In this study, football players (N = 57) in grades 9-11 from 3 high schools chose to participate in 1 of 2 groups. Group WC (N = 39) participated in off-season strength training only. Group SP (N = 18) participated in both a winter sport (either wrestling or basketball) and an identical strength training program. All participants were tested at the close of football season (Pre) and at the end of the winter sports season (Post), a period of 4 months. Body composition (weight [W] and body fat percentage [BF]), strength (calculated 1RM [1 repetition maximum] max for barbell bench press [BP] and squat [SQ]), power (vertical jump [VJ] and seated shot put [UP]), and agility (18.3-m agility run [AG]) were measured. Both groups WC and SP increased significantly in W and BF and improved significantly in BP and VJ (p < 0.05). Only the WC group improved significantly in SQ and AG (p < 0.05). Only the SP group increased significantly in UP (p < 0.05). Only the difference in SQ was statistically greater in the WC than in the SP group (p < 0.05). Regardless of winter activity, football players gain significant amounts of BF resulting in overall W increases. Football players participating in winter sports improved significantly in measurements of strength and power. There appears to be no clear advantage to devoting time solely to strength training.