Browse

It has been suggested that core stability and plyometric training (CPT) can enhance athletes’ postural control. Nevertheless, the effects of an integrated core and plyometric training program on rhythmic gymnastics (RG) performance are unclear. This study aimed to evaluate the effects of an integrated functional CPT program on young rhythmics gymnasts’ postural performance. A sample of 44 young female rhythmic gymnasts from a competitive team (age = 10.5 ± 1.8 years) participated in the study. The subjects were randomly divided into a control group and an experimental group. Pre- and posttest design was used. Postural control was assessed using single-leg stance tests and RG-specific balances over a force platform and evaluated by expert RG judges. The experimental group (n = 23) completed an 8-week functional CPT program based on RG technical requirements. Meanwhile, the control group (n = 21) received their usual training sessions. A mixed model of analysis of variance was applied to evaluate the effects of an intrasubject factor and an intersubject factor on each of the dependent variables. After 8 weeks, the experimental group obtained significant better results in some variables of the right support leg with eyes open and left support leg with eyes open single-leg support (p < .01), improvements were also found in some specific RG balances: Arabesque measured on the force platform (p < .01) and the side leg with help balance scored by the judges (p < .01). In conclusion, an integrated functional CPT program improved postural control in young rhythmic gymnasts. Coaches should consider using this CPT to improve RG performance.

The uncontrolled manifold (UCM) approach quantifies the presence of compensatory variability between musculoskeletal elements involved in a motor task. This approach has proved useful for identifying synergistic control strategies for a variety of everyday motor tasks and for investigating how control strategies are affected by motor pathology. However, the UCM approach is limited in its ability to relate compensatory motor variance directly to task performance because variability along the UCM is mathematically agnostic to performance. We present a new approach to UCM analysis that quantifies patterns of irregularity in the compensatory variability between motor elements over time. In a bimanual isometric force stabilization task, irregular patterns of compensation between index fingers predicted greater performance error associated with difficult task conditions, in particular for individuals who exploited a larger set of compensatory strategies (i.e., a larger subspace of the UCM). This relationship between the amount and structure of compensatory motor variance might be an expression of underlying processes supporting performance resilience.

For this research, we analyzed the immediate effects of warm-up condition (WC) or without warm-up condition (WWC) on amateur referees’ physical and cognitive functioning. Eight professional soccer referees from the Balearic Committee of Football Referees were the participants of this study. Body composition characteristics were measured and the scores on three tests were recorded: the Yo-Yo intermittent recovery, repeated-sprint ability, and psychomotor vigilance task. Regarding results, the psychomotor vigilance task was performed better after warm-up training (p = .002, η² = .79) with faster reaction times following WC (M = 318.2, SD = 27.1 ms) than WWC (M = 334.9, SD = 26.1). Similarly, the referees’ performance was better on the repeated-sprint ability test after WC (p = .002, d = 0.53) than WWC, with minimum and average power values higher after WC (M = 626.77, SD = 112.57) than WWC (M = 562.35, SD = 79.63). We conclude that re-warm-up training may mitigate the vigilance performance changes caused by effects of rest on soccer referees.

During upright standing, individuals often use co-contraction muscle activity at the ankle joint when encountering increased postural difficulty; however, this strategy has been shown to be maladaptive. The purpose of the current investigation was to examine the effect of sloped standing on postural sway and muscle co-contraction at the ankle joint as a function of postural difficulty. Twelve young (21.67 ± 1.11 years) adults performed upright standing on flat, declined, and inclined support surfaces. Center of pressure displacements indexed postural sway while electromyography data were collected for the tibialis anterior and gastrocnemius medialis muscles. A co-contraction index and a nonlinear coupling metric (cross-approximate entropy) were computed between ankle dorsiflexor and plantar flexor muscles (tibialis anterior/gastrocnemius medialis) activity. The results showed that higher degrees of postural difficulty led to increased amounts of sway as well as increased sway regularity. Lower co-contraction index was observed for higher degrees of postural difficulty; however, increased dynamic coupling occurred with deviations from the flat standing condition. Overall, increased postural difficulty as manipulated by sloped standing (in either inclined or declined conditions) resulted in individuals adopting a more regular sway trajectory that may be due, in part, to a stronger dynamic coupling strategy occurring at the neuromuscular level.

Biomechanical trajectories are often routed through a chain of processing steps prior to statistical analysis. As changes in processing parameter values can affect these trajectories, care is required when choosing data processing specifics. The purpose of this Research Note was to demonstrate a simple way to propagate data processing parameter uncertainty to statistical inferences regarding biomechanical trajectories. As an example application, the correlation between foot contact duration and vertical ground reaction force during constant-speed treadmill walking was considered. Uncertainty was modeled using plausible-range uniform distributions in three data processing steps, and Monte Carlo simulation was used to construct probabilistic representations of both individual vertical ground reaction force measurements and the ultimate statistical results. Whereas an initial, plausible set of parameter values yielded a significant correlation between contact duration and late-stance vertical ground reaction force, Monte Carlo simulations revealed strong sensitivity, with “significance” being reached in fewer than 40% of simulations, with relatively little net effect of parameter uncertainty magnitude. These results indicate that propagating processing parameter uncertainty to statistical results promotes a cautious, nuanced, and robust view of observed effects. By extension, Monte Carlo simulations may yield greater interpretive consistency across studies involving data processing uncertainties.

The purpose of the study was to investigate which changes in kinematics and muscle activity in healthy, middle-aged women are introduced to maintain balance on an unstable platform. Biodex Balance System tests were used in stable and unstable modes (sudden with eyes open/closed and gradual with eyes open). Simultaneously, lower-extremity kinematics and surface electromyography of back and legs muscles were captured. The dependence between balance scores, movement ranges, and root mean square of electromyography was assessed with multiple regression to evaluate the strategy used. The results showed multisegmental movements in sudden instability, and activity of at least one of the following muscles: gluteus maximus, erector spinae, and soleus in all conditions. Best balance scores were achieved when movements appeared in pelvis in transverse, and hip in frontal planes, worst when in pelvis in frontal, hip, and ankle in sagittal planes, and when mentioned muscles were activated. Further research is needed to identify the determinants of strategy choice.

This study compared electromyography of five leg muscles during a single walking task (WALK) to a dual task (walking + cognitive task; COG) in 40 individuals (20 M and 20 F) using a wavelet analysis technique. It was hypothesized that muscle activation during the dual task would differ significantly from the walking task with respect to both timing (H1) and frequency (H2). The mean overall intensity for the COG trials was 4.1% lower for the tibialis anterior and 5.5% higher for the gastrocnemius medialis than in the WALK trials. The changes between the WALK and COG trials were short 50 ms bursts that occurred within 100 ms of heel strike in the tibialis anterior, and longer activation periods during the stance phase in the gastrocnemius medialis. No changes in overall intensity were observed in the peroneus longus, gastrocnemius lateralis, or soleus. Furthermore, no clear frequency bands within the signal could further characterize the overall changes in muscle activity during the COG task. This advances our understanding of how the division of attentional resources affects muscle activity in a healthy population of adults.

This paper investigates whether a group of regular Yoga practitioners shows postural control differences compared with healthy controls while performing single-leg Yoga postures. Ten Yoga practitioners were compared with a control group of 10 nonpractitioners performing two single-leg support Yoga postures: Vrksasana (tree posture) and Natarajasana (dancer posture). Rambling and trembling decomposition of the center of pressure trajectories was implemented using a genetic algorithm spectral optimization that avoids using horizontal forces and was validated with bipedal posture data. Additionally, the center of mass was estimated from body kinematics using OpenSim and compared with the rambling outputs. During Natarajasana, no postural control adaptations were observed. For Vrksasana, the Yoga practitioners showed a lower center of pressure ellipse confidence interval area, center of pressure anteroposterior SD, and smaller rambling SD in the mediolateral direction, suggesting possible supraspinal feed-forward motor adaptations associated with Yoga training.