Performance in enduro mountain biking: the influence of training status, recovery, and vibration Lewis A. Kirkwood Ph.D 2019 Performance in enduro mountain biking: the influence of training status, recovery, and vibration Lewis Kirkwood A thesis submitted in partial fulfilment of the requirements of Edinburgh Napier University, the for the award of Doctor of Philosophy May 2019 i Abstract Enduro mountain bike racing (enduro) consists of timed downhill race stages linked by non-competitive transition stages and general classification is determined by accumulated race stage time. Limited research is available on the physiological requirements of enduro despite a large population of professional elite riders. For this thesis, nine elite enduro athletes (n=8 male, n=1 female; top 100 world ranking) were recruited. Measures of daily training load (TL) and resting heart rate variability (HRV) were collected between three laboratory based tests throughout a season of training and racing. The demands of an international race event were assessed by heart rate, terrain induced accelerations and vibration exposure. Leukocyte subset (Neutrophils, CD4+ T-cell, CD8+ T-cell, and NK cell) redistribution, cortisol and IL-6 concentration were assessed at each laboratory test (pre, post, 1h-post) and the race event (pre, 1h-post, 19h-post). Main findings were that successful performance in enduro requires a large aerobic capacity (VO2peak = 61.1 ± 5.2 -1 ml.kg.min , power VO2peak = 410.9 ± 18.2W) coupled with adequate skill, technique and muscle mass to ensure high velocities can be sustained over differing types of terrain. Elevated TL appears to be a key component of training habit and the upper limit of training volume before negative adaptation was identified (>800 A.U. LuTRIMP). No relationship was found between TL and HRV. No significant changes were observed in leukocyte subset redistribution between laboratory tests. The race event induced significantly larger changes in circulating numbers of certain leukocyte subsets when compared to the laboratory test and the magnitude of redistribution of CD4+ senescent T-cells was partially explained by vibration exposure (ΔR2 = -0.673, F(3,1) = 12.12, p = 0.04). A subsequent novel assessment of vibration loading in mountain biking revealed potentially damaging levels of vibration exposure that could be associated with long term health implications in enduro athletes -2 (Ai(8) range 5.47 to 6.61ms ). It was concluded that vibration exposure needs to be considered in future models of physiological loading in this discipline. ii Acknowledgements I would like to take this opportunity to thank all of the people who have helped me generate this thesis in one way or another. However great or small their contribution, I certainly could not have done this alone. Firstly, thanks to Professor Geraint Florida-James for all of his wisdom and guidance as a director of studies but also as a great friend. Thanks for believing in me for all these years, for all of the advice in all walks of life, and all the good times out on the bikes – I hope there will be plenty more. Secondly, thanks to Dr Lesley Ingram for all of your help and assistance over the years in various walks of life. Les, you have shown me how to get the work done but still have a great time – the beer is on me at the bar, as promised! Thank you to Dr Eva Malone for all of the help in creating this thesis and all the advice along the way. Thanks must also go to Dr Mark Taylor for all of the ‘Noddy diagrams’ and help navigating the world of human vibration. Thanks also to my friends, family and colleagues. In particular, a huge thank you to all of the PGR students at Edinburgh Napier that have helped me through this process with copious amounts of advice, support and most importantly laughter, particularly in 1.B.29. Every one of you has helped in some way. There are too many of you to mention, but a particular thanks has to go to Dave Lawson for always being there to talk about absolutely anything, anytime. I suppose thanks also has to go to Stu for the constant stream of abuse – I still don’t like you, but I might miss you. Paul, thanks for the funny stories and to Bruce for all of the old man wisdom. Of course, I wouldn’t have been able to generate this thesis without the willingness of the individuals that participated in the studies. I am eternally grateful for your time and dedication to providing such valuable information, so thank you again. Amanda, we might have only figured it out towards the end, but I could not have managed these final months without you. Thanks for distracting me with pizza, sticky toffee pudding, running, and cycling. I’m looking forward to plenty more adventures with you in the future! Lastly, this thesis is dedicated to my mum, Lesley Kirkwood. Thanks for always believing in me, for making be believe I can do anything I set my mind to, and most importantly for your endless love and support. Thanks for always pushing me to do better while still enjoying myself. No son could ever ask for more – think it’s about time we got that pint of Trade Winds! iii Publications The following published papers and conference proceedings have been produced from the work contained within this thesis. Published papers: Kirkwood, L., Ingram, L., Cunningham, J., Malone, E. and Florida- James, G. (2017) ‘Physiological characteristics and performance in elite vs non-elite enduro mountain biking.’, Journal Of Science & Cycling, 6(2), pp. 13–21. doi: 10.28985/171231.jsc.10 Peer reviewed unpublished conference proceedings: Kirkwood, L., Ingram, L., Malone, E. and Florida-James, G. (2016) ‘The physiological characteristics of elite vs non-elite enduro mountain bike cyclists’, in World Conference of Science & Cycling. Caen, France. Kirkwood, L., Ingram, L., Cunningham, J., Malone, E. and Florida- James, G. (2018) ‘Immunological responses and energy expediture at an international enduro mountain bike race’, in 1st symposium for UK Society for Exercise Immunology. Loughborough, UK. iv Table of Contents Chapter 1: General Introduction ................................................................. 1 Chapter 2: Literature review ........................................................................ 6 2.1. Physiological requirements of mountain biking .............................................. 7 2.1.1. Workload in enduro mountain biking ...................................................... 8 2.1.2. Contribution of terrain to workload in mountain biking .......................... 10 2.1.3. GPS activity profile ............................................................................... 11 2.1.4. Physiological correlates of off road-cycling performance ...................... 13 2.2. Basic principles of training .......................................................................... 14 2.2.1. Negative adaptation to training stimulus ............................................... 15 2.2.2. Models to measure training load .......................................................... 16 2.3. Monitoring autonomic nervous system activity response to training in athletes .......................................................................................................................... 20 2.3.1. Heart rate and heart rate variability ...................................................... 20 2.3.4. Effects of acute exercise and HRV ....................................................... 22 2.3.5. HRV and endurance performance ........................................................ 23 2.3.6. HRV and response to training stimulus ................................................ 24 2.4. The immune system and its role in coping with training and competition load. .......................................................................................................................... 26 2.4.1. Overview of immune system ................................................................ 26 2.4.2. Immune system and exercise ............................................................... 30 2.4.3. J-shaped curve .................................................................................... 30 2.4.4. S-shaped curve .................................................................................... 31 2.4.5. Open window and repeated bouts theory ............................................. 33 2.4.6. Leukocyte subset response to exercise ................................................ 35 2.4.7. Neutrophils ........................................................................................... 35 2.4.8. Lymphocytes ........................................................................................ 36 2.4.9. T-cells .................................................................................................. 36 2.4.10. NK cells .............................................................................................. 39 2.5. Vibration ...................................................................................................... 40 2.5.1. Vibration exposure in cycling ................................................................ 42 2.5.2. Vibration and performance ................................................................... 43 2.6. Immune and heart rate variability responses to combined exercise and vibration ............................................................................................................. 44 2.7. Summary of literature .................................................................................