Bipedal tasks require interlimb coordination that improves with practice and acquisition of skills. The purpose of this study was to compare interlimb force coordination during dance-specific rate-controlled consecutive bipedal jumps (sautés) between expert dancers and nondancers. To analyze coordination of vertical ground reaction forces recorded under each leg, the vector coding approach was used. Although there were no differences in the patterns of interlimb force coordination between groups, the dancers exhibited less variability of interlimb force coordination during the transition phase from weight acceptance to propulsion as well as during the propulsion phase itself. The interlimb force coordination variability was associated with task performance only during the transition phase, which highlights the potential importance of control during this phase. In conclusion, expert dancers were better at reducing interlimb force coordination variability during the task-relevant transition phase, which was related to better performance at maintaining jump rate and jump height consistency.
Hai-Jung Steffi Shih, Danielle N. Jarvis, Pamela Mikkelsen and Kornelia Kulig
Hardeep Singh, Mark Lee, Matthew J. Solomito, Christian Merrill and Carl Nissen
Symptomatic spondylolysis/spondylolisthesis is thought to be caused by repetitive lumbar extension. About 8.9% of baseball pitchers that experience back pain will be diagnosed with spondylolysis. Therefore, this study aims to identify and quantify lumbar extension experienced during baseball pitching. It was hypothesized that young pitchers would exhibit less lumbar extension than older pitchers. A total of 187 healthy pitchers were divided into 3 age groups: youth, adolescent, and college. Kinematic data were collected at 250 Hz using a 3-D motion capture system. Lumbar motion was calculated as the difference between upper thoracic motion and pelvic motion over the pitching cycle. Lumbar “hyperextension” was defined as ≥20° past neutral. College pitchers had significantly greater lumbar extension compared with youth and adolescent pitchers at the point of maximum external rotation of the glenohumeral joint during the pitch cycle (−25° [13°], P = .04). For all age groups, lumbar hyperextension was present during the first 66% of the pitch cycle. Most pitchers spent 45% of pitch cycle in ≥30° of lumbar extension. Understanding that lumbar extension and hyperextension are components of the complex, multiplanar motions of the spine associated with baseball pitching can potentially help in both the prevention and management of symptomatic spondylolysis/spondylolisthesis.
Jinger S. Gottschall, Bryce Hastings and Zachary Becker
Popular topics for upper-body resistance training involve the differences between hand positions, open versus closed chain exercises, and movement variations for the novice to the advanced. It was hypothesized that there will be no difference between closed (push-up) versus open (bench press) chain exercises for the primary muscle group activity nor would there be a difference between push-ups on the toes versus knees with respect to the percent contribution of each muscle. Surface muscle activity was measured for 8 upper-body and core muscles during a sequence of push-up and bench press variations with a normalized weight for 12 active men. Each participant completed push-ups and bench press exercises at each of 3 hand positions. The results demonstrated that there were few differences between closed versus open chain exercises for the primary muscle groups with the exception of core activation. In addition, in general, narrow hand positions yielded greater activation, and there were no significant differences between push-ups on the toes versus knees with respect to the percent contribution for the primary muscle groups. In conclusion, closed chain exercises may be preferred for functional training, and knee push-ups may be ideal as a novice push-up variation.
Antoine Falisse, Sam Van Rossom, Johannes Gijsbers, Frans Steenbrink, Ben J.H. van Basten, Ilse Jonkers, Antonie J. van den Bogert and Friedl De Groote
Musculoskeletal modeling and simulations have become popular tools for analyzing human movements. However, end users are often not aware of underlying modeling and computational assumptions. This study investigates how these assumptions affect biomechanical gait analysis outcomes performed with Human Body Model and the OpenSim gait2392 model. The authors compared joint kinematics, kinetics, and muscle forces resulting from processing data from 7 healthy adults with both models. Although outcome variables had similar patterns, there were statistically significant differences in joint kinematics (maximal difference: 9.8° [1.5°] in sagittal plane hip rotation), kinetics (maximal difference: 0.36 [0.10] N·m/kg in sagittal plane hip moment), and muscle forces (maximal difference: 8.51 [1.80] N/kg for psoas). These differences might be explained by differences in hip and knee joint center locations up to 2.4 (0.5) and 1.9 (0.2) cm in the posteroanterior and inferosuperior directions, respectively, and by the offset in pelvic reference frames of about 10° around the mediolateral axis. The choice of model may not influence the conclusions in clinical settings, where the focus is on interpreting deviations from the reference data, but it will affect the conclusions of mechanical analyses in which the goal is to obtain accurate estimates of kinematics and loading.
Taylor K. Wise
Disordered eating (DE) plays a significant role in the overall health and athletic performance of collegiate athletes. The present study sought to determine how many NCAA Division I Football Bowl Subdivision Institutions have a policy that specifically addresses the prevention and management of DE for their participating athletes and to examine the content of the existing policies. The study searched for policies in the 128 FBS institutions through an online web-search and by contacting athletic department personnel. A total of 33 currently existing policies on athletes with eating disorders (EDs) were found, 13 of which were found online. A documentary analysis was then conducted to determine the type of information that policies include. Sixteen major themes were found throughout the analysis, including themes that related to prevention, risk factors, identification, treatment, referral, and return-to-play guidelines.
Sheryl Miller and Mary Fry
The purpose of this study was to examine the relationship of students’ perceptions of the motivational climate in their university exercise class to their body esteem (BE) and social physique anxiety (SPA). Students in physical activity classes at a Midwestern university completed a survey measuring their perceptions of the caring, task- and ego-involving features of the exercise class climate, BE (i.e., weight and appearance), and SPA. Canonical correlation analysis revealed one significant function for males and females. Loadings revealed males’ perceptions of a highly caring and task-involving climate with low emphasis on ego-involving climate features were associated with higher weight and appearance BE and lower SPA. Females were similar except the ego-involving climate did not significantly contribute to the model. Continued research may examine the link between motivational climate and BE, but mounting evidence suggests creating positive exercise environments is associated with participants’ adaptive responses, including BE and SPA.
Dana K. Voelker and Justine J. Reel
The number of studies examining eating disorders and body image in sport has increased, although several major challenges associated with conducting this research must be addressed to continue growth. In this paper, we describe these challenges based on our professional experiences and the academic literature. Mistrust of researchers and the area of study, communication gaps, and factors that affect data quality are among the strong barriers discussed. However, we suggest that these challenges may be addressed by building stronger partnerships between researchers and practitioners and offer critical steps for developing meaningful professional relationships that will help move the field forward.
Michelle R. Tanel, Tyler B. Weaver and Andrew C. Laing
While the literature has characterized balance control during quasi-static and/or dynamic tasks, comparatively few studies have examined relationships across paradigms. This study investigated whether quiet-stance postural steadiness metrics were associated with reactive control parameters (during both stepping and restabilization phases) following a lean-and-release perturbation. A total of 40 older adults participated. Postural steadiness (center of the pressure range, root mean square, velocity, and frequency) was evaluated in “feet together” and “tandem stance” positions. During the reactive control trials, the step length, step width, movement time, and reaction time were measured, in addition to the postural steadiness variables measured during the restabilization phase following the stepping response. Out of 64 comparisons, only 10 moderate correlations were observed between postural steadiness and reactive spatio-temporal stepping parameters (P ≤ .05, r = −.312 to −.534). However, postural steadiness metrics were associated with the center of pressure velocity and frequency during the restabilization phase of the reactive control trials (P ≤ .02, r = .383 to .775 for velocity and P ≤ .01, r = .386 to .550 for frequency). Although some elements of quasi-static center of pressure control demonstrated moderate associations with dynamic stepping responses, relationships were stronger for restabilization phase dynamics after foot-contact. Future work should examine the potential association between restabilization phase control and older adult fall-risk.
Rachel L. Wright, Joseph W. Bevins, David Pratt, Catherine M. Sackley and Alan M. Wing
Asymmetry in weight-bearing is a common feature in poststroke hemiparesis and is related to temporal asymmetry during walking. The aim of this study was to investigate the effect of an auditory cue for stepping in place on measures of temporal and weight-bearing asymmetry. A total of 10 community-dwelling adults (6 males and 4 females) with chronic poststroke hemiparesis performed 5 un-cued stepping trials and 5 stepping trials cued by an auditory metronome cue. A Vicon system was used to collect full body kinematic trajectories. Two force platforms were used to measure ground reaction forces. Step, swing, and stance times were used to calculate temporal symmetry ratios. Weight-bearing was assessed using the vertical component of the ground reaction force and center of mass–center of pressure separation at mid-stance. Weight-bearing asymmetry was significantly reduced during stepping with an auditory cue. Asymmetry values for step, swing, and stance times were also significantly reduced with auditory cueing. These findings show that auditory cueing when stepping in place produces immediate reductions in measures of temporal asymmetry and dynamic weight-bearing asymmetry.
Laura K. Fewell, Riley Nickols, Amanda Schlitzer Tierney and Cheri A. Levinson
Understanding the unique needs of athletes who undergo eating disorder (ED) treatment is sorely needed. This study explores changes of strength and power in athlete (n = 21) and non-athlete (n = 36) patients from intake to discharge. Maximal oxygen consumption, vertical jump, push-ups, hand grip strength, and body mass index (in anorexia nervosa; AN) were measured among treatment center patients. The number of push-ups and hand grip strength were significantly improved upon discharge in the full sample (ps < .005) and in AN only (ps < .001). Body mass index was also significantly higher in AN (p < .001). Maximal oxygen consumption and vertical jump did not significantly improve between admission and discharge in either group (ps > .40). This study is the first to investigate measures of strength in athletes engaged in intensive eating disorder treatment and indicates the need to address the psychological mindset around physical activity using exercise education as part of a comprehensive program. Recommendations for incorporating exercise into an intensive ED treatment center are also provided.