title: Increased running speed and pre-race muscle damage as risk factors for exercise-associated muscle cramps in a 56 km ultra-marathon: a prospective cohort study.
abstract: BACKGROUND
  Despite the high prevalence of exercise-associated muscle cramping (EAMC) in endurance runners, the aetiology and risk factors for this condition are not fully understood.
  
  
  OBJECTIVE
  The purpose of this prospective cohort study was to identify risk factors associated with the development of EAMC in ultra-distance runners.
  
  
  METHODS
  49 runners participating in a 56 km race completed a validated pre-race questionnaire. Pre-race muscle pain in the calves, hamstrings and quadriceps muscles was recorded (visual analogue scale) and pre-race serum creatine kinase (CK) activity was measured. 20 runners reported EAMC (EAMC group) during or within 6 h after the event, while 29 runners reported no cramping (CON group).
  
  
  RESULTS
  EAMC was not associated with age, body mass index, sex, recent and past personal best running times, pre-race muscle pain and pre-race training (duration and frequency). Runners in the EAMC group tended to report on average longer training sessions during the 3 days before the race (EAMC 1.2 (1.1), CON 0.6 (1.0); p=0.077). Significant risk factors for EAMC were a past history of EAMC (EAMC 100%, CON 48%; p<0.001) and a faster running time (min) for the first 28 km split time of the race (EAMC 144 (20), CON 157 (14); p=0.029) despite being matched for recent (<15 weeks before race) personal best times in the 42.2 km race. Pre-race CK activity tended to be higher in the EAMC group (EAMC 89 (80), CON 58 (35); p=0.066).
  
  
  CONCLUSIONS
  Novel risk factors for EAMC in distance runners are a past history of EAMC, faster running pace at the early stage of a race and possibly pre-race muscle damage.
authors.affiliation: Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, South Africa. martin.schwellnus@uct.ac.za
authors.forename: Martin P
authors.initials: MP
authors.lastname: Schwellnus
authors.forename: Siddieq
authors.initials: S
authors.lastname: Allie
authors.forename: Wayne
authors.initials: W
authors.lastname: Derman
authors.forename: Malcolm
authors.initials: M
authors.lastname: Collins
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009120:Muscle Cramp / Q000209:etiology* / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000293:injuries*; D059352:Musculoskeletal Pain / Q000209:etiology / Q000503:physiopathology; D011446:Prospective Studies; D012307:Risk Factors; D012420:Running / Q000502:physiology*