SPORTS EQUIPMENT: HOW THE TRANSFORMATION FROM PASSIVE TO DIGITAL SYSTEMS OPENS NEW DOORS AND PUTS NEW DEMANDS ON SPORTS BIOMECHANISTS

The digital transformation of almost every aspect of our lives is probably the most radical change observed in human history. As part of this revolution, almost every piece of sport equipment can be instrumented with sensor technology now or in the future. The massive amount of data that can be generated by these systems can be utilized to help athletes to optimize their movement technique and load management and also offers great opportunities to perform research studies on a much larger scale, with a much better temporal resolution. Nonetheless, the widespread rise of digital feedback and measurement systems needs careful consideration of comparability, reliability and validity issues and puts new demands on the skills of sports biomechanists. During my talk I would like to highlight these challenges in a systematic way using examples coming from my own scientific work. This includes examples from instrumented starting blocks and reaction detection systems, sensor equipped running shoe insoles that monitor load and performance variables of their users and finally load monitoring systems used in team sports. I will discuss issues arising from the use of different sensor technologies and technical constructions, issues of comparing the results of novel systems with the existing body of knowledge in our field and challenges arising in data reduction and reporting. From this, I will briefly derive requirements for the education of sports biomechanists to allow for keeping up with and making ideal use of the opportunities involved in the transformation of sports equipment into digital systems

SPRINT ACCELERATION BIOMECHANICS

Sprint start performance (SSP) is of prime importance in short sprint races. The purpose of this workshop was to present a method for the evaluation of SSP in a typical training environment. For this purpose, starting blocks, instrumented with 3D force sensors in the front and the rear block were utilized in combination with high-speed video cameras and light barriers. Performance related parameters could be extracted immediately from the captured force signals. Individual values were compared to a large reference database. Comparisons were made to reference values of athletes with similar sprint performance capacity. Optimisation potentials in technical and strength related aspects of SSP were highlighted for each start, based on the actual overall sprinting performance level of the athlete

SPRINT ACCELERATION MECHANICS

Sprint acceleration is a key feature in many sports performance. It is a direct determinant of performance and the focus of specific training in track and field events such as the 100- or 200-m, but is also paramount in other sports such as soccer or rugby. In the latter, the acceleration capability is a major physical determinant of performance, especially in decisive offensive and defensive actions. In addition, although the exact moment of occurrence is still debated, sprinting and the acceleration phase in particular are the most frequent tasks involved in hamstring strain injuries. Therefore, a better understanding of the mechanical determinants of sprint acceleration performance could help sport practitioners better design training programs, and likely better manage the complex muscle injury prevention / rehabilitation process. However, due to the very fast motion of the human body induced by maximal acceleration (running speeds of more than 10 m.s-1 are reached within a few seconds), and the necessary field (i.e. specific) measurements, valid scientific methods that provide direct, accurate and specific mechanical data over the course of an entire sprint (start + acceleration phases) are scarce

SHOT PUT KINEMATICS OF WORLD CLASS ATHLETES WITH AN INTELLECTUAL DISABILITY

The purpose of this study was to identify basic kinematics differences in shot put kinematics between athletes with an intellectual disability (ID athletes) and able minded athletes. Data collection took place at the 2010 INAS athletics world indoor championships for athletes with an intellectual disability. Four high speed (100Hz) video cameras were utilized to observe 3D kinematics of the shot using the DLT method. The performance of ID athletes observed in this study was much lower compared to the performance of world class able minded athletes described in the literature. An analysis of basic kinematic characteristics of the gliding technique of the ID athletes revealed that they use a reduced acceleration path to release the shot, leading to a reduced speed of release

THE INFLUENCE OF SOLE LONGITUDINAL BENDING STIFFNESS ON PUSHOFF BIOMECHANICS IN FULL EFFORT LINEAR ACCELERATION

The purpose of this study was to identify the effect of longitudinal bending stiffness (LBS) alterations of running shoes in the initial push-off of the front leg in a linear acceleration task. 14 male sport students were analysed using a full body 3D motion analysis in combination with ground reaction force measurements during the initial step of a full effort 5 m sprint. lncreasing LBS did not lead to a significant increase of normalized average acceleration power, but affected MTP and ankle biomechanics. Push-off time was systematically increased with increased LBS. Average ankle joint moments were reduced, even though average GRF lever arms were increased with higher LBS. Increasing the power generation capacities of ankle plantar flexors combined with LBS increase might be a promising combination to improve acceleration performance

SURFACE STIFFNESS AFFECTS JOINT LOADING IN RUNNING

The purpose of this study was to analyze adaptations in joint loading (joint moments) to running surfaces of different stiffness levels when running barefoot or shod at a speed of 3.5 m/s. Joint moments in the sagittal and frontal plane of movement were calculated using standard inverse procedures using a Vicon Nexus system and a Kistler force platform. Adaptations in joint moments were similar in direction when running on softer surfaces and when running shod compared to barefoot. Surface effects were much higher in barefoot running compared to shod running. Joint moments were increased at the hip and ankle and slightly decreased at the knee when running on harder surfaces or when running barefoot compared to shod. Joint loading adaptations corresponded with adaptations in the runner’s striking behaviour. The results of this study can be used to control loading intensity in the design of training regimes for athletes or recreational runners

IS AVERAGE SPEED CONTROL SENSITIVE ENOUGH TO ENSURE NONACCELERATED RUNNING IN THE ANALYSIS OF RUNNING MECHANICS?

The purpose of this study was to investigate whether average speed control by means of photocells is sufficient to guarantee the absence of center of mass velocity changes (CoMVC) and possible effects of such changes on running mechanics. A standard 3D inverse dynamics model was used to calculate kinematics and kinetics of 19 subjects running at 3,5m/s over a 25m track. CoMVC were controlled by calculating the ratio of propulsive to braking impulse (RPBI) of the GRF. Higher braking forces were achieved by increased negative work of the knee extensors while greater propulsive forces were mainly the effect of increased positive work of the plantar flexors. Differences in impact force were related to CoMVC. Implementation of RPBI control is recommended especially when sagittal plane mechanics and impact forces are to be investigated

BACK MUSCLE FATIGUE MIGHT LEAD TO ALTERNATED SPINE LOADING IN RECREATIONAL ERGOMETER ROWING

The purpose of this study was to investigate fatigue related changes in spinal kinematics and muscle activity of back muscles during a 2000 m all-out performance on a rowing ergometer. Kinematic data of the trunk and EMG data of eight back muscles were recorded for ten subjects. A novel approach analyzing the spinal curvature was utilized identifying a significant increase (p \u3c 0.05) for the thoracic spine. For the M. trapezius a significantly decreased mean frequency (p \u3c 0.05) was found. The lumbar spine and the M. erector spinae showed no significant changes (p \u3e 0.05). These results contrast with findings for elite rowers which might be explained by a different rowing technique. Increased spinal curvature is a factor for injury risk. Thus, rowing programs should include monitoring of spinal curvature and strengthening of the stabilizing muscles

LONG JUMP KINEMATICS OF WORD CLASS ATHLETES WITH AN INTELLECTUAL DISABILITY

The aim of this study was to describe performance related kinematics parameters in long jump of elite athletes with an intellectual disability (ID athletes) and to compare to elite athletes without intellectual disability (non-ID athletes). The 2010 INAS athletics world indoor championships were analysed. Three high speed (100Hz) video cameras were used to observe the run up in 2D. A laser device recorded the full run up velocity. Overall jumping performance was worse in ID athletes compared to literature values of non-ID athletes. This also reflects low maximal run up and take-off velocities, a high within subject variations in the landing distance and distance of the last 3 steps to the take-off board. The take-off angles were comparable to those of non-ID athletes. Future research should relate performance related parameters to the cognitive potential of the athletes

START BLOCK KINETICS: WHAT THE BEST DO DIFFERENT THAN THE REST

The purpose of this study was to analyze the push – off forces of male and female sprinters from a wide range of performance levels, including the currently two fastest sprinters in the world. A force start block was used to measure the forces applied to the front and rear blocks. In total, 430 full effort starts of over 99 subjects were analyzed. World – class athletes did not leave the blocks with a higher center of mass velocity, but with a shorter block time. They were able to produce higher maximum forces and rates of force development. Maximum forces were more balanced between the front and rear leg. These results further highlight the importance of high force capacities for a successful sprint start. The more evenly distributed maximum forces of the front and rear leg of world – class athletes might be a technical feature that could help lower level athletes to improve their performance. Training success should be monitored using force measurements in the blocks