Exercise-associated muscle cramping (EAMC) is a significant medical complication in distance runners, yet factors associated with EAMC are poorly documented.
To document risk factors associated with EAMC in runners.
Two ocean races (21.1 km, and 56 km).
Fifteen thousand seven hundred seventy-eight race entrants.
Participants completed a prerace medical history screening tool including: training, cardiovascular disease (CVD), risk factors for, and symptoms of CVD, history of diseases affecting major organ systems, cancer, allergies, medication use, and running injury. Runners were grouped as having a history of EAMC (hEAMC group = 2997) and a control group (Control = 12 781).
Independent factors associated with a higher prevalence ratio (PR) of hEAMC were any risk factor for CVD (PR = 1.16; P = 0.0002), symptoms of CVD (PR = 2.38; P < 0.0001), respiratory disease (PR = 1.33; P < 0.0001), gastrointestinal disease (PR = 1.86; P < 0.0001), nervous system or psychiatric disease (PR = 1.51; P < 0.0001), kidney or bladder disease, (PR = 1.60; P < 0.0001), haematological or immune disease (PR = 1.54; P = 0.0048), cancer (PR = 1.34; P = 0.0031), allergies (PR = 1.37; P < 0.0001), regular medication use (PR = 1.80; P < 0.0001), statin use (PR = 1.26; P = 0.0127), medication use during racing (PR = 1.88; P < 0.0001), running injury (PR = 1.66; P < 0.0001), muscle injury (PR = 1.82; P < 0.0001), tendon injury (PR = 1.62; P < 0.0001), and runners in the experienced category (PR = 1.22; P < 0.0001).
Novel risk factors associated with EAMC in distance runners were underlying chronic disease, medication use, a history of running injuries, and experienced runners. These factors must be identified as possible associations, and therefore be considered in the diagnosis and treatment of EAMC.
*Sport, Exercise Medicine and Lifestyle Institute (SEMLI), and Section Sports Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa;
†Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa;
‡International Olympic Committee (IOC) Research Centre, Pretoria, South Africa;
§Biostatistics Unit, South African Medical Research Council;
¶Statistics and Population Studies Department, University of the Western Cape; and
‖Institute of Sport and Exercise Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa.
Corresponding Author: Martin P. Schwellnus, MBBCh, MSc, MD, Sport, Exercise Medicine and Lifestyle Institute (SEMLI), Section Sports Medicine, Faculty of Health Sciences, University of Pretoria, South Africa, Sports Campus, Burnett St, Hatfield, Pretoria 0020, South Africa (firstname.lastname@example.org).
Partial support from the IOC Research Centre funding (South Africa). South African Medical Research Council (partial funding, statistical analysis).
The authors report no conflicts of interest.
M. P. Schwellnus: responsible for the overall content as guarantor, study concept, study planning, data collection, data interpretation, manuscript (first draft), manuscript editing, facilitating funding. W. Derman: data collection, data interpretation, manuscript editing. S. Swanevelder: study planning, data analysis including statistical analysis, data interpretation, manuscript editing. E. Jordaan: study planning, data analysis including statistical analysis, data interpretation, manuscript editing. D. C. Janse Van Rensburg: data interpretation, manuscript editing.
Received September 28, 2016
Accepted May 09, 2017