The effect of fatigue on climbing fluidity and hand movements.

In rock climbing, climbers use their arms to regulate their posture on the wall, which can lead to localised muscle fatigue. Evidence shows fatigue is the primary cause of falls, but little is known about how fatigue specifically affects climbing rhythm and hand movements. The present study examined climbing fluidity and hand movements on an indoor climbing wall before and after a specific fatiguing protocol. Seventeen climbers completed three repetitions of a challenging climbing route (21 on Ewbank scale) with different levels of localised arm fatigue. Climbers' movements were tracked using 3D motion capture, and their hand actions assessed using notational analysis. Seventy markers were used to create 15 rigid body segments and the participants' centre of mass. The global entropy index was calculated on the path of the participants' centre of mass. Climbers fell more often when fatigued, but there were no significant differences in hip jerk or global entropy index when fatigued. No significant differences were found between the number of exploratory or performatory hand movements with different amounts of fatigue. The results suggest that localised arm fatigue affects a climber's ability to prevent themselves from falling, but it does not specifically affect their fluidity.

Development of ELIP to Assess Physical Literacy for Emerging Adults: A Methodological and Epistemological Challenge.

Purpose: Following increased interest in physical literacy (PL), development of appropriate tools for assessment has become an important next step for its operationalization. To forward the development of such tools, the objective of this study was to build the foundations of the Évaluation de la Littératie Physique (ELIP), designed to help reduce existing tensions in approaches to PL assessment that may be resulting in a low uptake into applied settings. Methods: We followed two steps: (1) the development of the first version of ELIP by deploying a Delphi method (n = 30); and (2) the modification of items through cognitive interviews with emerging adults (n = 32). Results: The expert consensus highlighted four dimensions of PL to be assessed-physical; affective; cognitive; and social-with new perspectives, including a preference for broad motor tests over fitness. Conclusion: Results offer new insights into the assessment of emerging adults' PL, but ELIP still requires further work concerning validity, reliability, and sensitivity.

Quantifying synergies in two-versus-one situations in team sports: An example from Rugby Union.

Collective behaviors in team sports result in players forming interpersonal synergies that contribute to performance goals. Because of the huge amount of variables that continuously constrain players' behavior during a game, the way that these synergies are formed remain unclear. Our aim was to quantify interpersonal synergies in the team sport of Rugby Union. For that purpose we used the Uncontrolled Manifold Hypothesis (UCM) to identify interpersonal synergies that are formed between ball carrier and support player in two-versus-one situations in Rugby Union. The inter-player angle close to the moment of the pass was used as a performance variable and players running lines velocities as task-relevant elements. Interpersonal synergies (UCM values above 1) were found in 19 out of 55 trials under analysis, which means that on 34% of the trials, the players' running line velocities contribute to stabilizing the inter-player angle close the moment of the pass. The strength of the synergy fluctuates over time indicating the existence of a location effect during attack phases in Rugby Union. UCM analysis shows considerable promise as a performance analysis tool in team sports to discriminate between skilled sub-groups of players.

Does water temperature influence the performance of key survival skills?

Aquatic survival skills may be compromised in cold water thereby increasing the likelihood of drowning. This study compared physiological, psychological, and behavioral responses of humans treading water and swimming in cold and temperate water. Thirty-eight participants were classified as inexperienced (n = 9), recreational (n = 15), or skilled (n = 10) swimmers. They performed 3 tasks: treading water (120 seconds), swim at "comfortable" pace, and swim at "fast" pace in 2 water conditions (28°C vs 10°C). Heart rate, oxygen uptake, psychometric variables, spatio-temporal (swim speed, stroke rate, and stroke length), and coordination type were examined as a function of expertise. Tasks performed in cold water-generated higher cardiorespiratory responses (HR = 145 ± 16 vs 127 ± 21 bpm) and were perceived about 2 points more strenuous on the Borg scale on average (RPE = 14.9 ± 2.8 vs 13.0 ± 2.0). The voluntary durations of both treading water (60 ± 32 vs 91 ± 33 seconds) and swimming at a comfortable pace (66 ± 22 vs 103 ± 34 seconds) were significantly reduced in cold water. However, no systematic changes in movement pattern type could be determined in either the treading water task or the swimming tasks. Water temperature influences the physical demands of these aquatic skills but not necessarily the behavior. Training treading water and swimming skills in temperate water seems to transfer to cold water, but we recommend training these skills in a range of water conditions to help adapt to the initial "cold-shock" response.

Sports science needs more interdisciplinary, constraints-led research programmes: The case of water safety in New Zealand.

In the lead article of this special issue, Paul Glazier proposes that Newell's constraints model has the potential to contribute to a grand unified theory of sports performance in that it can help to integrate the disciplinary silos that have typically operated in isolation in sports and exercise science. With a few caveats discussed in this commentary, we agree with Glazier's proposal. However, his ideas suggest that there is a need to demonstrate explicitly how such an integration might occur within applied scientific research. To help fill this perceived 'gap' and thereby illustrate the value of adopting a constraints-led approach, we offer an example of our own interdisciplinary research programme. We believe our research on water safety is ideally suited to this task due to the diverse range of interacting constraints present and as such provides a tangible example of how this approach can unify different disciplinary perspectives examining an important aspect of sport performance.

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.

Coordination profiles of the expert field hockey drive according to field roles.

The aim of this study was to determine coordination profiles for the field hockey drive. Nine elite female players performed five drives each. They were asked to primarily maximize ball placement accuracy, and secondly to drive with high velocity. An optical motion capture system recorded the displacement of six markers on the joints of the players' arms as they performed the drives, and a radar gun measured the ball velocity after impact. Spatial, temporal, and velocity variables were then established. Discrete relative phases were also established at ball impact to examine medio-lateral and proximo-distal upper-arms coordination. The high standard deviation values in joint kinematics were indicative of inter-individual variability, i.e. several drive solutions. Cluster analysis was thus used and two profiles among the players were identified. For the two profiles, the global coordination pattern of movement (upper-arm coordination) was in-phase for the right arm, and out-of-phase for the left lead arm, suggesting a segmental sequencing. However, differences were noted on local kinematic parameters which led to the following categorization: the 'strong group' for defenders and the 'temporal-effectiveness group' for midfielders and forwards. The results support the value of individual analysis to better interpret and contrast the distinct roles of expert players.

Statistical modelling of gaze behaviour as categorical time series: what you should watch to save soccer penalties.

Previous research on gaze behaviour in sport has typically reported summary fixation statistics thereby largely ignoring the temporal sequencing of gaze. In the present study on penalty kicking in soccer, our aim was to apply a Markov chain modelling method to eye movement data obtained from goalkeepers. Building on the discrete analysis of gaze employed by Dicks et al. (Atten Percept Psychophys 72(3):706-720, 2010b), we wanted to statistically model the relative probabilities of the goalkeeper's gaze being directed to different locations throughout the penalty taker's approach (Dicks et al. in Atten Percept Psychophys 72(3):706-720, 2010b). Examination of gaze behaviours under in situ and video-simulation task constraints reveals differences in information pickup for perception and action (Attention, Perception and Psychophysics 72(3), 706-720). The probabilities of fixating anatomical locations of the penalty taker were high under simulated movement response conditions. In contrast, when actually required to intercept kicks, the goalkeepers initially favoured watching the penalty taker's head but then rapidly shifted focus directly to the ball for approximately the final second prior to foot-ball contact. The increased spatio-temporal demands of in situ interceptive actions over laboratory-based simulated actions lead to different visual search strategies being used. When eye movement data are modelled as time series, it is possible to discern subtle but important behavioural characteristics that are less apparent with discrete summary statistics alone.

Visual strategies of sub-elite cricket batsmen in response to different ball velocities.

When different interceptive skills are considered, humans tend not to pursuit track the approaching object along its entire trajectory to the point of interception. Previous research of cricket batsmen facing medium paced deliveries reported pursuit visual tracking of the ball for the first 100-150 ms of flight followed by a saccade to the predicted ball bounce location. The aim of this study was to examine eye movements of batsmen while facing a range of slow to medium pace delivery speeds. Thirteen sub-elite batsmen faced 36 deliveries from a ball machine in which the projection speed was randomly varied across a range of 17-25 ms(-1). The foveal gaze of the batsmen was recorded with a monocular eye movement registration system. Gaze strategies differed between participants in several ways, i.e., in the initial location of gaze prior to delivery (on the outlet of the ball machine or "parked" at a location on the predicted flight trajectory), the behavior immediately after ball release (pursuit tracking or saccade), and the behavior in mid-late flight (predictive saccade to the bounce point or "parafoveal" pursuit tracking). Across the range of delivery speeds used in the current study, it was possible to pursuit track the ball from release to bounce point but it was also possible to choose to make saccades along the trajectory. Depending on the spatio-temporal demands of the task and the intentions of the batsman a range of visual search strategies can be employed to support their actions.

Lythrum hyssopifolia (lesser loosestrife) poisoning of sheep in Victoria.

OBJECTIVE: To document an ovine disease attributed to the consumption of Lythrum hyssopifolia (lesser loosestrife). PROCEDURES: Historical and histological review of field and experimental cases. RESULTS: 1-20% mortality occurred in sheep flocks grazing paddocks where L. hyssopifolia was the predominant green vegetation. Well-documented disease outbreaks occurred in summer on nine farms across Victoria between 1974 and 2002. Liver damage occurred in all nine outbreaks, with kidney damage in at least eight. Hepatocyte necrosis was usually zonal to midzonal (zone 2) in the liver samples from four farms and periacinar (zone 3) in those from three farms, but some livers showed only single-cell necrosis. Multinucleate hepatocytes near necrotic areas were a feature in six cases. Proximal tubular epithelium appeared to be the primary renal target and brown granules were often present in renal tubules. Biochemical and histological evidence of liver and kidney damage was obtained from two sheep experimentally pen-fed harvested L. hyssopifolia. CONCLUSION: Chemicals in L. hyssopifolia are toxic to ovine hepatocytes and renal tubular epithelial cells.

Training habits and injuries of masters' level football players: a preliminary report.

OBJECTIVE: To profile training habits and injuries in football players participating in a national Masters tournament. METHODS: A cross-sectional retrospective study design was used to survey male football players attending the 2008 New Zealand Masters Games. Information regarding player demographics, football injuries, football related training, and risk factors for injury were collected. RESULTS: 199 Players were recruited, with a median age of 44 yrs (range 35-73) and a median football playing history of 15 yrs (range 0-66). Irrespective of age, 112 (84%) players included a warm-up and 104 (78%) included a stretching regime in their regular training programme. In the 12 months prior to the tournament, 128 football related injuries were reported by 93 players (64 injuries/100 players or 46 injured players/100 players). The most frequently injured region was the lower limb; specifically the lower leg (n=23), ankle (n=18), hamstring (n=17), knee (n=15), and Achilles tendon (n=15). CONCLUSION: This study provides a preliminary insight into the training habits and injury profiles of Masters football players. Despite all players including some form of injury prevention strategy in their training, a significant number of players experienced an injury in the 12 months prior to the tournament.

The effect of multidirectional mechanical vibration on peripheral circulation of humans.

The physiological response of humans to vibration has intrigued researchers for some time, and recently in relation to its potential as a non-pharmacological means to improve peripheral blood flow. A new vibration device [Arapal Technologies Ltd (ATL), Christchurch, New Zealand] for pain relief that purportedly delivers multidirectional vibration waveforms, has been developed. The aim of the study was to quantify the effect of 30 min of mechanical vibration (60 Hz) using two ATL massage devices concurrently upon local peripheral blood flow in healthy humans. On the basis of past work it was expected that acute exposure of the body to the vibratory stimulus would increase local peripheral blood flow. In a randomized cross-over design, mean blood flow (MBF) to the calf was measured using venous occlusion plethysmography before, during 3 min and after 30 min exposure to the vibratory devices or placebo (non-vibratory) devices. Statistical analysis revealed no consistent differences between conditions and considerable individual variability. The MBF increase tended to be higher in the vibration condition than the placebo condition (P=0.16, 95% likely range=-14.4% to 82.2%), the mean increase from resting blood flow at the post-test was 26+/-49% in the vibration condition and 12+/-39% in the placebo condition. It took approximately 22 min of exposure to the vibratory stimulus to elicit peak blood flow (18 min with the placebo). Improvements in local blood flow may be beneficial in the therapeutic alleviation of pain or other symptoms resulting from acute or chronic musculoskeletal injuries.

"Essential noise" - enhancing variability of informational constraints benefits movement control: a comment on Waddington and Adams (2003).

This commentary proposes a dynamical systems perspective to re-interpret data from a group of international soccer players demonstrating that wearing textured insoles in soccer boots enhanced tactile information from the sole of the foot and increased movement discrimination capacity in ankle inversion sensitivity tests to levels similar to those in barefoot conditions. Theoretical arguments on the functional role of variability induced in the sensorimotor system by textured insoles, acting as a form of "essential noise" to enhance the accuracy of foot positioning are presented. It seems that, far from interfering with motor performance, variability can actually enhance perception of information to support motor performance. The addition of intermittent, intermediate levels of noise in a perceptual motor context may benefit performers by helping them to pick up information signals from background structure. Movement system variability is conceived as noise induced resonance benefiting the pick up of information to regulate behaviour. Variability can be functional in practical programmes to offset negative effects of losses in sensory sensitivity through ageing, disease, illness, or injury.

Variation in general practitioner referral of patients with arterial disease.

AIM: To compare patterns of referral for arterial disease in two areas in the UK. METHODS: A postal questionnaire was used to survey general practitioner (GP) referral patterns for arterial disease. Questionnaires were sent to West Berkshire GPs in 1993 and 2000 and to Llantrisant GPs in 2000. RESULTS: A 70-year-old man with claudication at half a mile and an 80-year-old man with claudication at half a mile or 100 m were significantly more likely to be referred (P < 0.001) in West Berkshire in 2000 compared with 1993. This referral change also applied to an 80-year-old man with an aortic aneurysm who was more likely to be referred in 2000 (P < 0.01). Patients with gradual onset of rest pain were more likely to be referred urgently or as an emergency in 2000 (P < 0.05). When comparing the two areas in 2000, significant differences emerged in the likelihood of referring patients with intermittent claudication. Scepticism continues towards the value of AAA screening in West Berkshire with only about two-thirds of GPs thinking that it was of value. On the other hand in Llantrisant, 94% of GPs thought AAA screening was valuable (P < 0.001). There was a significant decrease in the number of GPs who felt that they would refer patients directly to a regional vascular centre in West Berkshire between the two time periods (P < 0.001). There was a difference in likelihood of referral to regional centres between the two areas in 2000 (33% versus 6%, P < 0.001). CONCLUSIONS: Vascular referral patterns change with time and vary from one area to another. This has implications for planning vascular services.

Wavelength conversion of 1.53-microm-wavelength picosecond pulses in an ion-implanted multiple-quantum-well all-optical switch.

An ultrafast high-contrast all-optical switch produced from a metal-organic vapor phase epitaxy-grown wafer incorporating a 50-period InGaAsP/InGaAsP multiple-quantum-well (MQW) saturable absorber (SA) and a distributed Bragg reflector is described. Postgrowth implantation with 4-MeV nitrogen ions reduces the MQW free-carrier lifetime, and hence the switch recovery time, to 5.2 ps. Incorporation of the MQW SA in an optical cavity results in switching contrast ratios greater than 10 dB. The all-optical switch is used to perform wavelength conversion of 2-ps pulses.

Grasping a better understanding of the intrinsic dynamics of rhythmical and discrete prehension.

In this study, the authors examined the influence of the intrinsic dynamics of discrete and rhythmical prehension. Six adults underwent a scaling procedure in which the movement time was systematically increased so that it corresponded with 6 frequencies: 0.5, 0.75, 1.0, 1.25, 1.5, and 1.75 Hz. In posttests, participants moved at their own preferred pace. No differences were found in the relative time to final hand closure (T[rfc]) between the rhythmical and discrete conditions. The variability of T[rfc] was shown to be less at the preferred step of scaling than during the posttest. With the scaling technique, one can guide participants into more stable movement patterns than they can achieve when the metronome is not present, because, when the metronome is present, their movements become anchored to the external pacing cue. Those findings provide support for the use of a scaling technique to identify the influence of the intrinsic dynamics during rhythmical and discrete movements.

Mechanical perturbation of the wrist during one-handed catching.

In the present study, the co-ordination of grasp and transport components of one-handed catching was examined following mechanical perturbations applied to the wrist. Six skilled catchers (mean age = 27.5 years) performed 64 trials in which tennis balls were projected at approximately 8 ms-1. The trial blocks consisted of 10 non-perturbed trials (NPTs) (baseline), and a block of 54 trials of which 20 trials were perturbed. The perturbation was in the form of a resistive force (12 N) applied via a piece of cord attached to a mechanical brake. In baseline trials participants reached maximal wrist velocity closer to the time of hand-ball contact (237 ms +/- 68) than in the perturbed (309 ms +/- 61) condition. Furthermore the wrist velocity profile of five out of six participants exhibited a double peak immediately after a perturbation. However, aperture variables such as the relative moment of final hand closure (approximately 70% of overall movement time) were not typically affected. The stability of grasp and transport coupling for one-handed catching was shown to vary from trial to trial. Skilled performers exploited redundant degrees of freedom in the motor system when faced with a sudden, unexpected change in task constraints.

Manipulating visual informational constraints during practice enhances the acquisition of catching skill in children.

Previous motor learning studies examining the effects of practicing to catch one-handed under varying informational constraints on subsequent skill acquisition are equivocal, perhaps due to the use of relatively inexperienced adult participants. Ecological theory predicts that directing the learner's search for information in the perceptual-motor workspace can enhance skill acquisition. This study manipulated visual informational constraints on novice children (ages 9-10 years) learning to catch one-handed. A crossover transfer design was implemented in which one group acted as controls while two other groups practiced either without visual restrictions before transferring to full vision, or vice versa. The data indicated that learners forced to seek additional information sources under restricted viewing conditions demonstrated a greater positive, accumulative residual effect on acquiring a catching skill. The findings contradict current work on the specificity of practice hypothesis and suggest that varying visual informational constraints to encourage exploratory practice may represent a significant pedagogical approach to motor learning in sport.