A low level of physical fitness and life-style-related diseases during childhood and adolescence are associated with an increased risk of cardiovascular disease during adulthood.1 Recent estimates suggest that many adolescents and children do not achieve the recommended level of physical activity2 that is required to cause a reduction in the risk for cardiovascular disease and physiological disorders during childhood and adolescence.3 Studies investigating the health-related physical fitness benefits of regular physical activity participation have focused primarily on aerobic exercise, including treadmill or outdoor running and cycle ergometry.4,5 However, adherence to these modes of physical activity (e.g., continuous running) in the general population, and especially in adolescents, is relatively low, perhaps because such activities are perceived as isolating and boring.6 There is, therefore, a need to find more enjoyable modes of training that elicit great adherence by optimizing intrinsic motivation while offering health benefits that match those accomplished by treadmill and cycle ergometry programs.7 In this context, recreational soccer may be a popular alternative for those seeking to improve their cardiovascular, metabolic, and musculoskeletal fitness.8,9 A growing body of research has highlighted the health benefits of recreational soccer training in sedentary but otherwise healthy adults10,11 and obese12 or various patient populations.13,14 Recent reviews15,16 suggest that regular participation in recreational soccer can enhance both physical fitness and health status in untrained individuals. It has been shown for example, that a period of 12-24 weeks of soccer training caused a 7%-15% increase in the maximum amount of oxygen utilized (VO2max) in previously untrained participants.15 Moreover, 12 weeks of soccer training in young and middle-aged men led to a significant decrease (15%) in low-density lipoprotein cholesterol.17 Only few studies have investigated the health effects of soccer-based training in adolescence.12,18 In these studies, it was reported that obese adolescent boys improved a range of health markers, such as a reduction in body fat and blood pressure, an increase in high-density lipoprotein cholesterol, and VO2max after 12 weeks of organized recreational soccer training. To the best of our knowledge, no data exist on the effects of recreational soccer in untrained normal-weight adolescents. Moreover, no data exist on the acute effects of different forms of small-sided games on perceived enjoyment for adolescent boys. The aims of the present study were therefore to (1) investigate the health-related physical fitness profiles of untrained adolescents compared with adolescent soccer players, (2) determine the intensity and enjoyment responses to different forms of small-sided games for adolescent boys, and (3) investigate the effects on health-related fitness measures of a shortterm (8 weeks) recreational soccer intervention performed with untrained boys.