The effect of increasing strength and approach velocity on triple jump performance

The triple jump is an athletic event comprising three phases in which the optimal phase ratio (the proportion of each phase to the total distance jumped) is unknown. This study used a planar whole body torque-driven computer simulation model of the ground contact parts of all three phases of the triple jump to investigate the effect of strength and approach velocity on optimal performance. The strength and approach velocity of the simulation model were each increased by up to 30% in 10% increments from baseline data collected from a national standard triple jumper. Increasing strength always resulted in an increased overall jump distance. Increasing approach velocity also typically resulted in an increased overall jump distance but there was a point past which increasing approach velocity without increasing strength did not lead to an increase in overall jump distance. Increasing both strength and approach velocity by 10%, 20%, and 30% led to roughly equivalent increases in overall jump distances. Distances ranged from 14.05 m with baseline strength and approach velocity, up to 18.49 m with 30% increases in both. Optimal phase ratios were either hop-dominated or balanced, and typically became more balanced when the strength of the model was increased by a greater percentage than its approach velocity. The range of triple jump distances that resulted from the optimisation process suggests that strength and approach velocity are of great importance for triple jump performance

Optimisation of phase ratio in the triple jump using computer simulation

© 2016 Elsevier B.V. The triple jump is an athletic event comprising three phases in which the optimal proportion of each phase to the total distance jumped, termed the phase ratio, is unknown. This study used a whole-body torque-driven computer simulation model of all three phases of the triple jump to investigate optimal technique. The technique of the simulation model was optimised by varying torque generator activation parameters using a Genetic Algorithm in order to maximise total jump distance, resulting in a hop-dominated technique (35.7%:30.8%:33.6%) and a distance of 14.05. m. Optimisations were then run with penalties forcing the model to adopt hop and jump phases of 33%, 34%, 35%, 36%, and 37% of the optimised distance, resulting in total distances of: 13.79. m, 13.87. m, 13.95. m, 14.05. m, and 14.02. m; and 14.01. m, 14.02. m, 13.97. m, 13.84. m, and 13.67. m respectively. These results indicate that in this subject-specific case there is a plateau in optimum technique encompassing balanced and hop-dominated techniques, but that a jump-dominated technique is associated with a decrease in performance. Hop-dominated techniques are associated with higher forces than jump-dominated techniques; therefore optimal phase ratio may be related to a combination of strength and approach velocity

Trade-offs between horizontal and vertical velocities during triple jumping and the effect on phase distances

The triple jump is an athletic event involving three ground contact phases during which athletes must trade off the maintenance of horizontal velocity against the generation of vertical velocity. Previous studies have indicated that individual athletes have a linear relationship between the loss in horizontal velocity and the gain in vertical velocity during each phase. This study used computer simulation to investigate the effects of constraining the takeoff velocities in the hop phase on the velocity trade-offs in this and subsequent phases. Kinematic data were obtained from an entire triple jump using a Vicon automatic motion capture system, and strength and anthropometric data were collected from the triple jumper. A planar 13-segment torque-driven subject-specific computer simulation model was used to maximise the distance of each phase by varying torque generator activation timings using a genetic algorithm. Vertical takeoff velocities in the hop phase were constrained to be 100%, ±10%, ±20%, and ±30% of the performance velocity, and subsequent phases were optimised with initial conditions calculated from the takeoff of the previous phase and with no constraints on takeoff velocity. The results showed that the loss in horizontal velocity during each contact phase was strongly related to the vertical takeoff velocity (R=0.83) in that phase rather than the overall gain in vertical velocity as found in previous studies. Maximum overall distances were achieved with step phases which were 30% of the total distance of the triple jump confirming the results of experimental studies on elite triple jumpers

Models incorporating pin joints are suitable for simulating performance but unsuitable for simulating internal loading

Simulation models of human movement comprising pin-linked segments have a potential weakness for reproducing accurate ground reaction forces during high impact activities. While the human body contains many compliant structures such a model only has compliance in wobbling masses and in the foot–ground interface. In order to determine whether accurate GRFs can be produced by allowing additional compliance in the foot–ground interface, a subject-specific angle-driven computer simulation model of triple jumping with 13 pin-linked segments was developed, with wobbling masses included within the shank, thigh, and trunk segments. The foot–ground interface was represented by spring-dampers at three points on each foot: the toe, ball, and heel. The parameters of the spring-dampers were varied by a genetic algorithm in order to minimise the differences between simulated GRFs, and those measured from the three phases of a triple jump in three conditions: (a) foot spring compression limited to 20 mm; (b) this compression limited to 40 mm; (c) no restrictions. Differences of 47.9%, 15.7%, and 12.4% between simulation and recorded forces were obtained for the 20 mm, 40 mm, and unrestricted conditions, respectively. In the unrestricted condition maximum compressions of between 43 mm and 56 mm were obtained in the three phases and the mass centre position was within 4 mm of the actual position at these times. It is concluded that the unrestricted model is appropriate for simulating performance whereas the accurate calculation of internal forces would require a model that incorporates compliance elsewhere in the link system

Is a single or double arm technique more advantageous in triple jumping?

Triple jumpers employ either an asymmetrical ‘single-arm’ action or symmetrical ‘double-arm’ action in the takeoff of each phase of the jump. This study investigated which technique is more beneficial in each phase using computer simulation. Kinematic data were obtained from an entire triple jump using a Vicon automatic motion capture system. A planar 13-segment torque-driven subject-specific computer simulation model was evaluated by varying torque generator activation timings using a genetic algorithm in order to match performance data. The matching produced a close agreement between simulation and performance, with differences of 3.8%, 2.7%, and 3.1% for the hop, step, and jump phases respectively. Each phase was optimised for jump distance and an increase in jump distance beyond the matched simulations of 3.3%, 11.1%, and 8.2% was obtained for the hop, step, and jump respectively. The optimised technique used symmetrical shoulder flexion whereas the triple jumper had used an asymmetrical arm technique. This arm action put the leg extensors into slower concentric conditions allowing greater extensor torques to be produced. The main increases in work came at the joints of the stance leg but the largest increases in angular impulse came at the shoulder joints, indicating the importance of both measures when assessing the impact of individual joint actions on changes in technique. Possible benefits of the double-arm technique include: cushioning the stance leg during impact; raising the centre of mass of the body at takeoff; facilitating an increase in kinetic energy at takeoff; allowing a re-orientation of the body during flight

A biomechanical evaluation of the combined elevation test

Objectives: To biomechanically evaluate the relationships between the outcome of the Combined Elevation Test, its component joint motions, and thoracic spine angles. Design: Cross-sectional study. Setting: Laboratory. Participants: 18 elite swimmers and triathletes (11 males and 7 females). Main outcome measures: Combined Elevation Test outcome in forehead and chin positions. Individual joint contributions to test outcome. Results: No sex differences were found in test components, or between head positions. Test outcome was greater in the forehead position than the chin position (34.3 cm vs 30.2 cm; p0.05). Conclusions: The Combined Elevation Test is an effective screening tool to measure upper limb mobility into shoulder flexion and scapula retraction in both sexes, and thoracic extension in women. It is recommended that the test be performed in the forehead position. If a subject performs poorly on the test, follow up assessments are required to identify the impairment location

Position tracking control in torque mode for a robotic running foot for footwear testing

Available automatic footwear testing systems still lack flexibility and bio-fidelity to represent the human foot and reproduce the wear conditions accurately. The first part of this article introduces a new design of the robotic running foot for footwear testing using cable conduit mechanisms. This robotic running foot is integrated with an upper leg mechanism to form a complete integrated footwear testing system. The cable conduit mechanisms help remove the bulky actuators and transmissions out of the fast-moving robotic foot. Thus, this robotic running foot design not only allows high-power actuators to be installed, but also avoids a significant dynamic mass and inertia effects on the upper leg mechanism. This means that the integrated footwear testing system can have multiple powered degrees of freedom in the robotic running foot and simulate much higher human running speeds than other available systems. However, cable conduit mechanisms cause significant challenges in control approaches, especially in high-speed systems, due to their nonlinear transmission characteristics. Furthermore, the robotic running foot actuators must operate in a torque/force control mode to reproduce the foot–shoe interaction during gaits while it is critical to control the foot joints’ position in the swing phase of gaits. The latter part of this article presents a study on position tracking control in torque mode for the robotic running foot joints using adaptive and proportional–integral–derivative control designs to evaluate the system’s ability to mimic the human foot kinematics in running. Both controllers proved their effectiveness, implying that the proposed control approach can be implemented on the integrated footwear testing system to control the foot joints’ position in the swing phase of running gaits

Direct torque control for cable conduit mechanisms for the robotic foot for footwear testing

© 2018 Elsevier Ltd As the shoe durability is affected directly by the dynamic force/pressure between the shoe and its working environments (i.e., the contact ground and the human foot), a footwear testing system should replicate correctly this interaction force profile during gait cycles. Thus, in developing a robotic foot for footwear testing, it is important to power multiple foot joints and to control their output torque to produce correct dynamic effects on footwear. The cable conduit mechanism (CCM) offers great advantages for designing this robotic foot. It not only eliminates the cumbersome actuators and significant inertial effects from the fast-moving robotic foot but also allows a large amount of energy/force to be transmitted/propagated to the compact robotic foot. However, CCMs cause nonlinearities and hysteresis effects to the system performance. Recent studies on CCMs and hysteresis systems mostly addressed the position control. This paper introduces a new approach for modelling the torque transmission and controlling the output torque of a pair of CCMs, which are used to actuate the robotic foot for footwear testing. The proximal torque is used as the input signal for the Bouc–Wen hysteresis model to portray the torque transmission profile while a new robust adaptive control scheme is developed to online estimate and compensate for the nonlinearities and hysteresis effects. Both theoretical proof of stability and experimental validation of the new torque controller have been carried out and reported in this paper. Control experiments of other closed-loop control algorithms have been also conducted to compare their performance with the new controller effectiveness. Qualitative and quantitative results show that the new control approach significantly enhances the torque tracking performance for the system preceded by CCMs

A kinematic algorithm to identify gait events during running at different speeds and with different footstrike types

Although a number of algorithms exist for estimating ground contact events (GCEs) from kinematic data during running, they are typically only applicable to heelstrike running, or have only been evaluated at a single running speed. The purpose of this study was to investigate the accuracy of four kinematics-based algorithms to estimate GCEs over a range of running speeds and footstrike types. Subjects ran over a force platform at a range of speeds; kinetic and kinematic data was captured at 1000 Hz, and kinematic data was downsampled to 250 Hz. A windowing process initially identified reduced time windows containing touchdown and toe-off. Algorithms based on acceleration and jerk signals of the foot markers were used to estimate touchdown (2 algorithms), toe-off (2 algorithms), and ground contact time (GCT) (4 algorithms), and compared to synchronous ‘gold standard’ force platform data. An algorithm utilising the vertical acceleration peak of either the heel or first metatarsal marker (whichever appeared first) for touchdown, and the vertical jerk peak of the hallux marker for toe-off, resulted in the lowest offsets (+3.1 ms, 95% Confidence Interval (CI): -11.8 to +18.1 ms; and +2.1 ms, CI: -8.1 to +12.2 ms respectively). This method also resulted in the smallest offset in GCT (-1.1 ms, CI: -18.6 to +16.4 ms). Offsets in GCE and GCT estimates from all algorithms were typically negatively correlated to running speed, with offsets decreasing as speed increased. Assessing GCEs and GCT using this method may be useful when a force platform is unavailable or impractical

Running technique is an important component of running economy and performance

© 2017 American College of Sports MedicineDespite an intuitive relationship between technique and both running economy (RE) and performance, and the diverse techniques employed by runners to achieve forward locomotion, the objective importance of overall technique and the key components therein remain to be elucidated. PURPOSE: To determine the relationship between individual and combined kinematic measures of technique with both RE and performance. METHODS: Ninety-seven endurance runners (47 female) of diverse competitive standards performed a discontinuous protocol of incremental treadmill running (4 min stages, 1 km.h increments). Measurements included three-dimensional full body kinematics, respiratory gases to determine energy cost, and velocity of lactate turnpoint (vLTP). Five categories of kinematic measures (vertical oscillation, braking, posture, stride parameters and lower limb angles) and locomotory energy cost (LEc) were averaged across 10-12 km.h (the highest common velocit