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Rafael Gnat, Agata Dziewońska, Maciej Biały and Martyna Wieczorek

Low back pain constitutes a multidimensional problem of largely unknown origin. One of the recent theories explaining its frequent occurrence includes speculative statements on patterns of central nervous system activity associated with the control of so-called local and global muscles of the lower trunk. The objective of the study was to verify whether there is a difference in the activity of the brain during selective, voluntary contraction of the local and global abdominal muscles as assessed by functional MRI. Twenty healthy subjects participated. An experimental design was applied with repeated measurements of the blood-oxygen-level–dependent signal from the brain during voluntary contraction of the local and global abdominal muscles, performed in random order. Prior to registration, a 2-week training period was introduced, aiming to master the experimental motor tasks. The magnetic resonance imaging (MRI) data were processed using the FMRIB Software Library (Oxford, UK). Brain areas showing significant activations/deactivations were identified and averaged across all participants, and intercondition differential maps were computed. Areas of significant intercondition differences were linked to the corresponding anatomical structures and ascribed to the default mode functional brain network and to the sensorimotor network. Contraction of the local abdominal muscles elicited more pronounced activity of the brain cortex, basal ganglia, and cerebellum. This suggests that motor control of the abdominal musculature consists of two modes of brain activity and that control of the local muscles may be a more challenging task for the brain. Moreover, contraction of the local muscles elicited more distinct deactivation of the default mode network, which may have implications for diagnostics and therapy of low back pain.

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Adam E. Jagodinsky, Rebecca Angles, Christopher Wilburn and Wendi H. Weimar

Current theoretical models suggest that ankle sprain copers exhibit movement adaptations contributing to the avoidance of chronic ankle instability. However, few studies have examined adaptations at the level of biomechanical motor synergies. The purpose was to examine characteristics of the support moment synergy between individuals with chronic ankle instability, copers, and healthy individuals. A total of 48 individuals participated in the study. Lower-extremity kinetics and variability in the moment of force patterns were assessed during the stance phase of walking trials. The copers exhibited reductions in the support moment during the load response and preswing phase compared with the chronic ankle instability group, as well as during the terminal stance and preswing phase compared the healthy group. The copers also exhibited reductions in the hip extensor moment and ankle plantarflexion moment compared with healthy and chronic ankle instability groups during intervals of stance phase. Variability of the support moment and knee moment was greater in the copers compared with the chronic ankle instability group. Dampening of the support moment and select joint moments exhibited by the copers may indicate an adaptive mechanism to mitigate loading perturbations on the previously injured ankle. Heightened motor variability in copers may be indicative of a more adaptable motor synergy compared with individuals with chronic ankle instability.

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Ben Langley, Nick Knight and Stewart C. Morrison

Medial tibial stress syndrome (MTSS) is a common running-related injury. Alterations in movement patterns and movement coordination patterns have been linked to the development of overuse injuries. The aim of this study was to compare transverse plane tibial and frontal plane rearfoot motion and the coordination of these movements between runners with MTSS and healthy controls. A total of 10 recreational runners with MTSS and 10 healthy controls ran at 11 km/h on a treadmill. A 3-camera motion analysis system operating at 200 Hz was used to calculate tibia and rearfoot motion. Stance phase motion patterns were compared between groups using multivariate analysis, specifically, Hotelling T 2 test with statistical parametric mapping. A modified vector coding technique was used to classify the coordination of transverse plane tibial and frontal plane rearfoot motion. The frequency of each coordination pattern displayed by each group was compared using independent samples t tests. Individuals with MTSS displayed significantly (P = .037, d = 1.00) more antiphase coordination (tibial internal rotation with rearfoot inversion) despite no significant (P > .05) differences in stance phase kinematics. The increased antiphase movement may increase the torsional stress placed upon the medial aspect of the tibia, contributing to the development of MTSS.

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Ryan Zerega, Carolyn Killelea, Justin Losciale, Mallory Faherty and Timothy Sell

Rupture of the anterior cruciate ligament (ACL) remains extremely common, with over 250,000 injuries annually. Currently, clinical tests have poor utility to accurately screen for ACL injury risk in athletes. In this study, the position of a knee marker was tracked in 2-dimensional planes to predict biomechanical variables associated with ACL injury risk. Three-dimensional kinematics and ground reaction forces were collected during bilateral, single-leg stop-jump tasks for 44 healthy male military personnel. Knee marker position data were extracted to construct 2-dimensional 95% prediction ellipses in each anatomical plane. Knee marker variables included: ellipse areas, major/minor axes lengths, orientation of ellipse axes, absolute ranges of knee position, and medial knee collapse. These variables were then used as predictor variables in stepwise multiple linear regression analyses for 7 biomechanical variables associated with ACL injury risk. Knee flexion excursion, normalized peak vertical ground reaction forces, and knee flexion angle at initial contact were the response variables that generated the highest adjusted R 2 values: .71, .37, and .31, respectively. The results of this study provide initial support for the hypothesis that tracking a single marker during 2-dimensional analysis can accurately reflect the information gathered from 3-dimensional motion analysis during a task assessing knee joint stability.

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Kimberly Bigelow and Michael L. Madigan

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Stuart A. McErlain-Naylor

The aim of this study was to investigate student experiences of publishing undergraduate research in biomechanics. A total of 29 former students with experience of publishing peer-reviewed undergraduate biomechanics research completed an online survey regarding their perceived benefits, level of involvement, and experiences in aspects of the research process. On average, students perceived their experiences to be “largely helpful” or greater in all aspects. Areas were identified corresponding to: the greatest perceived benefits (eg, understanding of the research process); the least perceived benefits (eg, statistical analysis skills); the greatest student involvement (eg, reading relevant literature); and the least student involvement (eg, developing hypotheses and/or methods). A thematic analysis of open question responses identified themes relating to: future career, skills, scientific process, intra- and interpersonal factors, and pedagogy. Common intended learning outcomes may be achieved through involvement in the research process independently of the level of staff involvement. Staff should be encouraged to involve students in publishable biomechanics research projects where this is possible without compromising research standards and should explore ways of recreating the publishing process internally for all students.

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Jongil Lim, Jiyeon Kim, Kyoungho Seo, Richard E.A. van Emmerik and Sukho Lee

The aim of this study was to examine how usage of mobile devices while simultaneously walking affects walking characteristics and texting performance of normal weight (NW) and obese (OB) individuals. Thirty-two OB (body mass index [BMI] = 34.4) and NW (BMI = 22.7) adults performed two 60-s walking trials at three-step frequencies along a rectangular walkway in two conditions (No Texting and Texting). Dual-task cost as well as unadjusted spatial and temporal gait characteristics were measured. Dual-task costs for the gait parameters as well as texting performance were not different between the groups, except for the lateral step variability showing a larger variability at the preferred frequency in OB individuals. For the unadjusted variables, OB exhibited longer double support, longer stance time, and lower turn velocity compared with NW. Overall, the results highlight a similar dual-task cost for the OB individuals compared with the NW individuals, in spite of underlying differences in gait mechanics.

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Lin Li, Yanxia Li, Chang-hong Wu and Hao Fu

The aim of the current work was to verify three-dimensional directional effects on the reproduction error precision of the human upper limb position. Thirty male subjects without history of upper limb pathology were recruited from Renmin University of China. A three-dimensional position reproduction task in six directions (up, down, left, right, far, and near) was performed by each subject. The results suggested that the proprioceptive sense of upper limb position depends on the direction, with smaller absolute errors in Directions 4 (right) and 5 (far) than in Directions 1 (up), 2 (down), 3 (left), and 6 (near). Proprioception near the end of the elbow joint range of motion may be more reliable and sensitive. Subjects reproduced fewer ranges in the horizontal plane (Directions 3, 5, and 6) and they overshot the target position along the z-axis (vertical direction) except for Direction 6. Overestimations of position in the z-axis may be caused by overestimations of force.

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Xiaoyue Hu, Jingxian Li and Lin Wang

Twenty-four healthy adults, including 12 females and 12 males, participated in the study. Each female participant completed three trials in three different phases of one menstrual cycle, which included follicular, ovulatory, and luteal phases. The study aimed to investigate whether there is any difference in joint kinetic sense, neuromuscular coordination, and isokinetic muscle strength (a) between healthy males and females at different phases of the menstrual cycle and (b) between females at different phases of the menstrual cycle. The outcome measures included the number of jumps in the square-hop test and ankle and knee proprioception, which were assessed by an electric-driven movable frame rotated at 0.4 deg/s and isokinetic muscle strength measured by a computerized dynamometer (Biodex). For the square-hop test (p = .006), ankle dorsiflexion/plantar flexion (p < .05), knee flexion/extension (p < .05), the relative peak torque of the isokinetic muscle strength at the 60° and 180° knee flexion/extension (p < .001), and the 30° and 120° ankle plantar flexion/dorsiflexion (p < .05) between females and males showed significant differences. For the females at different phases of the menstrual cycle, significant differences were found on ankle dorsiflexion (p = .003), plantar flexion (p = .023), knee extension (p = .029), the square-hop test (p = .036), and relative peak torque of isokinetic muscle strength at 180° knee flexion (p = .029). This study demonstrated that there are sex differences in lower limb proprioception and mechanical function. Females at ovulatory and luteal phases have better lower limb proprioception than at the follicular phase.