Get Sleep Or Get Stumped Sleep Behaviour in Elite South African Cricket Players During Competition

GET SLEEP OR GET STUMPED SLEEP BEHAVIOUR IN ELITE SOUTH AFRICAN CRICKET PLAYERS DURING COMPETITION BY KAYLA MCEWAN Submitted in fulfilment of the requirement for the Degree of Master of Science Department of Human Kinetics and Ergonomics Rhodes University Grahamstown, South Africa, 2020 Supervisor: Prof Candice Jo-Anne Christie Co-supervisor: Dr Jonathan Davy DECLARATION I, Kayla McEwan, hereby declare that the work on which this thesis is based is my original work (except where acknowledgements indicate otherwise) and that neither the whole work nor any part of it has been, is being, or is to be submitted for another degree in this or any other university. I empower the university to reproduce for the purpose of research either the whole or any portion of the contents in any manner whatsoever. Signature: ………………………………… Date: …………………………………….20/02/2020 Copyright © 2020 Rhodes University All rights reserved i ABSTRACT Introduction: Good sleep behaviour is associated with achieving optimal athletic performance and reducing the risk of injury. Elite cricket players have unique physical and cognitive demands, and must accommodate for congested competition and travel schedules (all of which increase the risk of disruptive sleep). Further, the political pressures and socioeconomic barriers in South African cricket could affect the sleep of the country’s elite players. Previous research in cricket has focussed on the impact that nutrition, equipment specifications, movement physiology and psychology could elicit on performance (where many professional teams hire support staff to supervise these disciplines); however, there is limited empirical application of sleep research in elite cricket players. Therefore, this study aimed to characterise the sleep behaviours of elite South African cricket players during periods of competition and investigate the relationship between pre-match sleep and cricket performance. Methods: A longitudinal field-based investigation was implemented to monitor the sleep behaviour of 26 elite South African cricket players (age: 28.6 ± 4.0 years; height: 1.8 ± 0.1 m; weight: 85.7 ± 10.8 kg; elite experience: 3.7 ± 4.0 years) during home and away competitive tours. The Morningness-Eveningness Questionnaire and Athlete Sleep Behaviour Questionnaire were administered to identify chronotype and poor sleep behaviours. Players completed an altered version of the Core Consensus Sleep Diary every morning post-travel, pre-match and post- match. Linear mixed model regression was used to compare differences in sleep variables between time-periods, match venues, player roles, match formats, sleep medication and racial groups. Spearman’s correlation (rs) was used to assess the relationship of substance use (alcohol and caffeine), age, elite experience and match performance with selected sleep indices. Statistical significance for all measures was accepted at p < 0.05. Hedge’s (g) were used as the measure of effect size. Results: Light-emitting technology use, effects of travel, late evening alcohol consumption and muscle soreness were the main factors that impacted sleep. Post- match total sleep time (06:31 ± 01:09) was significantly (p < 0.05) shorter compared to post- travel (07:53 ± 01:07; g = 1.19 [0.81;1.57]) and pre-match (08:43 ± 01:03; g = 1.97 [1.55;2.39]) total sleep time. Post-travel sleep onset latency and sleep efficiency were significantly (p < 0.05) shorter (g = 0.74 [0.29;1.29]) and higher (g = 1.35 [0.76;1.94]) at home than away. Although not significant (p > 0.05), allrounders took longer to fall asleep (g = 0.90 [0.23;1.57]), obtained less total sleep (0.76 [0.29;1.42]) and had lower morning freshness scores (g = 1.10 [0.42;1.78]) the night before a match compared to batsmen. Wake after sleep onset and get up time were moderately longer (g = 0.61 [0.22;1.26]) and later (g = 0.62 [0.27;1.17]) before ii Twenty20 matches compared to One-Day International matches respectively. Further, sleep duration significantly declined from pre-match to post-match during the multi-day Test format (p = 0.04, g= 0.75 [0.40;1.12]). Late alcohol consumption was significantly (p < 0.05) correlated with a decrease in total sleep time, regardless of match venue (home: rs (49) = -0.69; away: rs (27) = -0.57). During the away condition, an increase in age was significantly associated with longer wake after sleep onset durations (rs (13) = 0.52, p = 0.0003), while greater elite experience was significantly associated with longer total sleep time (rs (72) = 0.36, p = 0.02). The non-sleep medication group took significantly longer to fall asleep compared to the sleep medication group during the first week of the away condition (p = 0.02, g = 0.75 [0.25;1.26]) particularly on nights following transmeridian travel. Although not significant ( p > 0.05), Asian/Indian players had moderately longer sleep onset latencies (g = 1.07 [0.66;1.47]), wake after sleep onset durations (g = 0.86 [0.42;1.29]), and lower subjective sleep quality (g = 0.86 [0.46;1.26]) and morning freshness scores (g = 0.89 [0.47;1.27]) compared to Whites. Similarly, Black Africans had moderately lower subjective sleep quality scores compared to Whites (g = 0.71 [0.43;0.97]). Longer sleep onset latencies and shorter total sleep times were significantly (p < 0.05) associated with poorer One-Day International (rs (28) = -0.57) and Test (rs (12) = 0.59) batting performances respectively. Higher subjective sleep quality scores were significantly associated with better Twenty20 bowling economies (rs (8) = -0.52). Discussion: There was no evidence of poor pre-match sleep behaviour, irrespective of venue; however, the most apparent disruption to sleep occurred post-match (similar to that found in other team- sports). Most disparities in sleep between match venues existed post-travel, with better sleep behaviour observed during the home condition. The differences in sleep patterns found in all three match formats were expected given the variations in format scheduling and duration. Although sleep medication was shown to promote better sleep, its long-term effectiveness was limited. The results promote the implementation of practical strategies aimed to reduce bedtime light-emitting technology use, late evening alcohol consumption and muscle pain. Inter- individual sleep behaviour was found between player roles, age, experience level and race. Moderate associations existed between sleep and markers of batting performance, specifically for the longer, strategic formats of the game. Conclusion: The current study provided new insight of the sleep behaviour in elite South African cricket players during competition. Individualized sleep monitoring practices are encouraged, with specific supervision over older, less experienced players as well as the racial minorities and allrounders of the team. The poor post-match sleep behaviour, together with the sleep and performance correlations, provide iii ideal opportunities for future interventions to focus on match recovery and the use sleep monitoring as a competitive advantage. iv ACKNOWLEGDEMENTS I would like to express my heartfelt appreciation and thank you to the many people that have contributed to this research. Firstly to my supervisor- Prof. Candice Christie. Words cannot thank you enough for your guidance, support and the opportunities you have given me throughout the past few years. Your passion for research and the time you make for your students is admirable. To my co-supervisor- Dr Jonathan Davy. I truly appreciate your consistent encouragement, constructive feedback and exposing me to an exciting niche of sleep research. Thank you, Mr. Gregory King, (former strength and conditioning coach for the South African national male cricket team), for your immense gatekeeping assistance. Without you, this thesis would not have been possible and it has been a pleasure working with you. I would also like to thank the National Research Foundation for their financial assistance. It must be acknowledged that opinions or conclusion that have been expressed in this study are those of the mine and must not be seen to represent the views, opinions or conclusions of the National Research Foundation. To Cricket South Africa and all of the participating players, my sincerest thank you for your involvement, positivity and willingness to make this research possible. To my fellow cricket research squad - Lee, Cathy, Rob, Belinda and Devon. Thank you for your friendship, banter and countless coffee runs throughout this journey! To my family – Mom, Dad and Carmen. Words cannot express the amount of appreciation and love I have for you all. I cannot thank you enough for everything you have done to support me and keep me going no matter what. And finally to Jono, thank you for all of your encouragement, love and for bringing me snacks when I was stressed. It really helped get me through the last two years. v THESIS RESEARCH OUTPUTS Peer-reviewed publications • McEwan, K.M., Davy, J.P., & Christie, C.J. Get sleep or get stumped: Sleep quantification of elite South African cricket players during competition. Journal of Sport Sciences. Under revision. Conference publications • McEwan, K.M., Davy, J.P., & Christie, C.J. Get sleep or get stumped: Sleep quantification of elite South African cricket players during competition. 6th World Congress of Science and Medicine in Cricket hosted at Loughborough, UK, 8-11 July 2019. 1 TABLE OF CONTENTS DECLARATION......................................................................................................................

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