The effectiveness of penalty takers' deception: A scoping review.

Attackers are supposed to take advantage of producing deceptive actions in competitive ball sports, particularly in penalty situations. We conducted a scoping review of the experimental literature to scrutinize whether penalty takers do indeed benefit from using deceptive actions in penalty situations, especially by increasing the likelihood to score a goal. Studies using video-based and in-situ tasks in which soccer and handball goalkeepers try to save a penalty were evaluated. Results showed that penalty takers' manipulation of spatial information available to the goalkeeper during deception (i.e., by using misleading and/or disguising actions) is less effective in in-situ than video-based studies. We argue that this difference occurs because goalkeepers adapt differently to the spatiotemporal constraints in the video-based and in-situ tasks. Goalkeepers appear to prioritize picking up spatial information in video-based tasks while prioritizing temporal information in-situ tasks. Therefore, the manipulation of spatial information appears to be less effective in the more representative in-situ studies than in video-based studies. In order to deceive, penalty takers are advised to manipulate temporal information during on-field penalty situations.

Is Prescription of Specific Movement Form Necessary for Optimal Skill Development? A Nonlinear Pedagogy Approach.

Purpose: Nonlinear Pedagogy (NLP) proposes that skill development is a nonlinear process, advocating the integration of variability into practice to facilitate individualized movement patterns. However, the influence of a NLP for skills that emphasize a specific movement form is relatively unknown. This study aimed to investigate the impact of a NLP approach when learning a movement form based skill. Method: Sixteen beginners in the power clean (PC), were randomly assigned into a linear pedagogy (LP) condition receiving instructions that prescribed explicit movement form, and a NLP condition presented with analogy-based instructions and two task constraints. Both conditions completed seven lessons across 4-weeks. Results: There were no significant differences in the quantity of exploration, with both conditions demonstrating a similar range of movement patterns. These findings were coupled with a significant improvement in performance accuracy (reduced forward movement of the barbell; F × D) for both conditions. No significant differences were detected in the distribution of barbell trajectory types, with type one, three and four trajectories being exhibited to a similar degree in both conditions. Conclusion: Findings from this study suggests both NLP and LP pedagogies can successfully develop movement form based skills. Overall, both NLP and LP approaches appear to positively influence skill development. These findings have important implications for practitioners suggesting that deviations from instructed technique in learners (i.e., LP approach) do not negatively impact performance. However, further research is needed to determine whether these approaches can more effectively facilitate learners' search for movement solutions that "fit" their individual abilities.

Development of Defensive Actions in Small-Sided and Conditioned Games With Offensive Purposes in Futsal.

Based on ecological dynamics approach, non-linear pedagogy (NLP) have emerged with the goal of promoting a holistic approach through the use of small-sided and conditioned games (SSCGs), to optimize specific tactical defensive and offensive behaviors of players. This study analyzed the indirect effects of an intervention program, based on NLP (task design based on tactical principles of attack and numerical advantage of attacking team), in decision-making (DM) and execution (Ex) in defensive technical-tactical actions in U16 futsal. Eight futsal players (U16 years) participated in 12 training sessions, spread over two phases: preintervention and intervention. The Game Performance Evaluation Tool (GPET) instrument was used to analyze the DM and Ex of 2,600 defensive actions measured during competitive matches. Results showed significant improvements in marking actions (to the player with the ball: DM, p = 0.001; Ex, p = 0.001; and to the player without the ball: DM, p = 0.039; Ex, p = 0.046), improvements in blocking actions (DM, p = 0.015), and improvements in help-coverage actions (Ex, p = 0.014). No significant differences were found in the interception and tackling actions. This study has shown evidence that the NLP approach is an appropriate theoretical framework to enhance acquisition of defensive tactical behavior in futsal. However, not all actions improved. Therefore, coaches should design representative tasks to optimally develop technical-tactical training processes based on the phases of futsal game (offensive and defensive) and considering the level of opposition.

Effect of an Inside Floater on Soccer Players Tactical Behaviour in Small Sided and Conditioned Games.

The aim of this study was to verify the effect of an inside floater on soccer players' tactical behaviour in small-sided and conditioned games (SSCGs). The sample comprised 54 Brazilian top-level academy players. The instrument used to assess players' tactical behaviour was the System of Tactical Assessment in Soccer (FUT-SAT). Tactical behaviour was analysed through the number of tactical actions and the percentage of correct actions regarding the core tactical principles of soccer. Repeated measures test was used to compare tactical behaviour between games (SSCGs) with and without an inside floater. Pearson's r was used to verify the effect size of the inside floater on tactical behaviour. As for tactical actions, SSCGs with an inside floater displayed significantly lower means for the tactical principles of penetration (2.76 ± 1.63; p < .001), delay (6.11 ± 2.68; p < .018), defensive coverage (1.64 ± 1.14; p < .001) and significantly higher means for the tactical principle of defensive unity (14.98 ± 4.57; p < .032). With respect to the percentage of correct actions, SSCGs with an inside floater displayed significantly lower means for all tactical principles, except for offensive coverage (90.5 ± 18.48; p < 1.000). It was concluded that the inside floater allowed players to modify their behaviour in such a way that they adapted to the constraints imposed by the presence of an inside floater. Furthermore, the inside floater provided more difficulty for players, and thus may be considered an important task constraint to be added in SSCGs.

Dynamic bimanual force control in chronic stroke: contribution of non-paretic and paretic hands.

Dynamic force modulation is critical for performing skilled bimanual tasks. Unilateral motor impairments after stroke contribute to asymmetric hand function. Here, we investigate the impact of stroke on dynamic bimanual force control and compare the contribution of each hand to a bimanual task. Thirteen chronic stroke and thirteen healthy control participants performed bimanual, isometric finger flexion during visually guided, force tracking of a trapezoidal trajectory with force increment and decrement phases. We quantified the accuracy and variability of total force from both hands. Individual hand contribution was quantified with the proportion of force contributed to total force and force variability of each hand. The total force output was 53.10% less accurate and 56% more variable in the stroke compared with the control group. The variability of total force was 91.10% greater in force decrement than increment phase. In stroke group, the proportion of force and force variability contributed by each hand differed across the two phases. During force decrement, the proportion of force contributed by the non-paretic hand reduced and force variability of the non-paretic hand increased, compared with the increment phase. The control group showed no differences in each hand's contribution across the two force phases. In conclusion, dynamic bimanual force modulation is impaired after stroke, with greater deficits in force decrement than force increment. The non-paretic and paretic hands adapt differentially to dynamic bimanual task constraints. During force decrement, the non-paretic hand preferentially assumes force modulation, while the paretic hand produces steady force to meet the force requirements.

The goal of locomotion: Separating the fundamental task from the mechanisms that accomplish it.

Human locomotion has been well described but is still not well understood. This is largely true because the observable aspects of locomotion-neuromuscular activity that generates forces and motions-relate to both the task solution and the problem being solved. Identifying the fundamental task achieved in locomotion makes it possible to critically evaluate the motor control strategy used to accomplish the task goal. We contend that the readily observed movements and activities of locomotion should be considered mechanism(s). Our proposal is that the fundamental task of walking and running is analogous to flight, and should be defined in terms of the interaction of the individual's mass with the medium in which it moves: a low-density fluid for flight, or the supporting substrate for legged locomotion. A rigorous definition of the fundamental task can help identify the constraints and opportunities that influence its solution and guide the selection of appropriate mechanisms to accomplish the task effectively. The results from robotics-based modeling studies have demonstrated how the interaction of the mass and substrate can be optimized, making the goal of movement a defined trajectory of the individual's mass. We assessed these concepts by evaluating the ground reaction forces generated by an optimization model that satisfies the task but uses none of the mechanisms that are available to the human leg. Then we compared this model to normal human walking. Although it is obvious that the specific task of locomotion changes with a variety of movement challenges, clearly identifying the fundamental task of locomotion puts all other features in an interpretable context.

Influence of football size on kicking performance in youth Australian rules footballers.

In Australian rules football structured increases in ball size during development end with the transition to the Size 5 (adult) ball at the Under-15 age group. This study assessed changes in kick technique and performance in experienced junior performers when using Size 4 and 5 Australian rules footballs. Participants (n = 22, 13.77 ± 0.61 years) performed drop punt kicks in 2 representative tasks; a Decision-Making Test (DMT) (n = 14) and Set-Shot Test (SST) (n = 14 + 8). Results indicate participants sustained their level of kick performance (accuracy and quality of ball spin) in both tests when using a Size 5 football. Sustained kick performance in the DMT primarily resulted from adaptations to time-point technical measures at ball release. No significant differences were detected for technical measures between ball sizes in the SST. A dynamic kicking task (DMT) in combination with ball size manipulation may have placed greater demand on skill execution in comparison to a self-paced kicking task (SST). Results provide initial support for the utility of challenging representative dynamic and self-paced tasks, such as the DMT and SST used here for Australian football, for skill testing and practice in sport.

Influence of contextual task constraints on preferred stride parameters and their variabilities during human walking.

Walking is not always a free and unencumbered task. Everyday activities such as walking in pairs, in groups, or on structured walkways can limit the acceptable gait patterns, leading to motor behavior that differs from that observed in more self-selected gait. Such different contexts may lead to gait performance different than observed in typical laboratory experiments, for example, during treadmill walking. We sought to systematically measure the impact of such task constraints by comparing gait parameters and their variability during walking in different conditions over-ground, and on a treadmill. We reconstructed foot motion from foot-mounted inertial sensors, and characterized forward, lateral and angular foot placement while subjects walked over-ground in a straight hallway and on a treadmill. Over-ground walking was performed in three variations: with no constraints (self-selected, SS); while deliberately varying walking speed (self-varied, SV); and while following a toy pace car programmed to vary speed (externally-varied, EV). We expected that these conditions would exhibit a statistically similar relationship between stride length and speed, and between stride length and stride period. We also expected treadmill walking (TM) would differ in two ways: first, that variability in stride length and stride period would conform to a constant-speed constraint opposite in slope from the normal relationship; and second, that stride length would decrease, leading to combinations of stride length and speed not observed in over-ground conditions. Results showed that all over-ground conditions used similar stride length-speed relationships, and that variability in treadmill walking conformed to a constant-speed constraint line, as expected. Decreased stride length was observed in both TM and EV conditions, suggesting adaptations due to heightened awareness or to prepare for unexpected changes or problems. We also evaluated stride variability in constrained and unconstrained tasks. We observed that in treadmill walking, lateral variability decreased while forward variability increased, and the normally-observed correlation between wider foot placement and external foot rotation was eliminated. Preferred stride parameters and their variability appear significantly influenced by the context and constraints of the walking task.

Effect of speed on local dynamic stability of locomotion under different task constraints in running.

A number of studies have investigated effects of speed on local dynamic stability of walking, although this relationship has been rarely investigated under changing task constraints, such as during forward and backward running. To rectify this gap in the literature, the aim of this study was to investigate the effect of running speed on local dynamic stability of forward and backward running on a treadmill. Fifteen healthy male participants took part in this study. Participants ran in forward and backward directions at speeds of 80%, 100% and 120% of their preferred running speed. The three-dimensional motion of a C7 marker was recorded using a motion capture system. Local dynamic stability of the marker was quantified using short- and long-term largest finite-time Lyapunov exponents (LyE). Results showed that short-term largest finite-time LyE values increased with participant speed meaning that local dynamic stability decreased with increasing speed. Long-term largest finite-time LyEs, however, remained unaffected as speed increased. Results of this study indicated that, as in walking, slow running is more stable than fast running. These findings improve understanding of how stability is regulated when constraints on the speed of movements is altered. Implications for the design of rehabilitation or sport practice programmes suggest how task constraints could be manipulated to facilitate adaptations in locomotion stability during athletic training.