Doctoral Degrees (Exercise, Sport and Lifestyle Medicine)

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Browsing Doctoral Degrees (Exercise, Sport and Lifestyle Medicine) by browse.metadata.advisor "De Waal, Simon Jake"

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    The acute : chronic workload ratio and injury occurrence among South African PSL soccer players
    (Stellenbosch : Stellenbosch University, 2019-07) White, Ryan Colin; Grobbelaar, Heinrich Wilhelm; De Waal, Simon Jake; Swart, Jeroen; Stellenbosch University. Faculty of Medicine and Health Science. Dept. of Sport Science.
    ENGLISH ABSTRACT: Purpose: Soft-tissue, non-contact injuries (STNCI) are the most prevalent injuries in professional soccer. Considerable research has focussed on injury prevention and training load (TL) monitoring, however, the multifactorial nature of injury occurrence is often neglected. As such, both internal and external TL were examined in this study with the intention of enhancing current understanding of the mechanisms behind STNCI. The acute:chronic workload ratio (ACWR) was used to model the internally and externally derived workloads, providing a dynamic representation of preparedness and subsequent injury risk. This study aimed to identify and describe the association of both internal and external workload variables and injury risk in the subsequent week using the ACWR among professional South African Premier Soccer League (PSL) players. Article one: Article one examined the association between internally-derived TL (session rating of perceived exertion [sRPE]) and injury risk in the subsequent week utilising the ACWR and 1-, 2-, 3- and 4-weekly cumulative TL. TL data was collected from 41 professional male soccer players over one and a half seasons. In total, 85 STNCIs were recorded. Only the ACWR was significantly associated (p<0.05) with injury in the subsequent week. The workload-injury relationship was sigmoidal (s-shaped) in nature. An increased injury risk in the subsequent week was found at moderate-low (0.77-0.89; OR: 1.67, 95% CI: 1.23-2.27) and high (>1.14; OR: 1.26, 95% CI: 1.06-1.50) ACWR zones, while a low (<0.77; OR: 0.29, 95% CI: 0.14-0.61) ACWR zone exhibited a most likely beneficial effect compared to a moderate-high ACWR zone. Article two: Article two investigated the association between externally-derived (global positioning systems [GPS] and accelerometer-derived mechanical load indicators) and injury likelihood in the subsequent week utilising the ACWR. Total distance (TD), high intensity speed (HIS), high intensity acceleration (HIA) and high intensity deceleration (HID) data, was collected from 37 professional male soccer players over one and a half seasons. The workload-injury relationship was sigmoidal (s-shaped) and quadratic (u-shaped) in nature. Increased injury likelihood for the subsequent week was identified at high {(TD; >1.30, OR: 1.78, 95% CI: 0.72-4.38)(HIS; >1.41, OR: 1.74, 95% CI: 0.80-3.77)(HIA; >1.41, OR: 1.80, 95% CI 1.00-3.24)}, moderate-high (HID; >1.37, OR: 0.80, 95% CI 0.39- 2.76) and low (HIA; <0.77, OR: 1.29, 95% CI 1.00-1,66) ACWR zones, when compared to a moderate ACWR (~0.91 to ~1.20) zone. Conclusion: The workload-injury relationship was sigmoidal in nature and players exposed to acute de-loads and spikes in TL experienced an increased risk of subsequent injury. A moderate ACWR of between ~0.91 to ~1.20 represents the most realistic, optimal TL index to maintain or improve fitness and/or preparedness, while limiting injury likelihood. The similar sigmoidal nature of injury risk between internally and externally derived TL implies that sRPE may be a useful alternative to costly GPS systems in the world of injury prevention for soccer players - which is of significant importance in a South African context. Key words: Acute:chronic workload ratio, session rating of perceived exertion, global positioning systems, training load monitoring, team sport.