The importance of strength, power, and speed for American football players has been well documented at various levels of competition (2,3,6). These performance variables have been shown to differentiate starters from nonstarters and differentiate between different levels of competition within NCAA Division I football (2,3,6). As such, the primary focus for most collegiate strength and conditioning programs is directed at improving these performance variables to maximize the ability of each athlete to contribute to the success of the team. Although there have been a number of studies directed at the efficacy of various exercise programs used to train competitive athletes (12,15,18,23,28), much of this research does not account for training experience as a factor determining program efficacy. In fact, our basic understanding on the ability of collegiate athletes to make performance changes throughout their career is limited. Much of our knowledge may be based upon extrapolation from cross-sectional studies that have demonstrated that novice weightlifters will experience greater gains than experienced lifters (8,14,17). This has been the basis of the principle of diminishing returns (10,24) that suggests as athletes continue to train their rate of improvement decreases. However, there are only a limited number of studies that have examined longitudinal performance changes in competitive athletes.
Hunter et al. (22) examined male college basketball players and reported a 24 and 32% increase in bench press and squat strength, respectively, during their 4-year intercollegiate basketball career. Significant improvements in both the bench press and squat exercise were observed during each year of the athlete's career. Improvements in upper-body strength were consistent from year to year, but nearly half of the strength gains (15%) made in the squat exercise occurred within the first year of training. Subsequent years showed lower, but consistent improvements. Another study examining female intercollegiate basketball players reported 20-25% improvements in strength measures in these athletes from their freshman to senior years (27). The greatest improvements occurred during the early part of the athlete's career. Miller et al. (26) examining NCAA Division I football players reported that most strength and power development occurs with the first year of competition. Recently, Stodden and Galitski (29) examined longitudinal changes in anthropometric and performance variables in NCAA Division I football players and confirmed that although performance improvements can occur throughout the athlete's career, the greatest performance gains are generally seen during their first year of intercollegiate competition.
The studies to date that have examined longitudinal anthropometric and performance changes have all been conducted on Division I athletes. These athletes are generally larger, stronger, more powerful, and faster than lower level (Division II and III) NCAA athletes (6). In addition, these players are generally awarded scholarships to play at this level. These scholarships are based upon a high level of play demonstrated during the athlete's scholastic career. Thus, one could assume that these athletes in general possessed a greater athletic performance skill set than athletes participating at lower division (NCAA Division II and III) programs. It is also possible that these lower skilled athletes may have a greater potential for anthropometric and performance changes during their collegiate careers. Therefore, it was the purpose of this study to compare anthropometric and athletic performance variables during the playing career of Division III college football players.
Experimental Approach to the Problem
Two hundred and eighty-nine NCAA Division III college football players were assessed for height, body mass, body composition, 1-repetition maximum (1RM) bench press, 1RM squat, vertical jump height (VJ), vertical jump peak, and mean power, 40-yd sprint speed, agility, and line drill (LD) over an 8-year period. All testing occurred at the beginning of summer training camp in each of the seasons studied. Data from 8 years of testing were combined. For most athletes, this occurred over 4 seasons; however, for those athletes that red shirted (practiced for an entire season but did not play), this occurred for 5 seasons. All testing was performed in a single day by the same coaching staff. The order of testing began with anthropometric measures (height, body mass, body composition), followed by strength, VJ, speed, and agility. These tests were performed in the morning. The LD was performed in the afternoon after a 3-hour lunch break. Comparison of performance changes over a career was analyzed by initially combining all positions, then by examining backs (running backs, quarterbacks, wide receivers, and defensive backs) only, and linemen (centers, guards, tackles, defensive tackles, defensive ends, linebackers, and tight ends) only.
Data from 289 American football players of a NCAA Division III football team were analyzed. One hundred and forty-nine of these players were backs, and 140 were linemen. Data were collected during summer testing that occurred when athletes reported to the training camp for each competitive season. The data collected and analyzed were consistent with the athlete's informed consent used as part of their sport requirements consistent with the institution's policies of the College's Institutional Review Board for Use of Human Subjects in Research. Of the 289 players tested, 54 played and were tested for at least 4 years at the institution. Some of the athletes tested were already competing in the program when assessments began; thus, they may have played 4 years at the institution but data on their previous season(s) of competition were not available. Some of the athletes did not use all their years of eligibility (did not play 4 years because of injury or other personnel reasons) or other players transferred to the program after beginning their college football career at a different institution. The data from these players were used for the years they competed at this institution. Data for athletes that played a fifth year (n = 28) were included as well. These athletes were those that were ‘red shirted.’ This is a term used by the NCAA to describe an athlete who practices but does not play in a game. This allows the athlete to maintain an extra year of eligibility but gain valuable practice experience. Midway through the years of this study, the NCAA eliminated the general red-shirt rule and installed a medical red shirt only, meaning that only if an injury resulted in an athlete missing extensive playing time, was that player granted an extra year of eligibility. All assessments were conducted by the same study personnel over the 8-year experimental period. During the 8-year experimental period, the team was 45-34 and won a single conference championship and participated in 2 postseason events (an East Coast Athletic Conference Bowl game and NCAA playoffs).
Anthropometric assessments included height, body mass, and body fat percentage. Body mass was measured to the nearest 0.1 kg. Body fat percentage was estimated from skinfold caliper measures using the method of Durnin and Wormersely (5). The same research assistant performed all of the skinfold analysis assessments using standardized procedures.
During each testing session, players performed a 1RM strength test on the bench press and squat exercises to measure upper- and lower-body strength, respectively. The 1RM tests were conducted as previously described (11). Each athlete performed a warm-up set using a resistance that was approximately 40-60% of his perceived maximum and then performed 3-4 subsequent attempts to determine the 1RM. A 3- to 5-minute rest period was provided between each lift. No bouncing was permitted, because this would have artificially inflated strength results. Bench press testing was performed in the standard supine position: The subject lowered an Olympic weight lifting bar to midchest level and then pressed the weight upward until his elbows were fully extended. The squat exercise required a subject to rest an Olympic weight lifting bar across the trapezius at a self-chosen location. The squat was performed to the parallel position, which was achieved when the greater trochanter of the femur was lowered to the same level as the knee. A research assistant located laterally to the athlete strictly monitored the exercise range of motion. The athlete then lifted the weight until his knees were extended. Previous studies have demonstrated good test-retest reliabilities (r > 0.97) for these strength measures (13,14).
Vertical Jump Height and Power
Vertical jump height was measured using a Vertec™ (Sports Imports, Columbus, OH, USA). Before testing, each athlete's standing vertical reach height was determined. Vertical jump height was calculated by subtracting the standing reach height from the jump height after a countermovement vertical jump. Subjects performed 3 attempts. The highest VJ achieved was recorded. To determine power output VJs were converted to watts using the Harman et al. formula (9). Both peak and mean power outputs were determined.
Speed and Agility Measures
Speed was determined by a timed 40-yd (36.6-m) sprint. Sprint times were assessed using hand held stopwatches. Timing began on the player's movement out of a 3-point stance. Agility was determined by both a T test and Proagility test. The T test required the player to sprint in a straight line from a 3-point stance to a cone 9 m away. At that point, the athlete side shuffled to the left, without crossing his feet, to another cone 4.5 m away. As he touched the cone, he side shuffled to the right to a third cone 9 m away. The player then side shuffled back to the middle cone and back pedaled to the starting position. The protocol for the Proagility test was conducted as previously described (11). Three lines with 5 yd (4.5 m) between each line were marked on the field. The player straddled a middle line and sprinted to 1 line (4.5 m away) and touched the line. He then changed direction and sprinted to the far opposite line (9 m away), touched the line with the same hand used to touch the first line, reversed the direction, and returned to the starting point. All players were instructed to sprint through the finish line.
All speed and agility tests were performed on an Astroturf field, and times were measured using a hand-held stopwatch. The timer began upon the athlete's initial movement and stopped as the athlete crossed the finish line. The same investigators conducted all speed and agility tests during the 8 years of assessments. Each player performed 3 maximal attempts for all speed and agility tests, and the fastest time was recorded.
To assess anaerobic conditioning level all players performed 3 LDs. The LD was also performed on an Astroturf field. On command players sprinted from the end zone to the 10-yd line (9.1 m) and back, then sprint to the 20-yd line (18.3 m) and back, sprinted to the 30-yd line (27.4 m) and back and then sprinted to the 40-yd line (36.6 m) and back. All sprints were performed consecutively (total of 200 yd [182.9 m]). Athletes performed a total of 3 LDs with 2 minutes of rest between each sprint. Peak time of the 3 sprints and a fatigue rate (best time/worst time) was determined.
One-way analysis of variance was used to compare anthropometric and performance improvements from the athletes first year of competition to their final year of competition. In the event of a significant F ratio, least significant difference post hoc tests were used for pairwise comparisons. These analyses were done for athletes of all positions combined and for backs and linemen. A criterion alpha level of p ≤ 0.05 was used to determine statistical significance. All data are reported as mean ± SD.
Anthropometric changes during the athletes' playing career are shown in Table 1. When collapsed across position, no significant changes were seen in height or body fat percent during the athlete's collegiate playing career. A significant (p = 0.011) increase in body mass was seen between the athlete's fourth year of competition to their freshman year. Athletes playing a fifth season (red-shirt year) were significantly heavier than their first (p = 0.005) and second (p = 0.023) seasons. Examination of backs and linemen revealed no change in height or body fat percent from their first year of competition. Backs experienced a significant gain (p = 0.049) in body mass between their first and second years of eligibility. These players were able to maintain this significant gain in mass through their playing career, but no significant changes were observed between other years of competition. Significant gains (p = 0.017) in body mass were observed in linemen between their first and fourth years only.
Strength and power changes during the athlete's collegiate football playing career are shown in Table 2. A significant increase in bench press strength was seen between the first and second seasons (p = 0.000) for all players combined and was consistent with backs (p = 0.001) and linemen (p = 0.003) as well. Upper-body strength continued to significantly increase between the second and third years (p = 0.002) for all positions combined. This same finding was noted for linemen (p = 0.003) but not backs (p = 0.233). No additional upper-body strength improvements were observed between the third and fourth years of eligibility for any position; however, bench press strength for those athletes that red shirted and played a fifth year was significantly greater than years 3 (p = 0.000) and 4 (p = 0.001). When examined by position, following the improvements noted between the first and second seasons, other significant improvement in bench press strength for both backs and linemen were seen between years 2 and 5 (p = 0.014 and p = 0.000, respectively) and years 3 and 5 (p = 0.051 and p = 0.008, respectively).
Squat 1RM was significantly increased (p = 0.000) for all players across position between the first and second seasons of their career. Squat strength continued to significantly increase between the second and third seasons (p = 0.000) but reached a plateau between years 3 and 4 (p = 0.258). Strength improvements were observed by those athletes playing a fifth season (p = 0.001 between years 4 and 5). The 1RM squat for fifth-year seniors was significantly greater than any other year of competition. When examined by position, backs experienced significant strength gains only between the first and second seasons (p = 0.000), no other significant strength improvements were noted between other seasons. Linemen significantly improved their squat strength between years 1 and 2 (p = 0.016), years 2 and 3 (p = 0.000), no changes were observed between years 3 and 4 (p = 0.110), but 1RM squat strength for those athletes playing a fifth year was significantly greater than for those at any other competitive year.
When examined across all positions and backs specifically, VJ was significantly greater during the fourth year of competition compared to the previous 3 years of play. However, no significant difference was seen between the fifth year of competition and any other competitive season. A significant difference in VJ in linemen was seen between years 1 and 4 (p = 0.004) and years 1 and 5 (p = 0.030), and no other significant differences were noted. Vertical jump power (both peak and mean) was significantly increased from years 1 and 2 for all positions combined. Both peak and mean vertical jump power outputs were significantly higher during year 4 than during any previous season of competition. No other significant power performance changes were noted across positions. When examining power changes specific to position, the response for backs mimicked that reported for all positions combined; however, for linemen, significant increases in both peak and mean power were noted between years 1 and 3 (p = 0.002 and p = 0.004, respectively). Peak power output during year 4 was significantly greater than during years 1 (p = 0.000), 2 (p = 0.000), and 3 (p = 0.030), whereas mean power output during the fourth year was significantly greater than years 1 (p = 0.000) and 2 (p = 0.001) only. No further improvement in either peak or mean jump power outputs were observed in linemen participating in a fifth year of competition.
Speed, agility, and anaerobic conditioning changes are depicted in Table 3. When examined across position, no significant changes in speed were noted during the athletes' collegiate football playing career. However, significant improvements in speed were seen between years 1 and 3 (p = 0.015) in backs, whereas a trend toward improvement was observed in linemen in that same comparison (p = 0.081). Linemen that competed a fifth year were significantly faster than their first (p = 0.023) and second (p = 0.041) years of competition. Similar to speed, only limited improvements were noted. When comparing all positions, significant decreases in time for the T drill were noted only between the first and third seasons (p = 0.054), whereas no improvements were noted in the proagility drill. Position comparisons revealed no significant improvements in the T drill for backs but significant decreases in time for the proagility drill between years 1 and 3 (p = 0.038) and years 2 and 4 (p = 0.044). In contrast, linemen exhibited no changes in performance in the proagility run, but a significant decrease in time for the T drill was observed between years 1 and 3 (p = 0.026). This performance improvement was maintained throughout the remainder of the linemen's career without any further change.
No differences were noted during the athletes' collegiate playing career in the LD for any position or when positions were combined. Analysis of the fatigue index for backs and linemen combined revealed a significant improvement between years 1 and 2 (p = 0.000). The fatigue index during the fourth year of eligibility was significantly greater than any other competitive year, and continued to improve for athletes participating in a fifth year of competition (p = 0.028). Fatigue rates for backs was significantly improved between years 1 and 2 (p = 0.003) and remained steady through the fourth year of competition. Backs that played a fifth year of eligibility had a significantly greater fatigue rate than those who played any other competitive year. Significant improvements in the fatigue rate for linemen were seen between years 1 and 3 (p = 0.017) and between years 3 and 4 (p = 0.028). No other significant improvements were noted.
Results of this study indicate that during the career of NCAA Division III football players strength and power gains are achieved throughout their playing career. Strength gains appear to be much greater in the lower body compared to the increases seen in the upper body. These strength changes were consistent between backs and linemen. Improvements in speed and agility were more limited in magnitude and appeared to occur during the latter stages of the athletes' playing career. Although peak time for the LD (a measure of anaerobic conditioning) did not change throughout the playing career of these athletes, a greater effort toward improved conditioning (reflected by an improved fatigue rate) appeared to occur for each subsequent season.
The strength levels of the athletes examined in this study were similar to both 1RM bench press and 1RM squat values previously reported for NCAA Division I (25) and Division II (7) football players. The increases in strength seen during the course of the athletes' collegiate career (31.0% improvement in the 1RM bench press and 36.0% increase in squat strength) were similar to those reported for NCAA Division I football players (26), but slightly greater (31 vs. 24%) than that reported for Division I Men's college basketball (22). Strength improvements were observed throughout the athlete's career. However, the pattern of strength gains was interesting. Initial gains in strength were similar between the first and second (7.9 and 9.1% strength increase in the bench press and squat exercises, respectively) and second and third (6.7 and 8.8% strength increase in the bench press and squat exercises, respectively) years of competition. Although the rate of strength increases were reduced between the third and fourth years (3.1% in the 1RM bench press and 3.2% in the 1RM squat), for athletes that red shirted and played a fifth year, the percent strength gains achieved between the fourth and fifth years were the highest observed for the athletes career (13.3% strength gain noted in the 1RM bench press and a 14.8% gain in 1RM squat). This response pattern was different from that observed by other longitudinal investigations on collegiate football and basketball players. Miller et al. (26) reported that the majority of the strength gains observed in their investigation on Division I football players occurred during the first 2 years of competition. This was similar to the responses observed in women's college basketball (27). However, Hunter et al. (22) reported that increases in 1RM bench press were consistent during 4 years of competition in men's Division I college basketball but that 50% of the strength gains seen in the squat exercise occurred between the first and second years of the athlete's career.
This biphasic response in strength improvement is difficult to explain. Differences in the rate of improvement are likely related to the experience level of the athlete. Athletes at the beginning of their career would be expected to make larger gains in strength compared to the latter stages of their career. Häkkinen et al. (8) have suggested that experienced, resistance-trained athletes may need up to 2 years to achieve significant strength improvements. However, this still would not explain the nearly twofold greater improvement in strength observed during the off-season of the last competitive year compared to the first 2 years of training. Although speculative, the second peak in strength gains observed in the last year of competition may be a reflection of the use of performance enhancing drugs. In NCAA Division III football, drug testing does not occur until the playoffs, so any team not making the postseason will not be tested. During this 8-year study, the team made the NCAA playoffs on 1 occasion. No positive drug tests occurred during that postseason, but drug tests took place nearly 3.5-4 months after the preseason assessments, which is potentially enough time for the drugs to clear from the system (16). Anecdotal reports from team members do suggest that a number of fifth-year seniors did experiment with performance enhancing drugs before the start of their last competitive season. However, the same was also said for several fourth-year seniors as well.
The results of this study indicate that speed, agility, and vertical jump changes are more difficult to achieve during the career of these athletes. Vertical jump power was significantly greater at year 2 compared to the athlete's initial year of competition and significantly greater at year 4 vs. all previous seasons. This appears to be a function of increases in both body mass and VJ. Only during the fourth year of competition did VJ increase significantly compared to the previous 3 competitive seasons. The results of this study indicate that VJ, speed, and agility are fitness components that are more difficult to improve during an athletes' career. This is consistent with other longitudinal studies examining collegiate football and basketball players (22,26,27). It is likely that these performance variables are a function of the genetic factors that impact the athletic potential of all athletes. Specifically, muscle fiber type and anthropometric measures such as height, limb length, and muscle insertion points are quite variable and are genetically determined. Although fiber subtypes can be transformed through training (1,25), the ability to stimulate fiber type changes are not an expected adaptation of prolonged training programs (4).
An additional consideration regarding vertical jump, speed, and agility performance changes is the effectiveness of the off-season conditioning programs. Of great importance in this study is that players followed the same off-season conditioning program during the 8-year period. The program used during the 8 years of assessment has been published in a number of other studies examining different training paradigms (12,18) or nutritional supplements (19-21). The training programs were consistent for incorporating speed, agility, and plyometric exercises. In addition, a combination of Olympic exercises, power lifting, and ballistic training were incorporated into the periodized resistance training program. Previous studies from our laboratory examining the effectiveness of these different training paradigms have indicated that significant speed, agility, and power performance changes in competitive athletes are difficult to achieve during a single off-season training program (12,17). This study further suggests that significant changes can be made during an athlete's career but that these changes are slow and may only become statistically significant after 3-4 years of training.
No changes were seen in the time for the LD during the athlete's collegiate playing career. Significant improvements in the fatigue rate observed between the first and second years of play reflect the adherence to the summer conditioning program that the athletes were not privy before their first year. Significant improvements in fatigue rate during the fourth and fifth years of competition may reflect the added emphasis that the players gave in off-season preparation during their last season of competition.
Appropriately designed resistance training programs do appear to result in significant strength and body mass gains throughout the football career of NCAA Division III athletes. Changes in agility, speed, and vertical jump observed during an athlete's collegiate career indicate that these performance variables are more difficult to alter. However, the approximate 0.2 seconds and 5-cm improvements in 40-yd sprint time and VJ seen in this study suggest that athletes can improve speed and jumping ability but with limitations. That is, collegiate football players can become faster and jump higher, but the ability to transform a slow athlete to a fast one appears to be limited.
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