Feasibility of vertical force-velocity profiles to monitor changes in muscle function following different fatigue protocols.

PURPOSE: This study aimed to explore the feasibility of vertical force-velocity (F-V) profiles to monitor changes in muscle function following different fatigue protocols. The between-day reliability of vertical F-V profiles and the acute effects of two fatigue protocols on the changes of lower limb muscle function were examined. METHODS: Twelve resistance trained males completed a preliminary session to determine their back squat one-repetition maximum (1RM). Afterwards, they randomly performed two experimental sessions that only differed in the fatigue protocol applied: heavy-load traditional (HLT; five repetitions at 80% 1RM) and light-load ballistic (LLB; five repetitions at 30% 1RM) squat protocols. Participants' vertical F-V profiles (maximum theoretical force [F0], maximum theoretical velocity [v0], and maximum power output [Pmax]) were calculated before and immediately after each fatigue protocol. RESULTS: F0, v0, and Pmax showed acceptable to good between-day reliability (coefficient of variation ≤ 4.4%; intraclass correlation coefficient ≥ 0.84). Both fatigue protocols promoted a comparable reduction in Pmax (-10.1% for HLT and -12.2% for LLB). However, the LLB squat protocol reduced more v0 (-9.7%) than F0 (-0.4%), while the HLT squat protocol reduced F0 (-8.4%) more than v0 (-4.1%). CONCLUSIONS: The vertical F-V profile can be used to monitor changes in muscle function given its acceptable between-day reliability and its high sensitivity to detect the acute effect of force-oriented and velocity-oriented fatigue protocols on specific maximal neuromuscular capacities.

Evaluating the Effectiveness of Apps Designed to Reduce Mobile Phone Use and Prevent Maladaptive Mobile Phone Use: Multimethod Study.

BACKGROUND: Mobile apps are a popular strategy for reducing mobile phone use and preventing maladaptive mobile phone use (MMPU). Previous research efforts have been made to understand the features of apps that have the potential to reduce mobile phone use and MMPU. However, there has been a lack of a comprehensive examination of the effectiveness of such apps and their features. OBJECTIVE: This paper investigated existing apps designed to reduce mobile phone use and prevent MMPU and examined the evidence of their effectiveness. The research aimed to provide a comprehensive analysis of app features that can reduce mobile phone use and MMPU, while also assessing their effectiveness. In addition, we explored users' perceptions of these apps and the various features the apps offer to understand potential adoption issues and identify opportunities. METHODS: This study used 3 methods: a review of scientific evidence, content analysis, and sentiment analysis. RESULTS: Our study comprehensively examine the common features of 13 apps designed to reduce mobile phone use. We extracted and classified the features into 7 types: self-tracking, social tracking, goal setting, blocking, gamification, simplification, and assessment. The effectiveness of these apps in reducing mobile phone use and MMPU varied from weak to strong. On the basis of content analysis, self-tracking and goal setting were the most frequently used features, whereas gamification and assessment were used the least frequently. The intervention strategies that effectively reduce mobile phone use and MMPU included using grayscale mode, app limit features, and mixed interventions. Overall, users tended to accept these apps, as indicated by sentiment scores ranging from 61 to 86 out of 100. CONCLUSIONS: This study demonstrates that app-based management has the potential to reduce mobile phone use and MMPU. However, further research is required to evaluate the effectiveness of app-based interventions. Collaborations among researchers, app developers, mobile phone manufacturers, and policy makers could enhance the process of delivering, evaluating, and optimizing apps aimed at reducing mobile phone use and MMPU.

Data Collection Procedures and Injury Definitions in Badminton: A Consensus Statement According to the Delphi Approach.

ABSTRACT: Previous studies involving injury surveillance in badminton players have used nonstandardized injury definitions and data collection methodologies. The purpose of this study was to apply a Delphi method to (1) reach a consensus on an injury definition in badminton and (2) develop a standardized badminton injury report form. An Injury Consensus Group was established under the auspices of the Badminton World Federation, and initial injury definitions and injury report form were developed. An internal panel was formed from the Injury Consensus Group, and an external panel was selected based on a combination of profession, experience in the field, sport-specific knowledge/expertise, and geographical location to obtain a widely representative sample. Through 2 rounds of voting by the external panel, consensus was reached on both the definition of an injury in badminton and a standardized injury report form. The agreed injury definition was "Any physical injury sustained by a player during a match or training regardless if further diagnostic tests were done or if playing time was lost" and the injury report form contained the following 7 sections: Injury record, Diagnosis, Injury mechanism, Regarding pain, Pain and return to play/training after injury, Grade of severity, and Recurrence. We recommend the use of the definitions and methods presented in this consensus statement for the reporting of injury in all international and domestic badminton players. This should make future injury surveillance reports directly comparable and hence more informative in recognizing trends over time and differences between countries.

Lumbar bone stress injuries and risk factors in adolescent cricket fast bowlers.

Cricket fast bowling is associated with a high prevalence of lumbar bone stress injuries (LBSI), especially in adolescent bowlers. This has not been sufficiently explained by risk factors identified in adult players. This study aimed to examine the incidence of LBSI in adolescent fast bowlers over a prospective study and potential risk factors. Forty asymptomatic male fast bowlers (aged 14-17 years) received baseline and annual lumbar dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) scans, and musculoskeletal and bowling workload assessment; 22 were followed up after one year. LBSI prevalence at baseline and annual incidence were calculated. Potential risk factors were compared between the injured and uninjured groups using T-tests with Hedges' g effect sizes. At baseline, 20.5% of participants had at least one LBSI. Subsequent LBSI incidence was 27.3 ± 18.6 injuries per 100 players per year (mean ± 95% CI). Injured bowlers were older on average at the beginning of the season preceding injury (16.8 versus 15.6 years, g = 1.396, P = 0.047). LBSI risk may coincide with increases in bowling workload and intensity as bowlers step up playing levels to more senior teams during late adolescence whilst the lumbar spine is immature and less robust.

The relationship between bowling intensity and ground reaction force in cricket pace bowlers.

This study examined the relationship between perceived bowling intensity, ball release speed and ground reaction force (measured by peak force, impulse and loading rate) in male pace bowlers. Twenty participants each bowled 36 deliveries, split evenly across three perceived intensity zones: low = 70% of maximum perceived bowling effort, medium = 85%, and high = 100%. Peak force and loading rate were significantly different across the three perceived intensity zones in the horizontal and vertical directions (Cohen's d range = 0.14-0.45, p < 0.01). When ball release speed increased, peak force and loading rate also increased in the horizontal and vertical directions (ηp2 = 0.04-0.18, p < 0.01). Lastly, bowling at submaximal intensities (i.e., low - medium) was associated with larger decreases in peak horizontal force (7.9-12.3% decrease), impulse (15.8-21.4%) and loading rate (7.4-12.7%) compared to decreases in ball release speed (5.4-8.3%). This may have implications for bowling strategies implemented during training and matches, particularly for preserving energy and reducing injury risk.

Predicting Hemiwicking Dynamics on Textured Substrates.

The ability to predict liquid transport rates on textured surfaces is key to the design and optimization of devices and processes such as oil recovery, coatings, reaction-separation, high-throughput screening, and thermal management. In this work we develop a fully analytical model to predict the propagation coefficients for liquids hemiwicking through micropillar arrays. This is carried out by balancing the capillary driving force and a viscous resistive force and solving the Navier-Stokes equation for representative channels. The model is validated against a large data set of experimental hemiwicking coefficients harvested from the literature and measured in-house using high-speed imaging. The theoretical predictions show excellent agreement with the measured values and improved accuracy compared to previously proposed models. Furthermore, using lattice Boltzmann (LB) simulations, we demonstrate that the present model is applicable over a broad range of geometries. The scaling of velocity with texture geometry, implicit in our model, is compared against experimental data, where good agreement is observed for most practical systems. The analytical expression presented here offers a tool for developing design guidelines for surface chemistry and microstructure selection for liquid propagation on textured surfaces.

Resuscitating Cardiopulmonary Resuscitation Training in a Virtual Reality: Prospective Interventional Study.

BACKGROUND: Simulation-based technologies are emerging to enhance medical education in the digital era. However, there is limited data for the use of virtual reality simulation in pediatric medical education. We developed Virtual Doc as a highly immersive virtual reality simulation to teach pediatric cardiopulmonary resuscitation skills to medical students. OBJECTIVE: The primary objectives of this study were to evaluate participant satisfaction and perceived educational efficacy of Virtual Doc. The secondary aim of this study was to assess the game play features of Virtual Doc. METHODS: We conducted a prospective closed beta-testing study at the University of New South Wales (Sydney, Australia) in 2018. All medical students from the 6-year undergraduate program were eligible to participate and were recruited through voluntary convenience sampling. Participants attended a 1-hour testing session and attempted at least one full resuscitation case using the virtual reality simulator. Following this, participants were asked to complete an anonymous postsession questionnaire. Responses were analyzed using descriptive statistics. RESULTS: A total of 26 participants were recruited, consented to participate in this study, and attended a 1-hour in-person closed beta-testing session, and 88% (23/26) of participants completed the anonymous questionnaire and were included in this study. Regarding participant satisfaction, Virtual Doc was enjoyed by 91% (21/23) of participants, with 74% (17/23) intending to recommend the simulation to a colleague and 66% (15/23) intending to recommend the simulation to a friend. In assessment of the perceived educational value of Virtual Doc, 70% (16/23) of participants agreed they had an improved understanding of cardiopulmonary resuscitation, and 78% (18/23) agreed that Virtual Doc will help prepare for and deal with real-life clinical scenarios. Furthermore, 91% (21/23) of participants agreed with the development of additional Virtual Doc cases as beneficial for learning. An evaluation of the game play features as our secondary objective revealed that 70% (16/23) of participants agreed with ease in understanding how to use Virtual Doc, and 74% (17/23) found the game play elements useful in understanding cardiopulmonary resuscitation. One-third (7/23, 30%) found it easy to work with the interactive elements. In addition, 74% (17/23) were interested in interacting with other students within the simulation. CONCLUSIONS: Our study demonstrates a positive response regarding trainee satisfaction and perceived educational efficacy of Virtual Doc. The simulation was widely accepted by the majority of users and may have the potential to improve educational learning objectives.

Scaling the cricket pitch to fit junior players.

Studies in several sports have shown the benefits of adapting the playing environment to fit junior players. Frequently the changes are pragmatic choices based on space constraints or existing line markings, or the result of simple scaling based on stature. In this study, a method of scaling the cricket pitch length is presented which is based on the age-specific size and performance of the bowlers and batters. The objective was a pitch length which enabled young bowlers to bowl good length deliveries while releasing the ball at a more downward angle, similar to elite bowlers. The steeper release angle has the benefit of reducing the sensitivity of the ball flight distance to the variability of ball release. Based on data from county standard under-10 and under-11 players a pitch length of 16.22 yards (14.83 m) was calculated, 19% shorter than previously recommended for under-11s in England. A shorter pitch also increases the temporal challenge for batters, encouraging a wider variety of shots and improved anticipation skills. Pitch lengths scaled in this way to fit the players' abilities as they develop will enable a more consistent ball release by bowlers and more consistent temporal demand for batters.

Comparing power hitting kinematics between skilled male and female cricket batters.

Organismic, task, and environmental constraints are known to differ between skilled male and female cricket batters during power hitting tasks. Despite these influences, the techniques used in such tasks have only been investigated in male cricket batters. This study compared power hitting kinematics between 15 male and 15 female batters ranging from university to international standard. General linear models were used to assess the effect of gender on kinematic parameters describing technique, with height and body mass as covariates. Male batters generated greater maximum bat speeds, ball launch speeds, and ball carry distances than female batters on average. Male batters had greater pelvis-thorax separation in the transverse plane at the commencement of the downswing (ß = 1.14; p = 0.030) and extended their lead elbows more during the downswing (ß = 1.28; p = 0.008) compared to female batters. The hypothesised effect of gender on the magnitude of wrist uncocking during the downswing was not observed (ß = -0.14; p = 0.819). The causes of these differences are likely to be multi-factorial, involving aspects relating to the individual players, their history of training experiences and coaching practices, and the task of power hitting in male or female cricket.

Optimising the front foot contact phase of the cricket fast bowling action.

Cricket fast bowling is a dynamic activity in which a bowler runs up and repeatedly delivers the ball at high speeds. Experimental studies have previously linked ball release speed and several technique parameters with conflicting results. As a result, computer simulation models are increasingly being used to understand the effects of technique on performance. This study evaluates a planar 16-segment whole-body torque-driven simulation model of the front foot contact phase of fast bowling by comparing simulation output with the actual performance of an elite fast bowler. The model was customised to the bowler by determining subject-specific inertia and torque parameters. Good agreement was found between actual and simulated performances with a 4.0% RMS difference. Varying the activation timings of the torque generators resulted in an optimised simulation with a ball release speed 3.5 m/s faster than the evaluation simulation. The optimised technique used more extended front ankle and knee joint angles, increased trunk flexion and a longer delay in the onset of arm circumduction. These simulations suggest the model provides a realistic representation of the front foot contact phase of fast bowling and is suitable to investigate the limitations of kinematic or kinetic variables on fast bowling performance.

Auto detecting deliveries in elite cricket fast bowlers using microsensors and machine learning.

Cricket fast bowlers are at a high risk of injury occurrence, which has previously been shown to be correlated to bowling workloads. This study aimed to develop and test an algorithm that can automatically, reliably and accurately detect bowling deliveries. Inertial sensor data from a Catapult OptimEye S5 wearable device was collected from both national and international level fast bowlers (n = 35) in both training and matches, at various intensities. A machine-learning based approach was used to develop the algorithm. Outputs were compared with over 20,000 manually recorded events. A high Matthews correlation coefficient (r = 0.945) showed very good agreement between the automatically detected bowling deliveries and manually recorded ones. The algorithm was found to be both sensitive and specific in training (96.3%, 98.3%) and matches (99.6%, 96.9%), respectively. Rare falsely classified events were typically warm-up deliveries or throws preceded by a run. Inertial sensors data processed by a machine-learning based algorithm provide a valid tool to automatically detect bowling events, whilst also providing the opportunity to look at performance metrics associated with fast bowling. This offers the possibility to better monitor bowling workloads across a range of intensities to mitigate injury risk potential and maximise performance.

Effect of racket-shuttlecock impact location on shot outcome for badminton smashes by elite players.

A logarithmic curve fitting methodology for the calculation of badminton racket-shuttlecock impact locations from three-dimensional motion capture data was presented and validated. Median absolute differences between calculated and measured impact locations were 3.6 [IQR: 4.4] and 3.5 [IQR: 3.5] mm mediolaterally and longitudinally on the racket face, respectively. Three-dimensional kinematic data of racket and shuttlecock were recorded for 2386 smashes performed by 65 international badminton players, with racket-shuttlecock impact location assessed against instantaneous post-impact shuttlecock speed and direction. Mediolateral and longitudinal impact locations explained 26.2% (quadratic regression; 95% credible interval: 23.1%, 29.2%; BF10 = 1.3 × 10131, extreme; p < 0.001) of the variation in participant-specific shuttlecock speed. A meaningful (BF10 = ∞, extreme; p < 0.001) linear relationship was observed between mediolateral impact location and shuttlecock horizontal direction relative to a line normal to the racket face at impact. Impact locations within one standard deviation of the pooled mean impact location predict reductions in post-impact shuttlecock speeds of up to 5.3% of the player's maximal speed and deviations in the horizontal direction of up to 2.9° relative to a line normal to the racket face. These results highlight the margin for error available to elite badminton players during the smash.

Postictal electroencephalographic (EEG) suppression: A stereo-EEG study of 100 focal to bilateral tonic-clonic seizures.

OBJECTIVES: We aimed to describe intracerebral aspects of postictal generalized electroencephalography suppression (PGES) following focal to bilateral tonic-clonic ("secondarily generalized tonic-clonic") seizures (GTCS) recorded using stereoelectroencephalographic (SEEG), and to correlate these with electroclinical features. METHODS: Three independent observers scored semiologic and SEEG features. Patient and epilepsy characteristics were collected. Descriptive statistics and multivariate analysis were performed. The operational definition of PGES on SEEG used strict criteria (absence of visible signal at 20 µV/mm amplitude, in all readable channels). Postictal regional suppression (RS) was identified if only a subset of implanted electrodes showed absence of signal. RESULTS: We evaluated 100 seizures in 52 patients. Interobserver agreement was good (κ 0.72 for clinical features and 0.73 for EEG features). PGES was present in 27 of 100 and RS without PGES present in 42 of 100 seizures. Region of RS included epileptogenic zone in 43 of 51 (86%). No effect of sampling (multilobar or bilateral exploration) was seen. Oral tonicity (mouth opening and/or tonic vocalization during the tonic phase of GTCS) was associated with the presence of PGES (P = 0.029; negative predictive value [NPV] 0.91). Bilateral upper limb extension during the tonic phase correlated with PGES (P = 0.041; NPV 0.85). Association of both oral tonicity and bilateral upper limb extension had a high NPV of 0.96. SIGNIFICANCE: SEEG recordings confirm true absence of signal during postictal EEG suppression. PGES is unlikely when both upper limb extension and oral tonicity are absent. We hypothesize that bilateral tonic seizure discharge at bulbar level brainstem regions is associated with the production of oral signs and may relate to mechanisms of PGES.

Overloading among crash-involved vehicles in China: identification of factors associated with overloading and crash severity.

OBJECTIVE: Motor vehicle overloading is correlated with the possibility of road crash occurrence and severity. Although overloading of motor vehicles is pervasive in developing nations, few empirical analyses have been performed on factors that might influence the occurrence of overloading. This study aims to address this shortcoming by seeking evidence from several years of crash data from Guangdong province, China. METHODS: Data on overloading and other factors are extracted for crash-involved vehicles from traffic crash records for 2006-2010 provided by the Traffic Management Bureau in Guangdong province. Logistic regression is applied to identify risk factors for overloading in crash-involved vehicles and within these crashes to identify factors contributing to greater crash severity. Driver, vehicle, road and environmental characteristics and violation types are considered in the regression models. In addition to the basic logistic models, association analysis is employed to identify the potential interactions among different risk factors during fitting the logistic models of overloading and severity. RESULTS: Crash-involved vehicles driven by males from rural households and in an unsafe condition are more likely to be overloaded and to be involved in higher severity overloaded vehicle crashes. If overloaded vehicles speed, the risk of severe traffic crash casualties increases. Young drivers (aged under 25 years) in mountainous areas are more likely to be involved in higher severity overloaded vehicle crashes. CONCLUSIONS: This study identifies several factors associated with overloading in crash-involved vehicles and with higher severity overloading crashes and provides an important reference for future research on those specific risk factors.

Muscle-Tendon Unit Parameter Estimation of a Hill-Type Musculoskeletal Model Based on Experimentally Obtained Subject-Specific Torque Profiles.

The aim of this study was to generate a subject-specific musculoskeletal muscle model, based on isometric and isovelocity measurements of the whole lower extremity. A two-step optimization procedure is presented for optimizing the muscle-tendon parameters (MTPs) for isometric and isovelocity joint torque profiles. A significant improvement in the prediction of joint torque profiles for both the solely isometric and a combined isometric and dynamic method of optimization when compared to the standard scaling method of the AnyBody Modeling System (AMS) was observed. Depending on the specific purpose of the model, it may be worth considering whether the isometric-only would be sufficient, or the additional dynamic data are required for the combined approach.

A shorter cricket pitch improves decision-making by junior batters.

This study sought to determine whether playing on a shorter cricket pitch would lead batters to make more appropriate decisions about whether to play front foot or back foot shots. Based on an analysis of the shots played by top order batters against seam bowling in county under-10 matches, an age-specific "good length" region between 5.0 yards and 6.5 yards (4.57 to 5.94 m) from the batters' stumps was derived. This was where batters were uncertain whether to play on the front or back foot. It was then possible to define deliveries as "short" or "full" depending upon whether they bounced further from or nearer to the batter than the good length region. Club under-11 and county under-10 match data revealed that when playing on a 16-yard pitch batters played more back foot shots to short balls, and county batters also played more front foot shots to full balls compared with matches on the currently recommended 20- or 19-yard pitches. For batters, a shorter pitch should strengthen the coupling between the perception of delivery length and appropriate shot selection, and the increased task demand should lead to improved anticipation, both key features of skilled batting.

Are Planar Simulation Models Affected by the Assumption of Coincident Joint Centers at the Hip and Shoulder?

Planar simulation models which assume coincident joint centers at the hip and shoulder are often used to investigate subject-specific maximal performances rather than 3-dimensional models due to the viability of determining subject-specific parameters. To investigate the effect of coincident joint centers on model accuracy, 3 variants of a 16-segment planar subject-specific angle-driven model were evaluated using an elite cricket fast bowling performance: (a) planar representation assuming coincident joint centers, (b) planar representation with noncoincident hip joint centers, and (c) planar representation with noncoincident hip and shoulder joint centers. Model (c) with noncoincident hip and shoulder joint centers best matched the recorded performance with better estimates of the ground reaction force (mean RMS differences: (a) 18%, (b) 12%, and (c) 11%) and ball release velocity (mean RMS differences: (a) 3.8%, (b) 3.2%, and (c) 1.7%) due to a better representation of the mass center location and link system endpoint velocity. Investigations into the subject-specific performance of maximal effort movements, where nonsagittal plane rotations of the pelvis and torso could affect model accuracy, should consider the use of noncoincident hip and shoulder joint centers within a planar model rather than using a simple planar model or a full 3-dimensional model.

Should I Text or Call Here? A Situation-Based Analysis of Drivers' Perceived Likelihood of Engaging in Mobile Phone Multitasking.

This study investigated how situational characteristics typically encountered in the transport system influence drivers' perceived likelihood of engaging in mobile phone multitasking. The impacts of mobile phone tasks, perceived environmental complexity/risk, and drivers' individual differences were evaluated as relevant individual predictors within the behavioral adaptation framework. An innovative questionnaire, which includes randomized textual and visual scenarios, was administered to collect data from a sample of 447 drivers in South East Queensland-Australia (66% females; n = 296). The likelihood of engaging in a mobile phone task across various scenarios was modeled by a random parameters ordered probit model. Results indicated that drivers who are female, are frequent users of phones for texting/answering calls, have less favorable attitudes towards safety, and are highly disinhibited were more likely to report stronger intentions of engaging in mobile phone multitasking. However, more years with a valid driving license, self-efficacy toward self-regulation in demanding traffic conditions and police enforcement, texting tasks, and demanding traffic conditions were negatively related to self-reported likelihood of mobile phone multitasking. The unobserved heterogeneity warned of riskier groups among female drivers and participants who need a lot of convincing to believe that multitasking while driving is dangerous. This research concludes that behavioral adaptation theory is a robust framework explaining self-regulation of distracted drivers.

Does shortening the pitch make junior cricketers bowl better?

In order to get bounce and movement seam bowlers need to bowl the ball "into" the pitch. Standard deliveries by elite players are typically projected at around 7° below horizontal. In contrast, young players currently often need to release the ball almost horizontally in an effort to get the ball to bounce close enough to the batter. We anticipated that shortening the pitch could be a simple way to help young bowlers to release the ball at a better angle and with more consistency. Twenty county or best in club age group under 10 and under 11 seam bowlers were analysed bowling indoors on two different pitch lengths. They were found to project the ball on average 3.4° further below horizontal on a 16 yard pitch compared with a 19 yard pitch, while ball speed and position at release changed negligibly. Pitch length did not affect the consistency of the release parameters. The shorter pitch led to a ball release angle closer to that of elite bowlers without changing release speed, and this should enable players to achieve greater success and develop more variety in their bowling.

The effect of ball impact location on racket and forearm joint angle changes for one-handed tennis backhand groundstrokes.

Recreational tennis players tend to have higher incidence of tennis elbow, and this has been hypothesised to be related to one-handed backhand technique and off-centre ball impacts on the racket face. This study aimed to investigate for a range of participants the effect of off-longitudinal axis and off-lateral axis ball-racket impact locations on racket and forearm joint angle changes immediately following impact in one-handed tennis backhand groundstrokes. Three-dimensional racket and wrist angular kinematic data were recorded for 14 university tennis players each performing 30 "flat" one-handed backhand groundstrokes. Off-longitudinal axis ball-racket impact locations explained over 70% of the variation in racket rotation about the longitudinal axis and wrist flexion/extension angles during the 30 ms immediately following impact. Off-lateral axis ball-racket impact locations had a less clear cut influence on racket and forearm rotations. Specifically off-longitudinal impacts below the longitudinal axis forced the wrist into flexion for all participants with there being between 11° and 32° of forced wrist flexion for an off-longitudinal axis impact that was 1 ball diameter away from the midline. This study has confirmed that off-longitudinal impacts below the longitudinal axis contribute to forced wrist flexion and eccentric stretch of the wrist extensors and there can be large differences in the amount of forced wrist flexion from individual to individual and between strokes with different impact locations.