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.     

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.     

Perceived benefits of marathon running in males and females

The differences in both perceived benefits and attitudes toward running between male and female runners, and between runners who classified themselves as competitive runners (CR) or recreational runners (RR), was the focus of this study. Four-hundred and two runners completed the Ten-Minute Survey for Runners within two weeks of completing a marathon. RR, more so than CR, perceived greater benefits from running. However, CR expressed a more positive attitude toward running and its role in their lives than did RR. Men perceived running to be more beneficial to them than women. However, women, more so than men, felt running had a positive effect on self-image and their lives were richer because of running. Future research concerns on the effects of competition on the lives of women are explored.     

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.     

Energy expenditure and enjoyment of small-sided soccer games in overweight boys

When space is limited, it would be preferable to play multiple small-sided soccer games (SSG) simultaneously on small courts, rather than a single game, to maximise participation. Given that the layouts of most gymnasiums incorporate several badminton courts, we examined whether energy expenditure and enjoyment of SSG on a badminton court (6.1 × 13.4 m) were comparable to larger court dimensions (volleyball and basketball courts; 9 × 18 m and 14.2 × 26.5 m, respectively). Twelve overweight boys played 30 min three-a-side SSG on each court in a counterbalanced design. During SSG, energy expenditure was estimated via accelerometry, heart rate was monitored and ratings of perceived exertion (RPE) and enjoyment were obtained. Energy expenditure was similar between badminton and volleyball courts, but lower than the basketball court (p < .05). Mean% HR_max was significantly lower on the badminton court than the volleyball and basketball courts (p < .05). There was no effect of court size on RPE or enjoyment (p > .05). These results suggest that it may be preferable to play SSG on a larger court when space is available. Alternatively, when space is limited the difference in energy expenditure between court sizes can be accounted for by an additional 2.3 min of play on a badminton court.     

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.     

Effects of the stress of marathon running on implicit and explicit memory

We tested the idea that real-world situations, such as the highly strenuous exercise involved in marathon running, that impose extreme physical demands on an individual may result in neurohormonal changes that alter the functioning of memory. Marathon runners were given implicit and explicit memory tasks before or immediately after they completed a marathon. Runners tested immediately upon completing the marathon showed impairment in the explicit memory task but enhancement in the implicit memory task. This postmarathon impairment in explicit memory is similar to that seen with amnesic patients with organic brain damage. However, no previous studies have shown a simultaneous enhancement in the implicit memory task, as shown by the marathon runners in the present study. This study indicates that human memory functioning can be dynamically altered by such activities as marathon running, in which hundreds of thousands of healthy normal individuals routinely partake.     

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.     

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.     

Inter-individual variability in the upper-lower limb breaststroke coordination

The aim of the present study was to examine inter-individual variability in upper-lower limb breaststroke coordination. First, inter-individual variability was compared between recreational and comparative swimmers. Second, as recreational swimmers revealed more variable inter-limb coordination than competitive swimmers, inter-individual variability was assessed among recreational swimmers to identify coordination profiles. The elbow-knee continuous relative phase (CRP) was used to analyze upper-lower limbs coupling during a breaststroke cycle. Twenty-four recreational and twenty-four competitive swimmers swam 25 m at 80% of their maximal speed. Underwater and aerial side views were mixed and genlocked. Angular position, velocity and CRP were calculated for the knee and elbow joints by digitizing body markers from the side view. The kinematics of three cycles were filtered, averaged and normalized in terms of percentage of total cycle duration. The topography of the mean CRP curve of the recreational swimmers resembled a ‘W-shape’, whereas an ‘inverse U-shape’ was seen in the competitive swimmers. However, higher inter-individual variability was observed among the recreational swimmers than among the competitive swimmers (38.1° vs. 19.4°; p < .05), suggesting that several profiles of inter-limb coordination may exist in recreational swimmers. Coordination profiling showed that three clusters could classify the recreational swimmers.     

The effect of local kinematic changes on anticipation judgments

Skilled tennis players rely on a more global than local perceptual strategy when anticipating an opponent’s shot direction in tennis (Williams, Huys, Cañal-Bruland, & Hagemann, 2009). Global perceptual strategy refers to the pick-up of dynamic information across different body areas rather than from a single source such as the arm or racket. We extend previous work by examining the spatiotemporal characteristics of visual information pick-up when anticipating shot direction in tennis. We perturbed information from various body locations by interchanging the dynamics of selected areas with those from strokes played to the opposite side of the court. In addition, we presented each manipulation under four different temporal occlusion conditions (from 240 ms prior to racket-ball contact) to examine the time course of information extraction. Skilled tennis players outperformed less skilled counterparts in predicting shot direction, even at early phases of the opponent’s motion. Moreover, skilled players showed significant decrements in performance when the arms and racket were perturbed, highlighting the relevance of distal information when anticipating opponents’ intentions.     

The dynamical structure of handball penalty shots as a function of target location

We used principal components analysis (PCA) to investigate variations in the dynamical structure of handball penalty shots as a factor of target location and phase of shot. Participants completed a total of 10 successful shots to each of four target locations in the handball goal. Three dimensional movement time series data were analyzed. Also, data were analyzed across three temporally distinct time windows in line with the evolving kinematic chain. Statistical analyses were undertaken to determine differences across target locations. There were no significant differences between dynamical structures as a factor of target or phase. Covariance between time evolutions as a factor of target reduced in line with the ranking of the component. When shots were analyzed as three distinct time windows, only the low time evolution covariances suggested differences between targets in any time window. Our findings show that the dynamical structure underpinning the handball penalty shot does not differ greatly across locations. However, the time evolution of principal components suggests there are some variations in dynamics which may differentiate shot direction.     

Continuous visual control of interception

People generally try to keep their eyes on a moving target that they intend to catch or hit. In the present study we first examined how important it is to do so. We did this by designing two interception tasks that promote different eye movements. In both tasks it was important to be accurate relative to both the moving target and the static environment. We found that performance was more variable in relation to the structure that was not fixated. This suggests that the resolution of visual information that is gathered during the movement is important for continuously improving predictions about critical aspects of the task, such as anticipating where the target will be at some time in the future. If so, variability in performance should increase if the target briefly disappears from view just before being hit, even if the target moves completely predictably. We demonstrate that it does, indicating that new visual information is used to improve precision throughout the movement.     

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.     

Action specificity increases anticipatory performance and the expert advantage in natural interceptive tasks

The relationship between perception-action coupling and anticipatory skill in an interceptive task was examined using an in-situ temporal occlusion paradigm. Skilled and novice cricket batsmen were required to predict the direction of balls bowled towards them under four counterbalanced response conditions of increasing perception-action coupling: (i) verbal, (ii) lower-body movement only, (iii) full-body movement (no bat), and (iv) full-body movement with bat (i.e., the usual batting response). Skilled but not novice anticipation was found to improve as a function of coupling when responses were based on either no ball-flight, or early ball-flight information, with a response requiring even the lowest degree of body movement found to enhance anticipation when compared to a verbal prediction. Most importantly, a full-body movement using a bat elicited greater anticipation than an equivalent movement with no bat. This result highlights the important role that the requirement and/or opportunity to make bat-ball interception may play in eliciting skill differences for anticipation. Results verify the importance of using experimental conditions and task demands that closely reflect the natural performance environment in order to reveal the full nature of the expert advantage.     

Mood change and marathon running: A pilot study using a Swedish version of the POMS test

Regular exercise is said to have positive effects on mood, especially if the exercise intensity is low to moderate. However, the acute effects resulting from participation in a strenuous competition, such as a marathon race, have been studied less. The present investigation used the Profile of Mood States (POMS) test to measure mood, before and after the 1989 Stockholm Marathon. A total of 106 male runners (mean age 40.0 years), with finishing times between 3h and 3h 45 min participated as subjects. Results showed great changes between pre- and post-marathon scores, most of them significant at the p less than 0.001 level. Furthermore, differences between a faster and a slower group of runners were demonstrated with regard to mood states, even though plasma glucose levels were comparable. It is concluded that participation in a marathon race greatly effects mood, mainly in a more negative way than low to moderately intense exercise does.     

Anticipation skill and susceptibility to deceptive movement

The ability to detect deceptive movement was examined in skilled and novice rugby players. Participants (14 per group) attempted to predict direction change from video of expert and recreational rugby players changing direction with and without deceptive movement. Confidence associated with judgments was recorded on each trial to seek evidence regarding use of inferential (heuristic-based) and direct-perceptual (invariant-based) judgments. Novices were found to be susceptible to deceptive movement whereas skilled participants were not; however, both skilled and novice participants were more confident on trials containing deceptive movement. The data suggest that the skill-level difference in sensitivity to advance visual information extends to deceptive information. The implications of this finding, and the importance of considering the underlying process of anticipation skill, are discussed.     

Hitting the wall in the marathon: Phenomenological characteristics and associations with expectancy,gender, and running history

ObjectivesThis study was designed to identify salient characteristics of hitting the wall in the marathon and to assess the frequency of self-reported occurrence of the wall as a function of expectancy, gender, and running history.DesignA correlational research design was used.MethodParticipants (218 men and 97 women) from three Eastern Seaboard marathons in the United States responded to items regarding general demographic information and expectation of the wall prior to the marathon. After the marathon, participants were asked to report the occurrence of the wall, whether they experienced each of 24 potential characteristics of the wall, and the impact of these characteristics on performance.ResultsApproximately 43% of participants reported that they hit the wall during the marathon. Logistic regression analysis indicated that generalized fatigue, unintentionally slowing pace, desire to walk, and shifting focus to survival were salient characteristics of the wall. Logistic regression analyses indicated that male gender, expectancy of hitting the wall, shorter distance of longest training run, and previous episodes of hitting the wall were associated with reports of hitting the wall.ConclusionsSeveral robust characteristics of the wall were identified. Occurrence of the wall phenomenon appears to be more prevalent among men than among women and may be influenced by expectancy.     

Inter-individual variability of forces and modular muscle coordination in cycling: A study on untrained subjects

The aim of this study was to investigate the muscle coordination underlying pedaling in untrained subjects by using the muscle synergies paradigm, and to connect it with the inter-individual variability of EMG patterns and applied forces. Nine subjects performed a pedaling exercise on a cycle-simulator. Applied forces were recorded by means of instrumented pedals able to measure two force components. EMG signals were recorded from eight muscles of the dominant leg, and Nonnegative Matrix Factorization was applied to extract muscle synergy vectors W and time-varying activation coefficients H. Inter-individual variability was assessed for EMG patterns, force profiles, and H. Four modules were sufficient to reconstruct the muscle activation repertoire for all the subjects (variance accounted for >90% for each muscle). These modules were found to be highly similar between subjects in terms of W (mean r = .89), while most of the variability in force profiles and EMG patterns was reflected, in the muscle synergy structure, in the variability of H. These four modules have a functional interpretation when related to force distribution along the pedaling cycle, and the structure of W is shared with that present in human walking, suggesting the existence of a modular motor control in humans.