Trounson, Karl Michael K ORCID: 0000-0002-8328-2167 (2024) Acute effects of lightweight wearable resistance on coordination in general athletic skills among field-based athletes. PhD thesis, Victoria University.

Abstract

Within field-based sport strength and conditioning, growing emphasis on the technical elements of general athletic skills, e.g. running, accelerating, and change of direction (COD), has required coaches to consider contemporary pedagogical approaches. These approaches are increasingly grounded in a complex systems perspective of movement. Constraints on complex systems limit degrees of freedom, which direct behavioural trajectories. Constraints therefore represent control parameters coaches can manipulate to encourage adoption of movements that may benefit performance, or induce variability, facilitating movement exploration and implicit skill development. Lightweight wearable resistance (WR) is a constraint worth considering in this framework. This thesis investigated the acute effects of WR on performance and coordination of overground running, early and late acceleration, and COD among field-based athletes. Biomechanical analyses describing nonlinear changes in movement, body segment interactions, and movement variability were implemented. Consideration was given to individual-level WR effects given pedagogical interventions aimed at altering technique are often individual-based. Study one considered WR in overground running. Statistical parametric mapping of lower limb sagittal plane kinematics revealed that athletes exhibited decreased ankle plantarflexion following toe-off and increased knee flexion during weight acceptance with lower limb WR addition equivalent to 5% of body weight. A subset of participants exhibited increased repetition-to-repetition joint angle variability at one or more joints upon WR addition. Coaches must consider the varying responses between individuals and recognise that loading above a certain magnitude may limit movement options. Study two investigated WR in early acceleration. Hierarchical agglomerative clustering showed that relatively heavy thigh WR affected whole body coordination to a greater extent than relatively heavy shank WR among five Australian Rules football athletes. Within thigh WR, posteriorly oriented WR led to altered pelvic position and greater hip extension, while anteriorly oriented WR led to accentuated shoulder movement. Coaches may use the findings as a starting point for WR application to direct coordination in acceleration, noting varying individual responses. In late acceleration, which was the focus of study three, the effects of anterior and posterior thigh WR on kinetic and kinematic parameters were investigated. Peak propulsive force and propulsive impulse appeared accentuated by anterior thigh WR, while hip joint absolute rotational work during hip extension increased with posterior thigh WR. Neither WR configuration affected acceleration technique according to a “front-side mechanics” technical model of sprinting. The findings indicate parameters that may be emphasised by WR during late acceleration. Lastly, study four was a case study on the effects of fixed trunk WR and randomly varying WR during a COD task, modified vector coding of pelvis-thorax inter-segment coordination revealed the highest coordination variability between segments in the randomly varying WR condition. COD times in this condition were also faster on average. Randomly varying WR between-repetitions may confer technical benefits through exposure to a variety of potentially beneficial movement patterns. This thesis informs strength and conditioning coaching using WR by describing relationships between WR loading and subsequent movement patterns. Findings build on emerging complex systems-based pedagogical approaches in the field, which recognise the utility of execution variability and individualised interventions.

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