Training football athletes, like many team sports, has a multitude of factors that requires consideration of a multitude of factors in order to develop a complete performance program. Size, strength, and power are just a few of the factors that can be affected by resistance training (RT). Multiple studies have shown that the presence of size, strength, and power together can predict success in college football players (2,3,8). Sport coaches, and strength and conditioning coaches have realized the importance of these, among other performance variables and have shifted their off-season performance programs to help improve those variables. The increase of size, strength, and power in the off-season then in turn believed to translate into better on-the-field performance.
Resistance training has been shown to have many influences on changing body mass, strength, and power of athletes (8). However, in the scientific literature, there are few studies that have retrospectively examined an RT program completed by football student athletes to determine changes in body mass, strength, and power. Hoffman et al. (12–16) are one of the few that have retrospectively examined National Collegiate Athletic Association (NCAA) Division III football RT programs. However, there have been few, if any, retrospective studies done at the NCAA Division I level. Investigations concerning performance data can be found in the literature (19,20), but there seems to be a deficiency of information concerning the actual RT program as a focus of the investigation at the NCAA Division I level.
In its most basic form, designing RT programs is the manipulation of the acute program variables (17). Periodization is defined by Fleck and Kraemer (6) as “planned changes in the acute program variables … in an attempt to bring about continued and optimal fitness.” Strength and conditioning coaches have the job of manipulating the acute program variables in a periodized manner for a program in hopes of improving on-the-field performance of football players through improved body mass, strength, and power. The 2 most common models of periodization are linear periodization and nonlinear periodization (5). Linear periodization is the increase of intensity and decrease of volume over time in order to achieve peak performance at the end of the training period. Linear periodization generally focuses on 1 training goal for a “block” of time and then moves onto the next training “block,” and as an example would have 8 consecutive training sessions only focused on strength.
Nonlinear periodization was the chosen model of periodization in this study because it has the unique ability to prioritize 1 variable, but it does not neglect the others while maintaining or developing other components to a lesser extent. Nonlinear periodization is the continuous variation of increased or decreased intensity and volume throughout a training period (whether it be day by day or week by week) (5). Nonlinear periodization allows multiple factors (hypertrophy, strength, and power) to be trained over a period of time and a higher degree of flexibility towards the ever-changing schedule of a typical Division I NCAA student athlete. For example, the majority of training sessions could increased strength, but training sessions focused on increasing size or power could be administered throughout. An example would be, for every 4 strength sessions, there may be 2 hypertrophy sessions and 2 power sessions. This model still allows hypertrophy and power while prioritizing the development of strength. As mentioned previously, it is the combination of body mass, speed, and strength is highly regarded in the sport of football, (2,3,8). A nonlinear periodization model allows for the prioritization of a training goal (i.e., strength), without neglecting other important factors (i.e., hypertrophy and power).
The athletes were classified into 3 different groups based on playing year in an effort to maximize gains in mass, strength, or power. First-year players were put into group 1 and set to prioritize training for hypertrophy, second- and third-year players into group 2 to prioritize training for strength, and fourth- and fifth-year players were placed into group 3 to prioritize training for power. Miller et al. (19) showed that the greatest gains in body mass and strength in NCAA Division I football players occurred during the first 2 years of their career. The strength and conditioning staff wanted the least RT experienced athletes to focus on gaining mass (group 1), knowing some gains in strength would be made because of such a low training age. Furthermore, it was desirable for the moderately RT experienced athletes to focus on gaining strength (group 2). Häkkinen et al. (10) showed that highly resistance trained strength athletes make very insignificant gains in strength over a relatively short period of training, and may need up to 2 years to see significant gains. With this considered, the strength and conditioning staff wanted the most experienced strength trained athletes (group 3) to focus on power gains over the 10-week off-season performance program, risking efforts that would result in insignificant gains in strength.
It was hypothesized that (a) group 1 would see the greatest increase in body mass, (b) group 2 would see the greatest increase in bench press maximum and back squat maximum (strength measures), and (c) group 3 will see the largest increase in power clean maximum and maximum countermovement vertical jump height (CMVJ) (power measures).
Experimental Approach to the Problem
Seventy-two NCAA Division I American football players were assessed for body mass, predicted 1-repetition maximum (1RM) barbell bench press, predicted 1RM barbell back squat, 1RM barbell power clean, and maximum CMVJ with arm swing height by the strength and conditioning staff. The pre timepoint consisted of testing data from March, and the post timepoint consisted of testing data from August. The same testing protocols, strength and conditioning coaches, and testing schedules (bodyweight, vertical jump, and squat on Monday; power clean and bench press on Tuesday) were used. All the subjects participating in the 10-week off-season football performance program had a minimum of 5 months of RT experience. The subjects were placed into 3 different groups depending on playing year, with 1 group prioritizing hypertrophy, another prioritizing strength, and the third emphasizing power.
Data from 72 experienced resistance-trained American football players on an NCAA Division I football team were retrospectively analyzed. The study was approved by the University of Connecticut Institutional Review Board for the use of human subjects in research for retrospective data analyses of training data. The subjects were classified into 1 of 3 groups that differed by training focus for the whole summer training period. The subjects were divided into 3 groups based on eligibility status (first year, second year, …, fifth year). All first-year athletes were put in group 1, second- and third-year athletes were put in group 2, and fourth- and fifth-year athletes were put in group 3. One second-year and fifth-year athlete were placed into group 1 because he was returning from shoulder surgery. The first group trained with their prioritization on body mass gains (increase bodyweight), the second group trained with their prioritization on strength gains (increase bench press maximum and back squat maximum), and the third group trained with their prioritization on power gains (increase power clean maximum and vertical jump height).
Of the 72 subjects, 60 met the inclusion criteria (20 from each group) of having at least 4 out of 5 test numbers from pre and post testing. Reasons for not having all missed testing points were included medical restrictions or suspensions. The descriptive statistics for each group is listed in Table 1.
All subjects successfully completed both testing segments (spring and fall) and their respective assigned workouts. All the subjects successfully completed the training with no major issues or injuries.
Body mass was measured to the nearest 0.1 kg using a Tanita BWB-800 Scale (Tanita, Tokyo, Japan) on the first day of testing during each test period.
Strength and Power Measures
To measure the predicted 1RM of the bench press and back squat, the athletes tested at a weight and did as many reps as possible until fatigue or failure in technique. A modified version of Hoffman's (13) strength testing protocol was used. Only 1 attempt at the test was allowed. Then, the Epley Equation of ((0.033 × reps) × weight) + weight) was used to determine their predicted 1RM (6).
To measure the 1RM of the power clean, the athletes were given 3 separate attempts at performing the exercise for 1 repetition. The highest successful attempt was then recorded and used as the athlete's max.
Countermovement Vertical Jump Height
Countermovement vertical jump height with arm swing was measured using a Vertec (Sports Imports, Columbus, OH, USA). Hoffman et al.’s (15) testing protocol was used. Each athlete's standing vertical reach was measured before the vertical jump height test. The subjects were each allowed 3 attempts at a CMVJ with no step. The maximum height of 3 attempts was then used, and the standing reach was subtracted from it (CMVJ touch—standing vertical touch = CMVJ height).
Football Performance Program
The off-season RT program for each group was 4 d·wk−1 (Monday, Tuesday, Thursday, and Friday) for 10 weeks. Week 7 was the athlete's week home and used as active recovery with light RT and light conditioning. Also, week 10 was the athlete's post testing week. Each group trained with direct supervision from a Certified Strength and Conditioning Specialist by the National Strength and Conditioning Association. Each session started with a 15-minute full-body dynamic warm-up, then linear speed on Mondays, general conditioning on Tuesdays, lateral speed on Thursdays, and sport-specific conditioning on Friday. At the end of each workout, a Muscle Milk Collegiate shake was given to each athlete (250 kcal, 7 g of fat, 28 g of carbohydrate, and 18 g of protein).
Group 1 used a planned nonlinear periodization split program with Legs and Shoulders (LS) and Chest and Back (CB) splits (Table 2). Group 1's RT program consisted of 2 volume days (hypertrophy), 1 power day (power), and 1 strength day (strength) for the LS and CB per 2-week cycle. Over the 10-week training period, group 1 trained for hypertrophy 16 times, strength 8 times, and power 8 times. See Table 3 for specific acute program variables of the workout for group 1.
Group 2 also used a planned nonlinear periodization split program with LS and CB splits (Table 3) Group 2's RT program consisted of 1 volume day (hypertrophy), 1 power day (power), and 2 strength days (strength) for the LS and CB per 2 week cycle. Over the 10-week training period, group 2 trained for hypertrophy 8 times, strength 16 times, and power 8 times.
Group 3 also used a planned nonlinear periodization split program with upper and lower splits (see Table 3). Group 3's RT program consisted of 1 maximum effort (strength), 2 dynamic efforts (power), and 1 submaximum effort (hypertrophy) day each for the upper and lower body per 2 weeks (22). The first 2 power workouts (1 for upper and 1 for lower) were done as general strength. Over the 10-week training period, group 3 trained for hypertrophy 8 times, strength 10 times, and power 14 times. See Table 5 for specific acute program variables of the workout frequency characteristics for each training prioritization group.
Data are presented as means ± SD unless otherwise noted. All data sets met the assumptions for linear statistics or a log10 transformation was applied and then rechecked. The test-retest reliability was p ≥ 0.91. Data were analyzed using a 2-way analysis of variance with repeated measures (group × time) with a Fishers least significant difference post hoc analysis. In this investigation, significance was set at p ≤ 0.05.
The primary findings of this investigation were that group 1 saw significant increases in the bench press maximum, back squat maximum, and power clean maximum; group 2 saw significant increases in the bench press maximum, back squat maximum, and power clean maximum; and group 3 saw significant increases in only power clean maximum. No group saw significant changes in body mass or CMVJ height over the 10-week summer training period.
Unexpectedly, there were no significant changes in body mass in any group over the summer training program. Also, there were no significant differences between any of the groups in Spring or Fall. However, this might well be because 7 out of the 20 subjects from group 1 were nonresponders to the performance program with respect to increases in body mass (Table 6).
Bench Press Strength
As expected, significant increases in the bench press maximum were seen in group 1 and group 2, as shown in Table 7. Groups 1–3 were all significantly different from each other in the Spring; however, in the Fall, groups 2 and 3 were no longer statistically different.
Back Squat Strength
Also, as expected, significant increases in back squat maximum were seen in group 1 and group 2, as shown in Table 8 (p ≤ 0.05). Like the bench press maximum, groups 1–3 were all significantly different from each other in the Spring, and in the Fall, groups 2 and 3 were no longer statistically different from each other in squat performance.
Groups 1–3 saw significant increases in power clean maximum, as shown in Table 9. Group 1 was significantly different from groups 2 and 3 in the Spring and in the Fall.
Countermovement Vertical Jump
There were no significant changes the CMVJ height in any group (Table 10). Also, there were no significant differences between groups in the Spring or the Fall (p ≤ 0.05). However, 15 out of the 20 subjects from group 3 were nonresponders to the performance program for significantly increasing CMVJ height.
The primary findings of this investigation are that group 1 saw significant increases in the bench press maximum, back squat maximum, and power clean maximum; group 2 saw significant increases in bench press maximum, back squat maximum, and power clean maximum; and group 3 saw significant increases in only power clean maximum. No group saw significant changes in the body mass or CMVJ height yet changes were highly variable within each group with responders and nonresponders ultimately demonstrating the individuality of training responses in previously trained American football players and the potential need for individualized training programs beyond experienced-based grouping.
Unexpectedly, group 1 saw no significant increases in body mass over the 10-week summer program. This supports multiple (12,15,16) studies with RT in NCAA football athletes during the off-season. They (12,16) also showed that between years there were no significant differences, but there was from a player's first year to their fourth or fifth year. The findings of this investigation also support multiple RT studies done with strength athletes that saw no significant increases in body mass within a year (1,18). In our study, the lack of group mean changes within a 10-week training period seems to be realistic with obvious individual variability existing because of the differential adaptive potential of each player. The findings from the studies with football players in the off-season and recreationally resistance trained athletes leads the authors to believe that increases in body mass cannot be routinely expected in resistance trained athletes over a 10-week training period. Moritani and DeVries (21) classically showed that initial strength gains could be from neurological adaptations, not muscular changes. With that noted, even group 1's athletes did not have a training age of zero, which would lead us to believe that any increases in body mass paired with strength increases would lead to an increase in total body muscle cross-sectional area; however, no body composition data were taken, so that cannot be validated and may be an important aspect for future studies to evaluate.
As expected, groups 1 and 2 saw significant increases in both strength measures, maximum bench press and back squat. These results also support previous work by Hoffman et al. (12,16) studies, which reported significant strength increases during off-season football programs. Fleck and Kraemer (7) mention that untrained subjects typically see the greatest increase in strength, which could explain why group 1 observed significant increases in strength, despite prioritizing hypertrophy. Group 1 was not untrained but had about 1.5 years less experience, on average, in a structured, professionally run strength and conditioning program when compared with Group 2.
Group 3 did not see significant changes in either of the strength measures. This could be explained by the higher training age and experience of group 3 and the prioritization on power instead of strength. Häkkinen et al. (9,10) showed in 2 separate studies that in elite, strength trained athletes it becomes a much greater challenge to increase strength and hypertrophy. The athletes in group 3 have on average 4.4 years of experience in a structured, periodized, regimented performance program with dedicated, experienced strength and conditioning and sports medicine professionals. Relative to team-sport standards, one may call the athletes in group 3 elite, strength trained athletes, which would then put them in the same category as that of the subjects in Häkkinen et al.’s studies. Possible barriers that lead to no significant increases in strength measures in group 3 could be (a) the non-RT components of the football performance program, specifically conditioning, (b) the limited training time because of restraints on the NCAA athletes (8 h·wk−1 of training in the off-season), (c) malnutrition relative to an elite, strength trained Division I football player, and (d) the acute program variables of the RT program focusing on power over strength.
All 3 groups saw significant increases in power clean maximum. One of Hoffman et al.’s (12) studies of NCAA football off-season RT programs had 2 groups, 1 prioritizing Olympic lifting and the other prioritizing traditional power lifting. Bench press in the Olympic lifting group was seen as an accessory exercise, whereas the bench press was seen as a major exercise in the traditional power lifting group. In this current investigation, part of group 3's prioritization of power included a greater increase in frequency, volume, and exercise variety of Olympic style lifts (power clean, hang snatch, hang clean, and clean pulls) with less of a focus on traditional barbell back squat and barbell bench press. In Hoffman et al.’s (12) study, the group that put a higher priority on bench press saw greater increases in bench press maximum, paralleling the current investigation where group 3 put less of a priority on the strength measures and more on the power measures, and saw a greater increase in the power clean maximum. These 2 examples practically show the definition of testing specificity, which “gains in strength are in part specific to the type of muscle action used in training,” and “… strength gains is caused by neural adaptations resulting in the ability to recruit the muscles to perform a particular type of muscle action” (6).
As with body mass, significant increases in CMVJ were not observed over the 10-week summer training programs, even in Group 3, which prioritized power. Nevertheless, individual variations were found across a distribution that included responders and nonresponders, reaffirming the importance of training individualization. These findings are in agreement with those of other RT studies done with collegiate football RT studies (12,15,16,23). Hoffman et al. (15) mention that speed, agility, and power measures are difficult to significantly change, especially within a year, even more so within a 10-week summer training program in which prior adaptations already exist. The findings of this investigation related to CMVJ, the findings from studies listed previously in this paragraph that relate to collegiate football, and the literature from other sports that require conditioning (24) lead the authors to believe that the need for conditioning hinders the ability to significantly increase CMVJ within a summer training program. If a strength and conditioning coach determines that the CMVJ is a priority, then there will have to be a paradigm shift in the way team sports are conditioned or the way team sports program for increases in CMVJ. As found in this investigation and others, back squat maximums increase significantly, which would account for an increase in the force part component of the power equation (power = force × velocity) (12,16). However, in those same studies, the CMVJ is not significantly increasing, which we believe is because of the conditioning component of the performance program. Discussing conditioning required by team sports and the physiological adaptations and stresses from it is beyond the scope of this investigation, but it can be further investigated in another study.
An interesting finding of this investigation was the significant difference of the strength measures (bench press maximum and back squat maximum) between groups 2 and 3 in Spring, but then no significant difference in Fall (after the off season performance program). This finding seems to statistically illustrate group 2 “maturing” into group 3 after the summer performance program. This program design of having 3 different groups based on eligibility was in its first iteration, so no data could be analyzed to see if 1 group “maturing” into another was a phenomenon or a random finding. Studies in RT progressions and even more so in their individualization are just starting to evolve in the sport of American football with much more to do to better understand off season training program progressions and periodization models.
Examining this 1 approach used to train student athletes in a summer training period can provide some insights into training program progression models. Individual responses to training still can vary from the group response and point to the potential need for individual responses changes in the RT and conditioning programs that might represent the future for conditioning in this sport and others. We feel that this study helps to continue to “bridge the gap” between the science community and the practical world of strength and conditioning by examining this one now popular summer off-season component of the yearly training cycle that was implemented with a team in a collegiate strength and conditioning setting.
Prioritization on strength (without neglecting other areas) appears to have the best overall effect on the RT portion of an off-season football performance program. A nonlinear periodization model allows just that, prioritization of 1 training goal without neglecting others. Strength and Conditioning coaches in the collegiate realm should use a nonlinear periodization model with a prioritization on strength because it provides the best “bang for your buck,” without ignoring other factors (e.g., power, volume). The NCAA limits the amount of hours student athletes are allowed to train, so the strength and conditioning coach must attempt to make the most time efficient, yet appropriate program as possible. Short-term goals to significantly increase the body mass and CMVJ were unable to be reached; however, the short-term goals of the strength measures (bench press maximum and back squat maximum) and power clean maximum were able to be attained with the RT programs for group 1 and group 2. Training very experienced collegiate athletes (fourth- and fifth-year players) may need a paradigm shift away from the typical training of the collegiate realm toward the training of Olympic and power lifting athletes to see significant increases in performance variables.
The authors would like to thank all the Coaches and student-athletes from the football team at the University of Connecticut who participated in the project. They also thank Coach Drew Wilson now at the University of Maryland for his help in the project. The authors have no conflict of interests to declare and no grant funding was used to support this study.
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Keywords:Copyright © 2014 by the National Strength & Conditioning Association.
resistance exercise; collegiate athletics; non-linear periodization