Validating an inertial measurement unit for cricket fast bowling: a first step in assessing the feasibility of diagnosing back injury risk in cricket fast bowlers during a tele-sport-and-exercise medicine consultation.

This study aimed to validate an array-based inertial measurement unit to measure cricket fast bowling kinematics as a first step in assessing feasibility for tele-sport-and-exercise medicine. We concurrently captured shoulder girdle relative to the pelvis, trunk lateral flexion, and knee flexion angles at front foot contact of eight cricket medium-fast bowlers using inertial measurement unit and optical motion capture. We used one sample t-tests and 95% limits of agreement (LOA) to determine the mean difference between the two systems and Smallest Worth-while Change statistic to determine whether any differences were meaningful. A statistically significant (p < 0.001) but small mean difference of -4.7° ± 8.6° (95% Confidence Interval (CI) [-3.1° to -6.4°], LOA [-22.2 to 12.7], SWC 3.9°) in shoulder girdle relative to the pelvis angle was found between the systems. There were no statistically significant differences between the two systems in trunk lateral flexion and knee flexion with the mean differences being 0.1° ± 10.8° (95% CI [-1.9° to 2.2°], LOA [-22.5 to 22.7], SWC 1.2°) and 1.6° ± 10.1° (95% CI [-0.2° to 3.3°], LOA [-19.2 to 22.3], SWC 1.9°) respectively. The inertial measurement unit-based system tested allows for accurate measurement of specific cricket fast bowling kinematics and could be used in determining injury risk in the context of tele-sport-and-exercise-medicine.

Individual Differences and Transfer of Visual Anticipation in Expert Female Field Hockey Goalkeepers.

SIGNIFICANCE: Visual anticipation is vital for performance in several domains such as driving, military, and high-speed interceptive sports, as it enables performers to handle severe time constraints. There has been little investigation into individual differences of anticipation skill transfer within a domain, which can guide training of anticipation to improve performance. PURPOSE: The purpose of this study was to investigate individual differences in the transfer of anticipation within a domain, specifically anticipation of the field hockey penalty corner drag-flick across different opponents. METHODS: Eight female Australian international and national field hockey goalkeepers participated. Goalkeepers completed female and male opponent penalty corner drag-flick temporal occlusion tests that presented contextual defensive runner positioning relative to the penalty spot, drag-flicker kinematics, and ball flight. RESULTS: Drag-flick movement time and ball velocity were significantly different across female and male opponents confirming that a transfer continuum existed. Five goalkeepers could transfer integration of runner contextual and drag-flicker kinematic information to anticipate loose runs above chance from female to male opponent tests. None of the goalkeepers could transfer integration of contextual and kinematic information for the tight runs across female to male opponents. CONCLUSIONS: An individual differences approach with truly expert performers provided unique insights into the mechanism of anticipation transfer within a domain. The findings of this study contribute to theoretical and applied knowledge, which can guide the training of anticipation skill to prepare individuals for superior performance.

Women in motorsport: A case report of driving posture and performance after double mastectomy.

INTRODUCTION: Here we report a case study of an experienced amateur female racing driver (age = 59) with self-reported fatigue of the muscles of the shoulder girdle post bilateral mastectomy and breast reconstruction. This case study describes how adjustment of her driving posture affected measures of muscle fatigue (sEMG) and driving performance (lap-time). METHODS: Bilateral surface electromyographic activity of sternocleidomastoid, cervical erector spinae, anterior deltoid and pectoralis major, angles of inclination of the cervical and lumbar spine in the sagittal plane and lap-times were measured at: 1) baseline, 2) after an initial adjustment of driving posture, and 3) after a readjustment of driving posture. Mean lap-times improved from 136.81 s (SD = 2.12) at baseline to 134.63 s (SD = 1.8) after readjustment. RESULTS: Both sternocleidomastoid and left cervical erector spinae fatigued more slowly after readjustment but right cervical erector spinae fatigued more quickly. There was no change in the rates of fatigue of either pectoralis major or anterior deltoid. CONCLUSION: The improvement in her performance was associated with a change in the posture and movement pattern of her head rather than her shoulder girdle. It is likely that this improved her ability to visually perceive and steer the racing line.

Biomechanical correlates of running performance in active children.

OBJECTIVES: Examine the running kinematics in healthy, physically active prepubescent children and to determine if specific biomechanical factors correlate with running performance. DESIGN: Cross-sectional study. METHODS: Fifteen children (age 9years, ±11months) completed a 1km time trial before undergoing three-dimensional running motion analysis. RESULTS: A strong positive correlation was observed between the biomechanical variables of stride length (p<.01), contact time (p<.01) and ankle dorsiflexion angle (p=.04) with time trial performance. Between variable analyses revealed a strong positive correlation between peak angles of hip adduction and knee flexion. There was no correlation between hip adduction and knee flexion peak angles or the vertical displacement of centre of mass with trial performance. CONCLUSIONS: The results of this study show that children with a better time trial performance display longer stride length, shorter contact time and mid or forefoot strike pattern. These findings have implications for targeted technique intervention in children's running training to improve running performance.

Effect of halo-type frontal cockpit protection on overtaking.

In 2018, the Fédération Internationale de l'Automobile introduced the halo frontal cockpit protection system into Formula 1. While extensive testing was conducted to confirm that the halo protects the driver from contact, the halo's effect on the driver during overtaking was not tested prior to its introduction. Here, we describe the effect of a halo-type structure on the neck muscle activity of one of the authors, a national-level amateur racing driver, during on-track simulations designed to practise overtaking. We found that the halo-type structure caused an increase in the rates of fatigue and workloads of sternocleidomastoid and cervical erector spinae. The results suggest that the driver adopted a forward and right laterally flexed head position, presumably to clear the central pillar from his visible field. This has the potential to increase compressive loading of the cervical spine and affect the ability to use visual cues during steering manoeuvres.

Effect of a halo-type structure on neck muscle activation of an open-cockpit race car driver training under qualifying conditions.

The Fédération Internationale de l'Automobile recently mandated the use of the halo frontal cockpit protection system to mitigate the risk of impact to the driver's head. Here we describe the effect of a halo-type structure on the neck muscle activity of one of the authors, who is a national-level amateur racing driver, during a full qualifying session. We found that the workload of sternocleidomastoid increased and the workload of cervical erector spinae decreased with the halo fitted which is indicative of a forward head position. Left sternocleidomastoid and right cervical erector spinae fatigued more rapidly; whereas, left cervical erector spinae fatigued more slowly. There was no change in the rate of fatigue of right sternocleidomastoid. In combination with a forward head position, this suggests an increase in lateral flexion during head rotation which may affect accuracy of navigation. Thus, drivers may need to be trained to adapt to the halo to mitigate the effects on head position and movement.

On using wearable tri-axial accelerometers to examine the striking phase kinematics of expert specialist drag flickers on-field.

Analysing player kinematics during a match using "gold-standard" 3D video-based motion analysis techniques is a difficult prospect indeed. The development of small, wireless, wearable sensors offers the potential to reduce the challenges of measuring kinematics during match-play without hindering performance. The present study examined the viability of using wireless tri-axial accelerometers to examine whether key performance measures of drag flicks executed by expert specialist drag-flickers are predicted by the kinematics of the striking phase. Linear mixed models were used to examine whether the speed and accuracy of players' drag flicks were predicted by the duration of stick-ball contact, and the kinematics of the lead lower limb at stick-ball contact and ball release. Results revealed that stick and lead lower limb kinematics significantly predicted shot accuracy but not shot speed. Shorter drag-time predicted more accurate flicks (p = 0.03) as did a more vertical leg at stick-ball contact (p = 0.016) and a more horizontal thigh at ball release (p = 0.001). This may indicate that there are more ways to produce fast drag flicks than accurate ones. This study illustrates that wireless tri-axial accelerometers can be used on-field to measure the effects of kinematics on key performance measures.

A biomechanical comparison in the lower limb and lumbar spine between a hit and drag flick in field hockey.

Research has revealed that field hockey drag flickers have greater odds of hip and lumbar injuries compared to non-drag flickers (DF). This study aimed to compare the biomechanics of a field hockey hit and a specialised field hockey drag flick. Eighteen male and seven female specialised hockey DF performed a hit and a drag flick in a motion analysis laboratory with an 18-camera three-dimensional motion analysis system and a calibrated multichannel force platform to examine differences in lower limb and lumbar kinematics and kinetics. Results revealed that drag flicks were performed with more of a forward lunge on the left lower limb resulting in significantly greater left ankle dorsiflexion, knee, hip and lumbar flexion (Ps<0.001) compared to a hit. Drag flicks were also performed with significantly greater lateral flexion (P < 0.002) and rotation of the lumbar spine (P < 0.006) compared to a hit. Differences in kinematics lead to greater shear, compression and tensile forces in multiple left lower limb and lumbar joints in the drag flick compared to the hit (P < 0.05). The biomechanical differences in drag flicks compared to a hit may have ramifications with respect to injury in field hockey drag flickers.

Does skill specialisation influence individual differences in drag flicking speed and accuracy?

Research has revealed that individual soccer goalkeepers respond differently to penalty shots, depending on their specific perceptual and motor capabilities. However, it remains unclear whether analogous differences exist between individual penalty takers, and if specialising in penalty taking affects the occurrence of differences between individuals. The present study examined individual differences in penalty shot speed and accuracy for specialists in penalty taking versus non-specialists. Expert specialist field hockey drag flickers and equivalently skilled non-specialists performed drag flicks towards predetermined targets placed in the face of a standard field hockey goal. Comparisons in shot speed and accuracy were made at a group level (specialists vs. non-specialists) as well as between individuals. Results revealed differences in both speed and accuracy between specialists, but only differences in speed between non-specialists. Specialists generated significantly greater shot speed than non-specialists (P < .001) and were more accurate to some, but not all, targets (top left, P < .006, bottom left P < .001). In addition, it was found that in specialists increasing practice correlated with decreasing accuracy. This may indicate that excessive practice could potentially reduce a specialist's accuracy in shooting towards specific targets.

Physical demand of seven closed agility drills.

The present study aimed to quantify the demand of seven generic, closed agility drills. Twenty males with experience in invasion sports volunteered to participate in this study. They performed seven, closed agility drills over a standardised 30-m distance. Physical demand measures of peak velocity, total foot contacts, peak impacts, completion time, and maximum heart rate were obtained via the use of wearable sensor technologies. A subjective rating of perceived exertion (RPE) was also obtained. All measures, with the exception of maximum heart rates and RPE were able to delineate drills in terms of physical and physiological demand. The findings of this study exemplify the differences in demand of agility-type movements. Drill demand was dictated by the type of agility movement initiated with the increase in repetitiveness of a given movement type also contributing to increased demand. Findings from this study suggest agility drills can be manipulated to vary physical and physiological demand. This allows for the optimal application of training principles such as overload, progression, and periodisation.

The prevalence and severity of injuries in field hockey drag flickers: a retrospective cross-sectional study.

The drag flick is the preferred method of scoring during a penalty corner in field hockey. Performing the drag flick requires a combination of strength, coordination and timing, which may increase susceptibility to injuries. However, injury prevalence in drag flickers has not previously been investigated. Therefore, this study compared the injury prevalence and severity of lower limb and lower back injuries between drag flickers and non-drag flickers in field hockey. A total of 432 local, national and international adult field hockey players (242 males, 188 females) completed an online questionnaire to retrospectively determine the 3-month prevalence and severity of ankle, knee, hip and lower back injuries. Of this group, 140 self-identified as drag flickers and 292 as non-drag flickers. The results showed that drag flickers had significantly higher prevalence of hip (OR: 1.541; 95% CI: 1.014, 2.343) and lower back injury (OR: 1.564; 95% CI: 1.034, 2.365) compared to non-drag flickers. No significant differences were observed between drag flickers and non-drag flickers in injury prevalence at the ankle and knee. There were no significant between-group differences in injury severity scores. Overall, the prevalence of hip and lower back injuries was significantly higher in drag flickers compared to non-drag flickers.

Does expert perceptual anticipation transfer to a dissimilar domain?

The purpose of this experiment was to extend theoretical understanding of transfer of learning by investigating whether expert perceptual anticipation skill transfers to a dissimilar domain. The capability of expert and near-expert rugby players as well as novices to anticipate skill type within rugby (learning sport) was first examined using a temporal occlusion paradigm. Participants watched video footage of an opponent performing rugby skill types that were temporally occluded at different points in the opponent's action and then made a written prediction. Thereafter, the capability of participants to transfer their anticipation skill to predict pitch type in baseball (transfer sport) was examined. Participants watched video footage of a pitcher throwing different pitch types that were temporally occluded and made a written prediction. Results indicated that expert and near-expert rugby players anticipated significantly better than novices across all occlusion conditions. However, none of the skill groups were able to transfer anticipation skill to predict pitch type in baseball. The findings of this paper, along with existing literature, support the theoretical prediction that transfer of perceptual anticipation is expertise dependent and restricted to similar domains.

Pick-up of early visual information to guide kinetics and kinematics within a group of highly skilled baseball batters.

This pilot study integrated sport expertise and biomechanics methodologies within a baseball batting task. Purpose was to examine differences within a highly skilled group of baseball batters to use visual information to guide weight transfer and bat movements. One batter who played at Major League Baseball (MLB) level was compared to five batters who played at Australian Baseball League (ABL) level in a case-control design. Batters faced pitchers in a simulated competition and attempted to hit pitches, while vision was temporally occluded during ball flight or not occluded. Time of weight transfer (kinetics), as well as bat downswing initiation and duration (kinematics) from the point of ball release, were compared between the MLB batter and ABL batters. Results indicated that the MLB batter coordinated his striking pattern by completing his weight transfer earlier than the ABL batters. His bat downswing was also initiated earlier than some ABL batters, but there was no difference in duration of bat downswing between batters. All batters initiated bat downswing prior to completion of weight transfer. Understanding of motor expertise is furthered using a novel methodology.

Expertise facilitates the transfer of anticipation skill across domains.

It is unclear whether perceptual-motor skill transfer is based upon similarity between the learning and transfer domains per identical elements theory, or facilitated by an understanding of underlying principles in accordance with general principle theory. Here, the predictions of identical elements theory, general principle theory, and aspects of a recently proposed model for the transfer of perceptual-motor skill with respect to expertise in the learning and transfer domains are examined. The capabilities of expert karate athletes, near-expert karate athletes, and novices to anticipate and respond to stimulus skills derived from taekwondo and Australian football were investigated in ecologically valid contexts using an in situ temporal occlusion paradigm and complex whole-body perceptual-motor skills. Results indicated that the karate experts and near-experts are as capable of using visual information to anticipate and guide motor skill responses as domain experts and near-experts in the taekwondo transfer domain, but only karate experts could perform like domain experts in the Australian football transfer domain. Findings suggest that transfer of anticipation skill is based upon expertise and an understanding of principles but may be supplemented by similarities that exist between the stimulus and response elements of the learning and transfer domains.

Timing of in situ visual information pick-up that differentiates expert and near-expert anticipation in a complex motor skill.

The timing of visual information pick-up for visual anticipation was examined by comparing the capability of multiple skill groups, expert and near-expert karate athletes and novices, to block attacks using an in situ temporal occlusion paradigm. Participants stood facing a karate opponent and then attempted to block attacks (kicks and punches), whilst their vision of attacks was occluded: (a) prior to onset of opponent motion (O1), (b) after preparatory head movement (O2), and (c) after initiation of the attacking motion (O3). A no occlusion control condition provided complete vision of attacks (O4). Results revealed that expert anticipation was not significantly different to that of near-experts at O1, but was significantly different to the other group across O2-O4. Expert anticipation, however, was significantly above chance across all occlusion conditions, but near-experts performed above chance at O3 and O4, whilst novices were better than chance at O4. Unexpectedly, unique evidence was found that expert anticipation could be differentiated from near-expert anticipation in the earliest occlusion condition, where it was found that only experts were capable of using visual information from a static opponent to anticipate and block attacks above chance. The findings further understanding of expert visual anticipation to guide motor skills beyond existing expert-novice comparisons.

A model for the transfer of perceptual-motor skill learning in human behaviors.

This paper presents a preliminary model that outlines the mechanisms underlying the transfer of perceptual-motor skill learning in sport and everyday tasks. Perceptual-motor behavior is motivated by performance demands and evolves over time to increase the probability of success through adaptation. Performance demands at the time of an event create a unique transfer domain that specifies a range of potentially successful actions. Transfer comprises anticipatory subconscious and conscious mechanisms. The model also outlines how transfer occurs across a continuum, which depends on the individual's expertise and contextual variables occurring at the incidence of transfer