PhD Research

Below is the abstract from my thesis which was conferred by the Flinders University HDR board on 13 November 2023. This completed document can be accessed here.

Abstract

Jumping and sprinting actions are frequent in many individual and team sports such as basketball, field hockey, soccer and track and field. Both sporting actions are underpinned by the mechanical characteristics which govern human movement including force, velocity, and power. From a biomechanical perspective, to improve an athlete’s performance in these actions, the mechanical characteristics contributing to performance must be quantified. One neuromuscular diagnostic assessment which can be utilized to describe mechanical characteristics of the human body is known as force-velocity (F-v) profiling, or mechanical profiling. This thesis explored field-based F-v profiling as a methodological approach to quantify and improve physical performance in previously untested team and individual population groups, plus demonstrated new and novel applications using this methodology to create greater links between mechanical data and coaching practice.

Additionally, this thesis is significant as it assesses the utility of using a macroscopic inverse dynamics approach to model biomechanical characteristics in the vertical and horizontal direction. Specifically, Samozino’s field method, hereinafter known as the SAM method, provides indirect measures of the mechanical characteristics of jumping and sprinting actions and does not aim to replace gold standard measurement tools such as force-plate technology. Yet, the convenience to practitioners of bringing the laboratory to the field to provide meaningful data to inform training related practice, without the need for expensive technology warrants further validation and exploration from a theoretical, conceptual and practical perspective.

My original contribution to knowledge through this thesis comprises of five studies and two practical application chapters. Chapter 1 presents a general introduction to the thesis while providng a background to the F-v relationship. Chapter 2 is a narrative review which aims to critically appraise the literature when using field methods to determine F-v profiles in jumping and sprinting actions. Overall, conjecture exists regarding the reliability and validity of using field-based F-v profiling methodology to determine mechanical characteristics which warranted further research. In addition, limited research exists exploring the use of mechanical profiling to inform physical preparation strategies in short and long-term intervention studies and in different population groups. Finally, the review identified and addressed a gap in the literature in translating the information obtained from the mechanical profile into how a coach could utilize the data to individualize athlete training programmes.

Chapter 3 (Study 1) established the validity and reliability of Samozino’s field method to determine jump-based mechanical characteristics when compared to force plate technology. The findings showed both fixed and proportional bias between criterion and predictor, thereby raising concerns for practitioners when performing countermovement jumps with a barbell and hexbar to establish valid F-v variables using the SAM method when compared to force plate technology.

Chapter 4 (Study 2) used a cross-sectional approach to investigate differences between positional group and sex in club-based field hockey players. The results of this study identified significant differences in mechanical characteristics between sexes. Mechanical characteristics between positional groups (i.e., attackers vs defenders) further identified force or velocity dominant mechanical profiles however these were sex-specific. This suggests the physical preparation strategies to improve neuromuscular performance should be individualised by both sex and positional group. 

Chapter 5 (Study 3) is another observational cross-sectional analysis which aimed to determine to relationships between matched mechanical characteristics from F-v profiles in the vertical and horizontal orientation in a field hockey cohort. The findings of this study indicate vertical and horizontal F-v profiling explain the same key lower-limb mechanical characteristics, despite the orientation of the movement task, suggesting coaches could potentially use mechanical profiling methods interchangeably and prescribe physical preparation interventions to assess neuromuscular function plus mechanical strengths and weaknesses by performing one F-v assessment only.

Chapter 6 (Study 4) investigated the influence of a short-term sprint-specific training intervention on the horizontal F-v profile in junior Australian football (AF) players. The findings indicate the F-v profile adapts to specific training stimulus with the experimental group reporting significant changes to force and power and sprint performance when compared to the control group. Furthermore, it identified practitioners could consider using a combined sprint training methodology to enhance mechanical characteristics and sprint performance in junior Australia football populations.

Chapter 7 (Study 5) used a case-study research design to longitudinally analyse changes to the horizontal F-v profile and sprint performance across a training year. The primary aim was to investigate changes to mechanical characteristics across a track and field season (~45 weeks) in two male sprint athletes (100m and 200m) who qualified for their national championships. The findings identified significant changes to maximal power and spatio-temporal variables over 30-meters coincided with improved sprint performance. Therefore, the estimated mechanical data collected across a training year may provide insight to practitioners about how the underpinning mechanical characteristics affect sprint performance during specific phases of training.

Chapter 8 and chapter 9 draws on the learnings of the cross-sectional, interventional, and case study to provide an evidence-based approach for the practitioner to analyse F-v data, plus categorize and individualize training prescriptions to enhance sprint performance in team and individual sport athletes. Furthermore, both chapters also aim to provide practical training-related recommendations and guidelines to influence programme design and attempt to provide a conceptual framework to guide training prescription and enhance biomechanical and technical characteristics contributing to sprint mechanical characteristics and sprint performance.

Chapter 10 provides a commentary of the overall utility and application of using the SAM method to determine F-v profiles and meaningfully inform training-related practice from a strength and conditioning perspective. This study considers the remaining gaps in the literature, acknowledges the strengths and limitations to the methodology and thesis and delivers additional recommendations to those identified in the narrative review. The evidence gathered provides theoretical and practical guidelines about best practice approaches for utilizing the field method(s) to inform and enhance physical performance in jumping and sprinting actions.

Overall, the current program of research has progressed an important aspect in the field of applied sports biomechanics, offering greater insights into the application of mechanical profiling to enhance physical performance in new sporting populations. The findings provide evidence to suggest (1) F-v characteristics are beneficial to individualise physical preparation strategies in field hockey athletes and demonstrate a level of mechanical transfer, (2) horizontal mechanical characteristics adapt to specific training methodology thereby addressing mechanical strengths and weaknesses, (3) monitoring horizontal mechanical characteristics over longer periods can further direct training strategies such as periodisation models and programme design to enhance sprint performance in track sprinters, and 4) use of specific training programmes and a conceptual framework to provide greater structure for practitioners to address mechanical strengths, weaknesses and imbalances based on biomechanical and technical characteristics of physical performance.  This body of research has significant implications for coaches and sports biomechanists who want to improve physical performance by enhancing lower limb mechanical characteristics via training and physical preparation strategies. 

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