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Yun Wang and Kazuhiko Watanabe

The notion of limb dominance has been commonly used in the upper extremity, yet the two lower extremities are often treated as equal for analytical purposes. Attempts to determine the effects of limb laterality on gait have produced conflicting results. The purpose of this study was to determine if limb dominance affects the vertical ground reaction force and center of pressure (COP) during able-bodied gait. The Parotec system (Paromed GmbH, Germany) was used to collect plantar foot pressure data. Fifteen subjects volunteered to participate in this study. The coefficient of variation of the COP displacement in the mediolateral direction and the variability of peak force beneath the lateral forefoot in the nondominant foot were significant greater than in the dominant foot. Moreover, COP velocity in the anterior-posterior direction during the terminal stance phase showed greater value in the dominant foot. Our study provides support for limb laterality by showing limb dominance affected the vertical ground reaction force and center of pressure during walking gait. This finding suggests it is an important issue in movement science for clinicians and would assist in improving sports performance and rehabilitation program.

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Erin Hanlon and Cynthia Bir

Soccer heading has been studied previously with conflicting results. One major issue is the lack of knowledge regarding what actually occurs biomechanically during soccer heading impacts. The purpose of the current study is to validate a wireless head acceleration measurement system, head impact telemetry system (HITS) that can be used to collect head accelerations during soccer play. The HIT system was fitted to a Hybrid III (HIII) head form that was instrumented with a 3-2-2-2 accelerometer setup. Fifteen impact conditions were tested to simulate impacts commonly experienced during soccer play. Linear and angular acceleration were calculated for both systems and compared. Root mean square (RMS) error and cross correlations were also calculated and compared for both systems. Cross correlation values were very strong with r = .95 ± 0.02 for ball to head forehead impacts and r = .96 ± 0.02 for head to head forehead impacts. The systems showed a strong relationship when comparing RMS error, linear head acceleration, angular head acceleration, and the cross correlation values.

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Steven H. Ryder, Robert J. Johnson, Bruce D. Beynnon and Carl F. Ettlinger

Athletes are particularly at risk for anterior cruciate ligament injury, and there is some evidence that female athletes are more at risk than males. The conflicting principles of stability and mobility are at odds within the knee, setting the stage for potentially serious injuries. Some investigators suggest that the size of the intercondylar notch should be used to identify athletes at risk for ACL damage, but more research is required before clinical decisions can be based on notch width measurements. Athletic shoe modifications and artificial playing surfaces may influence the incidence of ACL injures. Functional knee braces appear to have beneficial strain shielding effect on the ACL for anterior directed loads and internal–external torques applied to the tibia, but this effect appears to decrease as the magnitude of these anterior directed loads and torques increases. Ski equipment is often pointed to as a contributing factor in ACL injuries, but there is no evidence that modifications in ski equipment will decrease ACL disruptions. An education program based on recognizing the events that lead to ACL injury in skiing may reduce knee injuries in the future.

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James J. Hannigan, Louis R. Osternig and Li-Shan Chou

Weak hip muscle strength and excessive hip motion during running have been suggested as potential risk factors for developing patellofemoral pain syndrome (PFPS) in females, but not males. There is conflicting evidence on the relationship between hip strength and hip kinematics, which may be partly due to sex differences in the relationship between these parameters. Hip, pelvis, and trunk kinematics were collected while 60 healthy, habitual runners (23 females, 37 males) ran overground, and isometric hip abduction and external rotation strengths were measured bilaterally. Pearson correlation coefficients quantified sex-specific correlations between hip strength and kinematics, and unpaired t tests assessed sex differences in hip strength and kinematics. Hip abduction strength was moderately and inversely correlated to hip adduction excursion in females, and pelvic internal rotation excursion in males. Hip external rotation strength was moderately and inversely correlated to trunk flexion excursion in females. Finally, females displayed less hip external rotation strength and greater excursion at the hip and trunk during running compared to males. Despite the significant correlations, the relatively low r 2 values suggest that additional factors outside of strength contribute to a substantial portion of the variance in trunk, pelvis, and hip kinematics.

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Asuman Saltan and Handan Ankarali

Objective:

To compare classification levels and trunk stabilization of wheelchair basketball players and to identify their norm values of trunk balance.

Participants:

113 wheelchair basketball players in the super and first Turkish leagues.

Interventions:

A modified Wheelchair Skills Test (WST) (version 4.1) was used to evaluate trunk stabilization. Two skills were chosen that correspond to the stationary wheelie activity in WST, the 30-s stationary wheelie and stationary wheelie in 180°.

Main Outcome Measure:

There are no statistical differences between WST rates and point means.

Results:

The skills and success and safety rates of the players with 1.5 points (51.9%, 44.4%) were lower than those of the players with 1.0 point (70%, 66.7%). In players with 2.5 and 2.0 points, the most successful and safest percentage values were 78.6%, 78.6% and 82.1%, 75%.

Conclusions:

Although it is expected that trunk stabilization would be better in players with high points, in our study we encountered conflicting results between the points and sitting balance or trunk stabilization. Our study supports the studies in the literature suggesting modifications in the functional-classification system.

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Olivier Oullier, Benoît G. Bardy, Thomas A. Stoffregen and Reinoud J. Bootsma

Surfaces shorter in extent than the feet elicit multi-joint coordination that differs from what is elicited by stance on extensive surfaces. This well-known effect arises from the mechanics of the actor-environment interaction. Multi-joint control of stance is also known to be influenced by non-mechanical aspects of a situation, including participants' task or intention. Intentional constraints do not originate in mechanics, and for this reason one might suppose that constraints imposed by mechanics would dominate constraints imposed by intentions, when the two were in conflict. We evaluated this hypothesis by varying participants' supra-postural task during stance on a short surface. While standing on a 10-cm wide beam, participants were exposed to optic flow generated by fore-aft oscillations of a moving room. Participants faced a target attached to the front wall of the moving room and were asked either to look at the target (with no instruction to move) or intentionally to track it with their head (i.e., to keep the target-head distance constant). Within trials, we varied the frequency of room (and target) motion, from 0.15 to 0.75 Hz, in steps of 0.05 Hz. In both conditions, ankle and hip rotations exhibited antiphase coordination, but behavior was not identical across conditions. Coupling between motion of the room and the head was stronger for the tracking task than for the looking task, and the stability of ankle-hip coordination was greater during tracking than during looking. These results indicate that the influence of support surface mechanics did not eliminate the influence of the supra-postural task. Environment-based and task-based constraints interacted in determining the coordination of hips and ankles during stance.

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Andrew E. Littmann, Masaki Iguchi, Sangeetha Madhavan, Jamie L. Kolarik and Richard K. Shields

Context:

There is conflicting evidence in the literature regarding whether women with anterior cruciate ligament reconstruction (ACLR) demonstrate impaired proprioception. This study examined dynamic-position-sense accuracy and central-nervous-system (CNS) processing time between those with and without long-term ACLR.

Objective:

To compare proprioception of knee movement in women with ACLR and healthy controls.

Design:

Cross-sectional.

Setting:

Human neuromuscular performance laboratory.

Participants:

11 women (age 22.64 ± 2.4 y) with ACLR (1.6–5.8 y postsurgery) and 20 women without (age 24.05 ± 1.4 y).

Interventions:

The authors evaluated subjects using 3 methods to assess position sense. During knee flexion at pseudorandomly selected speeds (40°, 60°, 80°, 90°, and 100°/s), subjects indicated with their index finger when their knee reached a predetermined target angle (50°). Accuracy was calculated as an error score. CNS processing time was computed using the time to detect movement and the minimum time of angle indication. Passive and active joint-position sense were also determined at a slow velocity (3°/s) from various knee-joint starting angles.

Main Outcome Measurements:

Absolute and constant error of target angle, indication accuracy, CNS processing time, and perceived function.

Results:

Both subject groups showed similar levels of error during dynamic-position-sense testing, despite continued differences in perceived knee function. Estimated CNS processing time was 260 ms for both groups. Joint-position sense during slow active or passive movement did not differ between cohorts.

Conclusions:

Control and ACLR subjects demonstrated similar dynamic, passive, and active joint-position-sense error and CNS processing speed even though ACLR subjects reported greater impairment of function. The impairment of proprioception is independent of post-ACLR perception of function.

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Jill Alexander and David Rhodes

Context: The effect of local cooling on muscle strength presents conflicting debates, with literature undecided as to the potential implications for injury, when returning to play following cryotherapy application. Objective: To investigate concentric muscle strength following local cooling over the anterior thigh compared with the knee joint in males and females and the temporal pattern over a 30-minute rewarming period. Design: Repeated-measures crossover design. Method: Twelve healthy participants randomly assigned to receive cooling intervention on one location, directly over either the anterior thigh or the knee, returning 1 week later to receive the cooling intervention on opposite location. Muscle strength measured via an isokinetic dynamometer at multiple time points (immediately post, 10-, 20-, and 30-min post) coincided with measurement of skin surface temperature (T sk) using a noninvasive infrared camera. Results: Significant main effects for time (P ≤ .001, η 2 = .126) with preice application higher than all other time points (P ≤ .05) were demonstrated for both peak torque and average torque. There were also significant main effects for isokinetic testing speed, sex of the participant, and position of the ice application for both peak torque and average torque (P ≤ .05). Statistically significant decreases in T sk were reported in both gender groups across all time points compared with preintervention T sk for the anterior thigh and knee (P < .05). Conclusions: Reductions reported for concentric peak torque and average torque knee-extensor strength in males and females did not fully recover to baseline measures at 30-minute postcryotherapy interventions. Sports medicine practitioners should consider strength deficits of the quadriceps after wetted ice applications, regardless of cooling location (joint/muscle) or gender.

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Jeffrey J. Chu and Graham E. Caldwell

Studies on shock attenuation during running have induced alterations in impact loading by imposing kinematic constraints, e.g., stride length changes. The role of shock attenuation mechanisms has been shown using mass-spring-damper (MSD) models, with spring stiffness related to impact shock dissipation. The present study altered the magnitude of impact loading by changing downhill surface grade, thus allowing runners to choose their own preferred kinematic patterns. We hypothesized that increasing downhill grade would cause concomitant increases in both impact shock and shock attenuation, and that MSD model stiffness values would reflect these increases. Ten experienced runners ran at 4.17 m/s on a treadmill at surface grades of 0% (level) to 12% downhill. Accelerometers were placed on the tibia and head, and reflective markers were used to register segmental kinematics. An MSD model was used in conjunction with head and tibial accelerations to determine head/arm/trunk center of mass (HATCOM) stiffness (K1), and lower extremity (LEGCOM) stiffness (K2) and damping (C). Participants responded to increases in downhill grade in one of two ways. Group LowSA had lower peak tibial accelerations but greater peak head accelerations than Group HighSA, and thus had lower shock attenuation. LowSA also showed greater joint extension at heelstrike, higher HATCOM heelstrike velocity, reduced K1 stiffness, and decreased damping than HighSA. The differences between groups were exaggerated at the steeper downhill grades. The separate responses may be due to conflicts between the requirements of controlling HATCOM kinematics and shock attenuation. LowSA needed greater joint extension to resist their higher HATCOM heelstrike velocities, but a consequence of this strategy was the reduced ability to attenuate shock with the lower extremity joints during early stance. With lower HATCOM impact velocities, the HighSA runners were able to adopt a strategy that gave more control of shock attenuation, especially at the steepest grades.

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Sean M. Burfeind and Nicole Chimera

Context:

Athletes participating in upper-extremity-dominant sports such as softball and volleyball are at increased risk for glenohumeral-joint pain and injury. For these athletes, an integral part of many injuryprevention and -rehabilitation programs includes improving joint proprioception. One way to measure joint proprioception is through the reproduction of joint angles, or joint-reposition sense (JRS). Kinesiology tape is purported to enhance neuromuscular feedback; therefore, it may influence JRS. However, conflicting findings and the lack of research in the upper extremity warrant further investigation.

Objective:

To determine the effects of kinesiology tape on shoulder-joint proprioception by actively reproducing joint angles, or measurement of JRS.

Design:

Randomized controlled trial.

Setting:

College laboratory.

Participants:

9 men and 7 women 24 ± 3 y old.

Intervention:

SpiderTech kinesiology tape precut Shoulder Spider was applied to the shoulder of participants block randomized to the experimental group, following product-specific instructions, to measure its influence on JRS compared with a control group.

Main Outcome Measurement:

JRS-error scores in shoulder flexion, extension, internal rotation, and external rotation (ER).

Results:

There was a significant interaction between groups pre- to postintervention resulting in decreased JRS errors in flexion (P = .04) and ER (P = .03) in the experimental compared with the control group. The 95% confidence intervals suggest a clinically relevant difference in the variability of JRS errors between postintervention movements for the experimental group in flexion and ER, such that the control group demonstrated much more variability in JRS errors than the experimental group.

Conclusions:

After the application of kinesiology tape the JRS errors were smaller in flexion and ER. This may be of clinical significance in improving proprioception and thus improving joint stability. Additional research should determine the effectiveness of kinesiology tape in reducing joint injury.