Search

Introduction: The aim of this study was to explore effects of fatigue in lower back muscles on the performance of countermovement jumps (CMJ), jump shots (JS) and landing impact. Methods: Twelve male healthy collegiate basketball players (age: 22.8 ± 2.7 yrs, stature: 178.0 ± 5.1 cm, body mass: 74.5 ± 6.8 kg) volunteered to participate in this study. Data were collected utilizing a 3D motion analysis system, force plate, and surface electromyography. Field-goal percentage, the lowest point of the center of mass (CoM), the angles of joints during taking off phase and landing, and the electromyography parameters of the rectus femoris, erector spinae lumbalis, and of the lower limbs when performing CMJ and JS were recorded. Lower back muscle fatigue intervention was introduced and followed by a post-test to explore the effects of fatigue in the lower back muscles. Statistical analysis was performed using paired-samples 't'-test. Results: After lower back muscle fatigue, field-goal percentages dropped, and lowest point of CoM was increased during JS. Ankle plantar flexion of the hopping leg during CMJ and JS increased, and their knee flexion angles of the hopping leg were reduced when landing. CMJ and JS changed the contribution ratio of both legs after low back fatigue. Conclusions: Temporary low back muscles fatigue decreased the athletes’ performance and causes a change in landing strategy.

(1) Background: To understand the movement characteristics of soccer players when cutting in two directions (45° for the right and left cutting movements) through biomechanical analysis of the lower limbs to identify the cutting direction of the attacker; (2) Methods: A motion analysis system was used to capture the movements of 12 male professional soccer players dribbling to the left and right. Kinematics of the players’ cutting were analyzed, and the paired t-test was used for statistics, with a significant level of α = 0.05; (3) Results: When cutting towards the right, the height of the hip joint during the run-up was low (effect size, ES = 0.41, p = 0.031) at 91.8 ± 7.0 cm. When cutting towards the left, the value was 94.6 ± 6.7 cm. While cutting, the front foot was abducted by 4.3 ± 4.0° at landing when cutting towards the right and adducted by 2.7 ± 5.1° when cutting towards the left (ES = 0.38, p = 0.003); (4) Conclusions: When the attacker carries out the cutting action while approaching the defender, the cutting direction may be predicted by observing the attacker’s hip and foot movements.

The aim of this study was to investigate the effects of rectus abdominis (RA) fatigue on the jumping performance and landing loads of volleyball players during countermovement jumps (CMJs) and spike jumps (SPJs). Twelve healthy university volleyball players were evaluated using a three-dimensional motion analysis system, force plates, and surface electromyography (EMG). The lowest center of mass (Min-CoM), maximum jumping height (Max-JH), angles of joints at take-off and landing, joint moment of the lower limbs, and EMG parameters of the RA, erector spinae, and lower limb muscles, when performing the CMJs and SPJs, were recorded before and after a 10 min RA muscle fatigue intervention. After RA fatigue, the Max-JH was significantly reduced, and the lowest Min-CoM was significantly increased. The take-off angles changed significantly at the ankle (SPJ), knee (CMJ), and hip (SPJ), and the plantar flexion torque changed significantly at the SPJ touchdown. The contribution ratio of the feet during SPJs and CMJs changed after fatigue. Temporary RA fatigue decreases the jump height of athletes and causes a change in the landing strategy.

Adjacent segment degeneration typically follows anterior cervical spine fusion. However, the primary cause of adjacent segment degeneration remains unknown. Therefore, in order to identify the loading effects that cause adjacent segment degeneration, this study examined the loading effects to superior segments adjacent to fused bone following anterior cervical spine fusion. The C3–C6 cervical spine segments of 12 sheep were examined. Specimens were divided into the following groups: intact spine (group 1); and C5–C6 segments that were fused via cage-instrumented plate fixation (group 2). Specimens were cycled between 20° flexion and 15° extension with a displacement control of 1°/second. The tested parameters included the range of motion (ROM) of each segment, torque and strain on both the body and inferior articular process at the superior segments (C3–C4) adjacent to the fused bone, and the position of the neutral axis of stress at under 20° flexion and 15° extension. Under flexion and Group 2, torque, ROM, and strain on both the bodies and facets of superior segments adjacent to the fused bone were higher than those of Group 1. Under extension and Group 2, ROM for the fused segment was less than that of Group 1; torque, ROM, and stress on both the bodies and facets of superior segments adjacent to the fused bone were higher than those of Group 1. These analytical results indicate that the muscles and ligaments require greater force to achieve cervical motion than the intact spine following anterior cervical spine fusion. In addition, ROM and stress on the bodies and facets of the joint segments adjacent to the fused bone were significantly increased. Under flexion, the neutral axis of the stress on the adjacent segment moved backward, and the stress on the bodies of the segments adjacent to the fused bone increased. These comparative results indicate that increased stress on the adjacent segments is caused by stress-shielding effects. Furthermore, increased stress and ROM of the adjacent segments after long-term bone fusion may accelerate degeneration in adjacent segment.

Two methods have been used to produce a maximal voluntary isometric contraction (MVIC) of the superficial quadriceps femoris muscles for normalization of electromyographic (EMG) data. The purposes of this study were to compare the myoelectic activity of MVIC of manual muscle testing (MMT) versus Cybex maximal isometric testing. Eighteen normal subjects were recruited. MMT and Cybex testing for MVIC of the dominant leg were performed. EMG activities of the vastus medialis, vastus lateralis and rectus femoris were recorded during MMT and Cybex trials. EMG amplitude and median frequency obtained from the two methods (MMT and Cybex testing) were used for statistical analysis of these three muscles. Statistically, the difference in the mean of the EMG signal amplitude and median frequency between MMT and Cybex testing were not significant. Considering cost and time, MMT for MVIC technique appears to be reliable and highly valuable.

BACKGROUND: More than 1000 scientific papers have been devoted to flatfoot issue. However, a bimodal distribution of flatfoot indices in school-aged children has never been discovered. The purposes of this study were to establish a new classification of flatfoot by characteristic in frequency distribution of footprint index and to endue the classification with discrepancy in physical fitness. METHODS/PRINCIPAL FINDINGS: In a longitudinal survey of physical fitness and body structure, weight bearing footprints and 3 physical fitness related tests were measured in 1228 school-aged children. Frequency distribution of initial data was tested by Kolmogorov-Smirnov test for normality and a unique bimodal distribution of footprint index was identified. The frequency distribution of footprint index manifests two distinct modes, flatfoot and non-flatfoot, by deconvolution and bootstrapping procedures. A constant intersection value of 1.0 in Staheli's arch index and 0.6 in Chippaux-Smirak index could distinguish the two modes of children, and the value was constant in different age, sex, and weight status. The performance of the one leg balance was inferior in flatfoot girls (median, 4.0 seconds in flatfoot girls vs. 4.3 seconds in non-flatfoot girls, p = 0.04, 95% CI 0.404-0.484). DISCUSSION: The natural bimodality lends itself to a flatfoot classification. Bimodality suggests development of the child's foot arch would be a leap from one state to another, rather than a continuous growth as body height and weight. The underlying dynamics of the human foot arch and motor development will trigger research prospects.

Background: To investigate how unilateral cage-instrumented posterior lumbar interbody fusion (PLIF) affects the three-dimensional flexibility in degenerative disc disease by comparing the biomechanical characteristics of unilateral and bilateral cage-instrumented PLIF. Methods: Twelve motion segments in sheep lumbar spine specimens were tested for flexion, extension, axial rotation, and lateral bending by nondestructive flexibility test method using a nonconstrained testing apparatus. The specimens were divided into two equal groups. Group 1 received unilateral procedures while group 2 received bilateral procedures. Laminectomy, facectomy, discectomy, cage insertion and transpedicle screw insertion were performed sequentially after testing the intact status. Changes in range of motion (ROM) and neutral zone (NZ) were compared between unilateral and bilateral cage-instrumented PLIF. Results: Both ROM and NZ, unilateral cage-instrumented PLIF and bilateral cage-instrumented PLIF, transpedicle screw insertion procedure did not revealed a significant difference between flexion-extension, lateral bending and axial rotation direction except the ROM in the axial rotation. The bilateral group's ROM (-1.7 ± 0. 8) of axial rotation was decreased significantly after transpedicle screw insertion procedure in comparison with the unilateral group (-0.2 ± 0.1). In the unilateral cage-instrumented PLIF group, the transpedicle screw insertion procedure did not demonstrate a significant difference between right and left side in the lateral bending and axial rotation direction. Conclusions: Based on the results of this study, unilateral cage-instrumented PLIF and bilateral cage-instrumented PLIF have similar stability after transpedicle screw fixation in the sheep spine model. The unilateral approach can substantially reduce exposure requirements. It also offers the biomechanics advantage of construction using anterior column support combined with pedicle screws just as the bilateral cage-instrumented group. The unpleasant effect of couple motion resulting from inherent asymmetry was absent in the unilateral group. [ABSTRACT FROM AUTHOR]

Purpose: This study was conducted to evaluate the kinematic responses and the restorative effectiveness of three posterior fixations in a canine atlantoaxial (C[sub 1-2]) complex model. Methods: Nine canine ligamentous C[sub 1-2] complexes were non-destructively tested in an intact condition, after ligamentous destabilization, and after bilateral stabilization with each of three posterior fixation methods: (1) Halifax inter-laminar clamps; (2) sub-laminar wiring; and (3) individual fixation of the C[sub 1] lateral mass and the C[sub 2] pedicle with screws and plates. Specimens were subjected to a relevantly applied loads through a loading frame rigidly attached to the C[sub 1]. Two sets of three markers was separately attached to the mounting jigs of the C[sub 1] and the C[sub 2] to record the spatial locations after each loading step with a Vicron 370 system. The load-deformation data were analyzed. Results: Under a realistic loading paradigm, destabilized canine C[sub 1-2] complex had 3-dimensional motion ranges highly consistent with the corresponding values observed in destabilized cadaveric human C[sub 1-2] complex following a non-destructive loading paradigm. All the three posterior fixations significantly restricted the motion range of axial rotation loads (P<0.05). However, fixation either with posterior inter-articular screws and plates or inter-laminar clamps also effectively restricted the motion ranges of flexion/extension and lateral bending loads, whereas posterior wiring did not. Conclusion: We described a destabilized canine C[sub 1-2] complex model. Under a realistic loading paradigm, the model had kinematic analogue of destabilized human C[sub 1-2] complex. Our results indicated that posterior stabilization using inter-articular fixation techniques or inter-laminar clamps could effectively restrict hypermotility caused by C[sub 1-2] ligamentous destabilization, and, therefore, appeared to be reliable fixation methods. In contrast, posterior wiring alone would preserve more residual motions, and, thus, might need other adjunctive fixations to offer an optimal condition for solid bony fusion. [ABSTRACT FROM AUTHOR]