Exercise Associated Muscle Cramps in Cyclists : Epidemiology, clinical characteristics and risk factors

Abstract

Background: Exercise associated muscle cramping (EAMC) is a common medical condition encountered by endurance athletes, yet information regarding EAMC in cyclists in lacking. Aim of the study: To determine the epidemiology, clinical characteristics, and independent risk factors associated with EAMC in cyclists participating in a mass participation cycling event. Design: Cross-sectional study Setting: 2016 Cape Town Cycle Tour (CTCT), South Africa Participants: 22560 consenting cycle race entrants Methods: Epidemiological data (lifetime prevalence and annual incidence) and clinical characteristics (main muscle groups affected, timing of onset, severity [mild - severe] and frequency of serious forms of EAMC [sEAMC]) in cyclists with a history of EAMC (hEAMC) are reported on. A multiple regression analysis was applied in order to determine if the following factors were associated risk factors for EAMC in cyclists with a hEAMC: chronic disease composite score, cycling training / racing history (years of recreational cycling, years of participation in distance cycling events > 2 hours, average number of training sessions per week, average weekly cycling distance in the last 12 months, and average training speed), history of chronic disease (history of cardiovascular disease [CVD], risk factors for CVD, symptoms of CVD, metabolic/hormonal disease, respiratory disease, gastrointestinal disease, nervous system/psychiatric disease, kidney/bladder disease, haematological/immune system disease, and cancer) and allergies, and history of cycling injuries. Results: A total of 35914 cyclists entered the race, 27349 completed the online pre-race medical screening questionnaire, and 22560 gave informed consent for the use of their data in this study (62.82% of all race entrants). The lifetime prevalence of EAMC was 30.6%, with an annual incidence of 18.7%. The quadriceps muscle group was the most commonly affected muscle group (47.7%), the most common time period for the onset of EAMC was during the fourth quarter of the race (63.0%), and mild (less than 5 minutes) EAMC occurred more frequently (67.0%) than other forms of EAMC. Serious EAMC was reported by 5.6% of the study population, and included whole body EAMC (3.2%) and EAMC associated with dark urine (2.2%). Novel independent risk factors associated with an increased risk of hEAMC in cyclists were: a higher chronic disease composite score (PR=1.34 per 2 unit increase; p<0.0001), a history of any allergies (PR=1.17; p<0.0001), a history of an acute onset injury (PR=1.31; p<0.0001), a history of a gradual onset injury (PR=1.29; p<0.0001), and increased number of years participating in cycling events of > 2 hours (PR=1.34 per 2 unit increase, p<0.0001). Increased number of years as a recreational cyclist (PR=0.96 per 5 unit increase, p=0.0012) and increased average weekly training/racing frequency in the last 12 months (PR=0.95 per 2 unit increase, p=0.0015) were associated with a decreased risk of EAMC. From the univariate analysis, we identified a significantly higher prevalence of lifetime hEAMC in male cyclists (PR=2.16; p<0.0001), and a higher prevalence of hEAMC in the ≥51-year age category (37.6%). Conclusion: One in three cyclists report a lifetime hEAMC. In cyclists with a hEAMC, the quadriceps muscle group is the most commonly affected muscle group, EAMC commonly occurs in the last quarter of the race, most EAMC cases are reported as mild, and sEAMC is not common. The results from this study could influence the future prevention and management programmes of EAMC in recreational cyclists, and assist medical personnel in the planning and implementation of medical care at mass participation cycling events. A higher chronic disease composite score, a history of allergies, a history of injury (acute onset or gradual onset) and training / racing variables are novel independent risk factors associated with a hEAMC in cyclists taking part in a mass participation cycling event. Risk factors for EAMC need to be taken into consideration when implementing prevention and management programmes of EAMC in cyclists. Clinicians should also consider that in some cases, EAMC may be associated with underlying chronic diseases or allergies, and/or the medications used to treat such conditions. In addition, injury history and training variables need to be considered in the prevention and management of EAMC in cyclists.

Keywords: muscle cramping, exercise associated muscle cramping, EAMC, cyclists, clinical characteristics, epidemiology, risk factors, chronic disease