ATHLETE-SPECIFIC ANALYSES OF LEG JOINT KINETICS DURING MAXIMUM VELOCITY SPRINT RUNNING

The effect of variations in joint kinetics on sprint performance in individual athletes is not yet known. To investigate biomechanical contributions to maximum velocity sprint running, data were collected from one elite male sprinter performing maximum effort 60 m sprints. High-speed video (200 Hz) and ground reaction force (1000 Hz) data were collected at the 45 m mark. Horizontal velocity and joint kinetics, via inverse dynamics, were calculated for two trials. The velocity of the step was closely linked to step length, knee angular velocity before touchdown, peak-to-peak centre of mass oscillation, hip extension moment during stance and ankle positive work before take-off. The study revealed the potential for athlete-specific, detailed biomechanical analysis and feedback to aid the technical work of athletes and their coaches across a range of sporting skills

CHANGES IN SPLIT VELOCITIES DURING SPRINT PERFORMANCE DEVELOPMENT

Sprint times and split velocities are invaluable measures for coaches and athletes monitoring sprint training and performance development. This study analysed sprint times and 10 m split velocities as performance of three developing athletes developed over a five week training period. All significantly improved their 60 m sprint times over the training period (p < 0.05). Sprint performance developed individually with a tendency for maximal velocities to increase early in the training period and start and acceleration velocities later. All athletes’ performances fluctuated between weeks, possibly due to a period of experimental learning in their process of skill development. This study will inform further analysis of the kinematic and kinetic parameters determining velocity, with the aim of identifying the key variables responsible for these changes

Modeling the stance leg in two-dimensional analyses of sprinting:Inclusion of the MTP joint affects joint kinetics

Two-dimensional analyses of sprint kinetics are commonly undertaken but often ignore the metatarsalphalangeal (MTP) joint and model the foot as a single segment. Due to the linked-segment nature of inverse dynamics analyses, the aim of this study was to investigate the effect of ignoring the MTP joint on the calculated joint kinetics at the other stance leg joints during sprinting. High-speed video and force platform data were collected from four to five trials for each of three international athletes. Resultant joint moments, powers, and net work at the stance leg joints during the first stance phase after block clearance were calculated using three different foot models. By ignoring the MTP joint, peak extensor moments at the ankle, knee, and hip were on average 35% higher (p .05), respectively, than those calculated with the MTP joint included. Peak ankle and knee joint powers and net work at all joints were also significantly (p < .05) different. By ignoring a genuine MTP joint plantar flexor moment, artificially high peak ankle joint moments are calculated, and these also affect the calculated joint kinetics at the knee

Measurement Error in Estimates of Sprint Velocity from a Laser Displacement Measurement Device

This study aimed to determine the measurement error associated with estimates of velocity from a laser-based device during different phases of a maximal athletic sprint. Laser-based displacement data were obtained from 10 sprinters completing a total of 89 sprints and were fitted with a fifth-order polynomial function which was differentiated to obtain instantaneous velocity data. These velocity estimates were compared against criterion high-speed video velocities at either 1, 5, 10, 30 or 50 m using a Bland-Altman analysis to assess bias and random error. Bias was highest at 1 m (+ 0.41 m/s) and tended to decrease as the measurement distance increased, with values less than + 0.10 m/s at 30 and 50 m. Random error was more consistent between distances, and reached a minimum value (±0.11 m/s) at 10 m. Laser devices offer a potentially useful time-efficient tool for assessing between-subject or between-session performance from the mid-acceleration and maximum velocity phases (i. e., at 10 m and beyond), although only differences exceeding 0.22-0.30 m/s should be considered genuine. However, laser data should not be used during the first 5 m of a sprint, and are likely of limited use for assessing within-subject variation in performance during a single session

LOWER LIMB JOINT KINETICS IN THE SPRINT START PUSH-OFF

Previous studies have analysed lower limb joint kinetics during sprint performance, but not addressed the earliest contact out of the blocks. The aim of this study was to report lower limb joint moments and powers during the first stance phase of the sprint push-off. One competitive male sprinter performed 10 maximal sprint starts. An automatic motion analysis system (CODA, 200 Hz) with synchronised force plate data (1000 Hz) were used to collect kinematic profiles at the hip, knee and ankle and ground reaction forces for the first stance phase. Cluster markers defined the orientation of the lower limb segments in 3D. Knee and hip kinetics differed to the later phases of sprint, whereas similarities were found at the ankle. This study highlights the need for the push-off phase to be considered separately from both research and practical perspectives

THE EFFECT OF DIGITAL FILTERING PROCEDURES ON KNEE JOINT MOMENTS IN SPRINTING

Inverse dynamics analyses are commonly used to obtain resultant joint moment data during sprinting. This study aimed to determine the effects of using different combinations of cut-off frequencies applied to the kinematic and kinetic input data on the determined knee joint moments. Input data from a sprinter during the first stance phase were recorded, and ten different combinations of cut-off frequency were applied. When the kinetic cut-off frequency exceeded the kinematic one, as is common, larger peaks and rapid fluctuations were evident in the knee joint moment soon after contact due to inconsistent frequency content between the input data. In contrast, when the cut-off frequencies were matched, the peaks and fluctuations were minimal, and it is suggested that they may be anomalies of data processing and not genuine aspects of sprint kinetics

A CASE STUDY OF STRIDE FREQUENCY AND SWING TIME IN ELITE ABLE-BODIED SPRINT RUNNING: IMPLICATIONS FOR AMPUTEE DEBATE

Recent research into trans-tibial double-amputee sprint performance has debated the possible inherent advantages, disadvantages and limitations to sprinting with prosthetic limbs compared to healthy limbs. Biomechanical data gathered throughout a training season from an elite able-bodied sprinter provide a new perspective on this debate. Peak stride frequency was measured at 2.62 Hz, and the corresponding swing time was estimated to be 0.287 s in the able-bodied sprinter. Published swing time and stride frequency values from the double-amputee at maximum velocity, thought to be beyond biological limits, therefore may not be so, although previously published research has provided evidence that some joint kinetic values from the double-amputee have not been shown in elite able-bodied sprinting

A CASE STUDY OF STRIDE FREQUENCY AND SWING TIME IN ELITE ABLEBODIED SPRINT RUNNING: IMPLICATIONS FOR AMPUTEE DEBATE

Recent research into trans-tibial double-amputee sprint performance has debated the possible inherent advantages, disadvantages and limitations to sprinting with prosthetic limbs compared to healthy limbs. Biomechanical data gathered throughout a training season from an elite able-bodied sprinter provide a new perspective on this debate. Peak stride frequency was measured at 2.62 Hz, and the corresponding swing time was estimated to be 0.287 s in the able-bodied sprinter. Published swing time and stride frequency values from the double-amputee at maximum velocity, thought to be beyond biological limits, therefore may not be so, although previously published research has provided evidence that some joint kinetic values from the double-amputee have not been shown in elite able-bodied sprinting

CUSTOM-BUILT WIRELESS PRESSURE SENSING INSOLES FOR DETERMINING CONTACT-TIMES IN 60M MAXIMAL SPRINT RUNNING

The purpose of this study was to evaluate a custom-built wireless pressure sensing insole system for recording ground contact times in sprinting. Despite interest in the foot contact time/running velocity relationship, no study has examined the contact times in a maximal 60 m sprint. Insole data were collected on three athletes during maximal indoor sprint runs. Simultaneous kinematic data for start and maximum velocity phases were recorded with a CODA system to validate insole contact times and determine velocity. Insole derived contact times were accurate to ±4 ms. Preliminary data indicate a usable contact time/velocity relationship. It is anticipated that these data will provide support for the use of wireless technology in sprint performance monitoring, and facilitate novel insights into the contact time/sprint running velocity relationship