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Anzell, AR, Potteiger, JA, Kraemer, WJ, and Otieno, S. Changes in height, body weight, and body composition in American football players from 1942 to 2011. J Strength Cond Res 27(2): 277–284, 2013—The purpose of this study was to document changes in height (cm), body weight (kg), and body composition (%fat) of American football players from 1942 to 2011. Published articles were identified from databases and cross-referencing of bibliographies. Studies selected met the requirements of (1) having 2 of 3 dependent (height, body weight, and body composition) variables reported in the results; (2) containing a skill level of college or professional; (3) providing measured not self-reported data; and (4) published studies in English language journals. The data were categorized into groups based on skill level (college and professional). The player positions were grouped into 3 categories: mixed linemen (offensive and defensive linemen, tight ends, and linebackers), mixed offensive backs (quarterback and running backs), and mixed skilled positions (defensive backs and wide receivers). Linear regression was used to provide slope estimates and 95% confidence intervals (CIs). Unpaired t-tests were used to determine whether an individual regression slope was significantly different from zero. Statistical significance was set at p < 0.017. College level players in all position groups have significantly increased body weight over time (95% CI: mixed lineman 0.338–0.900 kg·y−1; mixed offensive backs 0.089–0.298 kg·y−1; mixed skilled 0.078–0.334 kg·y−1). The college level mixed linemen showed a significant increase over time for height (95% CI: 0.034–0.188 cm·y−1) and body composition (0.046–0.275% fat per year). Significant increases in body weight over time were found for professional level mixed lineman (95% CI: 0.098–0.756 kg·y−1) and mixed offensive backs (95% CI: 0.1800–0.545 kg·y−1). There were no other significant changes at the professional level. These data demonstrate that body weight of all college players and professional mixed lineman have significantly increased from 1942 to 2011.