Journal of Strength & Conditioning Research:
Changes in Height, Body Weight, and Body Composition in American Football Players From 1942 to 2011
Anzell, Anthony R.1; Potteiger, Jeffrey A.2; Kraemer, William J.3; Otieno, Sango4
1Departments of Biomedical Sciences, and
2Movement Sciences, Grand Valley State University, Grand Rapids, Michigan
3Department of Kinesiology, University of Connecticut, Storrs, Connecticut
4Department of Statistics, Grand Valley State University, Grand Rapids, Michigan
Address correspondence to Dr. Jeffrey A. Potteiger, firstname.lastname@example.org.
Abstract: 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.
In an effort to improve performance, competitive athletes devote considerable time and effort into mastering a sport by practicing and developing a set of skills required for the sport. Athletes also participate in extensive training and conditioning in an effort to maximize fitness and develop appropriate body size and body composition for successful performance. In many competitive sports, it is easy to visually observe that athletes appear much larger in body size than in past years. This is particularly noticeable in American football. Of all the position players, offensive and defensive linemen tend to be the tallest, heaviest, and have the highest percentage of body fat. Other position players such as linebackers, fullbacks, and tight ends appear to have had significant body mass changes and show impressive musculature compared with previous generations of players. Wide receivers, running backs, and defensive backs appear to have the least significant alterations in body size but still have visually noticeable changes in body composition compared with those who have played the position many years ago. The changes in body size and body composition are in part because of improved strength and conditioning programs, better overall training practices, enhanced nutritional intake, and possibly even the use of performance enhancing drugs.
Overall body size has always played an important role in American football, but anecdotally there seems to be a dramatic change in the size of present day American football players. Although numerous studies have documented the body size and body composition of American football athletes of various playing positions from both college and professional players in different time periods, only a few studies have reported the body size and body composition of players over time (24,44,51). Furthermore, we have found no studies that documented the changes in body size and body composition over the past 70 years. Through a systematic data collection process using peer-reviewed journals, the changes in height, body weight, and body composition for American football players over the past 70 years can be recorded and evaluated over time.
The purpose of this study was to document the changes in height, body weight, and body composition of American football players from the years 1942 to 2011. We provide this information for use by athletic coaches and trainers, strength and conditioning specialists, and sports science researchers. This information should serve as a reference for the changes in body height, weight, and composition that have occurred over time, as well as a reference for what the average body height, weight, and composition of football athletes may be for positions at the college and professional level. The primary hypothesis was that college and professional level players would have a significant increase in height and body weight over the observed time period. The secondary hypothesis was that offensive and defensive lineman would have a significant increase in body composition over the observed time period.
Experimental Approach to the Problem
Intuitively, it seems that the body height, weight, and composition of an American football player have noticeably changed from the early playing days to the present time. However, there has been no systematic documentation of any possible changes. The playing career of a college football player is typically limited to 4–6 years, whereas the playing career of a professional player is highly variable and can typically last between 1 and 15 years. Consequently, a longitudinal prospective study of individual changes in body height, weight, and composition would be challenging and be limited to the time period studied. Therefore, this cross-sectional study was designed to investigate, by the playing level and playing position, the differences in body height, weight, and composition for college and professional football players over the past 70 years through a systematic review of data reported in academic journal articles.
Detailed searches were performed using Sport Discus and Index Medicus for English language studies from September 1, 1971 to August 1, 2011. Words and phrases used in searches included “football,” “height,” “body weight,” and “body composition.” Cross-referencing of bibliographies from previously retrieved studies and articles was conducted. Seventy-five studies were identified for review. A total of 55 studies were selected for inclusion and data analyses. Studies selected met the requirements of (1) having at least 2 of the 3 dependent variables (body height, body weight, and body composition) reported in the Results section; (2) containing a reported skill level of either college or professional; (3) providing measured data, not self-reported data; and (4) published studies in English language journals only.
Data were recorded in a Microsoft Excel spreadsheet. Each data entry represented a group of subjects from a study in which there was a measurement of a dependent variable. Variables recorded from each study were the following: body height (cm), body weight (kg), body composition (%fat), method of obtaining body composition, number of subjects in calculated mean, skill level (college, professional), and football playing position (quarterback, running back, wide receivers, defensive backs, tight ends, linebackers, offensive linemen, and defensive linemen).
For statistical analyses and presentation, the data were split into 2 groups based on skill level (college and professional). In each skill level, all players were grouped together and then each of the playing positions were grouped into 3 different categories: mixed linemen (offensive and defensive linemen, tight ends, and linebackers), mixed offensive backs (quarterback and running backs), and mixed skilled players (defensive backs and wide receivers). We also combined all data together for both college and professional players. R-software for statistical computing (http://www.r-project.org/) was used to generate scatterplots and compute simple linear regression slopes and corresponding 95% confidence intervals (CI) by regressing 3 primary variables (body height, body weight, and body composition) against year for college and professional football players’ data. To determine whether the individual regression slope was significantly different from zero, a t-test for simple linear regression was used at 5% significance level. Statistical significance was set at p < 0.017, to correct for multiple testing.
Data for college football players were collected from the following articles for body height (1,4–15,18–20,22–28,30–35,38–41,43,44,46,47,49,52) (54,57–59), body weight (1,3–15,18–20,22–28,30–35,38–41,43–47,49,51,52) (54,57–59), and body composition (1,3–9,11,14,18,24,25,28,30–32,34,38–41,43–47,49,51,52) (54,57,58,60). Data for professional football players were collected from the following articles for height (2,29,48,50,55,58,61), body weight (2,17,29,48,50,55,58,61), and body composition (2,17,29,50,55,58,61).
Figures 1 and 2 illustrate the change in body height from 1959 to 2011 for college football players and from 1942 to 2011 for professional football lineman, respectively. The average change in body height for every year was between −0.048 and 0.502 cm for mixed offensive backs, 0.034–0.188 cm for mixed lineman, −0.073 to 0.119 cm for mixed skilled, and −0.011 to 0.112 cm for all positions combined. We can state with 95% confidence that these results are significantly different from zero for mixed lineman but not for mixed offensive backs, mixed skilled players, and all positions combined (Table 1). For professional football players, the average change in body height for every year is somewhere between −0.214to 0.316 cm for mixed offensive backs, −0.073to 0.096 cm for mixed lineman, −0.207 to 0.061 cm for mixed skilled, and −0.080 to 0.107 cm for all positions combined. We can state with 95% confidence that these results are not significantly different from zero for mixed offensive backs, mixed lineman, mixed skilled players and all players combined (Table 2).
Figures 1 and 2 illustrate the change in body weight from 1959 to 2011 for college football players and from 1942 to 2011 for professional football players. The average change in body weight for every year is somewhere between 0.089 and 0.208 kg for mixed offensive backs, 0.338–0.900 kg for mixed lineman, 0.078–0.334 kg for mixed skilled, and 0.160–0.570 kg for all positions combined. We can state with 95% confidence that these results are significantly different from zero for mixed lineman, mixed skilled players, and all players combined, but not for mixed offensive backs (Table 1). For professional football players, the average change in body weight for every year is somewhere between 0.180 and 0.545 kg for mixed offensive backs, 0.098–0.756 kg for mixed lineman, −0.015 to 0.305 kg for mixed skilled, and −0.046 to 0.570 kg for all positions combined. We can state with 95% confidence that these results are significantly different from zero for mixed offensive backs and mixed lineman, but not significantly different from zero for mixed skilled players and all players combined (Table 2).
Figures 1 and 2 illustrate the change in body composition from 1959 to 2011 for college football players and from 1942 to 2011 for professional football lineman. The average change in body composition for every year is somewhere between −0.133 and 0.127% fat for mixed offensive backs, 0.046–0.275% fat for mixed lineman, −0.053 to 0.164% fat for mixed skilled, and 0.030–0.278% fat for all positions combined. We can state with 95% confidence that these results are significantly different from zero for mixed lineman and for all players combined, but not for mixed offensive backs and mixed skilled players (Table 1). For professional football players, the average change in body composition for every year is somewhere between −0.071 and 0.236% fat for mixed offensive backs, −0.053 to 0.170% fat for mixed lineman, −0.065 to 0.139% fat for mixed skilled, and −0.082 to 0.142% fat for all positions combined. We can state with 95% confidence that these results are not significantly different from zero for mixed offensive backs, mixed lineman, mixed skilled players, and all players combined, respectively (Table 2).
The data used in this study cover 70 years and were derived from published journal articles in which a measured body height, body weight, and body composition were reported. Regression slopes were calculated for college and professional football players for each of the dependent variables for the following playing positions: mixed linemen, mixed offensive backs, mixed skilled players, and all positions combined. The results of this study show that over time there has been a significant increase in body weight for all college football players (mixed linemen, mixed offensive backs, mixed skilled, and all positions combined) and for profession football players (mixed linemen and mixed offensive backs). The results also show that there was a significant increase in percent body fat for college football players (mixed lineman and all positions combined). The obtained results also show that there has been no significant change in body height for college level players, whereas for professional level players there has been no significant change over time in both body height and body composition.
As the game of American football has evolved at the college and professional level with a greater demand for bigger athletes, there is greater emphasis on year-round training, proper nutrition, and the desire to be as physically large as possible while still maximizing running speed and quickness. This has led football players to use year-round advanced training programs, consume nutritionally appropriate diets, and use performance enhancing ergogenic aids to increase muscle size and strength.
Physical training is an important component for the development of muscle size. Early in the history of football, there was little training performed for the specific purpose of increasing body size. Training regimens consisted of callisthenic types of activities and little formal resistance exercise training (personal correspondence with older former college and professional players). Furthermore, off-season training was often limited to a short time period before the start of the season. Over time, a transition to year-round training using exercises specifically designed to increase muscle size and strength has occurred. These new and improved programs have helped athletes increase their body weight during training. Additionally, the prevalence of professionally educated and trained strength and conditioning coaches has increased so that all college and professional football teams have individuals working in these positions. For example, the founding of the National Strength and Conditioning Association in 1978 gave rise to knowledgeable professionals helping athletes increase body size through proper training and conditioning programs. All these training factors have probably contributed to the increase in body weight and body composition.
Another factor contributing to the changes observed in body weight and body composition over time is the use of improved nutritional intake. This is especially true as it relates to adequate carbohydrate and protein intake during training (53). Numerous studies have demonstrated the importance of adequate carbohydrate and protein intake during training for the purpose of increasing body weight and muscle mass (53). Furthermore, an appropriate macronutrient intake is especially important during periods of heavy training when attempting to increase muscle mass (53).
The use of performance enhancing ergogenic aids designed to increase muscle strength and size may also be a likely contributor to the change in body weight observed among college and professional football players. Several ergogenic aids have been shown to significantly increase body weight and muscle mass: creatine (56), beta-hydroxy-beta-methylbutyrate (36), and anabolic steroids (21). In particular, anabolic steroids, when combined with a resistance exercise training program, result in an increase in body weight and muscle mass (16,21,37). The use of anabolic steroids has been prevalent in football at many levels and may have also likely contributed to the changes in weight observed over the past 70 years. The use of anabolic steroids to increase muscle mass was first reported in the early 1940s (21,42). Although college and professional football governing bodies have outlawed the use of steroids, it has been reported that many players, particularly offensive and defensive linemen, use them in an effort to increase body size and muscular strength (21).
A number of rule changes may have also contributed to the change in body weight and body composition among college and professional American football players over the past 70 years. As the game of football developed, there have changes to the rules governing the sport. In 1951, a rule was implemented that no offensive guard or tackle including the center could catch the ball on a forward pass. This limited the offensive lineman's job to just blocking and took away the skilled aspect for that position group. Additionally, in 1971, a rule against blocking below the waist was implemented. This rule change took away the use of the chop block and scramble block, both of which provided an advantage for small and quick offensive linemen. As a consequence, there was an increased demand for larger and stronger linemen. It is also possible that different types of offensive and defensive schemes have contributed to the changes in body size and composition over the past 70 years. For example, larger offensive linemen provide better pass protection for the quarterback on a team that might use a passing offense. Additionally, larger defensive linemen, because of their large size, make effectively running the football in the middle of the line more difficult to accomplish.
There are several factors that could be considered as limitations to this study. First, the mixed levels (divisions 1, 2, and 3) of college football players reported in the research literature may have masked more profound changes in the division 1 level subjects. Although no published studies have directly compared height, body weight, and body composition across college level divisions, the larger, stronger, and faster players are more commonly found in the division 1 level. Second, the evolution of the game through various playing eras could result in one type of offensive or defensive strategy prevailing at a particular time or with a particular team and therefore influencing the results for a specific time period. Finally, combining the various positions together for the analysis could also influence the changes in the dependent variables. For example, wide receivers could get taller in height and defensive backs shorter in height. In a combined group, these changes would be diluted in the data set. However, despite these limitations, we feel confident that the data presented in this article supports what is intuitively known, that college and professional football players have increased body size during the past 70 years.
Results from this study could be used in a number of general ways as athletes and programs constantly change. The reported values may be representative of the body size and composition of college and professional football athletes. This would provide a standard size for comparing changes in body height, body weight, and composition in professional and collegiate football players per position. Coaches and athletes could use the results to set obtainable goals dealing with body size and composition. This study could also be used to examine the health implications of excessive weight gains in specific position groups. As observed in the study, there has been a significant increase in weight and a change in body composition in mixed linemen. These increases are seen as necessary in professional and collegiate football players, but for the nonathletic person in America, the weight and body composition values would be viewed as having a negative effect on health. Finally, this study can be used to provide a context for how American football has evolved over the past 70 years. The game has changed significantly and the changes in body size and composition have played a huge factor in how the game is played.
1. Barker M, Wyatt TJ, Johnson RL, Stone MH, O'Bryant HS, Poe C, Kent M. Performance factors, psychological assessment, physical characteristics, and football playing ability. J Strength Cond Res 7: 224–233, 1993.
2. Behnke AR, Feen BG, Welham WC. The specific gravity of healthy men. JAMA 118: 495–498, 1942.
3. Bemben MG, Bemben DA, Loftiss DD, Knehans AW. Creatine supplementation during resistance training in college football athletes. Med Sci Sports Exerc 33: 1667–1673, 2001.
4. Berg K, Latin RW, Baechle TR. Physical and performance characteristics of NCAA Division I Football Players. Res Q Exerc Sport 61: 395–401, 1990.
5. Bolonchuk WW, Lukaski HC. Changes in somatotype and body composition of college football players over a season. J Sports Med Phys Fitness 27: 247–252, 1987.
6. Borchers JR, Clem KL, Habash DL, Nagaraja HN, Stokley LM, Best TM. Metabolic syndrome and insulin resistance in Division 1 collegiate football players. Med Sci Sports Exerc 41: 2105–2110, 2009.
7. Buell JL, Calland D, Hanks F, Johnston B, Pester B, Sweeney R, Thorne R. Presence of metabolic syndrome in football lineman. J Athl Train 43: 608–616, 2008.
8. Byrd RJ, Smith DP, Byrd. Body composition, pulmonary function, and maximal oxygen consumption of college football players. J Sports Med Phys Fitness 16: 301–308, 1976.
9. Carey DG, Serfass RC. Comparison of the validity of two methods for assessing body composition in college football players. J Strength Cond Res 13: 106–110, 1999.
10. Clancy SP, Clarkson PM, DeCheke ME, Nosaka K, Freedson PS, Cunningham JJ, Valentine B. Effects of chromium picolinate supplementation on body composition, strength, and urinary chromium loss in football players. Inter J Sport Nutr 4: 142–153, 1994.
11. Collins MA, Millard-Stafford ML, Sparling PB, Snow TK, Rosskopf LB, Webb SA, Omer J. Evaluation of the BOD POD® for assessing body fat in collegiate football players. Med Sci Sports Exerc 31: 1350–1356, 1999.
12. Costill DL, Hoffman WM, Kehoe FM, Miller SJ, Myers WC. Maximum anaerobic power among college football players. J Sports Med Phys Fitness 8: 103–106, 1968.
13. DeMartini JK, Martschinske JL, Casa DJ, Lopez RM, Ganio MS, Walz SM, Coris EE. Physical demands of National Collegiate Athletic Association Division I football players during preseason training in the heat. J Strength Cond Res 25: 2935–2943, 2011.
14. dos Remedios KA, dos Remedios RL, Loy SF, Holland GJ, Vincent WJ, Conley LM, Heng M. Physiological and field test performance changes of community college football players over a season. J Strength Cond Res 9: 211–215, 1995.
15. Fahlman MM, Engels HJ. Mucosal IgA and URTI in American college football players: A year longitudinal study. Med Sci Sports Exerc 37: 374–380, 2005.
16. Friedl KE, Dettori JR, Hanna CJ, Patience TH, Plymate SR. Comparison of the effects of high dose testosterone and 19-nortestosterone to a replacement dose of testosterone on strength and body composition in normal men. J Steroid Biochem Mole Biol 40: 607–612, 1991.
17. Gettman LR, Storer TW, Ward RD. Fitness changes in professional football players during preseason conditioning. Phys Sports Med 15: 92–101, 1987.
18. Haskins S, Bernhardt DT, Koscik RL. Screening for insulin resistance and cardiovascular risk in collegiate football linemen. Clin J Sport Med 21: 233–236, 2011.
19. Hoffman JR, Kang J. Strength changes during an in-season resistance-training program for football. J Strength Cond Res 17: 109–114, 2003.
20. Hoffman JR, Kang J, Ratamess NA, Faigenbaum AD. Biochemical and hormonal responses during an intercollegiate football season. Med Sci Sports Exerc 37: 1237–1241, 2005.
21. Hoffman JR, Kraemer WJ, Bhasin S, Storer T, Ratamess NA, Haff GG, Willoughby DS, Rogol AD. Position stand on androgen and human growth hormone use. J Strength Cond Res 23: S1–S59, 2009.
22. Hoffman JR, Maresh CM, Newton RU, Rubin MR, French DN, Volek JS, Sutherland J, Robertson MD, Gomez AL, Ratamess NA, Kang J, Kraemer WJ. Performance, biochemical, and endocrine changes during a competitive football game. Med Sci Sports Exerc 34: 1845–1853, 2002.
23. Hoffman JR, Ratamess NA, Cooper JJ, Kang J, Chilakos A, Faigenbaum AD. Comparison of loaded and unloaded jump squat training on strength/power performance in college football players. J Strength Cond Res 19: 810–815, 2005.
24. Hoffman JR, Ratamess NA, Kang J. Performance changes during a college playing career in NCAA Division III football athletes. J Strength Cond Res 25: 2351–2357, 2011.
25. Houmard JA, Israel RG, McCammon MR, O'Brien KF, Omer J, Zamora BS. Validity of a near-infrared device for estimating body composition in a college football team. J Strength Cond Res 5: 53–59, 1991.
26. Housh TJ, Johnson GO, Marty L, Eischen G, Eischen C, Housh DJ. Isokinetic leg flexion and extension strength of university football players. J Orthop Sports Phys Ther 9: 365–369, 1988.
27. Jones K, Hunter G, Fleisis G, Escamilla R, Lemak L. The effects of compensatory acceleration on upper-body strength and power in collegiate football players. J Strength Cond Res 13: 99–105, 1999.
28. Kaiser GE, Womack JW, Green JS, Pollard B, Miller GS, Crouse SF. Morphological profiles for first-year National collegiate athletic Association Division I football players. J Strength Cond Res 22: 243–249, 2008.
29. Kraemer WJ, Torine JC, Silvestre R, French DN, Ratamess NA, Spiering BA, Hatfield DL, Vingren JL, Volek JS. Body size and composition of National Football League players. J Strength Cond Res 19: 485–489, 2005.
30. Kreider RB, Ferreira M, Greenwood M, Wilson M, Grindstaff P, Plisk SS, Reinardy J, Cantler E, Almada AL. Effects of calcium B-HMB supplementation during training on markers of catabolism, body composition, strength and sprint performance. J Exerc Physiol 3: 48–59, 2000.
31. Kreider RB, Ferreira M, Wilson M, Grindstaff P, Plisk SS, Reinhardy J, Cantler E, Almada AL. Effects of creatine supplementation on body composition, strength, and sprint performance. Med Sci Sports Exerc 30: 73–82, 1998.
32. Mayhew JL, Bemben MG, Piper FC, Ware JS, Rohrs DM, Bemben DA. Assessing bench press power in college football players: The seated shot put. J Strength Cond Res 7: 95–1100, 1993.
33. Mayhew JL, McCormick T, Levy B, Evans G. Strength norms for NCAA Division II college football players. Strength Cond J 9: 67–69, 1987.
34. Mayhew JL, Piper FC, Schwegler TM, Ball TE. Contributions of speed, agility and body composition to anaerobic power measurement in college football players. J Strength Cond Res 3: 101–106, 1989.
35. Mayhew JL, Ware JS, Bemben MG, Wilt B, Ward TE, Farris B, Juraszek J, Slovak JP. The NFL-225 Test as a measure of bench press strength in college football players. J Strength Cond Res 13: 130–134, 1999.
36. Nissen SL, Sharp RL. Effect of dietary supplements on lean mass and strength gains with resistance exercise: A meta-analysis. J Appl Physiol 94: 651–659, 2003.
37. Nordstrom A, Hogstrom G, Eriksson A, Bonnerud P, Tegner Y, Malm C. Higher muscle mass but lower gynoid fat mass in athletes using anabolic androgenic steroids. J Strength Cond Res 26: 246–250, 2012.
38. Novak LP, Hyatt RF, Alexander JF. Body composition and physiologic function of athletes. JAMA 205: 764–770, 1968.
39. Ode JJ, Pivarnek JM, Reeves MJ, Knous JL. Body mass index as a predictor of percent fat in college athletes and nonathletes. Med Sci Sports Exerc 39: 403–409, 2007.
40. Oppliger RA, Nielsen DH, Shetler AC, Crowley ET, Albright JP. Body composition of collegiate football players: Bioelectrical impedance and skinfolds compared to hydrostatic weighing. J Orthop Sports Phys Ther 15: 187–192, 1992.
41. Ransone J, Neighbors K, Lefebvre R, Chromiak JA. The effect of [beta]-hydroxy [beta]-methylbutyrate on muscular strength and body composition in collegiate football players. J Strength Cond Res 17: 34–39, 2003.
42. Reents S. Androgenic-anabolic steroids. In: Sport and Exercise Pharmacology. Champaign, IL: Human Kinetics, 2000. pp. 161–181.
43. Schmidt WD. Strength and physiological characteristics of NCAA Division III American football players. J Strength Cond Res 13: 210–213, 1999.
44. Secora CA, Latin RW, Berg KE, Noble JM. Comparison of physical and performance characteristics of NCAA Division I football players: 1987 and 2000. J Strength Cond Res 18: 286–291, 2004.
45. Seiler S, Taylor M, Diana R, Layes J, Newton P, Brown B. Assessing anaerobic power in collegiate football players. J Strength Cond Res 4: 9–15, 1990.
46. Shields CL, Whitney FE, Zomar VD. Exercise performance of professional football players. Am J Sports Med 12: 455–459, 1984.
47. Siders WA, Bolonchuk WW, Lukaski HC. Effects of participation in a collegiate sport season on body composition. J Sports Med Phys Fitness 31: 571–576, 1991.
48. Sierer SP, Battaglini CL, Mihalik JP, Shields EW, Tomasini NT. The National Football League Combine: Performance differences between drafted and nondrafted players entering the 2004 and 2005 drafts. J Strength Cond Res 22: 6–12, 2008.
49. Smith JF, Mansfield ER. Body composition prediction in university football players. Med Sci Sports Exerc 16: 398–405, 1984.
50. Snow TK, Millard-Stafford ML, Rosskopf LB. Body composition profile of NFL football players. J Strength Cond Res 12: 146–149, 1998.
51. Stodden DF, Galitski HM. Longitudinal effects of a collegiate strength and conditioning program in American football. J Strength Cond Res 24: 2300–2308, 2010.
52. Stone MH, Sanborn K, Smith LL, O'Bryant HS, Hoke T, Utter AC, Johnson RL, Boros R, Hruby J, Pierce KC, Stone ME, Garner B. Effects of in-season (5 weeks) creatine and pyruvate supplementation on anaerobic performance and body composition in American football players. Int J Sport Nutr 9: 146–165, 1999.
53. Tarnopolsky MA. Building muscle: Nutrition to maximize bulk and strength adaptations to resistance exercise training. Eur J Sport Sci 8: 67–76, 2008.
54. Thompson CW. Changes in body fat, estimated from skinfold measurements of varsity college football players during a season. Res Q 30: 87–93, 1959.
55. Tucker AM, Vogel RA, Lincoln AE, Dunn RE, Ahrensfield DC, Allen TW, Castle LW, Heyer RA, Pellman EJ, Strollo PJ, Wilson PWF, Yates AP. Prevalence of cardiovascular disease risk factors among National Football League players. JAMA 301: 2111–2119, 2009.
56. Volek JS, Kraemer WJ. Creatine supplementation: Its effect on human muscular performance and body composition. J Strength Cond Res 10: 200–210, 1996.
57. White J, Mayhew JL, Piper FC. Prediction of body composition in college football players. J Sports Med Phys Fitness 20: 317–324, 1980.
58. Wickkiser JD, Kelly JM. The body composition of a college football team. Med Sci Sports Exerc 7: 199–202, 1975.
59. Wilder N, Gilders RM, Hagerman FC, Deivert RG. The effects of a 10-week, periodized, off-season resistance-training program and creatine supplementation among collegiate football players. J Strength Cond Res 16: 343–352, 2002.
60. Wilkerson GB, Bullard JT, Bartal DW. Identification of cardiometabolic risk among collegiate football players. J Athl Train 45: 67–74, 2010.
61. Wilmore JH, Haskell WL. Body composition and endurance capacity of professional football players. J Appl Physiol 33: 546–567, 1972.
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