Influence of inverse dynamics methods on the calculation of inter-segmental moments in vertical jumping and weightlifting

<p>Abstract</p> <p>Background</p> <p>A vast number of biomechanical studies have employed inverse dynamics methods to calculate inter-segmental moments during movement. Although all inverse dynamics methods are rooted in classical mechanics and thus theoretically the same, there exist a number of distinct computational methods. Recent research has demonstrated a key influence of the dynamics computation of the inverse dynamics method on the calculated moments, despite the theoretical equivalence of the methods. The purpose of this study was therefore to explore the influence of the choice of inverse dynamics on the calculation of inter-segmental moments.</p> <p>Methods</p> <p>An inverse dynamics analysis was performed to analyse vertical jumping and weightlifting movements using two distinct methods. The first method was the traditional inverse dynamics approach, in this study characterized as the 3 step method, where inter-segmental moments were calculated in the local coordinate system of each segment, thus requiring multiple coordinate system transformations. The second method (the 1 step method) was the recently proposed approach based on wrench notation that allows all calculations to be performed in the global coordinate system. In order to best compare the effect of the inverse dynamics computation a number of the key assumptions and methods were harmonized, in particular unit quaternions were used to parameterize rotation in both methods in order to standardize the kinematics.</p> <p>Results</p> <p>Mean peak inter-segmental moments calculated by the two methods were found to agree to 2 decimal places in all cases and were not significantly different (p > 0.05). Equally the normalized dispersions of the two methods were small.</p> <p>Conclusions</p> <p>In contrast to previously documented research the difference between the two methods was found to be negligible. This study demonstrates that the 1 and 3 step method are computationally equivalent and can thus be used interchangeably in musculoskeletal modelling technology. It is important that future work clarifies the influence of the other inverse dynamics methods on the calculation of inter-segmental moments. Equally future work is needed to explore the sensitivity of kinematics computations to the choice of rotation parameterization.</p

Recent data on cellular component turnover: Focus on adaptations to physical exercise

Significant progress has expanded our knowledge of the signaling pathways coordinatingmuscle protein turnover during various conditions including exercise. In this manuscript, the multiplemechanisms that govern the turnover of cellular components are reviewed, and their overall rolesin adaptations to exercise training are discussed. Recent studies have highlighted the central role ofthe energy sensor (AMP)-activated protein kinase (AMPK), forkhead box class O subfamily protein(FOXO) transcription factors and the kinase mechanistic (or mammalian) target of rapamycin complex(MTOR) in the regulation of autophagy for organelle maintenance during exercise. A new cellulartrafficking involving the lysosome was also revealed for full activation of MTOR and protein synthesisduring recovery. Other emerging candidates have been found to be relevant in organelle turnover,especially Parkin and the mitochondrial E3 ubiquitin protein ligase (Mul1) pathways for mitochondrialturnover, and the glycerolipids diacylglycerol (DAG) for protein translation and FOXO regulation.Recent experiments with autophagy and mitophagy flux assessment have also provided importantinsights concerning mitochondrial turnover during ageing and chronic exercise. However, data inhumans are often controversial and further investigations are needed to clarify the involvement ofautophagy in exercise performed with additional stresses, such as hypoxia, and to understand theinfluence of exercise modality. Improving our knowledge of these pathways should help developtherapeutic ways to counteract muscle disorders in pathological conditions

MODELLING SCAPULAR BIOMECHANICS TO ENHANCE INTERPRETATION OF KINEMATICS AND PERFORMANCE DATA IN ROWING

Rowing involves repetitive, high intensity loading on the glenohumeral joint. Shoulder pain is associated with muscle weakness and imbalance, resulting in long-lasting overuse injuries. The goal of this study was to explore three-dimensional shoulder biomechanics during rowing to identify parameters that influence technique. Eleven athletes had their movement recorded by motion capture while using an instrumented ergometer. Kinetics and kinematics drove a computational model which output joint and muscle forces across the shoulder. Results suggest that subtle muscular changes identified by the model can be sensitively mapped to performance variables. When evaluated alongside ergometer-derived power metrics, biomechanics parameters can provide athletes and coaches a fuller picture of performance potential, injury risk, and training program efficacy

FATIGUE LEADS TO ALTERED SPINAL KINEMATICS DURING HIGH PERFORMANCE ERGOMETER ROWING

Low back injuries in rowing are attributed to intense, repetitive, loading through the spine. Good technique and postural control are essential to maximize performance and minimize injury risk. This motion capture study recorded 3D spinal kinematics of 14 athletes during rowing at varying speeds on an instrumented ergometer and correlated motion with power metrics and athlete demographics. Sagittal plane rotation decreases in the lumbar spine and increases in the thoracic spine as speed increases. Transverse and frontal planes have little influence on force output. Declining postural control can be seen within each trial and worsened with higher rate. Assessments of form differences across athletes using relative motion between spine segments at critical stroke points show greater lumbar flexion (compared to thoracic) at the catch and neutral alignment at max handle force

Influence of post-exercise hot-water therapy on long-term adaptations to training in elite short-track speed skaters

International audienceThis study aimed to investigate the effects of regular hot water bathing (HWB), undertaken 10 min after the last training session of the day, on chronic adaptations to training in elite athletes. Six short-track (ST) speed skaters completed four weeks of post-training HWB and four weeks of post-training passive recovery (PR) according to a randomized cross-over study. During HWB, participants sat in a jacuzzi (40 °C; 20 min). According to linear mixed models, maximal isometric strength of knee extensor muscles was significantly increased for training with HWB (p 0.05), including aerobic peak power output, the decline rate of jump height during 1 min-continuous maximal countermovement jumps (i.e. anaerobic capacity index), and the force-velocity relationship. Regarding specific tasks on ice, a small effect of training was found on both half-lap time and total time during a 1.5-lap all-out exercise (p = 0.0487; d = 0.23 and p = 0.0332; d = 0.21, respectively) but no additional effect of HWB was observed. In summary, the regular HWB protocol used in this study can induce additional effects on maximal isometric strength without compromising aerobic and anaerobic adaptations or field performance in these athletes

A perspective on using experiment and theory to identify design principles in dye-sensitized solar cells

Dye-sensitized solar cells (DSCs) have been the subject of wide-ranging studies for many years because of their potential for large-scale manufacturing using roll-to-roll processing allied to their use of earth abundant raw materials. Two main challenges exist for DSC devices to achieve this goal; uplifting device efficiency from the 12 to 14% currently achieved for laboratory-scale ‘hero’ cells and replacement of the widely-used liquid electrolytes which can limit device lifetimes. To increase device efficiency requires optimized dye injection and regeneration, most likely from multiple dyes while replacement of liquid electrolytes requires solid charge transporters (most likely hole transport materials – HTMs). While theoretical and experimental work have both been widely applied to different aspects of DSC research, these approaches are most effective when working in tandem. In this context, this perspective paper considers the key parameters which influence electron transfer processes in DSC devices using one or more dye molecules and how modelling and experimental approaches can work together to optimize electron injection and dye regeneration. This paper provides a perspective that theory and experiment are best used in tandem to study DSC device

Non-European Union doctors in the National Health Service: why, when and how do they come to the United Kingdom of Great Britain and Northern Ireland?

BACKGROUND: As many as 30% of doctors working for the National Health System (NHS) of the United Kingdom of Great Britain and Northern Ireland (UK) have obtained their primary qualifications from a country outside the European Union. However, factors driving this migration of doctors to the UK merit continuing exploration. Our objective was to obtain training and employment profile of UK doctors who obtained their primary medical qualification outside the European Union (non-European doctors) and to assess self-reported reasons for their migration. METHODS: We conducted an online survey of non-European doctors using a pre-validated questionnaire. RESULTS: One thousand six hundred and nineteen doctors of 26 different nationalities completed the survey. Of the respondents, 90.1% were from India and over three-quarters migrated to the UK mainly for 'training'. Other reasons cited were 'better pay' (7.2%), 'better work environment' (7.1%) and 'having family and friends in the UK' (2.8%). Many of the respondents have been in the UK for more than a year (88.8%), with 31.3% having spent more than 3 years gaining experience of working in the NHS. Most respondents believe they will be affected by recent changes to UK immigration policy (86.6%), few report that they would be unaffected (3.7%) and the rest are unsure (9.8%). CONCLUSION: The primary reason for many non-European doctors to migrate to the UK is for training within the NHS. Secondary reasons like better pay, better work environment and having friends and family in the UK also play a role in attracting these doctors, predominantly from the Indian subcontinent and other British Commonwealth countries