Does lateral banking and radius affect well-trained sprinters and team-sports players during bend sprinting?

This study investigated the short-term responses of step characteristics in sprinters and team-sports players under different bend conditions. Eight participants from each group completed 80 m sprints in four conditions: banked and flat, in lanes two and four (L2B, L4B, L2F, L4F). Groups showed similar changes in step velocity (SV) across conditions and limbs. However, sprinters produced significantly shorter ground contact times (GCT) than team sports players in L2B and L4B for both left (0.123 s vs 0.145 s and 0.123 s vs 0.140 s) and right steps (0.115 s vs 0.136 s and 0.120 s vs 0.141 s) (p > 0.001-0.029; ES = 1.15-1.37). Across both groups, SV was generally lower in flat conditions compared to banked (Left: 7.21 m/s vs 6.82 m/s and Right: 7.31 m/s vs 7.09 m/s in lane two), occurring due to reduced step length (SL) rather than step frequency (SF), suggesting that banking improves SV via increased SL. Sprinters produced significantly shorter GCT in banked conditions that led to non-significant increases in SF and SV, highlighting the importance of bend sprinting specific conditioning and training environments representative of indoor competition for sprint athletes.

Learning the high bar longswing:II. energetics and the emergence of the coordination pattern.

This paper is Part II of a study of the effects of practice on young adult novice gymnasts learning the movement coordination pattern of the longswing. The focus was the early stage of learning a critical component of the longswing, namely: through joint motion to inject mechanical energy into the upswing segment effectively to complete the longswing circle. Twenty-five novice male gymnasts received expert instruction while practicing two sessions a week for 3 weeks between a pre- and a post-practice assessment test trial. Seven novices completed a full circle by the end of Test 4. Completion of the longswing was positively related to the angular velocity generated in the gravity driven free fall of the initial segment and the greater rate of energy input in the upward segment. A successful performance in terms of the emergent movement pattern requires coordination of the onset, rate and level of energy input to counterbalance the negative influence of gravity on the second half upwards segment. The development of the complete longswing through the emergence of the collective variable dynamics (Paper 1) and biomechanical energetics of the gymnast (Paper 2) informs coaches, scientists and clinicians regarding task decomposition and learning the longswing.

Learning the High Bar Longswing:I. Task Dynamics and Emergence of the Coordination Pattern.

We studied novice gymnasts (N = 25) learning to form the longswing movement coordination pattern. The focus was the emerging behavioural organisation of centre of mass (CM) dynamics and the relative phase of the bar-CM angular motion. Seven novices learned a complete longswing by the end of the study, 8 novices showed no improvement in proportion of circle completed, and the remainder produced modest but persistent increments of final swing height without achieving a full circle. The radial angular velocity generated in the free fall phase and the circle location of bar-CM relative phase progressively and predominantly predicted circle completion. Bar-CM relative phase produced a consistent qualitative relation within- and between-subjects characteristic of a collective variable with the bar leading the CM on the initial downward antiphase segment and the CM leading on the upward antiphase segment. The ratio of these phases was related by the last practice session to degree of circle completion. The findings showed strong individual differences in the effect of practice on the early steps of learning the movement coordination where the progressive emergence of the longswing circle is driven by exploiting the positive- and minimising the negative-influence of gravity on the bar-CM coordination dynamics (candidate collective variable).

Kinematic factors associated with start performance in World-class male sprinters.

The aim was to investigate the kinematic factors associated with successful performance in the initial acceleration phase of a sprint in the best male athletes in the World at the 2018 World Indoor Athletics Championships. High speed video (150 Hz) was captured for eight sprinters in the men's 60 m final. Spatio-temporal and joint kinematic variables were calculated from the set position to the end of the first ground contact post-block exit (GC1). Normalised average horizontal external power (NAHEP) defined performance and was the dependent variable for a series of regression analyses. Clear relationships were found between GC1 NAHEP and 10-m time, 60-m time, change in velocity, acceleration and contact time in the first ground contact (r = -0.74, -0.64, 0.96, 0.91 and -0.56, respectively). Stepwise multiple linear regression of joint kinematic variables in the first ground contact revealed that trunk angle at take-off and thigh separation angle at take-off explained nearly 90% of variation in GC1 NAHEP (R2 = 0.89). The athletes' projection at take-off with a forward leaning trunk and large thigh separation is characteristic therefore of excellent initial acceleration performance and this will be a good visual guide for technical coaching instruction. This was the first study of its kind to adopt such a research design in a World-class sample in a representative environment. Future studies that combine detailed kinematic and kinetic data capture and analysis in such a setting will add further insight to the findings of this investigation.

The importance of duration and magnitude of force application to sprint performance during the initial acceleration, transition and maximal velocity phases.

Successful sprinting depends on covering a specific distance in the shortest time possible. Although external forces are key to sprinting, less consideration is given to the duration of force application, which influences the impulse generated. This study explored relationships between sprint performance measures and external kinetic and kinematic performance indicators. Data were collected from the initial acceleration, transition and maximal velocity phases of a sprint. Relationships were analysed between sprint performance measures and kinetic and kinematic variables. A commonality regression analysis was used to explore how independent variables contributed to multiple-regression models for the sprint phases. Propulsive forces play a key role in sprint performance during the initial acceleration (r = 0.95 ± 0.03) and transition phases (r = 0.74 ± 0.19), while braking duration plays an important role during the transition phase (r = -0.72 ± 0.20). Contact time, vertical force and peak propulsive forces represented key determinants (r = -0.64 ± 0.31, r = 0.57 ± 0.35 and r = 0.66 ± 0.30, respectively) of maximal velocity phase performance, with peak propulsive force providing the largest unique contribution to the regression model for step velocity. These results clarified the role of force and time variables on sprinting performance.

Phase analysis in maximal sprinting: an investigation of step-to-step technical changes between the initial acceleration, transition and maximal velocity phases.

The aim of this study was to investigate spatiotemporal and kinematic changes between the initial acceleration, transition and maximum velocity phases of a sprint. Sagittal plane kinematics from five experienced sprinters performing 50-m maximal sprints were collected using six HD-video cameras. Following manual digitising, spatiotemporal and kinematic variables at touchdown and toe-off were calculated. The start and end of the transition phase were identified using the step-to-step changes in centre of mass height and segment angles. Mean step-to-step changes of spatiotemporal and kinematic variables during each phase were calculated. Firstly, the study showed that if sufficient trials are available, step-to-step changes in shank and trunk angles might provide an appropriate measure to detect sprint phases in applied settings. However, given that changes in centre of mass height represent a more holistic measure, this was used to sub-divide the sprints into separate phases. Secondly, during the initial acceleration phase large step-to-step changes in touchdown kinematics were observed compared to the transition phase. At toe-off, step-to-step kinematic changes were consistent across the initial acceleration and transition phases before plateauing during the maximal velocity phase. These results provide coaches and practitioners with valuable insights into key differences between phases in maximal sprinting.

World-Class Male Sprinters and High Hurdlers Have Similar Start and Initial Acceleration Techniques.

The effect of the inclusion of a high hurdle 13.72 m after the start line on elite sprint start and initial acceleration technique has yet to be investigated or understood. This highly novel study addresses that lack of information in an exceptional manner, through detailed biomechanical analysis of the world's best sprint and hurdle athletes, with data collected in situ at the 2018 IAAF World Indoor Championships, held in Birmingham, UK. High speed videos (150 Hz) were compared for eight sprinters and seven hurdlers for the start and initial acceleration phase of the finals of the men's 60 m and 60 m hurdles. Temporal and kinematic data were supplemented by vector coding analysis to investigate mechanisms by which these world-class athletes translate their centres of mass (CM) up to the fourth touchdown post-block exit. The sprinters and hurdlers coordinated their lower limb and trunk movement in a similar manner throughout the start and initial acceleration phases, which contributes new conceptual understanding of the mechanisms that underpin start and initial acceleration performance. Differences between groups were initiated from block set-up, with the hurdlers utilising a larger block spacing, but with the front block nearer to the start line than sprinters. Even after accounting for stature, the biggest differences in the raising of the CM occurred during the block phase, with hurdlers greater than sprinters (difference in vertical CM displacement scaled to stature = -0.037, very large effect size). Subsequent flight phases showed the biggest differences in the translation of the CM, in part due to longer flight times in the hurdlers, whilst the techniques of the two groups generally converged during the ground contact phases of initial acceleration. In highlighting that similar techniques are used by world-class sprinters and hurdlers, despite differing task constraints, this study has provided invaluable insights for scientists, coaches, and athletes, that will inform further developments in understanding and practice across both sprints and hurdles.

First and Second Step Characteristics of Amputee and Able-Bodied Sprinters.

CONTEXT: In sprint events, the first 2 steps are used to accelerate the center of mass horizontally and vertically. Amputee athletes cannot actively generate energy with their running-specific prosthesis. It is likely that sprint acceleration mechanics, including step asymmetry, are altered compared with able-bodied athletes. PURPOSE: To investigate spatiotemporal and kinetic variables of amputee compared with able-bodied sprinters. METHODS: Kinematic and kinetic data of the first and second stance were collected from 15 able-bodied and 7 amputee sprinters (2 unilateral transfemoral, 4 unilateral transtibial, and 1 bilateral transtibial) with a motion-capture system (250 Hz) and 2 force plates (1000 Hz). In addition, bilateral asymmetry was quantified and compared between groups. RESULTS: Compared with able-bodied athletes, amputee athletes demonstrated significantly lower performance values for 5- and 10-m times. Step length, step velocity, and step frequency were decreased and contact times increased. Peak horizontal force and relative change of horizontal velocity were decreased in both stances. Peak vertical force and relative change of vertical velocity were lower for the amputee than the able-bodied group during the first stance but significantly higher during the second stance. During the first stance, able-bodied and amputee sprinters displayed a similar orientation of the ground-reaction-force vector, which became more vertically orientated in the amputee group during second stance. Amputee sprinters showed significantly greater asymmetry magnitudes for vertical force kinetics compared with able-bodietd athletes. CONCLUSION: A running-specific prosthesis does not replicate the function of the biological limb well in the early acceleration phase.

The effects of artificial surface temperature on mechanical properties and player kinematics during landing and acceleration.

BACKGROUND: Artificial turf is considered a feasible global alternative to natural turf by many sports governing bodies. Consequently, its ability to provide a safe and consistent playing surface regardless of climate becomes essential. The aims of this study were to determine the effects of artificial surface temperature on: (1) mechanical properties of the turf and (2) the kinematics of a turf-sport related movement. METHODS: Two identical artificial turf pitches were tested: one with a cold surface temperature (1.8°C-2.4°C) and one with a warm surface temperature (14.5°C-15.2°C). Mechanical testing was performed to measure the surface properties. Four amateur soccer players performed a hurdle jump to sprint acceleration movement, with data (contact time, step length and hip, knee and ankle kinematics) collected using CODASport (200 Hz). RESULTS: The temperature difference had a significant influence on the mechanical properties of the artificial turf, including force absorption, energy restitution, rotational resistance, and the height where the head injury criterion was met. Both step length (p = 0.008) and contact time (p = 0.002) of the initial step after the landing were significantly longer on the warm surface. In addition, significant range of motion and joint angular velocity differences were found. CONCLUSION: These findings highlight different demands placed on players due to the surface temperature and suggest a need for coaches, practitioners, and sports governing bodies to be aware of these differences.