• rough play and breaking the rules (unsporting behaviour)
• not being properly trained and/or not having sufficiently good technique
• lack of fitness
• overuse of muscles and fatigue
• not doing enough warming up, stretching exercises and/or cooling down
• bad weather conditions (rain, cold, ice, heatwave)
• starting sports again too soon after an injury
• poor sports kit (e.g. old equipment or wrong footwear)