John R. Harry, Leland A. Barker, Jeffrey D. Eggleston and Janet S. Dufek
The ability to rapidly complete a jump landing has received little attention in the literature despite the need for rapid performance in a number of sports. As such, our purpose was to investigate differences between groups of individuals who land quickly (FAST) and slowly (SLOW) relative to peak vertical ground reaction forces (vGRFs), loading rates, rates of vGRF attenuation, contributions to lower extremity mechanical energy absorption at the involved joints, and the onsets of preparatory joint flexion/dorsiflexion. Twenty-four healthy adults (26.1 [3.3] y, 75.7 [18.9] kg, 1.7 [0.1] m) were stratified into FAST and SLOW groups based on landing time across 8 jump-landing trials. Independent t tests (α = .05) and effect sizes (ESs; large ≥ 0.8) compared differences between groups. A greater rate of vGRF attenuation (P = .02; ES = 0.95) was detected in the FAST group. The FAST group also exhibited greater contributions to lower extremity energy absorption at the ankle (P = .03; ES = 0.98) and knee (P = .03; ES = 0.99) during loading and attenuation, respectively. The SLOW group exhibited greater contributions to energy absorption at the hip during loading (P = .02; ES = 1.10). Results suggest that individuals who land quickly utilize different energy absorption strategies than individuals who land slowly. Ultimately, the FAST group’s strategy resulted in superior landing performance (more rapid landing time).
Alison B. Pritchard Orr, Kathy Keiver, Chris P. Bertram and Sterling Clarren
Physical activity (PA) has been demonstrated to have positive effects on cognitive function, particularly executive function (EF) skills. Animal models suggest PA may be effective in ameliorating some of the neuropsychological effects of fetal alcohol spectrum disorder (FASD), but this approach has not been extended to humans. The purpose of this study was to develop a PA program, FAST Club, for children with FASD and to evaluate its effect on a measure of EF. Using a wait-list control design, 30 children age 7–14 yr participated in FAST Club for 2 × 1.5-hr sessions/week for 8 weeks. EF was assessed using the Children’s Color Trails Test. Significant improvements in T scores on the Children’s Color Trails Test were seen immediately postprogram, and this improvement was sustained at 3 months postprogram. These findings provide evidence to support the use of PA as a means to improve EF in children with FASD.
Srinidhi Bellamkonda, Samantha J. Woodward, Eamon Campolettano, Ryan Gellner, Mireille E. Kelley, Derek A. Jones, Amaris Genemaras, Jonathan G. Beckwith, Richard M. Greenwald, Arthur C. Maerlender, Steven Rowson, Stefan M. Duma, Jillian E. Urban, Joel D. Stitzel and Joseph J. Crisco
This study aimed to compare head impact exposures between practices and games in football players ages 9 to 14 years, who account for approximately 70% of all football players in the United States. Over a period of 2 seasons, 136 players were enrolled from 3 youth programs, and 49,847 head impacts were recorded from 345 practices and 137 games. During the study, individual players sustained a median of 211 impacts per season, with a maximum of 1226 impacts. Players sustained 50th (95th) percentile peak linear acceleration of 18.3 (46.9) g, peak rotational acceleration of 1305.4 (3316.6) rad·s−2, and Head Impact Technology Severity Profile of 13.7 (24.3), respectively. Overall, players with a higher frequency of head impacts at practices recorded a higher frequency of head impacts at games (P < .001, r 2 = .52), and players who sustained a greater average magnitude of head impacts during practice also recorded a greater average magnitude of head impacts during games (P < .001). The youth football head impact data quantified in this study provide valuable insight into the player exposure profile, which should serve as a key baseline in efforts to reduce injury.
Elizabeth L. Stegemöller, Joshua R. Tatz, Alison Warnecke, Paul Hibbing, Brandon Bates and Andrew Zaman
Auditory cues, including music, are commonly used in the treatment of persons with Parkinson’s disease. Yet, how music style and movement rate modulate movement performance in persons with Parkinson’s disease have been neglected and remain limited in healthy young populations. The purpose of this study was to determine how music style and movement rate influence movement performance in healthy young adults. Healthy participants were asked to perform repetitive finger movements at two pacing rates (70 and 140 beats per minute) for the following conditions: (a) a tone only, (b) activating music, and (c) relaxing music. Electromyography, movement kinematics, and variability were collected. Results revealed that the provision of music, regardless of style, reduced amplitude variability at both pacing rates. Intermovement interval was longer, and acceleration variability was reduced during both music conditions at the lower pacing rate only. These results may prove beneficial for designing therapeutic interventions for persons with Parkinson’s disease.
Katya Trousset, David Phillips and Andrew Karduna
Proprioception is assessed more often through joint position sense and kinesthesia than force sense. The purpose of this study is to investigate force sense at the shoulder. A total of 12 subjects were recruited. An ipsilateral force reproduction protocol at the shoulder at 50°, 70°, and 90° and 120%, 140%, and 160% baseline torque. Dependent variables were constant error (CE) and root mean square error. An effect was found for load on absolute (p = .001) and normalized CE (p < .001). CE decreased with increased load. An effect for angle was found for absolute root mean square error (p = .002), more accurate at 50° (p = .01), but no effect when normalized (p = .19). With increased loads, subjects undershot the target and CE approached zero. Because of the differing behavior in CE and root mean square error, and absolute and normalized data, force sense studies should examine error from these perspectives.
Shohei Shibata, Yuki Inaba, Shinsuke Yoshioka and Senshi Fukashiro
This study had two objectives: (a) revealing the difference in finger segments between the conventional and finger models during aimed throwing and (b) examining the central nervous system’s timing control between the wrist torque and finger torque. Participants were seven baseball players. Finger kinetics was calculated by an inverse dynamics method. In the conventional model, wrist flexion torque was smaller than that in the finger model because of the error in ball position approximation. The maximal correlation coefficient between the wrist torque and finger torque was high (r = .85 ± .10), and the time lag at maximal correlation coefficient was small (t = 0.36 ± 3.02 ms). The small timing delay between the wrist torque and finger torque greatly influenced ball trajectory. We conclude that, to stabilize release timing, the central nervous system synchronized the wrist torque and finger torque by feed-forward adjustments.
Joseph J. Crisco, Nikolas J. Osvalds and Michael J. Rainbow
The purpose of this study was to compute the 3-dimensional kinetics required to swing 3 youth baseball bats of varying moments of inertia. The 306 swings by 22 male players (age 13–18 y) were analyzed. Inverse dynamics with respect to the batter’s hands were computed given the known kinematics and physical properties of the bats. Peak force increased with larger bat moments of inertia and was strongly correlated with bat tip speed. By contrast, peak moments were weakly correlated with bat moments of inertia and bat tip speed. Throughout the swing, the force applied to the bat was dominated by a component aligned with the long axis of the bat and directed away from the bat knob, whereas the moment applied to the bat was minimal until just prior to ball impact. These results indicate that players act to mostly “pull” the bat during their swing until just prior to ball impact, at which point they rapidly increase the moment on the bat. This kinetic analysis provides novel insight into the forces and moments used to swing baseball bats.
Jaehun Jung, Willie Leung, Bridgette Marie Schram and Joonkoo Yun
The purpose of this study was to explore the current levels of physical activity among youth with disabilities using meta-analysis. The search identified 11 publications including 729 participants (age 4–20 yr). The overall effect size for 11 studies was Hedges g = 0.60 (SE = 0.18, 95% confidence interval [CI] [0.24, 0.96], p < .05, k = 11) using a random-effects model. The findings suggest that differences in physical activity levels between youth with and without disabilities are complex. Results indicated that youth without disabilities engaged in higher levels of physical activity of moderate to vigorous intensity (g = 0.66, SE = 0.18, p < .05). However, no differences were found in light-intensity physical activity (g = −0.03, SE = 0.16, p > .85). Results also suggested that the differences in physical activity between youth with and without disabilities were affected by age (<12 yr, g = 0.83, SE = 0.24, 95% CI [0.37, 1.29], p < .05, and >13 yr, g = 0.37, SE = 0.10, 95% CI [0.18, 0.57], p < .05; Q value = 3.20, df = 1, p < .05), with children with disabilities engaging in less physical activity than children without disabilities in younger ages. Differences in physical activity level between youth with and without disabilities are functions of intensity of physical activity and age but may not be of type of disability (Q value = 0.22, df = 1, p > .6).
Luis Columna, Denzil A. Streete, Samuel R. Hodge, Suzanna Rocco Dillon, Beth Myers, Michael L. Norris, Tiago V. Barreira and Kevin S. Heffernan
Despite having the desire to become physically active as a family, parents of children with visual impairments often lack the skills and resources needed to provide appropriate physical activities (PAs) for their children. The purpose of this study was to explore the intentions of parents of children with visual impairments toward including their children in PAs after participating in a PA program. In this descriptive qualitative study, the participants were 10 parents of children with visual impairments. A series of workshops were designed to provide parents with the skills and resources needed to promote PA for their family. Upon completion of the workshops, parents took part in one-on-one semistructured interviews that were subsequently transcribed and analyzed using a thematic line-by-line process. Two interdependent themes emerged from the data analyses: (a) eye-opening experiences and (b) transformed, more hopeful, and optimistic outlook. The results revealed that through the PA intervention, parents learned teaching strategies that were intended to increase their PA opportunities and garnered resources that allowed them to teach their children to participate in PA.