Comparison of longitudinal biomechanical adaptation to shoe degradation between the dominant and non-dominant legs during running

This study compared the biomechanical adaptation to running shoe degradation between the dominant (D) and non-dominant (ND) leg. Twenty-four runners performed a pre-test in the laboratory, completed 200 miles of road running in a pair of assigned shoes and then returned for a post-test. Kinetic and kinematic data of running in new and worn shoes were collected. Repeated measures ANOVA (Shoe × Leg) were used to analyze temporal, kinetic and kinematic variables (α = .05). A symmetry index (SI) was calculated for the temporal and kinetic variables and paired t-tests were used to compare the SI between shoe conditions. Stance time increased by approximately 7 ms in worn shoes (p = .027). Bilateral differences in the kinematic change (Shoe × Leg interaction) were seen in the torso (p < .05), knee (p < .05), marginally at the hip (p < .10) but not the ankle. No difference in kinetic variables or SI was observed. When running in worn shoes, the torso displayed reduced forward lean for both sides and to a greater extent during the D leg strike. The D hip and knee showed a more extended position for the worn shoe condition while an increased flexion was observed in the ND leg. Most of the kinematic differences observed were small and within the intra-subject variability measured during the same session. Future studies may consider performing a three-dimensional analysis at a higher sample rate and further explore whether asymmetrical adaptation is related to running injuries.     

Kinematics, kinetics, and electromyogram of ankle during drop landing: a comparison between dominant and non-dominant limb

The biomechanical difference between the dominant and non-dominant limb has seldom been studied during double-leg landing. The objective of this study was to evaluate the effectiveness of limb laterality on the ankle kinematics, kinetics and electromyogram (EMG) during drop landing. Sixteen healthy adults were recruited and dropped individually from platforms with three different heights (0.32 m, 0.52 m, and 0.72 m). The ground reaction force, ankle joint kinematics, and surface EMG of tibialis anterior (TA) and lateral gastrocnemius (LG) were measured in both lower extremities. Two-way analysis of variance was used to analyze the effects of laterality and dropping height. The peak angular velocities in dorsiflexion and abduction were significantly higher in the dominant ankle, whereas the pre- and post-landing EMG amplitudes of the TA were significantly higher in the non-dominant limb. Compared with the dominant side, the non-dominant ankle has a more effective protective mechanism in that excessive joint motion is restrained by greater ankle flexor activity. Compared with the non-dominant side, the dominant ankle joint is in greater injury risk during drop landing, and data measured in the dominant limb may produce more conservative conclusions for injury protection or prediction.     

The influence of monetary reward and punishment on psychological, physiological, behavioral and performance aspects of a golf putting task

The primary purpose of the present study was to examine kinematic characteristics and force control during a golf-putting task under a pressure condition. The secondary purpose was to provide an exploratory investigation of the relationship between changes in behavior (kinematics and force control) and performance on the one hand, and psychological (attention and affect) and physiological (arousal level) changes on the other hand. Twenty male novices performed 150 acquisition trials, followed by 10 test trials during a pressure condition induced by performance-contingent distracters: a cash reward or punishment. A three-dimensional motion analysis revealed that, during the pressure test, angular displacements of rotational movements at the horizontal plane and movement time of the arms and club during the backswing and downswing phases all decreased, while acceleration of the elbows during the downswing phase increased. Mean performance indices in all participants’ were unchanged in spite of the kinematic changes under the pressure condition. Multiple regression analyses indicated that the decrement in performance, as well as increased variability of movement time and speed, were more likely to increase when participants shifted their attention to movements. Furthermore, changes in heart rate and negative affect were related to both the increase in movement acceleration and a decrease in grip force. These findings suggest that performance and behavioral changes during golf-putting under pressure can be associated with attentional changes, along with the influences of physiological-emotional responses.     

Prediction of postural risk of fall initiation based on a two-variable description of body dynamics: Position and velocity of center of mass

This research addresses the question: what is the risk of fall initiation at a certain human posture? There are postures from which no one is able to keep their balance and a fall will surely initiate (risk = 1), and others from which everyone may regain their stability (risk = 0). In other postures, only a portion of people can control their stability. One may interpret risk to chance of a fall to be initiated, and based on the portion of fallers assign a risk value to a given human posture (postural risk). Human posture can be mapped to a point in a 2-dimensional space: the x − v plane, the axes of which are horizontal components of the position and velocity of the center of mass of the body. For every pair of (x, v), the outcome of the balance recovery problem defines whether a person with a given strength level is able to regain their stability when released from a posture corresponding to that point. Using strength distribution data, we estimated the portion of the population who will initiate a fall if starting at a certain posture. A fast calculation approach is also introduced to replace the time-consuming method of solving the recovery problem many times. Postural risk of fall initiation for situations expressed by (x, v) pairs for the entire x − v plane is calculated and shown in a color-map.     

Neurobiological degeneracy: Supporting stability,flexibility and pluripotentiality in complex motor skill

This paper investigated neurobiological degeneracy of the motor system that emerged as a function of levels of environmental constraint. Fourteen participants performed a breaststroke-swimming task that required them to develop a specific biomechanically expert pattern and in turn provide the basis for a suitable task vehicle to study the functional role of movement variability. Inter-limb coordination was defined based on the computation of continuous relative phase between elbow and knee oscillators. Unsupervised cluster analysis on arm–leg coordination revealed the existence of different patterns of coordination when participants achieved the same task goal under different levels of environmental constraints (i.e. different amounts of forward resistances). In addition, clusters differed in terms of higher order derivatives (e.g., joint angular velocity, joint amplitude), suggesting an effective role for degeneracy in learning by allowing the exploration of the key relationships between motor organization and interacting constraints. There is evidence to suggest that neurobiological degeneracy supports the potential for motor re-organization to enhance motor learning.     

Behavioural variability and motor performance: Effect of practice specialization in front crawl swimming

The aim was to examine behavioural variability within and between individuals, especially in a swimming task, to explore how swimmers with various specialty (competitive short distance swimming vs. triathlon) adapt to repetitive events of sub-maximal intensity, controlled in speed but of various distances. Five swimmers and five triathletes randomly performed three variants (with steps of 200, 300 and 400 m distances) of a front crawl incremental step test until exhaustion. Multi-camera system was used to collect and analyse eight kinematical and swimming efficiency parameters. Analysis of variance showed significant differences between swimmers and triathletes, with significant individual effect. Cluster analysis put these parameters together to investigate whether each individual used the same pattern(s) and one or several patterns to achieve the task goal. Results exhibited ten patterns for the whole population, with only two behavioural patterns shared between swimmers and triathletes. Swimmers tended to use higher hand velocity and index of coordination than triathletes. Mono-stability occurred in swimmers whatever the task constraint showing high stability, while triathletes revealed bi-stability because they switched to another pattern at mid-distance of the task. Finally, our analysis helped to explain and understand effect of specialty and more broadly individual adaptation to task constraint.     

Forecasting from ignorance: the use and usefulness of recognition in lay predictions of sports events

Whereas previous studies on how people make forecasts of sports events focused primarily on experts, we examined how laypeople do this task. In particular, we (a) tested the recognition heuristic [Goldstein, D. G., & Gigerenzer, G. (2002). Models of ecological rationality: the recognition heuristic. Psychological Review, 109, 75-90], which requires partial ignorance, against four alternative mechanisms in describing laypeople's forecasts for the European Soccer Championships 2004; (b) evaluated how well recognition predicted the outcomes of the matches compared to direct indicators of team strength (e.g., past performance, rankings); and (c) studied the less-is-more effect--the phenomenon that knowing less leads to more correct forecasts than knowing more--which can occur when the recognition heuristic is used. Two groups of participants (laypeople, experts) made forecasts for the first-round matches of the tournament. Of the five candidate mechanisms, the recognition heuristic predicted laypeople's forecasts best: when applicable, it accounted for 90% of the forecasts. The recognition heuristic correctly predicted the actual winner of the matches substantially better than chance but did not achieve the accuracy of direct indicators of team strength. The experts made more correct forecasts than the laypeople. Moreover, we found no benefit of ignorance among the group of laypeople, although the conditions for a less-is-more effect specified by Goldstein and Gigerenzer were fulfilled.     

Action preferences and the anticipation of action outcomes

Skilled performers of time-constrained motor actions acquire information about the action preferences of their opponents in an effort to better anticipate the outcome of that opponent's actions. However, there is reason to doubt that knowledge of an opponent's action preferences would unequivocally influence anticipatory responses in a positive way. It is possible that overt information about an opponent's actions could distract skilled performers from using the advance kinematic information they would usually rely on to anticipate actions, particularly when the opponent performs an ‘unexpected’ action that is not in accordance with his or her previous behaviour. The aim of this study was to examine how the ability to anticipate the outcome of an opponent's actions can be influenced by exposure to the action preferences of that opponent. Two groups of skilled handball goalkeepers anticipated the direction of penalty throws performed by opponents before and after a training intervention that provided situational probability information in the form of action preferences (AP). During the training phase participants in an AP-training group anticipated the action outcomes of two throwers who had a strong preference to throw in one particular direction, whilst participants in a NP-training group viewed players who threw equally to all directions. Exposure to opponents who did have an action preference during the training phase resulted in improved anticipatory performance if the opponent continued to bias their throws towards their preferred direction, but decreased performance if the opponent did not. These findings highlight that skilled observers use information about action preferences to enhance their anticipatory ability, but that doing so can be disadvantageous when the outcomes are no longer consistent with their generated expectations.     

Application of the Copenhagen Soccer Test in high-level women players – locomotor activities,physiological response and sprint performance

We evaluated the physiological response, sprint performance and technical ability in various phases of the Copenhagen Soccer Test for Women (CSTw) and investigated whether the locomotor activities of the CSTw were comparable to competitive match-play (CM). Physiological measurements and physical/technical assessments were performed during CSTw for eleven Norwegian high-level women soccer players. The activity pattern during CSTw and CM was monitored using the ZXY tracking system. No differences were observed between CSTw and CM with regards to total distance covered (10093 ± 94 and 9674 ± 191 m), high intensity running (1278 ± 67 and 1193 ± 115 m) or sprinting (422 ± 55 and 372 ± 46 m) (p > .05). During CSTw, average HR was 85 ± 2%HRmax with 35 ± 2% playing time >90%HRmax. Blood lactate increased (p < .05) from 1.4 ± 0.3 mM at rest to an average of 4.7 ± 0.5 mM during CSTw, with no changes during the test. Blood glucose was 5.4 ± 0.3 mM at rest and remained unaltered during CSTw. Sprint performance (2 × 20 m) decreased (p < .05) by 3% during CSTw (8.19 ± 0.06–8.47 ± 0.10 s). In conclusion, the locomotor activities during CSTw were comparable to that of high-level competitive match-play. The physiological demands of the CSTw were high, with no changes in heart rate, blood lactate or technical performance during the test, but a lowered sprint performance towards the end of the test.     

Characterization of speed fluctuation and drag force in young swimmers: A gender comparison

The aim of this study was to compare the speed fluctuation and the drag force in young swimmers between genders. Twenty-three young pubertal swimmers (12 boys and 11 girls) volunteered as subjects. Speed fluctuation was measured using a kinematical mechanical method (i.e., speedo-meter) during a maximal 25-m front crawl bout. Active drag, active drag coefficient and power needed to overcome drag were measured with the velocity perturbation method for another two maximal 25 m front crawl bouts with and without the perturbation device. Passive drag and the passive drag coefficient were estimated using the gliding decay velocity method after a maximal push-off from the wall while being fully immersed. The technique drag index was also assessed as a ratio between active and passive drag. Boys presented meaningfully higher speed fluctuation, active drag, power needed to overcome drag and technique drag index than the girls. There were no significant gender differences for active drag coefficient, passive drag and passive drag coefficient. There were positive and moderate-strong associations between active drag and speed fluctuation when controlling the effects of swim velocity. So, increasing speed fluctuation leads to higher drag force values and those are even higher for boys than for girls.