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Kinetic Analysis of the Fingers Under Different Ball Velocities During Overarm Throwing

Shohei Shibata, Yuki Inaba, Shinsuke Yoshioka, and Senshi Fukashiro

The purpose of this study is to examine changes in the kinetic parameters of the fingers caused by differences in ball velocity during overarm throwing. Six baseball players participated in the study, and the kinetics of the wrist and metacarpophalangeal (MP) joint were calculated using an inverse dynamics method. The results of Tukey’s multiple comparison tests showed that the torque and work of the wrist increased with increasing ball velocity (p < .05), indicating that wrist torque and work contributed to the adjustment of ball velocity. Peak MP joint torque also increased with ball velocity (p < .05), although the work of the MP joint remained relatively constant. We conclude that MP joint torque and work contribute to the achievement of stable ball release rather than adjusting ball velocity.

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The Feasibility of Using the Virtual Time-to-Contact Measure of Postural Stability to Examine Postural Recovery in People With Diabetes Mellitus

Chia-Cheng Lin, Sunghan Kim, Paul DeVita, Matt Becker, and Stacey Meardon

This study aimed to examine the feasibility of using time-to-contact measures during the perturbation protocol in people with diabetes mellitus. Three-dimension motion capture and force data were collected during 0.5-s perturbations in four directions (forward, backward, right, and left) and at two accelerations (20 and 40 cm/s2) to compute the time-to-contact. Time-to-contact analysis was divided into three phases: perturbation, initial recovery, and final recovery. The statistical analysis showed the main effects of Direction and Phase (p < .01) as well as a Direction by Phase interaction (p < .01). Backward perturbation with lower acceleration and backward/forward perturbation with higher acceleration had deleterious effects on postural stability in people with diabetes mellitus.

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Effects of Soccer Exercise on Balance Ability and Kinesthesia of the Lower Limb Joints in Children Aged 5–6 Years

Kebin Shen and Yunxi Liu

Age-, height- and weight-matched children were recruited to the experimental group (EG; n = 31) and control group (n = 32). Following a 16-week soccer training program, balance ability and dominant-side lateral knee and ankle kinesthesia changes were tested. Regarding balance ability, the Sway Index, when children stood on a firm or foam surface with their eyes closed in the static balance test, and the dynamic balance test time were 13.5%, 11.6%, and 14.3% lower in the EG than in the control group, respectively. The scores in the left and right directions were 23.7% and 24.2% higher in the EG, respectively. Regarding kinesthesia, the angle of knee extension and ankle metatarsal flexion and dorsiflexion were 13.4%, 20.0%, and 16.8% lower in the EG than in the control group. These results indicate children in the EG had a better performance. After soccer exercise, children aged 5–6 years displayed improved balance in the left and right directions and improved knee extension, ankle plantarflexion, and dorsiflexion kinesthesia.

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Effect of Long-Term Classical Ballet Dance Training on Postactivation Depression of the Soleus Hoffmann-Reflex

Hiroki Obata, GeeHee Kim, Tetsuya Ogawa, Hirofumi Sekiguchi, and Kimitaka Nakazawa

Classical ballet dancing is a good model for studying the long-term activity-dependent plasticity of the central nervous system in humans, as it requires unique ankle movements to maintain ballet postures. The purpose of this study was to investigate whether postactivation depression is changed through long-term specific motor training. Eight ballet dancers and eight sedentary subjects participated in this study. The soleus Hoffmann reflexes were elicited at after the completion of a slow, passive dorsiflexion of the ankle. The results demonstrated that the depression of the soleus Hoffmann reflex (i.e., postactivation depression) was larger in classical ballet dancers than in sedentary subjects at two poststretch intervals. This suggests that the plastic change through long-term specific motor training is also expressed in postactivation depression of the soleus Hoffmann reflex. Increased postactivation depression would strengthen the supraspinal control of the plantarflexors and may contribute to fine ankle movements in classical ballet dancers.

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Target Constraints Influence Locomotion Pattern to the First Hurdle

Athanasia Smirniotou, Flora Panteli, and Apostolos Theodorou

The study examined to what extent the manipulation of hurdle height (0.76-m hurdle, low hurdle 0.50 m, and white stripe) would affect visual regulation strategies and kinematic reorganization when approaching the first hurdle. In addition, the impact of constraints as a training tool in terms of creating movement patterns functional for and representative of competitive movement models was assessed. The approach phase to the first hurdle of 13 physical education students with no previous experience in hurdling was video recorded and analyzed. Emergence of different footfall variability curves and movement coordination patterns suggests that participants interact differently with features of the performance context. Contrary to the white stripe, the hurdle height required participants to initiate regulation and distribute adjustments over a larger number of steps, and afforded the preparation for takeoff in order to clear the hurdle. In task design, manipulation of task constraints should offer valuable information regarding the dynamics of movement.

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Volume 26 (2022): Issue 1 (Jan 2022)

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Effect of Object Texture and Weight on Ipsilateral Corticospinal Influences During Bimanual Holding in Humans

Laura Duval, Lei Zhang, Anne-Sophie Lauzé, Yu Q. Zhu, Dorothy Barthélemy, Numa Dancause, Mindy F. Levin, and Anatol G. Feldman

We tested the hypothesis that the ipsilateral corticospinal system, like the contralateral corticospinal system, controls the threshold muscle length at which wrist muscles and the stretch reflex begin to act during holding tasks. Transcranial magnetic stimulation was applied over the right primary motor cortex in 21 healthy subjects holding a smooth or coarse block between the hands. Regardless of the lifting force, motor evoked potentials in right wrist flexors were larger for the smooth block. This result was explained based on experimental evidence that motor actions are controlled by shifting spatial stretch reflex thresholds. Thus, the ipsilateral corticospinal system is involved in threshold position control by modulating facilitatory influences of hand skin afferents on motoneurons of wrist muscles during bimanual object manipulation.

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Implications of Optimal Feedback Control Theory for Sport Coaching and Motor Learning: A Systematic Review

Steven van Andel, Robin Pieper, Inge Werner, Felix Wachholz, Maurice Mohr, and Peter Federolf

Best practice in skill acquisition has been informed by motor control theories. The main aim of this study is to screen existing literature on a relatively novel theory, Optimal Feedback Control Theory (OFCT), and to assess how OFCT concepts can be applied in sports and motor learning research. Based on 51 included studies with on average a high methodological quality, we found that different types of training seem to appeal to different control processes within OFCT. The minimum intervention principle (founded in OFCT) was used in many of the reviewed studies, and further investigation might lead to further improvements in sport skill acquisition. However, considering the homogenous nature of the tasks included in the reviewed studies, these ideas and their generalizability should be tested in future studies.

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Altered Spatiotemporal Gaze Dynamics During Unexpected Obstacle Negotiation in a Fatigued State

Jacob W. Hinkel-Lipsker, Nicole M. Stoehr, Pranavi L. Depur, Michael A. Weise, Joshua A. Vicente, Stefanie A. Drew, and Sean M. Rogers

Humans use their peripheral vision during locomotion to perceive an approaching obstacle in their path, while also focusing central gaze on steps ahead of them. However, certain physiological and psychological factors may change this strategy, such as when a walker is physically fatigued. In this study, 21 healthy participants walked through a dark room while wearing eye tracking glasses before and following intense exercise. Obstacles were placed in random locations along their path and became illuminated when participants approached them. Results indicate that, when fatigued, participants had altered spatial gaze strategies, including more frequent use of central gaze to perceive obstacles and an increased gaze angular displacement. However, there were no changes in temporal gaze strategies following exercise. These findings reveal how physical fatigue alters one’s visual perception of their environment during locomotion, and may partially explain why people are at greater risk of trips and falls while fatigued.

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Are Men and Women Equally Affected by Load Carriage While Landing? Analysis of Balance in Spanish Infantry Soldiers

Eva Orantes-Gonzalez and J. Heredia-Jimenez

In this study, the effect of carrying combat equipment and a backpack on balance between men and women was analyzed by simulating a jump out of an armored fighting vehicle, together with the influence of body composition variables. Thirty-seven men and eight women participated in this study. Three landings were performed by simulating a jump from a wheeled armored vehicle carrying no load, carrying the combat equipment and backpack condition. A force plate was used to measure the amplitude and velocity displacement of the center of pressure and the stabilization time. A significant load effect was found on the total velocity and medial–lateral velocity. The weight of the combat equipment and the body composition variables did not correlate with the balance variables. Male and female soldiers showed similar body balance while carrying military combat equipment.