Whole-body biomechanical load monitoring from accelerometry in team sports

Contemporary research into training load in team sports primarily focusses on the physiological load demands, whereas the biomechanical load still remains largely unexplored. While the former refers to the work-energy relationship when the players move around the pitch, the latter refers to the external forces the players are exposed to from their movements around the pitch. Monitoring of the biomechanical load helps practitioners estimate the stresses on an athlete’s musculoskeletal structures as a consequence of the external forces acting on their body. Monitoring of the biomechanical load is currently restricted to laboratory settings, but the recent introduction of GPS devices with integrated accelerometers in team sports may enable practitioners to monitor whole-body biomechanical load during training sessions and match-play. The aim of this thesis was therefore to explore if body-worn accelerometry can be used for whole-body biomechanical load monitoring in team sports. The first study of this thesis showed that although a linear relationship exists between body-worn accelerometry (e.g. from GPS integrated accelerometers) and whole-body accelerations, the linear relationship based on Newton’s second law of motion is weak regardless of accelerometer location (trunk, pelvis or tibia). Body-worn accelerometry only measures the acceleration of the segment it is attached to and is therefore inadequate to measure the complex multi-segment dynamics of the whole body during team sports movements. The second study of this thesis did however offer a potential solution to that problem, and it was demonstrated that the complex multi-segment dynamics of the body and the associated ground reaction forces (GRF), a surrogate for whole-body biomechanical load, can be estimated with a mass-spring-damper model (MSD-model). Nonetheless, the MSD-model’s accuracy to estimate GRF slightly decreases for sharp changes of direction at high intensities, because the absorption of energy and generation of energy are decoupled. Finally, a novel approach to estimate GRF from the combination of trunk-mounted accelerometry and a MSD-model was introduced in this thesis. This approach showed that trunk accelerometry data has the potential to generate the eight model parameters required to estimate GRF from a MSD-model, though further work is required in particular towards improving the model’s ability to estimate GRF across a wide range of activities. The novel approach introduced in this thesis has the potential to give practitioners in team sports the opportunity to monitor whole-body biomechanical load due to player-ground interaction in the field, a necessity if they wish to predict the consequent musculoskeletal structural adaptations of training sessions and match-play

Training load monitoring in team sports: A novel framework separating physiological and biomechanical load-adaptation pathways

There have been considerable advances in monitoring the training load in running-based team sports in recent years. Novel technologies nowadays offer ample opportunities to continuously monitor the activities of a player. These activities lead to internal biochemical stresses on the various physiological sub-systems. However, they also cause internal mechanical stresses on the various musculoskeletal tissues. Based on the amount and periodization of these stresses, the sub-systems and tissues adapt. So by monitoring external loads one hopes to estimate internal loads to predict adaptation, and this through understanding the load-adaptation pathways. We propose a new theoretical framework in which physiological and biomechanical load-adaptation pathways are considered separately, shedding a new light on some of the previously published evidence. We hope that it can help the various practitioners in this field (trainers, coaches, medical staff, sport scientists) to align their thoughts when considering the value of monitoring load, and that it can help researchers design experiments that can better rationalise training load monitoring for improving performance whilst preventing injury

The relationship between whole-body external loading and body-worn accelerometry during team sports movements

Purpose: The aim of this study was to investigate the relationship between whole-body accelerations and body-worn accelerometry during team sports movements. Methods: Twenty male team sport players performed forward running, and anticipated 45° and 90° side-cuts at approach speeds of 2, 3, 4 and 5 m·s-1. Whole-body Centre of Mass (CoM) accelerations were determined from ground reaction forces collected from one foot-ground-contact and segmental accelerations were measured from a commercial GPS/accelerometer unit on the upper trunk. Three higher specification accelerometers were also positioned on the GPS unit, the dorsal aspect of the pelvis, and the shaft of the tibia. Associations between mechanical load variables (peak acceleration, loading rate and impulse) calculated from both CoM accelerations and segmental accelerations were explored using regression analysis. In addition one-dimensional Statistical Parametric Mapping (SPM) was used to explore the relationships between peak segmental accelerations and CoM acceleration profiles during the whole foot-ground-contact. Results: A weak relationship was observed for the investigated mechanical load variables regardless of accelerometer location and task (R2 values across accelerometer locations and tasks: peak acceleration 0.08-0.55, loading rate 0.27-0.59 and impulse 0.02-0.59). Segmental accelerations generally overestimated whole-body mechanical load. SPM analysis showed that peak segmental accelerations were mostly related to CoM accelerations during the first 40-50% of contact phase. Conclusions: Whilst body-worn accelerometry correlates to whole-body loading in team sports movements and can reveal useful estimates concerning loading, these correlations are not strong. Body-worn acclerometry should therefore be used with caution to monitor whole-body mechanical loading in the field

Biomechanical loading during running: can a two mass-spring-damper model be used to evaluate ground reaction forces for high-intensity tasks?

Running impact forces expose the body to biomechanical loads leading to beneficial adaptations, but also risk of injury. High-intensity running tasks, especially, are deemed highly demanding for the musculoskeletal system, but loads experienced during these actions are not well understood. To eventually predict GRF and understand the biomechanical loads experienced during such activities in greater detail, this study aimed to (1) examine the feasibility of using a simple two mass-spring-damper model, based on eight model parameters, to reproduce ground reaction forces (GRFs) for high-intensity running tasks and (2) verify whether the required model parameters were physically meaningful. This model was used to reproduce GRFs for rapid accelerations and decelerations, constant speed running and maximal sprints. GRF profiles and impulses could be reproduced with low to very low errors across tasks, but subtler loading characteristics (impact peaks, loading rate) were modelled less accurately. Moreover, required model parameters varied strongly between trials and had minimal physical meaning. These results show that although a two mass-spring-damper model can be used to reproduce overall GRFs for high-intensity running tasks, the application of this simple model for predicting GRFs in the field and/or understanding the biomechanical demands of training in greater detail is likely limited

Measuring biomechanical loads in team sports – from lab to field

The benefits of differentiating between the physiological and biomechanical load-response pathways in football and other (team) sports have become increasingly recognised. In contrast to physiological loads however, the biomechanical demands of training and competition are still not well understood, primarily due to the difficulty of quantifying biomechanical loads in a field environment. Although musculoskeletal adaptation and injury are known to occur at a tissue level, several biomechanical load metrics are available that quantify loads experienced by the body as a whole, its different structures and the individual tissues that are part of these structures. This paper discusses the distinct aspects and challenges that are associated with measuring biomechanical loads at these different levels in laboratory and/ or field contexts. Our hope is that through this paper, sport scientists and practitioners will be able to critically consider the value and limitations of biomechanical load metrics and will keep pursuing new methods to measure these loads within and outside the lab, as a detailed load quantification is essential to better understand the biomechanical load-response pathways that occur in the field

Mechanical Player Load™ using trunk-mounted accelerometry in football: Is it a reliable, task- and player-specific observation?

The aim of the present study was to examine reliability and construct convergent validity of Player Load™ (PL) from trunk-mounted accelerometry, expressed as a cumulative measure and an intensity measure (PL · min(-)(1)). Fifteen male participants twice performed an overground football match simulation that included four different multidirectional football actions (jog, side cut, stride and sprint) whilst wearing a trunk-mounted accelerometer inbuilt in a global positioning system unit. Results showed a moderate-to-high reliability as indicated by the intra-class correlation coefficient (0.806-0.949) and limits of agreement. Convergent validity analysis showed considerable between-participant variation (coefficient of variation range 14.5-24.5%), which was not explained from participant demographics despite a negative association with body height for the stride task. Between-task variations generally showed a moderate correlation between ranking of participants for PL (0.593-0.764) and PL · min(-)(1) (0.282-0.736). It was concluded that monitoring PL(®) in football multidirectional actions presents moderate-to-high reliability, that between-participant variability most likely relies on the individual's locomotive skills and not their anthropometrics, and that the intensity of a task expressed by PL · min(-)(1) is largely related to the running velocity of the task

Changes in immunocompetent cells after interstitial laser thermotherapy of breast cancer

To access publisher full text version of this article. Please click on the hyperlink in Additional Links field.BACKGROUND: Local tumour destruction has been shown to give rise to changes in immunocompetent cells. The aim of this study was to describe the effect of interstitial laser thermotherapy (ILT) of breast carcinoma in the tumour and in regional lymph nodes. METHODS: Seventeen women that underwent radical surgical excision after non-radical ILT were studied. ILT was performed at a steady-state temperature of 48°C for 30 min. Surgical excision was performed 12 (6-23) days after ILT. Six patients with breast cancer not treated with ILT before surgery served as controls. Immunohistological reactions were performed on core needle biopsies prior to treatment and on the excised specimens. RESULTS: ILT resulted in more CD8 lymphocytes and CD68 macrophages within the tumour (P < 0.05 and P < 0.01, respectively) and higher counts of CD20 (P < 0.05), CD68 (P < 0.001) and CD83 (P < 0.01) at the tumour border, when compared to pre-treatment values. In the control patients not receiving ILT, CD8 cells increased within the tumour after resection (P < 0.05). With the probable exception of CD25 Foxp3 cells, the presence of cancer in a lymph node influenced the findings in lymph nodes (examined for CD1a, CD25, Foxp3 CD25, CD83 cells). Thus, comparisons between ILT and control patients were restricted to patients without lymph node metastases. In these patients, ILT and resection were followed by a decrease in CD25 Foxp3 lymphocytes (P < 0.05), when compared to surgical resection alone. CONCLUSIONS: ILT induced changes in immunocompetent cells in patients with breast cancer. The stimulation of the immune system is an added feature of ILT in treatment of patients with breast cancer

Mechanisms Involved in Nicotinic Acetylcholine Receptor-Induced Neurotransmitter Release from Sympathetic Nerve Terminals in the Mouse Vas Deferens

Prejunctional nicotinic acetylcholine receptors (nAChRs) amplify postganglionic sympathetic neurotransmission, and there are indications that intraterminal Ca2+ stores might be involved. However, the mechanisms by which nAChR activation stimulates neurotransmitter release at such junctions is unknown. Rapid local delivery (picospritzing) of the nAChR agonist epibatidine was combined with intracellular sharp microelectrode recording to monitor spontaneous and field-stimulation-evoked neurotransmitter release from sympathetic nerve terminals in the mouse isolated vas deferens. Locally applied epibatidine (1 µM) produced ‘epibatidine-induced depolarisations’ (EIDs) that were similar in shape to spontaneous excitatory junction potentials (SEJPs) and were abolished by nonselective nAChR antagonists and the purinergic desensitizing agonist α,β-methylene ATP. The amplitude distribution of EIDs was only slightly shifted towards lower amplitudes by the selective α7 nAChR antagonists α-bungarotoxin and methyllcaconitine, the voltage-gated Na+ channel blocker tetrodotoxin or by blocking voltage-gated Ca2+ channels with Cd2+. Lowering the extracellular Ca2+ concentration reduced the frequency of EIDs by 69%, but more surprisingly, the Ca2+-induced Ca2+ release blocker ryanodine greatly decreased the amplitude (by 41%) and the frequency of EIDs by 36%. Ryanodine had no effect on electrically-evoked neurotransmitter release, paired-pulse facilitation, SEJP frequency, SEJP amplitude or SEJP amplitude distribution. These results show that activation of non-α7 nAChRs on sympathetic postganglionic nerve terminals induces high-amplitude junctional potentials that are argued to represent multipacketed neurotransmitter release synchronized by intraterminal Ca2+-induced Ca2+ release, triggered by Ca2+ influx directly through the nAChR. This nAChR-induced neurotransmitter release can be targeted pharmacologically without affecting spontaneous or electrically-evoked neurotransmitter release

Movement characteristics, physiological and perceptual responses of elite standard youth football players to different high intensity running drills

This is an Accepted Manuscript of an article published by Taylor & Francis in Science and Medicine in Football on 06/04/2018, available online: https://doi.org/10.1080/24733938.2018.1461235Purpose: To examine responses to high intensity running drills in youth football players. Methods: Seventeen players completed the YoYo Intermittent Recovery test level one (YYIR1) and a 15 m maximal sprint to quantify target running speeds. Players performed three conditions on separate occasions comprising: 12 x 15 s high intensity runs at 100% of the final YYIRT1 speed, 12 x ~4 s repeated sprints with ~26 s recovery, and combination running using both modalities. Heart rate was monitored continuously with PlayerLoadTM and movement characteristics using microtechnology. Ratings of perceived exertion and blood lactate responses were measured 2 min after the final repetition. The ratio of Flight:contraction time was calculated from a countermovement jump before and at 2 min and 14 hours after each condition. Data analysis used magnitude based inferences and effect sizes statistics. Results: Peak speed (1.1%; ES 0.23 ± 0.44) and mean speed over the initial 4s (6.3%; ES 0.45 ± 0.46) were possibly faster during combination compared to high intensity running with unclear differences when compared to repeated sprinting. This was despite most likely (21.6%; ES 7.65 ± 1.02) differences in prescribed speeds between conditions. There were likely reductions in F:C at 14 hours ratio after high intensity (-5.6%; ES –0.44 ± 0.32) and combination running (-6.8%; ES -0.53 ± 0.47). Changes in the repeated sprinting condition were unclear. Conclusions: Actual movement characteristics of high intensity running drills may not reflect those used to prescribe them whilst reductions in F:C ratio are still evident 14 hours after their completion