Physiotherapists could detect changes of 12 degrees or more in single-plane movement when observing forward bending, squat or hand-over-head: A cross-sectional experiment.

BACKGROUND: The visual accuracy of physiotherapists to detect changes in dynamic joint angles is currently unknown. OBJECTIVE: To investigate (i) the smallest detectable change in movement that physiotherapists could visually observe, and (ii) whether visual accuracy was associated with the functional activity observed or characteristics of the physiotherapist. METHODS: Thirty-four physiotherapists viewed and rated videos of squat, hand-over-head, forward bend functional activities and an artificial test condition (a reference movement followed by subsequent movements showing random differences in peak angle from 0° to 15°, so 18 sets of paired videos per functional activity). They rated each range of movement (same/more/less) relative to the reference movement, while their visual tracking was continuously monitored. Accuracy was calculated (multilevel regression) using two thresholds - two correct out of three viewings (2/3) and three correct out of three viewings (3/3). RESULTS: More than 80% of physiotherapists were able to detect 9° difference using the 2/3 threshold and 12° using the 3/3 threshold. There was no association (p > 0.05) between visual accuracy and experience, sex, or movement type, except when viewing shoulder abduction compared with knee flexion using the 3/3 threshold. The only association between accuracy and visual tracking characteristics was for assessing lumbar flexion, where use of more visual fixation areas and a shorter fixation time per area were more accurate. CONCLUSION: Physiotherapists were consistently accurate at detecting changes of ≥12° in single-plane, low-speed functional activities. Visual accuracy was not explained by experience or sex, and rarely associated with functional activity type or visual fixation.

Validity and Reliability of a Field Hockey-Specific Dribbling Speed Test.

ABSTRACT: Tapsell, LC, Binnie, MJ, Lay, BS, Dawson, BT, and Goods, PSR. Validity and reliability of a field hockey-specific dribbling speed test. J Strength Cond Res 36(6): 1720-1725, 2022-The present study aimed to design a valid and reliable test for field hockey players that concurrently assesses the skill of dribbling and sport-specific agility. In total, 27 male and 32 female subjects were recruited from amateur (n = 20), state-level (n = 22), and national-level (n = 17) field hockey teams. The test course was developed in consultation with state- and national-level field hockey coaches, and using match analyses from existing literature. Subjects were familiarized before completing a testing session that consisted of 3 maximal-effort trials through a field hockey-specific course while dribbling a hockey ball, and another 3 trials of the same course without dribbling the ball. Amateur and state subjects completed an additional session for test-retest reliability analysis. Electronic timing gates recorded time to complete the course with the ball (DRIBBLE), without the ball (SPRINT), and the difference between DRIBBLE and SPRINT (DELTA). With significance set at p < 0.05, subjects of higher playing levels recorded significantly faster DRIBBLE (p < 0.001) and significantly lower DELTA (p < 0.001) times. No significant difference was found between player levels for SPRINT (p = 0.484) times. Intraclass correlations were 0.84 and 0.81 for DELTA and DRIBBLE, respectively. In conclusion, the dribbling test trialed here has sufficient validity and reliability for use in performance testing of field hockey athletes and can be implemented across playing levels to objectively track skill progression.

Physical and perceptual cooling: Improving cognitive function, mood disturbance and time to fatigue in the heat.

This study investigated the effects of menthol swilling and crushed ice ingestion on cognitive function, total mood disturbance (TMD), and time to fatigue (TTF). Twelve male long-distance runners completed three counterbalanced running trials (3 × 30 minutes at 65% VO2peak and a TTF run at 100% VO2peak ) in hot, humid conditions (35.3 ± 0.3°C, 59.2 ± 2.5% relative humidity). Trials consisted of precooling with crushed ice ingestion and mid-cooling by menthol swilling (MIX), precooling with water ingestion and mid-cooling by menthol swilling (MENTH), and control (CON). Swilling with either 25 mL of menthol solution or placebo occurred upon entry to the heat, at 15-minute intervals during the run and prior to the TTF run. Core temperature, forehead skin temperature, tympanic temperature, perceived thermal sensation, and TMD were significantly lower with MIX compared with MENTH and CON (P < .05). Thirst was satiated in MIX compared with CON; however, MENTH did not have a significant effect. After 90 minutes of running and post-TTF run, fewer errors occurred in the executive control task (P < .05), as well as decision-making and working memory (P > .05; d = 0.5-0.79) between MIX and CON; however, MENTH had no effect compared with CON. The TTF run was significantly longer with MENTH (34.38%; P = .02) and MIX (39.06%; P = .001) compared with CON, with no difference between MENTH and MIX (P = .618). The physical reduction in core and internal head temperature seen with crushed ice ingestion may lead to improvements in cognitive function; however, both MENTH and MIX were sufficient for improving exercise performance.

Enhanced Decision Making and Working Memory During Exercise in the Heat With Crushed Ice Ingestion.

PURPOSE: To examine the effects of precooling via crushed ice ingestion on cognitive function during exercise in the heat. METHODS: Eleven active men ingested either 7 g·kg-1 of crushed ice (ICE) or thermoneutral water (CON) 30 minutes before running 90 minutes on a treadmill at a velocity equivalent to 65% VO2peak in hot and humid conditions (35.0°C [0.5°C], 53.1% [3.9%] relative humidity). Participants completed 3 cognitive tasks to investigate decision making (8-choice reaction time [CRT]), working memory (serial seven [S7]), and executive control (color multisource interference task [cMSIT]) on arrival, after precooling, and after running. RESULTS: Precooling significantly decreased preexercise core (Tcore) and forehead skin temperature in ICE compared with CON, respectively (Tcore 0.8°C [0.4°C], -0.2°C [0.1°C]; Thead -0.5°C [0.4°C], 0.2°C [0.8°C]; P ≤ .05). Postrun, ICE significantly reduced errors compared with CON for CRT (P ≤ .05; d = 0.90; 90% confidence interval, 0.13-1.60) and S7 (P ≤ .05; d = 1.05; 90% confidence interval, 0.26-1.75). Thermal sensation was lower after precooling with ICE (P ≤ .05), but no significant differences were recorded between conditions for cMSIT errors, skin temperature, heart rate, or ratings of perceived exertion or perceived thirst (P > .05). CONCLUSIONS: Precooling via ICE maintained cognitive accuracy in decision making and working memory during exercise in the heat. Thus, ICE may have the potential to improve sporting performance by resisting deleterious effects of exercise in a hot and humid environment on cognitive function.

Internal precooling decreases forehead and core temperature but does not alter choice reaction time during steady state exercise in hot, humid conditions.

This study aimed to determine if precooling via crushed ice ingestion reduces forehead skin temperature (Thead) and core temperature (Tcore) during exercise in the heat and whether it has an effect on choice reaction time (CRT). Ten males commenced a 30 min precooling period, ingesting either 7 g kg-1 of crushed ice (ICE) or room temperature water (CON) prior to cycling 60 min at 55% V̇O2peak in hot, humid conditions (35.0 ± 0.3 °C, 50.2 ± 2.1% Relative Humidity). The CRT task was completed upon arrival and after the precooling period in the lab, then at 15 min intervals during exercise in the heat. Precooling reduced Thead and Tcore to a greater degree in ICE (Thead: -0.8 ± 0.31 °C; Tcore: -0.9 ± 0.3 °C) compared with CON (Thead: -0.2 ± 0.3 °C; Tcore: -0.2 ± 0.2 °C) (p ≤ 0.001). Choice reaction time performance improved throughout the cycle for both conditions (p ≤ 0.05). Ice ingestion lowered thermal sensation (p = 0.003) and skin temperature (d = 0.88; Tskin), while heart rate, ratings of perceived exertion and thirst were similar between conditions (p > 0.05). Precooling effectively reduced Thead and Tcore but did not provide additional improvement in CRT during moderate exercise in the heat. Further investigation is required to determine whether the lower central and peripheral temperature after ice ingestion is beneficial for tasks of greater cognitive effort.

Different visual stimuli affect muscle activation at the knee during sidestepping.

Increasing knee stability via appropriate muscle activation could reduce anterior cruciate ligament (ACL) injury risk during unplanned sidestepping. High-level athletes may activate their knee muscles differently from low-level athletes when responding to quasi-game realistic versus non game-realistic stimuli. Eleven high-level and 10 low-level soccer players responded to a non game-realistic arrow-planned condition (AP), a quasi game-realistic one-defender scenario (1DS) and two-defender scenario (2DS), and an arrow-unplanned condition (AUNP), that imposed increasing time constraints to sidestep. Activation from eight knee muscles during sidestepping was measured during pre-contact and weight-acceptance. Knee flexor-extensor co-activation ratios were established. Muscle activation levels increased by approximately 27% solely in the 1DS in both sidestepping phases. In the 2DS, the shift from a flexor dominant co-activation strategy in pre-contact toward extensor dominance in weight-acceptance commenced earlier for the high-level players. Quasi game-realistic information allowed for anticipatory increases in knee muscle activation regardless of expertise levels but only when the time demands to respond were low (1DS). High-level players were better at interpreting complex game-realistic information (2DS) to activate their knee extensors earlier in preparation for single-leg landing during weight-acceptance.

Visual tracking behaviour of two-handed catching in boys with developmental coordination disorder.

BACKGROUND: Developmental coordination disorder (DCD) is a motor learning disability that affects coordination resulting in an inability to perform movement skills at an age appropriate level. One area suspected to contribute to the movement difficulties experienced are deficits in visuomotor control. AIMS: This study investigated visual tracking behaviour during catching in children with DCD. METHODS AND PROCEDURES: Twenty-four boys completed the study: 11 with DCD (9.43 years ±0.73) and 13 controls (9.16 years ± 0.68). Participants performed 10 central catching trials, with the best five used to evaluate tracking behaviour and motor responses. OUTCOMES AND RESULTS: Prior to ball release, the DCD group exhibited more fixations (p = 0.043) of lesser duration (p = 0.045). During flight, the DCD group took longer to initiate smooth pursuit (p = 0.003) however, once initiated, both groups were effectively able to maintain smooth pursuit. Despite initial delays, these had no impact on movement initiation time (p = 0.173), however, movement time was significantly slower in the DCD group (p = 0.031). CONCLUSIONS AND IMPLICATIONS: The results of this study demonstrate that catching performance in children with DCD likely reflect a combination of errors in attending to visual information and movement organisation.

Modulation of joint and limb mechanical work in walk-to-run transition steps in humans.

Surprisingly little information exists of the mechanics in the steps initializing the walk-to-run transition (WRT) in humans. Here, we assess how mechanical work of the limbs (vertical and horizontal) and the individual joints (ankle, knee and hip) are modulated as humans transition from a preferred constant walking velocity (vwalk) to a variety of running velocities (vrun; ranging from a sprint to a velocity slower than vwalk). WRTs to fast vrun values occur nearly exclusively through positive horizontal limb work, satisfying the goal of forward acceleration. Contrary to our hypothesis, however, positive mechanical work remains above that at vwalk even when decelerating. In these WRTs to slow running, positive mechanical work is remarkably high and is comprised nearly exclusively of vertical limb work. Vertical-to-horizontal work modulation may represent an optimization for achieving minimal and maximal vrun, respectively, while fulfilling an apparent necessity for energy input when initiating WRTs. Net work of the WRT steps was more evenly distributed across the ankle, knee and hip joints than expected. Absolute positive mechanical work exhibited a clearer modulation towards hip-based work at high accelerations (>3 m s-2), corroborating previous suggestions that the most proximal joints are preferentially recruited for locomotor tasks requiring high power and work production. In WRTs to very slow vrun values, high positive work is nevertheless done at the knee, indicating that modulation of joint work is not only dependent on the amount of work required but also the locomotor context.

Prolonged running increases knee moments in sidestepping and cutting manoeuvres in sport.

OBJECTIVES: To investigate how knee kinematics, kinetics and loading changes during sidestepping tasks following a prolonged running protocol performed in a laboratory setting. DESIGN: All participants performed sidestepping, and crossover cutting tasks in a randomised order before and after a 60min running protocol on a non-motorised treadmill that simulated an AF game. METHODS: Eight healthy male participants who partook in semi-professional and amateur Australian Football undertook a series of straight line runs, sidestepping (SS), and crossover cutting (XO) tasks before and after a simulated game of Australian football. Kinematic data were analysed at initial foot contact of the SS and XO manoeuvres and kinetic data were analysed during the weight acceptance phase of the stance. RESULTS: The knee was significantly more flexed at foot contact following fatigue compared to pre-fatigue states. Fatigue was also a factor contributing to significant increases in internal knee extension moments. Significant differences were also observed between SS and XO trials with flexion/extension moments, with notable differences in varus/valgus and internal/external rotation moments. CONCLUSIONS: Acute angles of knee flexion at foot strike in a fatigued state may place the joint at an increased risk of injury. Increases in knee extension moments in the fatigued state suggests the knee joint must withstand significantly high stresses once fatigued.

Poor Imitative Performance of Unlearned Gestures in Children with Probable Developmental Coordination Disorder.

It has been hypothesized that deficits in imitation, linked to abnormal functioning of the mirror neuron system (MNS), may contribute to the motor impairments associated with developmental coordination disorder (DCD). The authors aimed to examine imitation of complex novel postures and sequences of gestures in children with and without probable DCD (pDCD), using the postural praxis and sequencing praxis subtests of the Sensory Integration and Praxis Tests (Ayres, 1989 ). Participants were 29 boys with pDCD between 6.08 and 13.33 years old, and 29 group age-matched typically developing boys between 6.08 and 13.83 years old. Responses of children with pDCD on both imitation tasks were less accurate than controls, with group differences more apparent with increasing task complexity. Furthermore, as a group, children with pDCD were slower and had a higher number of non-mirror-imitated responses. There was considerable variability within the pDCD group, with some children displaying imitation scores within the normative range. Given the importance of imitation and visual learning for motor development, the difficulties in imitation displayed by some children with pDCD have the potential to impact on movement acquisition. Interventions to target imitation may be beneficial for these children. The results show that children with pDCD had difficulty imitating complex novel postures, children with pDCD had difficulty imitating gesture sequences, children with pDCD had slower responses than controls, group differences in imitation performance increased with task complexity, and not all children with pDCD displayed imitation deficits.

Development of a Kinect Software Tool to Classify Movements during Active Video Gaming.

While it has been established that using full body motion to play active video games results in increased levels of energy expenditure, there is little information on the classification of human movement during active video game play in relationship to fundamental movement skills. The aim of this study was to validate software utilising Kinect sensor motion capture technology to recognise fundamental movement skills (FMS), during active video game play. Two human assessors rated jumping and side-stepping and these assessments were compared to the Kinect Action Recognition Tool (KART), to establish a level of agreement and determine the number of movements completed during five minutes of active video game play, for 43 children (m = 12 years 7 months ± 1 year 6 months). During five minutes of active video game play, inter-rater reliability, when examining the two human raters, was found to be higher for the jump (r = 0.94, p < .01) than the sidestep (r = 0.87, p < .01), although both were excellent. Excellent reliability was also found between human raters and the KART system for the jump (r = 0.84, p, .01) and moderate reliability for sidestep (r = 0.6983, p < .01) during game play, demonstrating that both humans and KART had higher agreement for jumps than sidesteps in the game play condition. The results of the study provide confidence that the Kinect sensor can be used to count the number of jumps and sidestep during five minutes of active video game play with a similar level of accuracy as human raters. However, in contrast to humans, the KART system required a fraction of the time to analyse and tabulate the results.

Relationships Between Reactive Agility Movement Time and Unilateral Vertical, Horizontal, and Lateral Jumps.

Henry, GJ, Dawson, B, Lay, BS, and Young, WB. Relationships between reactive agility movement time and unilateral vertical, horizontal, and lateral jumps. J Strength Cond Res 30(9): 2514-2521, 2016-This study compared reactive agility movement time and unilateral (vertical, horizontal, and lateral) jump performance and kinetics between dominant and nondominant legs in Australian rules footballers (n = 31) to investigate the role of leg strength characteristics in reactive agility performance. Jumps involved jumping forward on 1 leg, then for maximum height or horizontal or lateral distance. Agility and movement time components of reactive agility were assessed using a video-based test. Correlations between each of the jumps were strong (r = -0.62 to -0.77), but between the jumps and agility movement time the relationships were weak (r = -0.25 to -0.33). Dominant leg performance was superior in reactive agility movement time (4.5%; p = 0.04), lateral jump distance (3%; p = 0.008), and lateral reactive strength index (4.4%; p = 0.03) compared with the nondominant leg. However, when the subjects were divided into faster and slower performers (based on their agility movement times) the movement time was significantly quicker in the faster group (n = 15; 12%; p < 0.001), but no differences in jump performance or kinetics were observed. Therefore, although the capacity for jumps to predict agility performance seems limited, factors involved in producing superior lateral jump performance in the dominant leg may also be associated with advantages in agility performance in that leg. However, because reactive strength as measured by unilateral jumps seems to play a limited role in reactive agility performance and other factors such as skill, balance, and coordination, and also cognitive and decision-making factors, are likely to be more important.

Motor imagery ability and internal representation of movement in children with probable developmental coordination disorder.

It has been hypothesised that deficits in the functioning of the mirror neuron system (MNS) and internal modelling may contribute to the motor impairments associated with DCD. These processes can be explored behaviourally through motor imagery paradigms. Motor imagery proficiency of children with and without probable DCD (pDCD) was examined using a complex hand rotation task to explore whether motor imagery strategies could be used during more complex tasks. Forty-four boys aged 7-13 years participated, 22 with pDCD (mean = 9.90 years ± 1.57) and 22 controls (mean = 9.68 years ± 1.53). Participants completed the task twice: with and without motor imagery instructions. Stimuli were presented in two rotational axes--palm/back, and eight 45° rotational steps. Both groups showed evidence of following the biomechanical and postural constraints of actual movements. Responses of children with pDCD were slower and less accurate than controls, with group differences increasing alongside task complexity. A greater impact of biomechanical constraints for accuracy was observed in the DCD group. The response characteristics of children with pDCD likely reflects a reduced capacity to mentally manipulate a body schema and reduced visuo-motor processing capabilities. Behaviourally, these processes are linked to MNS and internal modelling function, suggesting deficits in these systems may contribute to the movement difficulties characteristic of DCD.

A systematic review of mirror neuron system function in developmental coordination disorder: Imitation, motor imagery, and neuroimaging evidence.

PURPOSE: The aim of this systematic review was to investigate the evidence of abnormal functioning of the mirror neuron system (MNS) in children and adults with developmental coordination disorder (DCD), through examination of imitation, motor imagery, and neuroimaging literature. METHODS: The following databases were comprehensively searched for relevant articles: CINAHL Plus, Embase, MEDLINE, PsycINFO, Pubmed, and Web of Science. Full-text articles of all potentially relevant citations were obtained and assessed for eligibility by two authors. Outcome measures of interest at a motor behaviour level were any measures of imitation or motor imagery proficiency and, at a neurological level, were any measures of neural activity in MNS brain regions. Due to differences in outcome measures between studies and the variables reported, a narrative review was undertaken to synthesise findings from the studies. RESULTS: Overall, 31 articles met the inclusion criteria. Children and adults with DCD display deficits imitating meaningful and novel gestures and demonstrate different response patterns to controls when undertaking complex motor imagery tasks. Children with DCD present reduced activation and connectivity of frontal, parietal, and temporal MNS regions. CONCLUSIONS: Preliminary evidence indicates some deficit in the functioning of the MNS at a motor behaviour and neurological level. As no published neuroimaging studies have been designed specifically to explore MNS function, these results must be interpreted with caution. Further research to explore the MNS hypothesis in greater detail, particularly from a neuroimaging perspective, has the potential to provide information on the underlying mechanisms of DCD, inform future research into the aetiology of this disorder, and inform intervention approaches.

Joint-level mechanics of the walk-to-run transition in humans.

Two commonly proposed mechanical explanations for the walk-to-run transition (WRT) include the prevention of muscular over-exertion (effort) and the minimization of peak musculoskeletal loads and thus injury risk. The purpose of this study was to address these hypotheses at a joint level by analysing the effect of speed on discrete lower-limb joint kinetic parameters in humans across a wide range of walking and running speeds including walking above and running below the WRT speed. Joint work, peak instantaneous joint power, and peak joint moments in the sagittal and frontal plane of the ankle, knee and hip from eight participants were collected for 10 walking speeds (30-120% of their WRT) and 10 running speeds (80-170% of their WRT) on a force plate instrumented treadmill. Of the parameters analysed, three satisfied our statistical criteria of the 'effort-load' hypothesis of the WRT. Mechanical parameters that provide an acute signal (peak moment and peak power) were more strongly associated with the gait transition than parameters that reflect the mechanical function across a portion of the stride. We found that both the ankle (peak instantaneous joint power during swing) and hip mechanics (peak instantaneous joint power and peak joint moments in stance) can influence the transition from walking to running in human locomotion and may represent a cascade of mechanical events beginning at the ankle and leading to an unfavourable compensation at the hip. Both the ankle and hip mechanisms may contribute to gait transition by lowering the muscular effort of running compared with walking at the WRT speed. Although few of the examined joint variables satisfied our hypothesis of the WRT, most showed a general marked increase when switching from walking to running across all speeds where both walking and running are possible, highlighting the fundamental differences in the mechanics of walking and running. While not eliciting the WRT per se, these variables may initiate the transition between stable walking and running patterns. Those variables that were invariant of gait were predominantly found in the swing phase.

Does movement proficiency impact on exergaming performance?

There is growing interest in the use of consumer level exergames in movement skill acquisition. The purpose of this study was to investigate the relationship between movement proficiency and performance in virtual exergaming. Twenty seven children, aged 10-15years participated in an experiment completing the Movement Assessment Battery for Children 2 (MABC-2) and a series of XBOX360 Kinect Sports exergaming tasks. Significant correlations were observed between MABC-2 aiming and catching percentile and exergame javelin and target kick, where the more proficient movers tended to perform better in the exergame. Statistically significant correlations were observed between MABC-2 balance percentile and exergaming sprint and target kick performance. In this study children who scored better in real life gross motor movement tasks performed better in most related exergaming activities. This suggests current exergaming technology has advanced to a point where body movement unencumbered by a physical or remote game device tether can extract movements resembling real life tasks, translate them into game play and reward proficient movers with higher in-game performance. It is possible that benefit gained in an exergaming environment by more proficient movers was a result of either their more proficient movement, or a greater ability to adapt to the exergame.

Effects of different visual stimuli on postures and knee moments during sidestepping.

PURPOSE: Evasive sidestepping during sports commonly results in noncontact anterior cruciate ligament injuries. Sidestepping in response to different simple visual stimuli has been studied previously but never investigated using quasi-game-realistic visual conditions. We compared the biomechanics of high-level and low-level soccer players when sidestepping in response to projected, three-dimensional defender(s) and the traditionally used planned and unplanned arrow stimuli. METHODS: A three-dimensional motion analysis system captured the trunk and lower limb kinematics and ground reaction forces of 15 high-level and 15 low-level soccer players sidestepping in response to a one-defender scenario (1DS), two-defender scenario (2DS), arrow-planned condition (AP), and arrow-unplanned condition (AUNP). The temporal constraints imposed by the stimuli conditions resulted in increasing difficulty from AP, 1DS, 2DS, to AUNP. Selected joint kinematics and three-dimensional knee moments during the weight-acceptance phase of sidestepping were analyzed. RESULTS: Hip external rotation at initial foot contact was smaller when participants sidestepped in response to the projected defenders versus arrow conditions. Hip abduction was smallest in the AP, moderate in the defender scenarios, and largest in the AUNP. Peak knee valgus moments were 25% larger in the defender scenarios and 70% larger in the AUNP compared with the AP. High-level players exhibited decreased hip abduction and knee valgus moments in the 2DS compared with the low-level players. CONCLUSIONS: Compared with the arrow conditions, sidestepping in response to the defender(s) resulted in different postures and knee moments, which further differentiated between high-level and low-level players in the complex 2DS. These findings highlight the effects of stimuli realism and complexity on the visual-perceptual-motor skill of sidestepping, which has implications for anterior cruciate ligament injury prevention.

Visual search differs but not reaction time when intercepting a 3D versus 2D videoed opponent.

The authors aimed to identify differences in (a) visual search and (b) reaction time when athletes sidestepped to intercept 2D versus 3D videoed opponents. They hypothesized that participants would (a) fixate on different parts of the opponent's body and (b) react quicker when responding to the 3D versus 2D opponent due to the added depth cues. A customized integrated stereoscopic system projected the video stimuli and synchronously recorded the gaze and motor behaviors of 10 men when they responded to two- (2D) and three-dimensional (3D) opponents. The number and duration of gaze fixations were coded according to locations on the opponent's body (head, shoulders, arms, trunk, pelvis, legs) or otherwise (other). Mediolateral pelvic movement was used to infer reaction time. Participants spent 16% less time fixating on the trunk and 23% more time outside the 3D opponent's body compared with the 2D stimulus. No reaction time differences were found. Although participants fixated less on the 3D opponent's body and, by inference, invested less perceptual processing toward interpreting the opponent's movements compared with the 2D condition, they performed the interception task equally fast in both conditions. Three-dimensional depth cues may provide more meaningful information per fixation for successful task performance.

Decision-making accuracy in reactive agility: quantifying the cost of poor decisions.

Decision-making accuracy and the time cost of incorrect responses was compared between higher- (n = 14) and lower-standard (n = 14) Australian footballers during reactive agility tasks incorporating feint and nonfeint scenarios. Accuracy was assessed as whether the subject turned in the correct direction to each stimulus. With skill groups pooled, decision accuracy at the first (or only) stimulus (decision time 1) was 94 ± 7%, and it decreased to 83 ± 20% for the second stimulus (decision time 2; p = 0.01; d = 0.69). However, with skill groups separated, decision accuracy was similar between groups at decision time 1 (higher 95 ± 6% vs. lower 92 ± 7%; p = 0.6; d = 0.42), somewhat better in the higher-standard group at decision time 2 (88 ± 22% vs. 78 ± 17%; p = 0.08; d = 0.50). But the decrease in accuracy from decision time 1 to 2 was significant in the lower-standard group only (92 ± 7% to 78 ± 17%; p = 0.02; d = 1.04). However, with skill groups pooled but agility times examined exclusively in trials involving correct or incorrect decisions, incorrect decisions at decision time 1 during feint trials resulted in a shorter agility time (1.73 ± 0.24 seconds vs. 2.03 ± 0.39 seconds; p = 0.008; d = 0.92), whereas agility time was significantly longer in feint (incorrect at decision time 2 only; 2.65 ± 0.41 seconds vs. 1.97 ± 0.36 seconds; p < 0.001; d = 1.76) and nonfeint trials (1.64 ± 0.13 seconds vs. 1.51 ± 0.10 seconds; p = 0.001; d = 1.13). Therefore, although decision-making errors typically worsen reactive agility performance, successful anticipation of a feint can produce performance improvements. Furthermore, higher-standard footballers are less susceptible to such feints, perhaps because of superior anticipation. Training to improve decision-making accuracy, particularly involving feint movements, may therefore principally benefit lesser-skilled players and should be practiced regularly.

Comparison of ground reaction force asymmetry in one- and two-legged countermovement jumps.

This study examined whether ground reaction force (GRF) asymmetry of 2-legged countermovement jumps (CMJ) is related to 1-legged CMJ asymmetry. The GRF asymmetry of a 2-legged CMJ has been suggested as a preferred test to the 1-legged CMJ for functional strength and power deficit assessment. Twenty-eight men and 30 women performed 5 trials each of a 1-legged CMJ with the right limband the left limb, and a 2-legged CMJ. Vertical GRFs were collected from each lower limb using 2 force platforms. Although several GRF variables were calculated, vertical impulse correlated most strongly with jump height in all conditions (p < 0.05), and they were used in subsequent analyses. A moderate correlation was found for impulse asymmetry between the 1- and 2-legged CMJs for women (r = 0.45, p < 0.05), but not for men (r = 0.06, p = 0.76). In contrast, cross-tabulation analyses of subjects presented with the same dominant characteristics in the 1- and 2-legged CMJs revealed poor associations for both men (Freeman-Halton exact p = 0.61) and women (Freeman-Halton exact p = 0.19). Only 11 women recorded the same dominant limb for both 1- and 2-legged CMJs. This suggests that impulse asymmetries found in the 1- and 2-legged CMJ were unrelated. As the 1-legged CMJ relies on the extension forces generated entirely from 1 limb, variations in jump heights and GRF impulses by left and right limbs separately were more indicative of functional strength differences between sides. Hence, it is recommended that the 1-legged CMJ is used when examining functional strength asymmetry in the lower limbs. In contrast, factors causing asymmetry in GRF impulses during 2-legged CMJs are more complicated and require further investigation.