A biomechanical investigation of contemporary powerlifting training practices and their potential application to athletic development.

The contemporary training practices of powerlifters are presently being adopted by athletes from a variety of sports, seeking to improve their performance. The aims of this PhD were to: 1) identify the contemporary training practices of powerlifters; 2) investigate the biomechanical stimulus the training practices create; and 3) assess whether the training practices have the potential to improve the athletic performance of general athletes. The aims were achieved through the completion of five related studies. The first study employed questionnaires and interviews to identify the contemporary training practices used by elite powerlifters. The results demonstrated that elite powerlifters used a wide variety of training practices, many of which would not have been attributed to the group based on previous literature. The practices were categorised based on their underlying mechanical principles, so that the essential features could be investigated in the subsequent studies. A regression-based approach was used in the second study to identify the biomechanical variables associated with performance of common sporting tasks. Maximum force production, power, velocity and rate of force development (RFD) were shown to explain a large percentage of variation in performance of tasks such as sprinting, jumping and changing direction (adjusted R2 ranged from 0.43 to 0.86). These mechanical variables were then measured in a series of experimental studies to assess the potential of the contemporary powerlifting practices to improve athletes' physical performance. Assessments were based on a central paradigm in strength and conditioning, which asserts that improvements in the ability to express biomechanical variables (e.g. force and power) are best obtained with training practices that maximise acute production of the same variable. Based on the categorisation of the mechanical principles underlying the assessed training practices, three experimental studies were conducted that investigated: 1) the practice of performing traditional resistance exercises at maximum velocity; 2) the effects of manipulating the external resistance through the use of variable resistance material (chain resistance) and an unconventional barbell (the hexagonal barbell); and 3) the effects of altering the movement strategy used to perform the squat. The results of the studies clearly demonstrated that each of the practices investigated could be used to substantially alter - and, in most cases, enhance - the biomechanical stimulus created. The practice of performing traditional resistance exercises at maximum velocity revealed that all key mechanical variables were significantly increased (p < 0.05) compared with the standard practice of performing repetitions with a sub-maximum velocity. The results additionally demonstrated that, when performing a traditional resistance exercise such as the deadlift at maximum velocity, experienced resistance trained athletes could accelerate the load for the majority (75% to 90%+) of the movement. The second experimental study featuring the separate use of chain resistance and the hexagonal barbell to alter the characteristics of the external resistance demonstrated contrasting effects. The change in position of the external resistance when using the hexagonal barbell significantly (p < 0.05) increased the participants' ability to produce high force, power, velocity and RFD values across a range of loads in comparison with the same movement performed with a traditional straight barbell. In contrast, the results from the study evaluating the effects of adding chain resistance showed that, whilst force values were increased with the addition of chains, velocity, power and RFD values substantially decreased compared to standard repetitions performed with only barbell resistance. The results also demonstrated that the effects of the chain resistance were more noticeable with heavier chain and barbell loads. The final experiment investigated the effects of altering the movement strategy used to perform the back squat exercise. The results confirmed that changes to the movement strategy had a significant effect on a range of kinematic and kinetic variables. In particular, the contemporary techniques promoted by powerlifters resulted in substantial kinematic and kinetic changes at the hip and reduced kinetic output at the ankle joint. Collectively, the work from this PhD supports the selective use of contemporary powerlifting training practices for the development of athletic potential. Future research should build on the framework created in this thesis, progressing to longitudinal and ultimately implementation studies to increase the likelihood of transferring the results to practice

Contemporary training practices in elite british powerlifters:survey results from an international competition

The primary objective of this study was to investigate current powerlifting training methods in light of anecdotal evidence purporting increased similarity with the explosive training practices of weightlifters. The study also assessed the prevalence of contemporary training practices frequently recommended for powerlifters in the popular literature. A 20-item survey was distributed to 32 elite British powerlifters at an International competition. The subject group included multiple national, international, and commonwealth champions and record holders. Based on 2007 competition results, the average Wilks score of the group was 450.26 ± 34.7. The response rate for the surveys was 88% (28 of 32). The survey was sectioned into 6 areas of inquiry: a) repetition speed, b) explosive training load, c) resistance materials used, d) adjunct power training methods, e) exercise selection, and f) training organization. The results demonstrate that the majority of powerlifters train with the intention to explosively lift maximal and submaximal loads (79 and 82%, respectively). Results revealed that 39% of the lifters regularly used elastic bands and that 57% incorporated chains in their training. Evidence for convergence of training practices between powerlifters and weightlifters was found when 69% of the subjects reported using the Olympic lifts or their derivatives as part of their powerlifting training. Collectively, the results demonstrate that previous notions of how powerlifters train are outdated. Contemporary powerlifters incorporate a variety of training practices that are focused on developing both explosive and maximal strength

Comparative effect size distributions in strength and conditioning and implications for future research: a meta-analysis.

Controlled experimental designs are frequently used in strength and conditioning (S&C) to determine which interventions are most effective. The purpose of this large meta-analysis was to quantify the distribution of comparative effect sizes in S&C to determine likely magnitudes and inform future research regarding sample sizes and inference methods. Baseline and follow-up data were extracted from a large database of studies comparing at least two active S&C interventions. Pairwise comparative standardised mean difference effect sizes were calculated and categorised according to the outcome domain measured. Hierarchical Bayesian meta-analyses and meta-regressions were used to model overall comparative effect size distributions and correlations, respectively. The direction of comparative effect sizes within a study were assigned arbitrarily (e.g. A vs. B, or B vs. A), with bootstrapping performed to ensure effect size distributions were symmetric and centred on zero. The middle 25, 50, and 75% of distributions were used to define small, medium, and large thresholds, respectively. A total of 3874 pairwise effect sizes were obtained from 417 studies comprising 958 active interventions. Threshold values were estimated as: small = 0.14 [95%CrI: 0.12 to 0.15]; medium: 0.29 [95%CrI: 0.28 to 0.30]; and large = 0.51 [95%CrI: 0.50 to 0.53]. No differences were identified in the threshold values across different outcome domains. Correlations ranged widely (0.06 ≤ r ≤0.36), but were larger when outcomes within the same outcome domain were considered. The finding that comparative effect sizes in S&C are typically below 0.30 and can be moderately correlated has important implications for future research. Sample sizes should be substantively increased to appropriately power controlled trials with pre-post intervention data. Alpha adjustment approaches used to control for multiple testing should account for correlations between outcomes and not assume independence

Comparative effect size distributions in strength and conditioning and implications for future research: a meta-analysis.

Controlled experimental designs are frequently used in strength and conditioning (S&C) to determine which interventions are most effective. The purpose of this large meta-analysis was to quantify the distribution of comparative effect sizes in S&C to determine likely magnitudes and inform future research regarding sample sizes and inference methods. Baseline and follow-up data were extracted from a large database of studies comparing at least two active S&C interventions. Pairwise comparative standardised mean difference effect sizes were calculated and categorised according to the outcome domain measured. Hierarchical Bayesian meta-analyses and meta-regressions were used to model overall comparative effect size distributions and correlations, respectively. The direction of comparative effect sizes within a study were assigned arbitrarily (e.g. A vs. B, or B vs. A), with bootstrapping performed to ensure effect size distributions were symmetric and centred on zero. The middle 25, 50, and 75% of distributions were used to define small, medium, and large thresholds, respectively. A total of 3874 pairwise effect sizes were obtained from 417 studies comprising 958 active interventions. Threshold values were estimated as: small = 0.14 [95%CrI: 0.12 to 0.15]; medium: = 0.29 [95%CrI: 0.28 to 0.30]; and large = 0.51 [95%CrI: 0.50 to 0.53]. No differences were identified in the threshold values across different outcome domains. Correlations ranged widely (0.06 ≤ r ≤0.36), but were larger when outcomes within the same outcome domain were considered. The finding that comparative effect sizes in S&C are typically below 0.30 and can be moderately correlated has important implications for future research. Sample sizes should be substantively increased to appropriately power controlled trials with pre-post intervention data. Alpha adjustment approaches used to control for multiple testing should account for correlations between outcomes and not assume independence

Simulating association between training load and injury using the acute: chronic workload ratio and Bayesian methods in youth football.

Previous research has examined the relationship between relative workload and injury, where acute training load is expressed in relation to chronic training load using simple ratio scaling or non-linear models including the exponentially weighted moving average (EWMA). Research has demonstrated that higher relative workloads are associated with greater injury risk; however, statistical models generally report non-intuitive statistics such as odds ratios and as a result the practical consequences of increased player loading remain unclear. Here we combine training and injury data collected in youth football with a predictive simulation approach to model the number of injuries sustained across a range of seasonal workloads

The suitability of a quasi-Newton algorithm for estimating fitness-fatigue models: sensitivity, troublesome local optima and implications for future research (an in silico experimental design).

Fitting an FFM via NLS in practice assumes that a unique optimal solution exists and can be found by the algorithm applied. However, this idealistic scenario may not hold for two reasons: 1) the absolute minimum may not be unique; and 2) local minima, saddle points, and/or plateau features may exist that cause problems for certain algorithms. If there exist different parameter sets in the domain that share the same global minimum under standard NLS, then there is a situation where parameters aren't uniquely identified without additional constraints or regularisation terms. However, more likely is that problems with the typical FFM fitting process will stem from the existence of local minima, saddles, or plateau features that cause the algorithm to converge to a solution not equal to the global minimum. Local optima can provoke sensitivities in the fitting process for first and second-order algorithms that are by definition local optimisers. This manifests as sensitivity to initial parameter estimates (i.e. the starting point the algorithm initialises the search from). The extent of starting point sensitivity is largely unknown in the context of FFMs for common algorithms adopted and has not been studied directly. Given this concern, research reporting a single model solution derived from 'one shot' minimisation of NLS via typical first and second-order algorithms is fundamentally limited by possible uncertainty as to the suitability of fitted estimates as global minimisers. Therefore, the primary aim of this study was to investigate the sensitivity of a classical first-order search algorithm to selection of initial estimates when fitting a fitness-fatigue model (FFM) via nonlinear least-squares (NLS), and to subsequently assess the existence of local optima. A secondary aim of this study was to examine the implications of any findings in relation to previous research and provide considerations for future experimentation. The aims of the study were addressed through a computer experiment (in silico) approach that adopted a deterministic assumption the FFM completely specified athlete response. Under this assumption, two FFMs (standard, and fitness-delay) were simulated under a set of hypothetical model inputs and manually selected 'true' parameter values (for each FFM), generating a set of synthetic performance data. The two FFMs were refitted to the synthetic performance data without noise (and under the same model inputs) by the quasi-Newton L-BFGS-B algorithm in a repetitive fashion initiated from multiple starting points in the parameter space, attempting to at each search recover the true parameter values. Estimates obtained from this process were then further transformed into prediction errors quantifying in-sample model fit across the iterations and non-true solutions. Within the standard model scenarios, 69.1-70.3% of solutions found were the true parameters. In contrast, within the fitness-delay model scenarios, 17.6-17.9% of solutions found were the true parameters. A large number of unique non-true solutions were found for both the standard model (N=275-353) and the fitness-delay model (N=383-550) in this idealistic environment. Many of the non-true extrema found by the algorithm were local minima or saddles. Strong in-sample model fit was also observed across non-true solutions for both models. Collectively, these results indicate the typical NLS approach to fitting FFMs is harder for a hill-climbing algorithm to solve than previously recognised in the literature, particularly for models of higher complexity. The findings of this study add weight to the hypothesis that there exists substantial doubt in reported estimates across prior literature where local optimisers have been used or models more complex than the standard FFM applied, particularly when optimisation procedures reported have lacked the relevant detail to indicate that these issues have been considered. Future research should consider the use of global optimisation algorithms, hybrid approaches, or different perspectives (e.g. Bayesian optimisation)

ElECTROMYOGRAPHIC COMPARISON OF THE BACK SQUAT AND OVERHEAD SQUAT

The present study sought to compare the electrical activity of core and lower-body muscles during performance of the back squat and overhead squat. Fourteen male rugby union athletes performed repetitions of both squatting movements with 60, 75 and 90% of their respective 3RM loads. Additional comparisons were made with isolation exercises designed to target the core musculature and a further condition to equate the absolute load lifted. The overhead squat resulted in slight increases in activity of the rectus abdominus and external oblique, with larger decreases in activity of the erector spinae and lower-body muscles. The results show that the differences in muscle activity are largely a function of the absolute load lifted and that anterior core muscles are recruited to a greater extent during isolation exercises compared with squatting movements

Workplace interventions to improve sitting posture: a systematic review.

Evaluate the effectiveness of workplace interventions to improve sitting posture of workers that spend long periods of time seated at a visual display terminal. A systematic review of randomised controlled trials, non-randomised controlled trials and single-group intervention trials featuring workplace interventions with pre- and follow-up measurements of sitting posture was conducted (registered in PROSPERO, CRD#42015027648). Nine databases were searched for studies available between January 2005 and February 2016. 2519 articles were screened with 12 studies meeting the inclusion criteria. The included studies featured various ergonomic workplace interventions and comprised 4 randomised controlled trial (n = 457), 2 non-randomised controlled trials (n = 416) and 6 single-group intervention trials (n = 328). Due to clinical and methodological heterogeneity, pooling of data was not completed and a narrative summary of findings was developed using the Grading of Recommendations Assessment Development and Evaluation (GRADE) framework. The evidence for four review outcomes was assessed with medium to large positive improvements obtained for the majority of studies investigating changes to gross sitting posture, whereas mixed findings were obtained for more specific local segment assessments of sitting posture. The overall evidence quality for all review outcomes were identified as either 'low' or 'very low'. There is evidence which is limited in quality to indicate that ergonomic workplace interventions can improve gross sitting posture. More high quality research across a range of intervention types is required with longer follow-up durations and more advanced methods to assess sitting posture with greater frequency and less bias

Translating novel collective behaviour measures to concepts and principles of play as understood by football coaches.

A range of innovative performance analysis metrics have been applied in recent years to investigate aspects of football using tempo-spatial and network analyses. These approaches have gained traction within some professional teams to quantify and assess features of collective behaviour. However, metrics employed are rarely created from, or clearly link to, domain expertise and as a result coaches may be hesitant of their value. Therefore, the aim of this study was to identify coach perceptions of spatial temporal and network metrics and identify the feasibility of an iterative and collaborative process to developing metrics. Two rounds of semi-structured interviews were conducted with three Scottish youth international UEFA Pro License coaches (age: 47.0 ± 2.7 years) with a focus on aligning metrics with concepts and principles of play. An iterative approach was used centring around spatial-temporal and network metrics and their adaptation. Reflexive thematic analyses were conducted with final metrics categorized as resonant (accurately describing concept or principles of play), relevant (appropriate but with limitations that need improvement), or hesitant (skeptical of usefulness). Across the ten recognized principles of play, nine metrics were identified and adapted to varying degrees. Resonant metrics included: network intensity (mobility), distance between defenders (discipline), triangles (support), team length and distance between deepest defender and goal line (depth). Coaches recognize principles of play within complex collective behaviour metrics and should be encouraged to collaborate with analysts to develop support systems that may prove to be more valuable and usable

Reliability and validity of the running anaerobic sprint test (RAST) in soccer players.

To investigate the validity and relative and absolute reliability of the Running Anaerobic Sprint Test (RAST) in ama teur soccer players. Cross-sectional experimental design with an element of repeated measures. Twenty three males completed the RAST on two occasions and a Wingate test (WAnT) as criterion measure of anaero bic power. Criterion validity for the RAST was strong for peak power (r = 0.70, p < 0.001) and average power (r = 0.60, p = 0.002); however, the RAST significantly underestimated peak power compared to WAnT. The RAST showed very good relative reli ability for average power, ICC = 0.88 and good relative reliability for peak power, ICC = 0.72. Assessment of absolute reliability highlighted that although when averaged across a group, test and re-test scores will be similar, when monitoring individuals an individual's retest score may range between 0.81 and 1.2 times the original value for peak power and between 0.9 and 1.16 for average power. The RAST is a practicable field test to estimate levels of average anaerobic power. However, the results show that the RAST is not sensitive enough to detect strongly individual changes below 20 % and is therefore not recommended to continually monitor an individual's anaerobic power. Also, if true measures of peak power are required the RAST test is limited