The development of a novel rugby league match simulation protocol

The effectiveness of recovery interventions following prolonged multiple sprint team sports matches has rarely been studied despite the potential for exercise-induced muscle damage to adversely affect training in the days following games. The lack of research related to this topic is probably owing to the wide variability that exists in the movement demands of players between matches and the impact that this has on the subsequent rate and magnitude of recovery which makes it difficult to detect meaningful differences when conducting research with small sample sizes. Therefore, the purpose of this thesis was to develop a rugby league-specific match simulation protocol that replicates the movement demands, physiological responses and subsequent recovery from matches in order to study the effectiveness of recovery interventions. Hence, two time-motion analysis studies were conducted using a semi-automated image recognition system to inform the development of the rugby league match simulation protocol (RLMSP). Whilst mean total distance covered over the duration of the match was 8,503 m, ball in play and stoppage work-to-rest ratios were 1:6.9 and 1:87.4, respectively, for all players. Furthermore, a significant decline in high and very high intensity running locomotive rates were observed between the initial and final 20 min periods of the match. Thus a RLMSP was devised to replicate the overall movement demands, intra-match fatigue and recovery from a senior elite rugby league match. Not only was there a low level of variability in the movement demands during the RLMSP over consecutive trials, but with the exception of creatine kinase, the rate and magnitude of recovery following the RLMSP was similar to that that has been published following competitive matches. Therefore, the RLMSP devised in this thesis may be a more appropriate research tool for assessing the effectiveness of recovery interventions following match related exercise than following actual match play.Sponsored by Warrington Wolves Rugby League Football Clu

Environmental stressors and cooling interventions on simulated soccer performance

A thesis submitted to the University of Bedfordshire, in partial fulfilment of therequirements for the degree of Doctor of PhilosophyThe increasing globalization of elite soccer match-play means that soccer players are likely to compete in hot, hypoxic and hot-hypoxic environments over a season. Soccer match-play studies have identified a marked decline in soccer-specific physical performance in the heat and hypoxia due to increasing body temperatures and a reduction in partial pressure of oxygen (PO2), respectively. As hot environments are more prevalent in elite soccer match-play, cooling strategies have been assessed within the literature in an attempt to alleviate these heat-induced- decrements. However, utilising a soccer match-play design makes environmental and interventional inferences difficult to ascertain, as a plethora of match factors and adaptive pacing strategies cause high variability in key physical performance measures within soccer match-play. Therefore, the three experiments within thesis aimed to assess the reliability and validity of a non-motorised treadmill (NMT) based soccer-specific simulation [intermittent Soccer Performance Test - (iSPT)], to enable the reliable investigation of environmental stress on soccer performance and the efficacy of pre- and half-time-cooling to attenuate any heat- induced-decrements. The purpose of experiment 1 was to investigate the reliability and validity of iSPT which utilised a novel speed component called a ‘variable run’. This speed component quantified the distance covered at a self-selected speed above the second ventilatory threshold (VT2speed), which attempted to delimit a ‘high-intensity’ threshold. Twenty male University soccer players completed one maximal oxygen (O2) uptake (V̇ O2max ) test, three familiarisation (FAM) sessions and one peak speed assessment (PSA) on the NMT, before completing the iSPT twice (iSPT1 and iSPT2). The total distance, sprint distance and high-speed distance covered were 8,952 ± 476 m, 1,000 ± 74 m and 2156 ± 140 m, respectively. No significant difference (p>0.05) was found between repeated trials of the iSPT for all physical performance measures and physiological responses. Reliability measures between iSPT1 and iSPT2 showed good agreement [Coefficient of variation: 0.80] compared with statistical guidelines. Furthermore, the variable run phase showed high speed running capacity was significantly decreased (p<0.05) in the last 15 min compared to the first 15 min, showing parity with previous match-play data. Experiment 1 validated the iSPT as a NMT based soccer- specific simulation compared to previous match-play data, and is a reliable tool for assessing and monitoring the physical performance and physiological responses in soccer players. Successfully completing the aim of experiment 1 facilitated the quantification of hot (HOT), hypoxia (HYP) and hot-hypoxia (HH) mediated decrements on maximal soccer-specific performance in experiment 2. Twelve male University soccer players completed three FAM sessions, one PSA and four randomised crossover experimental trials of the intermittent Soccer Performance Test (iSPT) in normoxic-temperate (CON: 18oC 50% rH), HOT (30oC; 50% rH), HYP (1,000m; 18oC 50% rH) and HH (1,000m; 30oC; 50% rH). Physical performance and its performance decrements, body temperatures [rectal (Tre), skin (Tsk) and estimated muscle temperature (Tmu)], heart rate (HR), arterial blood oxygen saturation (SaO2), perceived exertion, thermal sensation (TS), body mass changes, blood lactate (Bla) and plasma volume were all measured. Performance decrements were similar in HOT and HYP [total distance (-4%), high- speed distance (~-8%) and variable run distance (~-12%) covered] and exacerbated in HH [total distance (-9%), high-speed distance (-15%) and variable run distance (-15%)] compared to CON. A 4% increase in peak sprint speed was present in HOT compared with CON and HYP and 7% greater in HH. The sprint distance covered was unchanged (p > 0.05) in HOT and HYP and only decreased in HH (-8%) compared with CON. Body mass (-2%), temperatures (+2- 5%) and TS (+18%) were altered in HOT. Furthermore, SaO2 (-8%) and HR (+3%) were changed in HYP. Similar changes in body mass and temperatures, HR, TS and SaO2 were evident in HH compared to HOT and HYP, however, Bla (p < 0.001) and plasma volume (p <0.001) were only significantly altered in HH. Perceived exertion was elevated (p < 0.05) by 7% in all conditions compared with CON. Regression analysis identified that absolute TS and absolute rise in Tsk and estimated Tmu (r = 0.82, r = 0.84 r = 0.82, respectively; p <0.05) predicted the hot-mediated-decrements in HOT. The hot, hypoxic and hot-hypoxic environments impaired physical performance during iSPT. Future interventions should address the increases in TS and body temperatures, to attenuate these decrements in physical performance. Experiment 3 of this thesis aimed to identify three pre- and half-time-cooling strategies to attenuate the heat-induced-decrements previously seen in experiment 2. Eight male University soccer players completed four randomised experimental trials of iSPT, three with cooling and one control (i.e. No pre- or half-time cooling: CON). The pre- and half-time-cooling interventions involved were 30-min or 15 min in duration, respectively. Ice slurry ingestion (SLURRY), ice packs (PACKS) covering the upper legs and mixed-methods (MM: PACKS and SLURRY) were utilised as the three cooling interventions. Physical performance and its performance decrements, body temperatures (Tre, Tsk and estimated Tmu), HR, perceived exertion, TS, body mass changes and Bla were all measured. Compared with CON, both PACKS and SLURRY pre-cooling significantly reduced (p > 0.05) central (Tre) and peripheral (Tsk and estimated Tmu) body temperatures prior to iSPT, respectively. However, body temperature and physical performance were unchanged during the first half of PACKS and SLURRY compared with CON. The MM pre-cooling significantly reduced all body temperatures and TS both prior to and during the first half which coincided with an improvement in total distance (+3%), high-speed distance (+4%) and variable run distance (+5%) covered. Half-time-cooling via PACKS, SLURRY and MM had no ergogenic effect (p> 0.05) upon physical performance in the second half, compared with CON. The 30 min of mixed-method pre-cooling, via ice packs placed upon the upper legs and ice slurry ingestion, significantly improved simulated soccer performance during the first half, however, future research should identify a valid half-time-cooling strategy to offer further improvements to physical performance in the second half. The main findings within this thesis revealed that the iSPT showed validity with previous soccer match-play data and strong reproducibility between two tests (iSPT1 and iSPT2). Furthermore, the variable run component showed efficacy as sensitive measure of the decrements in high-speed running capability. As the iSPT demonstrated low test-retest error compared with the statistical guidelines and previous NMT based soccer-specific simulations, any changes to physical performance can be attributed to an intervention and not the variability of the measure, unlike in soccer match-play situations. No difference was seen for all physical performance measures in both HOT and HYP, however, the heat and hypoxic-induced- decrements stem from increasing body temperatures and changes to both SaO2 and HR, respectively. Such decrements may have a detrimental effect upon the match outcome. These heat-induced-decrements were attenuated in the first half after 30 min of mixed-methods pre- cooling, however, the 15 min of mixed-methods half-time-cooling did not significantly improve any physical performance measure in the second half. The mixed-method pre-cooling strategy tested within this thesis could go some way in maintaining physical performance during the first half of soccer match-play in hot environments (~30oC). However, future laboratory based research within a controlled environment should look to assess different combinations, times and strategies of cooling which may be applicable to the time constraints associated with elite soccer

Design and Testing of a Traction/Distraction Knee Brace

A new knee brace design is required to provide non-surgical distraction of the knee joint for extended periods of time. This knee brace needs to apply traction force to the joint directly, rather than indirectly unloading one compartment. In providing such a design, this research had two objectives: 1) to design a lower-leg knee brace that can apply traction load to the knee; and 2) to test prototypes of these lower-leg knee brace components and relate the traction load to wearer discomfort and interface force. The first objective was met through prospective analysis and iterative design. A planar finite element (FE) model of the lower leg was used to analyse the effect of knee brace coverage. It was observed that increasing the coverage of the knee brace may reduce interface pressures and concentrations of force. A lower-leg knee brace was designed responding to this model, using fibreglass casts with embedded fasteners to transfer load. Braces were manufactured in three lengths for testing: 3”, 7”, and a combined (“mixed”) design with components from each. Nine participants were recruited for pilot testing of the lower leg knee brace. A mechanical test frame was built to apply traction load to the participants’ legs through each of the prototype knee braces. The load in the test frame was increased in 3kgf increments as interface force measurements were taken. Participants self-reported their discomfort on an 11-point Likert scale or Numerical Rating Scale (NRS). Results of the pilot study showed significant differences among the brace designs. The 3” design showed higher NRS scores than the 7” and mixed designs by a full NRS step. Graphical profiles of the interface force suggested that this difference may be the result of higher interface forces distributed across the smaller area of the 3” brace. However, no significant correlation between maximum interface force and self-reported pain was found. Parameters characterizing the shape of the participant’s lower legs indicated that leg shape may influence brace effectiveness. This study concluded that a rigid knee brace is indeed a valid design, but a longer knee brace interface is required for the anterior surface of the leg to improve comfort. This length may not be required for the posterior surface. Further, this study demonstrated simple relationships among applied load, interface force, and wearer discomfort. Future work will adapt this design to the upper leg and optimize the design to minimize force concentrations at the joints

Delaying consumption of a carbohydrate-rich breakfast does not impair afternoon intermittent exercise performance

Background: Omission of a carbohydrate-rich breakfast has been shown to impair afternoon/evening exercise performance, but previous studies have been limited by a lack of placebo control and the inclusion of complete omission of feeding until lunch, versus delaying the breakfast feeding. In this randomised, single-blind, placebo-controlled study, we hypothesised that introducing a placebo control would show no-difference to prolonged intermittent exercise performance in the afternoon versus consuming a high-carbohydrate breakfast. Methods: Ten regular intermittent games players completed two trials (EARLY and DELAY) that were matched for energy intake. In EARLY, participants consumed a high-carbohydrate breakfast shake (2 g·kg BM-1 maltodextrin, 1 ml·kg BM-1 orange squash, 0.15 g·kg BM-1 Xantham gum, 0.067 g·kg BM-1 artificial sweetener and 6 ml·kg BM-1 water) at 8am, followed by a taste and texture matched, but energy depleted, placebo (Identical minus Maltodextrin) at 10am. In DELAY the order of these shakes was reversed. In both trials, a standardised and individualised high carbohydrate lunch (888±107 Kcal, 145±28 g carbohydrate) was consumed at 12pm. Blood glucose and substrate oxidation measurements were conducted hourly throughout the day, and a subjective appetite rating taken after each meal. At 3pm, participants subsequently completed an 80-min intermittent exercise performance task, consisting of two, 40-min stages with 10-min of rest in between. Peak, mean, and end power output were measured during each sprint and averaged across each stage of the test for statistical analysis, with heart rate and RPE measured after each sprint. Results: The subjective appetite response followed a similar pattern during the morning of both trials, despite differing blood glucose and substrate oxidation results, which together confirmed the success of the single-blind placebo control. There were no differences in peak power (1st half: mean difference [95% CI]: 0.85 [-12 to 14] W, p=0.89, d=0.01); 2nd half: 1.6 [-12 to 15] W, p=0.79, d=0.01), mean power (1st half: mean difference: 2.2 [-12 to 17] W, p=0.73, d=0.01); 2nd half: mean difference: -2.2 [-16 to 11] W, p=0.72, d=0.02) or end power (1st half: mean difference: 6.9 [-11 to 25], p=0.42, d=0.05); 2nd half: mean difference: -1.7 [-16 to 12] W, p=0.80, d=0.01) in the DELAY compared to the EARLY condition. Conclusions: These data provide differing results to studies which focused on overt breakfast omission, rather than delaying breakfast using a placebo. This study provides preliminary suggestions that the results in other studies may likely be from a psychological, rather than physiological, mechanism

Muscle function and coordination of amputee and non-amputee stair ascent

textStair ascent is a common activity of daily living and is necessary for maintaining independence in a variety of community environments. However, it can be a biomechanically challenging task. For example, for transtibial amputees the loss of the ankle plantarflexors coupled with the task demands of stair ascent require amputees to develop compensatory mechanisms that utilize the prosthesis and remaining musculature. The overall goal of this research was to use advanced musculoskeletal modeling and simulation techniques in a series of studies to understand how individual muscles contribute to stair ascent in non-amputees and how unilateral transtibial amputees compensate with the prosthesis and remaining musculature during stair ascent. In the first study, a simulation of non-amputee stair ascent was developed to elucidate the contributions of individual muscles and the biomechanical mechanisms by which they accomplish stair ascent. The hip abductors, hip extensors, knee extensors and plantarflexors were found to work synergistically to generate, absorb and/or transfer mechanical power to accomplish stair ascent. In the second study, a simulation of transtibial amputee stair ascent was generated to identify functional deficits and compensations necessary for amputees to ascend stairs. The passive prosthesis was able to emulate the role of the uniarticular plantarflexors, but was unable to replicate the role of the biarticular plantarflexors. As a result, compensations from other muscles were necessary. In the final study, simulations of non-amputee and amputee stair ascent were used to determine the contributions of individual muscles and the prosthesis to dynamic balance control, which was quantified using whole-body angular momentum. The prosthesis was able to replicate the role of the plantarflexors in the regulation of sagittal-plane and, to a lesser extent, transverse-plane angular momentum. However, while the non-amputee plantarflexors contributed minimally to frontal-plane angular momentum, the prosthesis acted to rotate the body towards the contralateral leg, which required additional muscle compensations. By understanding the role of the individual muscles and prosthesis in achieving stair ascent and identifying the compensations used by amputees, this research provides a foundation for designing refined prostheses and targeted rehabilitation programs that improve an individual’s ability to ascend stairs.Mechanical Engineerin

Doctor of Philosophy

dissertationGeometric abnormalities of the human hip joint, as found in femoroacetabular impingement (FAI) and acetabular dysplasia, alter hip biomechanics and may be the primary causes of osteoarthritis in young adults. However, empirical evidence of direct correlations between abnormal geometry, altered biomechanics, and osteoarthritis is scarce. Also, clinical measures used to diagnose FAI and dysplasia still have substantial limitations, including questions about their reliability, assumptions about hip joint geometry and their ability to definitively distinguish pathologic from normal hips. The goals of this dissertation are twofold. First, a set of tools are presented and applied to quantify three-dimensional (3D) anatomical differences between hips with FAI and control subjects. The 3D tools were developed, validated and applied to patients with a subtype of FAI, called cam FAI, to improve basic understanding of the spectrum of FAI deformities, and to provide meaningful new metrics of morphology that are relatable to current diagnostic methods and translate easily for clinical use. The second goal of this dissertation is to improve our understanding of intra-articular hip contact mechanics as well as hip joint kinematics and muscle forces. To do so, a finite element study of intraarticular cartilage contact mechanics was completed with a cohort of live human subjects, using a validated modeling protocol. Finally, musculoskeletal modeling was used with gait data from healthy subjects and acetabular dysplasia patients to provide preliminary estimates of hip joint kinematics, kinetics, and muscle forces and compare differences between the groups. The translational methods of this dissertation utilized techniques from orthopaedics, computer science, physical therapy, mechanics, and medical imaging. Results from this dissertation offer new insight into the complex pathomechanics and pathomorphology of FAI and acetabular dysplasia. Application and extension of the work of this dissertation has the potential to help establish links between FAI and dysplasia with osteoarthritis and to improve patient care

Biomechanics

Biomechanics is a vast discipline within the field of Biomedical Engineering. It explores the underlying mechanics of how biological and physiological systems move. It encompasses important clinical applications to address questions related to medicine using engineering mechanics principles. Biomechanics includes interdisciplinary concepts from engineers, physicians, therapists, biologists, physicists, and mathematicians. Through their collaborative efforts, biomechanics research is ever changing and expanding, explaining new mechanisms and principles for dynamic human systems. Biomechanics is used to describe how the human body moves, walks, and breathes, in addition to how it responds to injury and rehabilitation. Advanced biomechanical modeling methods, such as inverse dynamics, finite element analysis, and musculoskeletal modeling are used to simulate and investigate human situations in regard to movement and injury. Biomechanical technologies are progressing to answer contemporary medical questions. The future of biomechanics is dependent on interdisciplinary research efforts and the education of tomorrow’s scientists

U-SAFT⁹⁰ simulates the internal and external loads of university-level soccer match play

Motion analysis has become more prevalent in contemporary soccer research, particularly within the elite sector. The study of motion-profiles can be used for identifying patterns in soccer match performance regarding both physical and technical elements. Deducing movement patterns and internal and external loading through in-depth study, it may then be possible to simulate competitive match-play specific to squad or individual needs. Modern technology allows match performance to be broken down into specific periods that subsequently enables the examination of work rate. Changes in work-rate may indicate fluctuations in performance which can also heighten the risk of injury and susceptibility to conceding to opponents. As a result, preparatory, conditioning and nutritional interventions can be employed directed towards sustaining performance levels.This thesis will firstly look at motion profiles of competitive soccer in an amateur population in order to quantify the internal and external physical demands and variation in work-rate compared to those previously scrutinised in elite soccer. The following experimental chapter utilises motion analysis data to create and validate a squad soccer-specific exercise protocol (SSEP) to use as a simulation of soccer match-play in both rehabilitation and laboratory settings.Motion analysis was determined with a 5Hz Global Positioning System to analyse total, high-intensity and sprint distance as well as producing mechanical ‘Accumulated Player Load’ values through an in-built accelerometer. This data was combined with concurrent heart rate data during matches to provide a measure of internal physiological load. Total distance was found to range between 7223-12158m, with an average of 9423m for the squad, declining 6% between halves (P 0.05).The findings in this thesis suggest patterns of physical demands in competitive amateur match play are similar to those of elite soccer, in terms of total, high-intensity and sprint distances but fall in the lower part of the range previously reported in motion-analysis studies. Changes in work-rate possibly due to fatigue are evident in motion profiles of amateur soccer players, similar to those observed in professionals. Furthermore heart rate analysis suggested cardiovascular strain is also high.Competitive amateur match-play can be simulated effectively with respect to inducing the same internal and external loads associated with a 90 minute soccer match. The implications of such findings are that the USAFT⁹⁰ can be used to simulate the locomotor, physiological and mechanical demands of amateur soccer matches in controlled environments. This may be useful for rehabilitation purposes and testing intervention strategies to gauge effect on performance. Future research should address positional differences and examine the effect of fatigue on work-rate in more detail for university-level soccer. This would accommodate individual and positional capabilities that were not simulated in USAFT⁹⁰