. Furthermore, seniority of the players may have an effect on the changes observed over the competitive season. Longitudinal effects over 4 years of strength and conditioning for American football players showed increases in body mass and lean body mass in the first 2 years of training (17), whereas strength and power performance was shown to improve throughout the college football career (11). Upperclassmen (juniors and seniors) in general experience more playing time and more reps during practices than the underclassmen (freshmen, red shirt freshmen, and sophomores). Based on these observations, we hypothesize that upperclassmen will lose more weight and lean mass compared with underclassmen due to increased activity and energy needs during games and practices. We expect to see gains in weight and lean mass in the off-season.