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Isabelle Schöffl, Frank Einwag, Wolf Strecker, Friedrich Hennig and Volker Schöffl

Flexor tendon pulley ruptures are the most common injury in rock climbers. Therapeutic standards usually include a prolonged use of taping applied as a replacement for the lost pulley in a circular fashion at the base of the proximal phalanx. Our biomechanical considerations, however, suggest a new taping method, the H-tape. The purpose of the study is to evaluate whether this new taping method can effectively change the course of the flexor tendon and therefore reduce the tendon–bone distance. In order to compare the effects of different taping methods described in the literature with the newly developed taping method, we performed standardized ultrasound examinations of 8 subjects with singular A2 pulley rupture and multiple pulley ruptures of A2 and A3 pulleys and determined the respective tendon–bone distance for the different taping methods, versus without tape at a preset position on the proximal phalanx. In a second approach, we evaluated the effect of the new taping method on the strength of the injured finger using a force platform on 12 subjects with different pulley ruptures with injuries older than 1 year. The new taping method decreased the tendon–bone distance in the injured finger significantly by 16%, whereas the other taping methods did not. The strength development was significantly better with the new tape for the crimp grip position (+13%), but there was no significant improvement for the hanging position. We recommend taping with the newly presented taping technique after pulley rupture.

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Zheng Wang, Kimberlee Jordan and Karl M. Newell

In this study, two force platforms were synchronized to investigate the coordination of the right and left foot center of pressure (COPR and COPL) and its relation to the COPNET in the control of 5 upright postures with and without visual information. The results revealed that the standard deviation (SD) of COPL, COPR, and COPNET progressively increased in the more challenging staggered and tandem stances, respectively, and to a lesser degree with the absence of visual information. Circular analysis of the relative phase of COPL and COPR revealed that the coupling pattern and variability were dependent on postural stances and the availability of vision. A negative correlation between the variability of the relative phase of the two feet COPs and the SD of the COPNET in the anterior-posterior (AP) direction was evident most strongly in the no vision conditions. Thus, the asymmetry of the mechanical constraints on the feet as a function of stance organize the coordination patterns of the feet COPs while the degree of adaptive variation between the feet COPs is dependent on both the mechanical constraints and the availability of vision.

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Neil E. Bezodis, Aki I.T. Salo and Grant Trewartha

Two-dimensional analyses of sprint kinetics are commonly undertaken but often ignore the metatarsal-phalangeal (MTP) joint and model the foot as a single segment. The aim of this study was to quantify the role of the MTP joint in the early acceleration phase of a sprint and to investigate the effect of ignoring the MTP joint on the calculated joint kinetics at the other stance leg joints. High-speed video and force platform data were collected from four to five trials for each of three international athletes. Resultant joint moments, powers, and net work at the stance leg joints during the first stance phase after block clearance were calculated using three different foot models. Considerable MTP joint range of motion (>30°) and a peak net MTP plantar flexor moment of magnitude similar to the knee joint were observed, thus highlighting the need to include this joint for a more complete picture of the lower limb energetics during early acceleration. Inclusion of the MTP joint had minimal effect on the calculated joint moments, but some of the calculated joint power and work values were significantly (P < .05) and meaningfully affected, particularly at the ankle. The choice of foot model is therefore an important consideration when investigating specific aspects of sprinting technique.

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Melvin R. Ramey and Keith R. Williams

Ground reaction forces were obtained for the three phases of the triple jump for four collegiate triple jumpers, two men and two women. A single force platform was used, which thereby required the subjects to execute three separate jumps to produce a single triple jump record. The vertical force records for each phase showed two peaks having magnitudes in the range of 7 to 12 times body weight (BW) and 3.3 to 5 BW, respectively. These magnitudes are substantially higher than has been reported by others for distance running, sprinting, and in some cases other jumps. The maximum horizontal forces act to decrease the velocity of the mass center, but to different degrees for the different subjects. The data show that for any phase of the jump there is considerable variability in the timing and magnitudes of the force records among the different subjects although general patterns are similar. The results suggest that the use of mean force data from a number of subjects may conceal important differences between the way individuals execute the jump.

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Peter Werner and Judith Rink

The purpose of this study was to describe the teaching behaviors of four teachers who had varying degrees of expertise in working with second grade students and to improve the teachers’ effectiveness. Four experienced teachers were asked to teach a six-lesson unit in jumping and landing skills to an intact class of their choice. Students were pre- and posttested on their ability to produce and reduce force using a force platform and a jump for distance without the platform. OSCD-PE (Rink, 1979) was used to describe the more general aspects of the teachers’ content development and managerial skills. Task presentation, nature of feedback, and appropriateness of student responses were obtained using the QMTPS (Rink & Werner, 1989). Additional information was obtained by counting practice trials and analyzing teacher written plans and approaches to content. Following the first teaching experience, the researchers gave feedback to the teachers and asked them to reteach the unit to a different class. Product and process measures were obtained in the same manner on the second teaching experience. Data were presented in a case study format. The results describe the importance of content knowledge, the ability to present information clearly, and holding students accountable for selected performance aspects.

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Vladimir M. Zatsiorsky and Marcos Duarte

The goal of this study was to explore the rambling-trembling decomposition in quiet standing. The center of pressure (COP) and the horizontal ground reaction force (Fhor) were registered in healthy subjects standing in an upright bipedal posture on a force platform. The COP positions at the instants when Fhor = 0 were identified (instant equilibrium points, IEP) for the anterior-posterior direction, then the COP time series, were partitioned into its components using 2 different techniques, rambling-trembling decomposition and gravity line decomposition. The two decomposition techniques provided very similar results. An unexpectedly large correlation between the trembling trajectory and the difference between COP and gravity line was found, r = 0.91 (range, 0.83 < r < 0.98). The correlation implies that the GL moves from an IEP to the subsequent IEP along a smooth trajectory that can be predicted by the spline approximation. A substantial negative cross-correlation at a zero time lag was observed between the trembling and the Fhor, -0.90 < r < -0.75. For the rambling trajectory, the coefficients of correlation with Fhor were low, -0.33 < r < -0.05. The data support the hypothesis that during quiet standing the body sways for two reasons: the migration of the reference point (rambling) and the deviation away from that point (trembling).

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Pablo Floria, Luis A. Gómez-Landero and Andrew J. Harrison

The purpose of this study was to determine if children exhibit greater variability in center of mass movement and kinetics compared with adults in vertical jumping. Countermovement jumps with arms (CMJA) and without arms (CMJ) performed by 20 female children and 20 female adults were examined using force platform. The data were analyzed using continuous methods to determine differences in variability between groups and between types of jump. Jumping variability was measured by using the average coefficient of variation of the force-, velocity-, displacement-, and rate of force development-time curves across the jump. The analysis indicated that children and adults had similar levels of variability in the CMJ but different levels in the CMJA. In the CMJA, the children had a greater coefficient of variation than adults in force- (20 ± 7% and 12 ± 6%), velocity- (41 ± 14% and 22 ± 9%), displacement- (8 ± 16% and 23 ± 11%) and rate of force development-time (103 ± 46% and 75 ± 42%) curves, as well as in force-velocity relationship (6 ± 2% and 4 ± 2%). The results of analysis suggest that the variability depends on both the level of maturation of the participants as well as the task complexity.

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Eliane Mauerberg-deCastro, Renato Moraes and Debra Frances Campbell

We tested the short-term effects of a nonrigid tool, identified as an “anchor system” (e.g., ropes attached to varying weights resting on the floor), on the postural stabilization of blindfolded adults with and without intellectual disabilities (ID). Participants held a pair of anchors–one in each hand, under three weight conditions (250 g, 500 g and 1,000 g), while they performed a restricted balance task (standing for 30 s on a balance beam placed on top of a force platform). These conditions were called anchor practice trials. Before and after the practice trials, a condition without anchors was tested. Control practice groups, who practiced blocks of trials without anchors, included individuals with and without ID. The anchor system improved subjects’ balance during the standing task, for both groups. For the control groups, the performance of successive trials in the condition without the anchor system showed no improvement in postural stability. The individuals with intellectual disability, as well as their peers without ID, used the haptic cues of nonrigid tools (i.e., the anchor system) to stabilize their posture, and the short-term stabilizing effects appeared to result from their previous use of the anchor system.

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Cyril Burdet and Patrice Rougier

To question the relation between uni- and bipedal postural skills, 21 subjects were required to stand on a force platform through uni- and bipedal conditions. These two protocols are commonly used paradigms to assess the balance capacities of healthy and disabled patients. The recorded displacements of the center of pressure (CP) were decomposed along mediolateral and anteroposterior axes and assessed through variance positions and parameters obtained from fractional Brownian motion (fBm) modeling to determine the nature and the spatiotemporal organization of the successive controlling mechanisms. The variances underline the relative independence of the two tasks. Nevertheless, as highlighted by the fBm framework, postural correction is initiated for the unipedal stance after shorter time delays and longer covered distances. When compared to bipedal standing, one of the main characteristics of unipedal standing is to induce better-controlled CP trajectories, as deduced from the scaling regimes computed from the fBm modeling. Lastly, the control of the CP trajectories during the shortest time intervals along the anteroposterior axis appears identical for both uni- and bipedal conditions. Unipedal and bipedal standing controls should thus be viewed as two complementary tasks, each providing specific and complementary insights into the postural control organization.

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Akinori Nagano, Shinsuke Yoshioka, Dean Charles Hay and Senshi Fukashiro

The purpose of this study was to test whether a light finger touch on one’s own body (upper legs) reduces postural sway. Ten healthy males participated. In the first part of the study, the participants stood upright with their eyes closed on a force platform while ground reaction force data were collected. Two conditions differing in the placement of the arms and fingers were tested. In the no-touch condition, the participants kept their hands in loose fists. In the finger-touch condition, the participants lightly touched the lateral sides of the upper legs with all fingers. Postural sway measures were calculated from the ground reaction force data. In the second part of the study, the participants stood upright on a pneumatic balance disk while ground reaction force data were collected. Experimental and measurement protocols were identical to those used in the first part of the study. The results showed that light finger touch on the upper legs significantly reduced postural sway on the balance disk up to ~7%. The data from this study suggest that decreased postural sway due to finger contact may improve balance control during other standing tasks.