González-Ravé, JM, Delgado, M, Vaquero, M, Juarez, D, and Newton, RU. Changes in vertical jump height, anthropometric characteristics, and biochemical parameters after contrast training in master athletes and physically active older people. J Strength Cond Res 25(7): 1866-1878, 2011—The purpose of this study was to determine the effects of 16 weeks of contrast training (CT) on older adults (with different levels of physical conditioning) in vertical jump performance (squat jump [SJ], countermovement jump [CMJ], CMJ during 15 seconds [CMJ15], depth jump [DJ]), body weight, fat percentage, muscle mass (MM), muscle cross-sectional area ([CSA] of the arm and thigh) and biochemical parameters (creatine kinase [CK], creatinine, and urea). Sixteen older (63.55 ± 6.89 years) recreational master runners (A) and 16 physically active older people (60.30 ± 5.18 years) though not athletes (NA), participated in the CT using a combination of heavy-resistance and explosive exercise. The dependent variables were measured pretraining and posttraining. The CT resulted in significant improvements (α = 0.05) for both groups in jump performance. The SJ height improved in NA by 21.68% and in A by 21.81%, the CMJ height increased in NA by 21.51% and in A by 14.81%, the DJ height increased in NA by 26.45% and in A by 7.43%, and CMJ15 increased in NA by 6.20% and in A by 6.17%). Significant improvements in MM (16.44% in NA and 14.78% in A), thigh CSA (19.68% in NA and 21.67% in A), and arm CSA (7.43% in NA and 5.52% in A), and significant decreases in creatinine (8.65%) and CK (25.49%) in A were observed. In conclusion, CT improved vertical jump performance and MM in both groups, regardless of the training history and current physical activity of each group. These improvements were accompanied by a slight decrease in body fat but no changes in total body weight. These findings suggest that CT can have a significant effect on maximal jump height and MM in NA and A.