The coupling between gaze behavior and opponent kinematics during anticipation of badminton shots

PurposeWe examined links between the kinematics of an opponent’s actions and the visual search behaviors of badminton players responding to those actions.MethodA kinematic analysis of international standard badminton players (n = 4) was undertaken as they completed a range of serves. Video of these players serving was used to create a life-size temporal occlusion test to measure anticipation responses. Expert (n = 8) and novice (n = 8) badminton players anticipated serve location while wearing an eye movement registration system.ResultsDuring the execution phase of the opponent’s movement, the kinematic analysis showed between-shot differences in distance traveled and peak acceleration at the shoulder, elbow, wrist and racket. Experts were more accurate at responding to the serves compared to novice players. Expert players fixated on the kinematic locations that were most discriminating between serve types more frequently and for a longer duration compared to novice players. Moreover, players were generally more accurate at responding to serves when they fixated vision upon the discriminating arm and racket kinematics.ConclusionsFindings extend previous literature by providing empirical evidence that expert athletes’ visual search behaviors and anticipatory responses are inextricably linked to the opponent action being observed.     

A minimal limit-cycle model to profile movement patterns of individuals during agility drill performance: Effects of skill level

Identification of control strategies during agility performance is significant in understanding movement behavior. This study aimed at providing a fundamental mathematical model for describing the motion of participants during an agility drill and to determine whether skill level constrained model components. Motion patterns of two groups of skilled and unskilled participants (n = 8 in each) during performance of a forward/backward agility drill modeled as limit-cycles. Participant movements were recorded by motion capture of a reflective marker attached to the sacrum of each individual. Graphical and regression analyses of movement kinematics in Hooke’s plane, phase plane and velocity profile were performed to determine components of the models. Results showed that the models of both skilled and unskilled groups had terms from Duffing stiffness as well as Van der Pol damping oscillators. Data also indicated that the proposed models captured on average 97% of the variance for both skilled and unskilled groups. Findings from this study revealed the movement patterning associated with skilled and unskilled performance in a typical forward/backward agility drill which might be helpful for trainers and physiotherapists in enhancing agility.     

Central neuronal motor behaviour in skilled and less skilled novices – Approaching sports-specific movement techniques

Research on motor behavioural processes preceding voluntary movements often refers to analysing the readiness potential (RP). For this, decades of studies used laboratory setups with controlled sports-related actions. Further, recent applied approaches focus on athlete-non-athlete comparisons, omitting possible effects of training history on RP. However, RP preceding real sport-specific movements in accordance to skill acquisition remains to be elucidated.Therefore, after familiarization 16 right-handed males with no experience in archery volunteered to perform repeated sports-specific movements, i.e. 40 arrow-releasing shots at 60 s rest on a 15 m distant standard target. Continuous, synchronised EEG and right limb EMG recordings during arrow-releasing served to detect movement onsets for RP analyses over distinct cortical motor areas. Based on attained scores on target, archery novices were, a posteriori, subdivided into a skilled and less skilled group. EMG results for mean values revealed no significant changes (all p > 0.05), whereas RP amplitudes and onsets differed between groups but not between motor areas. Arrow-releasing preceded larger RP amplitudes (p < 0.05) and later RP onsets (p < 0.05) in skilled compared to less skilled novices. We suggest this to reflect attentional orienting and greater effort that accompanies central neuronal preparatory states of a sports-specific movement.     

Kinematic and ground reaction force accommodation during weighted walking

Weighted walking is a functional activity common in daily life and can influence risks for musculoskeletal loading, injury and falling. Much information exists about weighted walking during military, occupational and recreational tasks, but less is known about strategies used to accommodate to weight carriage typical in daily life. The purposes of the study were to examine the effects of weight carriage on kinematics and peak ground reaction force (GRF) during walking, and explore relationships between these variables. Twenty subjects walked on a treadmill while carrying 0, 44.5 and 89 N weights in front of the body. Peak GRF, sagittal plane joint/segment angular kinematics, stride length and center of mass (COM) vertical displacement were measured. Changes in peak GRF and displacement variables between weight conditions represented accommodation. Effects of weight carriage were tested using analysis of variance. Relationships between peak GRF and kinematic accommodation variables were examined using correlation and regression. Subjects were classified into sub-groups based on peak GRF responses and the correlation analysis was repeated. Weight carriage increased peak GRF by an amount greater than the weight carried, decreased stride length, increased vertical COM displacement, and resulted in a more extended and upright posture, with less hip and trunk displacement during weight acceptance. A GRF increase was associated with decreases in hip extension (|r| = .53, p = .020) and thigh anterior rotation (|r| = .57, p = .009) displacements, and an increase in foot anterior rotation displacement (|r| = .58, p = .008). Sub-group analysis revealed that greater GRF increases were associated with changes at multiple sites, while lesser GRF increases were associated with changes in foot and trunk displacement. Weight carriage affected walking kinematics and revealed different accommodation strategies that could have implications for loading and stability.     

“I would have lost the respect of my friends and family if they knew I had bent the road rules”: Parents,peers, and the perilous behaviour of young drivers

Young novice drivers are at considerable risk of injury on the road. Their behaviour appears vulnerable to the social influence of their parents and friends. The nature and mechanisms of parent and peer influence on young novice driver (16–25 years) behaviour was explored via small group interviews (n = 21) and two surveys (n1 = 1170, n2 = 390) to inform more effective young driver countermeasures. Parental and peer influence occurred in pre-Licence, Learner, and Provisional (intermediate) periods. Pre-Licence and unsupervised Learner drivers reported their parents were less likely to punish risky driving (e.g., speeding). These drivers were more likely to imitate their parents and reported their parents were also risky drivers. Young novice drivers who experienced or expected social punishments from peers, including ‘being told off’ for risky driving, reported less riskiness. Conversely drivers who experienced or expected social rewards such as being ‘cheered on’ by friends – who were also more risky drivers – reported more risky driving including crashes and offences. Interventions enhancing positive influence and curtailing negative influence may improve road safety outcomes not only for young novice drivers, but for all persons who share the road with them. Parent-specific interventions warrant further development and evaluation including: modelling safe driving behaviour by parents; active monitoring of driving during novice licensure; and sharing the family vehicle during the intermediate phase. Peer-targeted interventions including modelling of safe driving behaviour and attitudes; minimisation of social reinforcement and promotion of social sanctions for risky driving also need further development and evaluation.     

Multiple timescales of body schema reorganization due to plastic surgery

Plastic surgery modifies the distribution of mass centers of a person’s body segments, changing his or her posture. The functional reorganization processes that lead subjects to re-integrate these body changes into a new stable body (posture) schema is poorly understood but current theories suggest the possible contribution of two components: a feedback mechanism that strongly depends on sensory input and an internal model that is relatively less dependent on sensory input and improves posture control, for example by compensating for delayed feedback. To assess the relative contributions of these two mechanisms during the functional reorganization of a posture scheme, we have conducted a longitudinal postural study in a population of healthy adults who were subject to breast plastic surgery to reduce or augment body weight. We measured participants’ orthostatic posture and ground reaction force immediately after, after 4 months, and 1 year after the surgery. To investigate the role of visual sensory information in the reorganization process we tested the participants with eyes open and closed. Our results indicate that participants find a new dynamical equilibrium within a few days. However, posture maintenance remains sub-optimal long after the center of masses and the resultant of ground reaction force stop changing; in some cases, for more than 4 months. Furthermore, the re-adaptation process is faster and more efficient in the eyes-open than in the eyes-closed condition. These results suggest that the reorganization involves different subsystems (responsible for the biomechanical changes, the re-calibration of feedback mechanisms, and the re-adaptation of internal models), which act at different timescales.     

Meta-analysis of targeted small-group reading interventions

Small-group reading interventions are commonly used in schools but the components that make them effective are still debated or unknown. The current study meta-analyzed 26 small-group reading intervention studies that resulted in 27 effect sizes. Findings suggested a moderate overall effect for small-group reading interventions (weighted g = 0.54). Interventions were more effective if they were targeted to a specific skill (g = 0.65), then as part of a comprehensive intervention program that addressed multiple skills (g = 0.35). There was a small correlation between intervention effects and group size (r = 0.21) and duration (r = 0.11). Small-group interventions led to a larger median effect size (g = 0.64) for elementary-aged students than for those in middle or high school (g = 0.20), but the two confidence intervals overlapped. Implications for research and practice are discussed.     

Children’s age modulates the effect of part and whole practice in motor learning

Motor skills can be learned by practicing the whole or part of a movement. In whole practice (WP), a skill is acquired by practicing the movement in its entirety, whereas in part practice (PP), a task is learned by practicing its components before combining them. However, the effectiveness of WP and PP in children is unclear. We, therefore, examined the effects of WP and PP on the learning of juggling among first-, third-, and fifth-graders. Children of each grade were pseudo-randomly assigned to the WP or PP group to learn cascade juggling in 6 days. After baseline assessments, the WP learners practiced three-beanbag juggling. The PP learners practiced one-beanbag juggling on the first 2 days, two-beanbag juggling on the following 2 days, and three-beanbag juggling on the last 2 days. Practice consisted of 40 trials each day. Skill retention and transfer trials (juggling in the opposite direction) were measured 24 h after training (number of catches). There was no significant difference between WP and PP in skill retention (WP: 1.28 ± 0.73; PP: 1.42 ± 046, p = .40) and transfer (WP: 1.31 ± 0.78; PP: 1.37 ± 0.55, p = .49). However, a time × grade × group interaction (p < .001) was observed in retention. Children of different grades received differential benefits from the WP and PP regimens. The fifth-graders learned better using WP, whereas the first- and third-graders showed better learning with PP. We discuss the three possible explanations for the results (neural maturity, explicit learning, and coordination capabilities).     

Skill differences in visual anticipation of type of throw in team-handball penalties

ObjectivesVisual identification and anticipation of an opponent's action intentions is crucial for successful performance in interactive situations such as team-handball penalties. We conducted two experiments to examine experienced and novice team-handball goalkeepers' ability to predict the type of throw in handball penalties and to identify the observers' reliance on local versus globally distributed spatial cues.Design and methodsIn Experiment 1, following a 2 (Skill) × 5 (Temporal Occlusion Condition) factorial design participants were provided with videos of team-handball penalties where the amount of viewing time was varied. In Experiment 2, another sample of experienced and novice goalkeepers watched videos of spatially manipulated penalties where specific parts of the thrower's body or the ball were either removed or presented in isolation (2 [Skill] × 9 [Display Condition] factorial design).ResultsIn Experiment 1, experienced goalkeepers outperformed novices and both groups similarly improved their performances with later occlusion conditions. In Experiment 2, experienced goalkeepers were again superior to novices, and local cues (e.g., ball and hand) were sufficient for better than chance predictions in both groups. Moreover, experienced in contrast to novice goalkeepers (i) suffered from the removal of and (ii) benefited from the addition of distal (i.e., throwing arm and ball) as well as proximal (i.e., upper body) kinematic features.ConclusionsOur research is in line with previous findings on perceptual-cognitive expertise in sports and suggests that experienced team-handball goalkeepers rely on multiple, globally distributed cues when making anticipatory judgments.     

Alterations in stride-to-stride variability during walking in individuals with chronic ankle instability

The aim of this study was to evaluate stride-to-stride variability of the lower extremity during walking in individuals with and without chronic ankle instability (CAI) using a nonlinear analysis. Twenty-five participants with self-reported CAI and 27 healthy control participants volunteered for this study. Participants walked on a motor-driven treadmill for 3 min at their selected speed. Lower extremity kinematics in the sagittal and frontal planes were recorded using a passive retroreflective marker motion capture system. The temporal structure of walking variability was analyzed with sample entropy (SampEn). The CAI group produced lower SampEn values in frontal-plane ankle kinematics compared to the control group (P = .04). No significant group differences were observed for SampEn values of other kinematics (P > .05). Participants with CAI demonstrated less stride-to-stride variability of the frontal plane ankle kinematics compared to healthy controls. Decreased variability of walking patterns demonstrated by participants with CAI indicates that the presence of CAI may be associated with a less adaptable sensorimotor system to environmental changes. The altered sensorimotor function associated with CAI may be targets for clinical interventions, and it is critical to explore how interventions protocols affect sensorimotor system function.     

The effect of swinging the arms on muscle activation and production of leg force during ski skating at different skiing speeds

The study investigated the effects of arm swing during leg push-off in V2-alternate/G4 skating on neuromuscular activation and force production by the leg muscles. Nine skilled cross-country skiers performed V2-alternate skating without poles at moderate, high, and maximal speeds, both with free (SWING) and restricted arm swing (NOSWING). Maximal speed was 5% greater in SWING (P < 0.01), while neuromuscular activation and produced forces did not differ between techniques. At both moderate and high speed the maximal (2% and 5%, respectively) and average (both 5%) vertical force and associated impulse (10% and 14%) were greater with SWING (all P < 0.05). At high speed range of motion and angular velocity of knee flexion were 24% greater with SWING (both P < 0.05), while average EMG of m. biceps femoris was 31% lower (all P < 0.05) in SWING. In a similar manner, the average EMG of m. vastus medialis and m. biceps femoris were lower (17% and 32%, P < 0.05) during the following knee extension. Thus, swinging the arms while performing V2-alternate can enhance both maximal speed and skiing economy at moderate and, in particularly, high speeds.     

Are novice drivers overconfident? A comparison of self-assessed and examiner-assessed driver competences in a Finnish and Swedish sample

Studies of subjective driving skill have usually assessed perceived driving skill in relation to the skills of the average driver. In order to examine whether novice drivers are overconfident with respect to their actual skills, a different method was used in the present study, where specific aspects of perceived driver competence were compared with assessments made by a driver examiner. A Finnish (n = 2847) and a Swedish (n = 805) sample of driving test candidates completed self-assessments and took a practical driving test; the instruments differed between the countries. The results indicated that about 50 percent of the Finnish and between 25 and 35 percent of the Swedish candidates made realistic assessments of their competence in the areas Vehicle manoeuvring, Economical driving and Traffic safety. The proportion of those who overestimated their competence was greater among the Swedish candidates than the Finnish candidates. This might be explained by greater possibilities of practicing self-assessment in the Finnish driver education. Furthermore, the results indicate that males are not overconfident to a greater extent than females. In conclusion, when perceived competence is related to actual competence instead of the skills of the average driver, the majority of drivers are no longer found to overestimate their skills.     

Effects of disease severity and medication state on postural control asymmetry during challenging postural tasks in individuals with Parkinson’s disease

The aim of this study was to investigate the effects of disease severity and medication state on postural control asymmetry during challenging tasks in individuals with Parkinson’s disease (PD). Nineteen people with PD and 11 neurologically healthy individuals performed three standing task conditions: bipedal standing, tandem and unipedal adapted standing; the individuals with PD performed the tasks in ON and OFF medication state. The participants with PD were distributed into 2 groups according to disease severity: unilateral group (n = 8) and bilateral group (n = 11). The two PD groups performed the evaluations both under and without the medication. Two force plates were used to analyze the posture. The symmetric index was calculated for various of center of pressure. ANOVA one-way (groups) and two-way (PD groups × medication), with repeated measures for medication, were calculated. For main effects of group, the bilateral group was more asymmetric than CG. For main effects of medication, only unipedal adapted standing presented effects of PD medication. There was PD groups × medication interaction. Under the effects of medication, the unilateral group presented lower asymmetry of RMS in anterior–posterior direction and area than the bilateral group in unipedal adapted standing. In addition, the unilateral group presented lower asymmetry of mean velocity, RMS in anterior–posterior direction and area in unipedal standing and area in tandem adapted standing after a medication dose. Postural control asymmetry during challenging postural tasks was dependent on disease severity and medication state in people with PD. The bilateral group presented higher postural control asymmetry than the control and unilateral groups in challenging postural tasks. Finally, the medication dose was able to reduce postural control asymmetry in the unilateral group during challenging postural tasks.     

Effectuation of adaptive stability and postural alignment strategies are decreased by alcohol intoxication

Human stability control is a complex process comprising contributions from several partly independent mechanisms such as coordination, feedback and feed-forward control, and adaptation. Acute alcohol intoxication impairs these functions and is recognized as a major contributor to fall traumas. The study aimed to investigate how alcohol intoxication at .06% and .10% blood alcohol concentration (BAC) affected the movement spans and control of posture alignment. The angular positions of the head, shoulder, hip and knees relative to the ankles were measured with a 3D motion analysis system in 25 healthy adults during standing with eyes open or closed and with or without vibratory balance perturbations.Alcohol intoxication significantly increased the movement spans of the head, shoulders, hip and knees in anteroposterior and lateral directions during quiet stance (p ⩽ .047 and p ⩽ .003) and balance perturbations (p < .001, both directions). Alcohol intoxication also decreased the ability to reduce the movement spans through adaptation in both anteroposterior (p ⩽ .011) and lateral (p ⩽ .004) directions. When sober and submitted to balance perturbations, the subjects aligned the head, shoulders, hip and knees more forward relative to the ankle joint (p < .001), hence adopting a more resilient posture increasing the safety margin for backward falls. Alcohol intoxication significantly delayed this forward realignment (p ⩽ .022). Alcohol intoxication did not cause any significant posture realignment in the lateral direction. Thus, initiation of adaptive posture realignments to alcohol or other disruptions might be context dependent and associated with reaching a certain level of stability threats.     

An especial skill in elite wheelchair basketball players

We aimed to investigate whether an especial skill is present in elite wheelchair basketball players when taking twenty shots with a regular basketball from five different distances (11 ft, 13 ft, 17 ft, & 19 ft) from the basket including the free throw line (15 ft). Twelve elite male basketball players participated. The results showed that as distance increased shot accuracy decreased in line with force by variability predictions for the 11 ft, 13 ft, 17 ft, & 19 ft distances. However, shot performance at the free throw line where players are more familiar with practicing free throw shots did not follow this trend. A linear regression line was drawn to predict performance at the free throw line based on nearer (11 ft & 13 ft) and farer (17 ft & 19 ft) distances to the basket, this was then compared to actual performance. A significant difference between actual and predicted scores was found (p < .05) supporting the presence of an especial skill. Significant positive correlations were found for the 11 ft and 17 ft distance, age, years of playing, and accumulated practice hours with performance at the 15 ft line (p < .05). These correlations imply the operation of generalization in the especial skill. This observation received support from applying a model in which shot accuracy as a function of distance was approximated by two regression lines.     

The relationship between visual attention and expertise in sports

ObjectivesGiven the prevalence of misperception and failed perception, particularly in attention-demanding team sports, surprisingly few studies have explored whether experts in team sports differ from other athletes and from non-athletes in their basic attention abilities.MethodIn this study, we examined group differences between experts in team handball (n = 40), athletes from non-team sports (n = 40), and novice athletes (n = 40) using a battery of three attention tasks: a functional field of view task, a multiple-object tracking task, and an inattentional blindness task.ResultsPerformance on the three attention tasks was largely independent, with no significant correlations among the tasks. Team sports experts showed no better performance on the basic attention tasks than did athletes from non-teams sports or novice athletes.ConclusionsThe finding that all basic attention tasks are largely independent provides preliminary support for the idea that attentional breadth, tracking performance, and inattentional blindness are distinct attentional processes. Our results demonstrate that sports expertise effects are unrelated to basic differences in attention—expertise does not appear to produce differences in basic attention and basic differences in attention do not appear to predict eventual expertise. Further experiments could focus on the ways in which more specific attentional strategies and processes contribute to sports performance.     

Biomechanical analyses of prolonged handwriting in subjects with and without perceived discomfort

Since wrist-joint position affects finger muscle length and grip strength, we studied its biomechanical relevance in prolonged handwriting. We recruited participants from young adults, aged 18–24, and separated them into control (n = 22) and in-pain (n = 18) groups, based whether or not they experience pain while handwriting. The participants then performed a writing task for 30 min on a computerized system which measured their wrist-joint angle and documented their handwriting kinematics. The in-pain group perceived more soreness and had a less-extended wrist joint, longer on-paper time, and slower stroke velocity compared to control group. There was no significant difference in handwriting speed and quality between the two groups. The wrist extension angle significantly correlated with perceived soreness. Ergonomic and biomechanical analyses provide important information about the handwriting process. Knowledge of pen tip movement kinematics and wrist-joint position can help occupational therapists plan treatment for individuals with handwriting induced pain.     

Differentiating technical skill and motor abilities in selected and non-selected 3–5 year old team-sports players

This study examined the difference in 22 3–5 year old boys selected to an advanced or non-advanced group on an English community-based professional club training program. Time to complete 15 m linear sprint and 15 m zig-zag agility tests, with and without a ball, were used to assess the children’s technical skill and motor ability. Age and body mass of both groups were the same, whereas height was greater and BMI was lower in the selected group (p < 0.01). Linear sprint times without and with the ball were 3.98 ± 0.35 and 4.44 ± 0.36 s, respectively for the selected and corresponding times were 4.64 ± 1.04 and 11.2 ± 5.37 s for the non-selected (p < 0.01, ES 0.8, 1.8). Similar results were found when a change of movement was included, both with and without the ball. A model of selection indicated that performance in an agility test with the ball and height had the greatest discriminatory power and explained 95.5% of between group variance. Selected players performed significantly better in tests when ball control was required. These findings suggest that technical proficiency and physical differences may influence team selection in three to five year old children.     

Multi-segmental thoracic spine kinematics measured dynamically in the young and elderly during flexion

In contrast to the cervical and lumbar region, the normal kinematics of the thoracic spine have not been thoroughly investigated. The aim of this study was to characterize normal multi-segmental continuous motion of the whole thoracolumbar spine, during a flexion maneuver, in young and elderly subjects. Forty-two healthy volunteers were analyzed: 21 young (age = 27.00 ± 3.96) and 21 elderly (age = 70.1 ± 3.85). Spinal motion was recorded with a motion-capture system and analyzed using a 3rd order polynomial function to approximate spinal curvature throughout the motion sequence. The average motion profiles of the two age groups were characterized. Flexion timing of the thoracic region of the spine, as compared to the lumbar spine and hips, was found to be different in the two age groups (p = 0.011): a delayed/sequential motion type was observed in most of the young, whereas mostly a simultaneous motion pattern was observed in the elderly subjects. A similar trend was observed in flexion of the lower thoracic segments (p = 0.017). Differences between age groups were also found for regional and segmental displacements and velocities. The reported characterization of the thoracic spine kinematics may in the future support identification of abnormal movement or be used to improve biomechanical models of the spine.