A biomechanical approach to evaluate overload and specificity characteristics within physical preparation exercises

An essential component of any physical preparation programme is the selection of training exercises to facilitate desired performance outcomes, with practitioners balancing the principles of sports training to inform exercise selection. This study aimed to advance biomechanical understanding of the principles of overload and specificity within exercise selection, utilising novel joint kinetic and intra-limb joint coordination analyses. Three-dimensional kinematic and kinetic data were obtained from six male sprinters (100 m PB, 10.64–11.00) performing block starts (competitive motor task) and seven training exercises that encompassed traditionally viewed general and more specific exercises. Results highlighted the challenging nature of exercise selection, with all exercises demonstrating capacity to overload relevant joint kinetic features of the block start. In addition, all exercises were able to promote the emergence of proximal and in-phase extension joint coordination patterns linked with block start execution, although traditionally viewed non-specific exercises elicited greater overall coordination similarity. The current research helps advance biomechanical understanding of overload and specificity within exercise selection, by demonstrating how exercise selection should not solely be based on perceived replication of a competitive motor task. Instead, practitioners must consider how the musculoskeletal determinants of performance are overloaded, in addition to promoting task specific coordination patterns

Effect of stroke rate on the distribution of net mechanical power in rowing

The aim of this study was to assess the effect of manipulating stroke rate on the distribution of mechanical power in rowing. Two causes of inefficient mechanical energy expenditure were identified in rowing. The ratio between power not lost at the blades and generated mechanical power (P

Why fencers should bounce: a new method of movement to engage the stretch-shortening cycle

While teaching a heel first contact style of footwork in fencing (also referred to as toe contribution avoidance) is in keeping with long standing traditions, it is not conducive to today’s modern style of fast paced and explosive fencing. Equally, fencers towards the elite-end seem to be gradually adopting a more spring-based style, as their body progressively and organically transitions to “ball of the foot” based footwork, in order for them to fence competitively in the manner they have intuitively associated with success. Therefore, if from a young age fencers are taught to make full use of the stretch shortening cycle (SSC) via “bouncing” or simply by initiating movement via the ball of the foot, this will expedite the learning process. It will demonstrate to them how the SSC can be used to move at greater speed, cover greater distances when advancing, retreating and lunging, and conserve the much-needed energy required to compete over day long competitions. This paper details the mechanistic underpinnings of the SSC and its application to the modern day fencer

An agonist-antagonist pitch production model

Prosody is a phenomenon that is crucial for numerous fields of speech research, accenting the importance of having a robust prosody model. A class of intonation models based on the physiology of pitch pro- duction are especially attractive for their inherent multilingual support. These models rely on an accurate model of muscle activation. Tradi- tionally they have used the 2nd order spring-damper-mass (SDM) mus- cle model. However, recent research has shown that the SDM model is not sufficient for adequate modelling of the muscle dynamics. The 3rd order Hill type model offers a more accurate representation of mus- cle dynamics, but it has been shown to be underdamped when using physiologically plausible muscle parameters. In this paper we propose an agonist-antagonist pitch production (A2P2) model that both validates and gives insight behind the improved results of using higher-order crit- ically damped system models in intonation modelling

Human sit-to-stand transfer modeling towards intuitive and biologically-inspired robot assistance

© 2016, Springer Science+Business Media New York. Sit-to-stand (STS) transfers are a common human task which involves complex sensorimotor processes to control the highly nonlinear musculoskeletal system. In this paper, typical unassisted and assisted human STS transfers are formulated as optimal feedback control problem that finds a compromise between task end-point accuracy, human balance, energy consumption, smoothness of motion and control and takes further human biomechanical control constraints into account. Differential dynamic programming is employed, which allows taking the full, nonlinear human dynamics into consideration. The biomechanical dynamics of the human is modeled by a six link rigid body including leg, trunk and arm segments. Accuracy of the proposed modelling approach is evaluated for different human healthy and patient/elderly subjects by comparing simulations and experimentally collected data. Acceptable model accuracy is achieved with a generic set of constant weights that prioritize the different criteria. Finally, the proposed STS model is used to determine optimal assistive strategies suitable for either a person with specific body segment weakness or a more general weakness. These strategies are implemented on a robotic mobility assistant and are intensively evaluated by 33 elderlies, mostly not able to perform unassisted STS transfers. The validation results show a promising STS transfer success rate and overall user satisfaction

Sprint start kinetics of amputee and non-amputee sprinters

The purpose of this study was to explore the relationship between the forces applied to the starting blocks and the start performances (SPs) of amputee sprinters (ASs) and non-amputee sprinters (NASs). SPs of 154 male and female NASs (100-m personal records [PRs], 9.58–14.00 s) and 7 male ASs (3 unilateral above knee, 3 unilateral below knee, 1 bilateral below knee; 100 m PRs, 11.70–12.70 s) with running specific prostheses (RSPs) were analysed during full-effort sprint starts using instrumented starting blocks that measured the applied forces in 3D. Using the NAS dataset and a combination of factor analysis and multiple regression techniques, we explored the relationship between force characteristics and SP (quantified by normalized average horizontal block power). Start kinetics were subsequently compared between ASs and NASs who were matched based on their absolute 100 m PR and their 100 m PR relative to the world record in their starting class. In NASs, 86% of the variance in SP was shared with five latent factors on which measured parameters related to force application to the rear and front blocks and the respective push-off directions in the sagittal plane of motion were loaded. Mediolateral force application had little influence on SP. The SP of ASs was significantly reduced compared to that of NASs matched on the basis of relative 100-m PR (−33.8%; d = 2.11, p < 0.001), while a non-significant performance reduction was observed when absolute 100-m PRs were used (−17.7%; d = 0.79, p = 0.09). These results are at least partially explained by the fact that force application to the rear block was clearly impaired in the affected legs of ASs