Wayne Spratford

Running in a minimalist and lightweight shoe is not the same as running barefoot: a biomechanical study

Aim The purpose of this study was to determine the changes in running mechanics that occur when highly trained runners run barefoot and in a minimalist shoe, and specifically if running in a minimalist shoe replicates barefoot running. Methods Ground reaction force data and kinematics were collected from 22 highly trained runners during overground running while barefoot and in three shod conditions (minimalist shoe, racing flat and the athletes regular shoe). Three-dimensional net joint moments and subsequent net powers and work were computed using Newton-Euler inverse dynamics. Joint kinematic and kinetic variables were statistically compared between barefoot and shod conditions using a multivariate analysis of variance for repeated measures and standardised mean differences calculated. Results There were significant differences between barefoot and shod conditions for kinematic and kinetic variables at the knee and ankle, with no differences between shod conditions. Barefoot running demonstrated less knee flexion during midstance, an 11% decrease in the peak internal knee extension and abduction moments and a 24% decrease in negative work done at the knee compared with shod conditions. The ankle demonstrated less dorsiflexion at initial contact, a 14% increase in peak power generation and a 19% increase in the positive work done during barefoot running compared with shod conditions. Conclusions Barefoot running was different to all shod conditions. Barefoot running changes the amount of work done at the knee and ankle joints and this may have therapeutic and performance implications for runners.

Accuracy and reliability of GPS devices for measurement of movement patterns in confined spaces for court-based sports.

The aim of this study was to assess the accuracy and reliability of global positioning system (GPS) measures of distance and speed, compared to a high-resolution motion analysis system, for confined movement patterns used in many court-based sports. A single male participant performed 10 repetitions of four respective drills replicating court-based movement patterns and six repetitions of a random movement drill that replicated tennis match-play movement patterns. Two 1Hz and two 5Hz GPS devices concurrently measured distance covered and speed of all court-based drills. A 22 camera VICON motion analysis system, operating at 100Hz, tracked the position of an 18mm reflective marker affixed to one of the GPS devices to provide the criterion movement data. Results indicated that both 1 and 5Hz GPS devices under reported distance covered as well as both mean and peak speed compared to the VICON system (P<0.05). The coefficient of variation for both GPS devices for distance and speed measures ranged between 4 and 25%. Further, the faster the speed and more repetitive the movement pattern (over a similar location), the greater the measurement error. The inter-unit reliability for distance and speed measures of both 1 and 5Hz systems for movements in confined spaces was generally low to moderate (r=0.10-0.70). In conclusion, for court-based sports or movements in confined spaces, GPS technology under reports distance covered and both mean and peak speed of movement.

Take your shoes off to reduce patellofemoral joint stress during running

Aim Elevated patellofemoral joint stress is thought to contribute to the development and progression of patellofemoral pain syndrome. The purpose of this study was to determine if running barefoot decreases patellofemoral joint stress in comparison to shod running. Methods Lower extremity kinematics and ground reaction force data were collected from 22 trained runners during overground running while barefoot and in a neutral running shoe. The kinematic and kinetic data were used as input variables into a previously described mathematical model to determine patellofemoral joint stress. Knee flexion angle, net knee extension moment and the model outputs of contact area, patellofemoral joint reaction force and patellofemoral joint stress were plotted over the stance phase of the gait cycle and peak values compared using paired t tests and standardised mean differences calculated. Results Running barefoot decreased peak patellofemoral joint stress by 12% (p=0.000) in comparison to shod running. The reduction in patellofemoral joint stress was a result of reduced patellofemoral joint reaction forces (12%, p=0.000) while running barefoot. Conclusions Elevated patellofemoral joint stress during shod running might contribute to patellofemoral pain. Running barefoot decreases patellofemoral joint stress.

The head tracks and gaze predicts: how the world's best batters hit a ball

Hitters in fast ball-sports do not align their gaze with the ball throughout ball-flight; rather, they use predictive eye movement strategies that contribute towards their level of interceptive skill. Existing studies claim that (i) baseball and cricket batters cannot track the ball because it moves too quickly to be tracked by the eyes, and that consequently (ii) batters do not – and possibly cannot – watch the ball at the moment they hit it. However, to date no studies have examined the gaze of truly elite batters. We examined the eye and head movements of two of the world’s best cricket batters and found both claims do not apply to these batters. Remarkably, the batters coupled the rotation of their head to the movement of the ball, ensuring the ball remained in a consistent direction relative to their head. To this end, the ball could be followed if the batters simply moved their head and kept their eyes still. Instead of doing so, we show the elite batters used distinctive eye movement strategies, usually relying on two predictive saccades to anticipate (i) the location of ball-bounce, and (ii) the location of bat-ball contact, ensuring they could direct their gaze towards the ball as they hit it. These specific head and eye movement strategies play important functional roles in contributing towards interceptive expertise.

Accuracy and Reliability of GPS Devices for Measurement of Sports-Specific Movement Patterns Related to Cricket, Tennis, and Field-Based Team Sports

Abstract Vickery, WM, Dascombe, BJ, Baker, JD, Higham, DG, Spratford, WA, and Duffield, R. Accuracy and reliability of GPS devices for measurement of sports-specific movement patterns related to cricket, tennis, and field-based team sports. J Strength Cond Res 28(6): 1697–1705, 2014—The aim of this study was to determine the accuracy and reliability of 5, 10, and 15 Hz global positioning system (GPS) devices. Two male subjects (mean ± SD; age, 25.5 ± 0.7 years; height, 1.75 ± 0.01 m; body mass, 74 ± 5.7 kg) completed 10 repetitions of drills replicating movements typical of tennis, cricket, and field-based (football) sports. All movements were completed wearing two 5 and 10 Hz MinimaxX and 2 GPS-Sports 15 Hz GPS devices in a specially designed harness. Criterion movement data for distance and speed were provided from a 22-camera VICON system sampling at 100 Hz. Accuracy was determined using 1-way analysis of variance with Tukeys post hoc tests. Interunit reliability was determined using intraclass correlation (ICC), and typical error was estimated as coefficient of variation (CV). Overall, for the majority of distance and speed measures, as measured using the 5, 10, and 15 Hz GPS devices, were not significantly different (p > 0.05) to the VICON data. Additionally, no improvements in the accuracy or reliability of GPS devices were observed with an increase in the sampling rate. However, the CV for the 5 and 15 Hz devices for distance and speed measures ranged between 3 and 33%, with increasing variability evident in higher speed zones. The majority of ICC measures possessed a low level of interunit reliability (r = −0.35 to 0.39). Based on these results, practitioners of these devices should be aware that measurements of distance and speed may be consistently underestimated, regardless of the movements performed.

The Effect of Assisted Jumping on Vertical Jump Height in High-Performance Volleyball Players

Assisted jumping may be useful in training higher concentric movement speed in jumping, thereby potentially increasing the jumping abilities of athletes. The purpose of this study was to evaluate the effects of assisted jump training on counter-movement vertical jump (CMVJ) and spike jump (SPJ) ability in a group of elite male volleyball players. Seven junior national team volleyball players (18.0±1.0 yrs, 200.4±6.7 cm, and 84.0±7.2 kg) participated in this within-subjects cross-over counter-balanced training study. Assisted training involved 3 sessions per week of CMVJ training with 10 kg of assistance, applied through use of a bungee system, whilst normal jump training involved equated volume of unassisted counter-movement vertical jumps. Training periods were 5 weeks duration, with a 3-week wash-out separating them. Prior to and at the conclusion of each training period jump testing for CMVJ and SPJ height was conducted. Assisted jump training resulted in gains of 2.7±0.7 cm (p<0.01, ES=0.21) and 4.6±2.6 cm (p<0.01, ES=0.32) for the CMVJ and SPJ respectively, whilst normal jump training did not result in significant gains for either CMVJ or SPJ (p=0.09 and p=0.51 respectively). The changes associated with normal jump training and assisted jump training revealed significant differences in both CMVJ and SPJ (p=<0.03) in favour of the assisted jump condition, with large effect (CMVJ, ES=1.22; SPJ, ES=1.31). Assisted jumping may promote the leg extensor musculature to undergo a more rapid rate of shortening, and chronic exposure appears to improve jumping ability.

Smart Textiles: Position and Motion Sensing for Sport, Entertainment and Rehabilitation

Innovation in textiles and clothing has embodied various combinations of new and existing materials to meet conventional needs of comfort and fashion. Interactive and intelligent textiles are emerging as many new textile materials are being used to form sensors in garments to intimately interact with the human form. Interactive textiles typically contain sensors located within a garment to detect physiological functions that are wirelessly connected to digital infrastructure and application specific software. These devices can be realised in conventional garments and have scope for application in diverse fields including entertainment, education, sport, military and medicine. Position and Motion Sensing devices will be discussed for each application, in terms of the value proposition, performance requirements, regulations, and existing technology. A case study of an entertainment device that uses limb motion to achieve an imaginary instrument, the Wearable Instrument Shirt (WIS) will be discussed in this context. The WIS combines a wearable sensor interface with software to map gestures and audio data files to form an easy-to-use gesture driven instrument that allows real-time interactive musical performances without any need for significant instrument or computer skills.

Detection of throwing in cricket using wearable sensors

One of the great controversies of the modern game of cricket is the determination of whether a bowler is using an illegal throw-like bowling action. Changes to the rules of cricket have reduced some of the confusion; yet, because of the complexities of the biomechanics of the arm, it is difficult for an umpire to make a judgement on this issue. Expensive laboratory-based testing has been able to quantify the action of a bowler and this testing is routinely used by cricket authorities to assess a bowling action. Detractors of the method suggest that it is unable to replicate match conditions, has long lead times for assessment and is only available to the elite. After extensive laboratory validation, we present a technology and method for an in-game assessment using a wearable arm sensor for differentiating between a legal bowling action and throwing. The method uses inertial sensors on the upper and lower arms that do not impede the bowling action. Suspect deliveries, as assessed by an expert biomechanist using high-speed video and motion capture, reveal valid distinctive inertial signatures. The technology is an important step in the monitoring of bowling action on-field in near real-time. The technology is suitable for use in competition as well as a training tool for developing athletes.

Lower Extremity Kinematics and Kinetics When Landing From Unloaded and Loaded Jumps

Countermovement jumps loaded with a weighted vest are often used for the training of lower body power to improve jump performance. However, it is currently unknown how this added load affects the lower extremity kinematics and kinetics, in particular whether this results in an increased injury risk. Therefore, the purpose of this investigation was to determine how lower extremity kinematics and kinetics during landing are affected by loaded jumps as demonstrated in a volleyball block jump landing. Ten elite male volleyball players performed block jump landings in an unloaded and loaded (9.89 kg) condition. Kinematic and kinetic landing data from the three highest jumps were collected and assessed. Paired samples t test was used to establish whether load condition had a significant effect on lower extremity kinematics and kinetics. Hip flexion was significantly greater in the unloaded condition compared with the loaded condition (p = .004). There was no significant difference in any other kinematic or kinetic variables measures between the unloaded and loaded conditions. These results suggest that landing from loaded volleyball block jumps does not increase injury risk compared with unloaded jumps in elite male volleyball players.

An event-related visual occlusion method for examining anticipatory skill in natural interceptive tasks

This article describes a new automated method for the controlled occlusion of vision during natural tasks. The method permits the time course of the presence or absence of visual information to be linked to identifiable events within the task of interest. An example application is presented in which the method is used to examine the ability of cricket batsmen to pick up useful information from the prerelease movement patterns of the opposing bowler. Two key events, separated by a consistent within-action time lag, were identified in the cricket bowling action sequence—namely, the penultimate foot strike prior to ball release (Event 1), and the subsequent moment of ball release (Event 2). Force-plate registration of Event 1 was then used as a trigger to facilitate automated occlusion of vision using liquid crystal occlusion goggles at time points relative to Event 2. Validation demonstrated that, compared with existing approaches that are based on manual triggering, this method of occlusion permitted considerable gains in temporal precision and a reduction in the number of unusable trials. A more efficient and accurate protocol to examine anticipation is produced, while preserving the important natural coupling between perception and action.