mixed model. Loaded walking increased very GRF and stiffness measure (all: P < .016). Loaded running increased every GRF measure and knee stiffness (all: P < .033). The foam surface increased peak vGRF (P = .002, P = .010) and knee stiffness (P < .001, P = .004) during the walk and run, and leg (P < .001) and ankle (P = .025) stiffness during the run. Males walked with greater peak vGRF (P = .012), and stiffer hip and ankle (P = .026; P = .012), but ran with a stiffer knee on the foam (P = .041) and stiffer hip on the firm (P = .005) surface than females. Loaded walking and running may elevate injury risk by increasing vertical GRFs and lower limb stiffness. Injury risk may also increase for locomotion over a foam surface, especially for males.

The review is based on theoretical advances in the field of motor control that view the neural control of movements as a subfield of natural science. We accept the theory of hierarchical control of movements with basic commands, reciprocal, and coactivation, at different levels of the hierarchy, from the control of whole-body actions to the control of individual joints and digits. The principle of abundance views the numerous elements participating in all actions as an important feature that allows movements to combine dynamical stability with adaptability. This principle is readily compatible with the uncontrolled manifold hypothesis. These concepts have been applied to analysis of consequences of fatigue, natural aging, and a range of neurological disorders, from large-fiber peripheral neuropathy to brain disorders. Mechanisms of rehabilitation of movement disorders and improvement of motor performance are discussed. Important pieces of information are missing in the described theoretical frameworks in particular those related to mapping between the theoretical levels of control and coordination and neurophysiological circuitry. New directions of studies are sketched that may lead to progress in understanding applied aspects of motor control.

Plantar fascia (PF) thickness and stiffness have been linked diagnostically to plantar fasciitis. Acute changes to these properties in response to submaximal running have been noted but not yet tested in maximal effort bouts. This study assessed the acute effects of high-intensity interval running on PF thickness and stiffness in healthy adults. Sixteen participants completed 5 maximal effort 400-m sprints with a 1:1 work-to-rest ratio, followed by additional maximal effort trials until fatigue. Thickness and stiffness at the calcaneal origin were measured prerun, postrun, and 30 minutes postrun via ultrasonography and shear wave elastography, respectively. PF thickness and stiffness did not differ between right and left foot (P > .05) and between males and females (P = .067). Thickness and stiffness decreased postrun (0.43 mm, P < .001; 1.54 m·s⁻¹, P < .001) and increased 30 minutes postrun (0.28 mm, P < .002; 1.0 m·s⁻¹, P < .001). No significant difference was found between prerun and 30 minutes postrun thickness (P = .134), but prerun stiffness was higher than 30 minutes postrun (P = .031). These findings indicate that although high-intensity interval running altered both PF thickness and stiffness, 30 minutes of rest allowed some level of recovery in the noninjured PF tissue.

Proximal control and lower extremity (LE) movement related to foot function may be an important factor for plantar fasciitis (PF) during running. This study aimed to investigate hip muscle activity and frontal plane LE kinematics during running between long-distance runners with and without PF. The electromyographic amplitude of the hip muscles (tensor fascia latae, gluteus medius, gluteus maximus) and frontal plane LE joint angles (ankle, knee, and hip range of motion during stance phase) of 30 habitually shod long-distance runners (15 with acute PF and 15 healthy controls) were simultaneously recorded using surface electromyography, 8 infrared cameras, and force plates while they ran barefoot at a speed of 3 to 3.67 m·s⁻¹. Independent t test and 2-way analysis of variance were used to analyze the differences for dependent variables. The PF group had significantly lower tensor fascia latae (P = .040, effect size = 0.259) and gluteus medius (P = .014, effect size = 0.197) activation during the swing phase and gluteus maximus (P = .012, effect size = 0.207) activation during the stance phase compared with the control group. Moreover, the PF group showed significantly greater joint angular excursions of the contralateral pelvic drop (P = .049, effect size = 0.75), hip adduction (P = .019, effect size = 0.91), knee abduction (P = .040, effect size = 0.79), and rearfoot eversion (P = .004, effect size = 1.14) during the stance phase than the control group. Adding assessment of hip muscle activity and LE joint angles during running would be beneficial for evaluating runners with PF.

The capacity to execute vertical jumps is an important motor skill that constitutes a basic requirement not only for many athletic activities but also for coping with everyday demands. As a relatively complex motor pattern, jumping develops considerably during the preschool years. Interestingly, the available literature on prerequisites for the vertical jump to develop is scarce, with only a few studies investigating the role of foot development in children’s changing jumping skills. The present study aims to shed light on the role of foot development in vertical jumping skills of preschoolers. The assessment of relevant aspects of motor development in a group of 463 children at four annual measurement points (mean age at first measurement, t1: 3.49 ± 0.26 years) provided the basis for the present longitudinal study of toe grip functionality in relation to the capacity to execute vertical jumps. A series of multilevel models were fitted to the data to predict children’s jumping skills as measured by means of a standardized motor development test at each time point. Independent of the influences of age and body mass index, toe grip functionality as a proxy for the strength and fine motor capacities of the toes was demonstrated to be a significant predictor, both longitudinally and concurrently, of children’s jumping skills at each of four measurement points. Establishing toe grip functionality at an early age in childhood as a predictor of children’s later jumping skills paves the way for the design and development of intervention approaches targeting these domains of motor development.

Context: The landing error scoring system (LESS) was developed to screen healthy individuals for anterior cruciate ligament  (ACL) injury risk factors using a jump landing task. The purpose of this study was to evaluate unique landing error components of a modified LESS scoring criteria to determine its clinical utility in patients following ACL reconstruction (ACLR). Design: An observational cross-sectional study design was implemented to determine if each individual error component of the modified LESS provided unique information in an ACLR patient population. Methods: Post-ACLR patients (N = 194 [47.9% female]) completed the LESS 7.91 (1.80) months after surgery. To complete the LESS, patients stood on a 30-cm plyometric box and jumped down to a ground target, at 50% of their height in front of the box, then completed a maximal vertical jump. The LESS was repeated 3 times. Two video cameras positioned 3 m from the landing area at a height of 1 m above the floor (frontal and sagittal) recorded all trials. Video analysis of landing kinematics was performed to determine scores for each error item using the modified LESS. Itemized error scores for each patient were evaluated using an exploratory factor analysis, and factors were retained if eigenvalues were greater than 1. Results: Our exploratory factor analysis yielded 2 factor groupings. The first factor (λ = 1.61) was comprised of 4 biplanar error items (ie, errors that occur in both the frontal and sagittal plane) that evaluated body segment positioning (eg, hip and knee flexion during landing). The second factor (λ = 1.02) was comprised of 2 errors occurring in the frontal plane that evaluated knee valgus and the overall impression of their landing strategy. Conclusions: Reducing the modified LESS errors to 6-items could improve the efficiency and clinical utilization of the LESS in ACLR patients. An abbreviated version of the modified LESS may guide clinicians’ decision making in gauging patients’ readiness to return to play after ACLR.

Context: Chronic ankle instability (CAI) is associated with altered gait mechanics and impaired sensorimotor function (eg, postural control). While corrective exercise programs are known to improve sensorimotor function in those with CAI, their impact on gait-related outcomes remains unclear. Design: A randomized controlled trial was conducted to investigate the effects of a corrective exercise program on gait kinetics and postural control in individuals with CAI. Methods: Seventy recreational and collegiate athletes with CAI (aged 18−35) completed the randomized controlled trial. Participants were recruited from the local sports community and randomly assigned to either a control group (n = 34) or an intervention group (n = 36). The intervention group participated in an 8-week National Academy of Sports Medicine (NASM) corrective exercise program, while the control group received no intervention. The NASM program targets muscle relaxation, lengthening, and activation, and finally, integration into functional movements. Gait kinetics, such as contact time, foot progression angle, and peak plantar forces, as well as postural control, were assessed at baseline and postintervention and submitted to 2-way repeated-measure analysis of variance to evaluate the effects of the intervention. Results: Significant interaction effects were observed for postural control (P < .01) and gait contact time (P = .001), indicating greater improvements in the NASM group compared to the control group. No significant group or interaction effects were observed for specific plantar force distribution regions or other gait outcomes (P > .05). Conclusion: The findings suggest that an 8-week NASM corrective exercise program improves postural control but has limited effects on gait kinetics in individuals with CAI.