Title

Motor capacity and sidestepping execution strategies in female athletes

Author Identifiers

Daniel Kadlec

https://orcid.org/0000-0002-6986-4689

Date of Award

2022

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Medical and Health Sciences

First Advisor

Sophia Nimphius

Second Advisor

Matt Jordan

Third Advisor

Jacqueline Alderson

Abstract

Non-contact anterior cruciate ligament (ACL) injuries during sidestepping occur when the imposed knee joint loading exceeds the load tolerance of the tissues. The load tolerance thresholds can be modified with appropriate training (e.g., resistance training and plyometrics) and thus increase injury resilience. However, despite such insights, the incidence of ACL injury has not decreased in recent years. Injury is of particular concern for female athletes who present with significantly higher rates than male athletes.

Understanding how different constraints shape an athlete’s movement strategy and affect the resultant joint loading when designing training interventions can help to mitigate injury risk. Motor capacities, such as muscular strength and power, act as boundaries on the safe execution of motor skills and shape the acquisition of movement strategies. Therefore, increasing single- and multi-joint strength enables a broader solution space for movement strategies and mitigates joint loading impact. Exposing athletes simultaneously to the motor skills intended to be improved is critical to effectively transfer new levels of motor capacities into the movement competency. Manipulating task constraints during sidestepping can be used in the training process to expose athletes to high joint loading and prepare them for “worst-case” scenarios. Such “worst-case” scenarios are characterised by certain segment alignments and joint positions previously determined as ACL risk factors in sidestepping movements (e.g., lateral foot placement, lateral trunk flexion or knee flexion at initial contact). Therefore, the purpose of this thesis was to increase the understanding of how to prepare athletes for “worst-case” sidestepping scenarios.

Chapter 2 established a theoretical framework for how different constraints can be utilised to a) manipulate the joint loading profile, such as the magnitude and distribution of joint loading, when sidestepping, thus specifically overloading, in particular, the knee joint, b) prepare for the imposed loading experienced during unplanned sidestepping, and c) how to facilitate a transfer from increases in motor capacities (e.g., single- and multi-joint strength) to improved motor skill (e.g., sidestepping). Subsequently, Study 1 demonstrated the reliability of single- and multijoint lower-body strength tests in recreationally trained female athletes. Such tests can be a valuable component of athlete monitoring for readiness and a component of a comprehensive physical test battery. Study 2 demonstrated that an individualised resistance training approach attenuates knee joint loading during unplanned sidestepping. The results of study 2 highlighted that individual strategies existed at the joint level when performing sidestepping that should be considered in subsequent training interventions. Study 3 demonstrated that the execution strategy, assessed by the single joint loading, changed based on external task constraints, particularly at the knee joint. Understanding how different task constraints affect the execution strategy is crucial when aiming to elicit specific adaptations around single joints.

The concepts and results of this thesis may have important implications for scientists and practitioners and shift how we think of athletic preparation. Exposing athletes progressively, continuously, and systematically to “worst-case” demands and the associated joint loading may increase injury resiliency and ultimately prepare for in situ demands. Further, possible approaches to facilitate the rate of transfer from increases in motor capacities (e.g., maximal muscle strength and maximal muscle power) to improvements in motor skills (e.g., jumping, sidestepping, sprinting) have been suggested. The results from this thesis provide support to seek the enhancement of an athlete’s ability to adapt and perform a multitude of execution strategies when completing the same motor task and withstand “worst-case” scenarios through increases in motor capacity and exposure to task variability.

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