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In pursuit of the ‘Unbreakable’ Athlete: what is the role of moderating factors and circular causation?
  1. Tim J Gabbett1,2,
  2. Rasmus Oestergaard Nielsen3,
  3. Michael Lejbach Bertelsen3,
  4. Natália Franco Netto Bittencourt4,5,
  5. Sérgio T Fonseca6,
  6. Shane Malone7,8,9,
  7. Merete Møller10,
  8. Eric Oetter11,
  9. Evert Verhagen12,13,
  10. Johann Windt14,15,16
  1. 1 Gabbett Performance Solutions, Brisbane, Queensland, Australia
  2. 2 University of Southern Queensland, Institute for Resilient Regions, Ipswich, Queensland, Australia
  3. 3 Section for Sports Science, Department of Public Health, Aarhus University, Aarhus, Denmark
  4. 4 Physical Therapy Department, Minas Tênis Clube, Belo Horizonte, Brazil
  5. 5 Department of Physical Education, Uni-BH University, Belo Horizonte, Brazil
  6. 6 Graduate Program in Rehabilitation Science, Physical Therapy Department, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
  7. 7 Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
  8. 8 Gaelic Sport Research Centre, Department of Science, Institute of Technology, Dublin, Ireland
  9. 9 High Performance Unit, Irish Rugby Football Union, Dublin, Ireland
  10. 10 Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark
  11. 11 Memphis Grizzlies, Memphis, Tennessee, USA
  12. 12 Department of Public and Occupational Health, Amsterdam Movement Science, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
  13. 13 UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
  14. 14 Experimental Medicine Program, University of British Columbia, Vancouver, British Columbia, Canada
  15. 15 Sports Medicine, United States Olympic Committee, Colorado Springs, Colorado, USA
  16. 16 United States Coalition for the Prevention of Illness and Injury in Sport, Colorado Springs, Colorado, USA
  1. Correspondence to Professor Tim J Gabbett, Gabbett Performance Solutions, Brisbane, QLD 4011, Australia; tim{at}

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The goal for sports medicine practitioners is to develop robust athletes, capable of withstanding high training and competition loads. For sports medicine professionals, understanding the workload–capacity relationship is central to achieving this goal. This editorial discusses how two different methodological frameworks—(1) moderation and (2) circular causation—align to develop physical capacity and injury resilience in athletes.

‘The Straw that Broke the Camel’s Back’

The Arab proverb ‘the straw that broke the camel’s back’ refers to a camel carrying a haystack that was so heavy a single piece of additional straw broke its back. In a sport setting, the ‘camel’ is the athlete, the ‘load of hay’ represents the maximal workload the athlete can tolerate safely (load capacity), and the ‘additional straw’ represents overload resulting in injury (capacity exceeded). The inherent biological qualities of the camel (eg, age, strength and so on) determine its cumulative straw-carrying capacity.

Basketball superstar Kobe Bryant had strong training ethic, well-developed physical qualities and was largely injury-free in the early stages of his career. He was a strong ‘camel’ accustomed to carrying large loads with ease. We speculate that his athletic pursuits in childhood and adolescence contributed to his high load capacity in adulthood. Indeed, weight-bearing physical activity during childhood and early puberty has a positive, and possibly enduring effect on bone strength.1 Furthermore, after a certain age, the eccentric heart hypertrophic adaptation …

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  • Contributors TJG and RON proposed and drafted the initial paper. All coauthors provided input to subsequent drafts of the paper.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests TJG works as a consultant to several high-performance organisations, including sporting teams, industry, military and higher education institutions. He serves in a voluntary capacity as Senior Associate Editor of BJSM.

  • Patient consent Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.