PT - JOURNAL ARTICLE AU - Ramires Alsamir Tibana AU - Nuno Manuel Frade de Sousa TI - Are extreme conditioning programmes effective and safe? A narrative review of high-intensity functional training methods research paradigms and findings AID - 10.1136/bmjsem-2018-000435 DP - 2018 Nov 01 TA - BMJ Open Sport & Exercise Medicine PG - e000435 VI - 4 IP - 1 4099 - http://bmjopensem.bmj.com/content/4/1/e000435.short 4100 - http://bmjopensem.bmj.com/content/4/1/e000435.full SO - BMJ OPEN SP EX MED2018 Nov 01; 4 AB - Extreme conditioning programmes (ECPs, eg , CrossFit, Insanity and Gym Jones) are a growing fitness regimen characterised by functional movements performed at high-intensity and with constantly varying movements. While the popularity and number of practitioners of ECPs are growing, a debate has been established between what is observed in the scientific literature and anecdotal reports from athletes, coaches and physicians about safety (incidence and prevalence of injuries and rhabdomyolysis) and benefits (physical and mental health). In this article, we review the prevalence and incidence of injuries, rhabdomyolysis, physiological responses and chronic adaptations to ECPs. The majority of the available evidence confirm that the estimated injury rate among athletes participating in ECPs is similar to that in weightlifting and most other recreational activities. Additionally, ECP sessions resulted in increased acute oxidative, metabolic and cardiovascular stress, and depending on the stimulus (intensity, duration and non-usual exercise) and training status of the practitioner, an ECP session may precipitate rhabdomyolysis. In the scientific literature, the current chronic effects of ECPs showed little or no effects on body composition and improvements in physical fitness and psychological parameters; however, further studies are important.