All 3 training programs followed a 4-day split routine, in which days 1 and 3 focused on exercises training the chest, shoulders, and triceps, and days 2 and 4 focused on exercises training the legs, back, and biceps. The eighth week of training coincided with the school's spring break, and study investigators instructed all subjects to use this as an active rest period and to not participate in any resistance-type exercise. The NP group used the same exercise intensity throughout the 15-week training program. No manipulation of training intensity was performed, and training volume differed only with the addition or subtraction of exercises that occurred during specific points of the training cycle (in conjunction with any change of exercise for the other training programs). The intensity used throughout the training program for NP was equivalent to that seen during the strength phase of PL (6-8 RM in the traditional power exercises and 3-4 RM in the Olympic movement exercises). Subjects were instructed to rest for 2-3 minutes between each set.
The PL group followed a traditional linear periodized training program (11), in which the training cycle was divided into several mesocycles. Each mesocycle differed in the intensity and volume of training. Subjects performed a 4-week preparatory/hypertrophy phase (subjects were instructed to rest for 1 minute between sets), a 6-week strength phase (subjects were instructed to rest 2-3 minutes between sets), and a 4-week power phase (subjects were instructed to rest 3 minutes between sets). The PNL group followed a nonlinear periodized training program in which the intensity and volume of exercise differed from workout to workout. Workouts would alternate from a power workout (3-5 RM in the power exercises and 1-2 RM in Olympic movement exercises, with a 3-minute rest between each set) to a hypertrophy workout (9-12 RM in the power exercises and 5-6 RM in the Olympic movement exercises, with a 1-minute rest between sets). During the last 5 weeks of training, all subjects participated in a 3-d·wk−1 speed and agility training program.
All subjects participated in strength and power assessments that were performed before the training program (PRE), after 7 weeks of training (MID), and at the end of the 15-week resistance training program (POST). Again, a 1-week break was taken after the seventh week of training for 1 week, and then training continued on from weeks 9 to 15. Because previous studies have shown that maximal strength assessment can potentiate anaerobic power performance during similar testing protocols (15), all subjects were required to perform maximal strength testing before the power assessments.
During each testing session, subjects performed a 1-repetition maximum (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 (12). Each subject performed a warm-up set using a resistance that was approximately 40-60% of his perceived maximum, and then he 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 weightlifting bar to midchest and then pressed the weight until his arms were fully extended. The squat exercise required the subject to rest an Olympic weightlifting 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. The subject then lifted the weight until his knees were extended. Previous studies have demonstrated good test-retest reliability (r > 0.97) for these strength measures in our laboratories (13,14).
Anaerobic Power Measures
Vertical jump testing performed on a force plate and a seated MBT were used to assess lower- and upper-body power, respectively. Before vertical jump testing, all subjects performed a 5-minute warm-up on a cycle ergometer. In addition, a movement-specific warm-up was then performed. Each subject was instructed to perform 5 vertical jumps at approximately 50% of their maximal effort, followed by an additional 5 jumps at approximately 75% of their maximal effort. After the warm-up, subjects then performed 5 maximal-effort vertical jumps with a countermovement. Subjects completed the 5 jumps consecutively.
During the countermovement jump testing, each subject began by standing erect on an AccuPower portable force plate (Advanced Medical Technology Inc., Watertown, Mass) with his hands on his hips. Before jumping, each subject was instructed to maximize the height of each jump while minimizing the contact time with the force plate between jumps. On a verbal signal, the subject lowered himself to a self-selected depth and immediately performed the required number of vertical jumps landing back on the force plate. For each jump, the subject's displacement of the center of mass was recorded for subsequent calculation of power data. The computer recorded force and displacement data, and a software package (AccuPower, Frappier Acceleration, Fargo, ND) was used to calculate power. Samples were collected at 200 Hz. The system was calibrated before each test. The highest power output of the 5 trials for each jump was recorded. High test-retest reliabilities (r > 0.90) have been previously reported with this testing apparatus (32).
The seated MBT was used to assess upper-body power (3). A 3-kg medicine ball was used for this test. Each subject was seated on a chair with a 90° angle at the tibiofemoral and acetabular-femoral joints. The subject would sit upright in the chair with both hands grasping the ball. The ball was maintained at chest level. Subjects were instructed to release the ball at a 45° angle. The subjects were allowed 2 practice throws. Once a subject felt comfortable with the technique, he was allowed 3 throws. Chalk was placed on the ball before each throw to provide measurement accuracy (e.g., determining where the ball landed). The throw with the greatest distance was recorded to the nearest centimeter.
To provide a subjective measure of the subjects' perceptions of the 3 different training protocols at the conclusion of the study (during the posttesting period at week 15), subjects were asked to rate 4 statements using the following 5-point rating scale: 1 = strongly disagree, 2 = disagree, 3 = no strong feeling either way, 4 = agree, and 5 = strongly agree. The first statement was, “I was able to maintain the prescribed intensity/volume of my workouts throughout the study,” and the second statement was, “I feel stronger and more powerful than I did at the start of the study.” The third statement was, “I felt that I had sufficient recovery between each workout session,” and the final statement was, “I felt that the program I was on provided me the best opportunity to increase my strength and power.”
Statistical evaluation of the data was accomplished by a repeated-measures analysis of variance. In the event of a significant F ratio, least significant difference post hoc tests were used for pairwise comparisons. A criterion alpha level of p ≤ 0.05 was used to determine statistical significance. All data are reported as mean ± SD.
Body mass, strength, and power changes can be observed in Table 2. No significant changes in body mass were seen from PRE in any group demonstrating the already high level of training-induced muscle mass that was already present in these athletes. All groups significantly increased both 1RM squat and 1RM bench press from PRE to MID. Results were still significantly greater than PRE at POST, but significant strength improvements were not seen from MID to POST in any group for either strength measure, again indicating a recovery phenomenon from the active rest period without any further tissue or neurological enhancements during the final 7-week training period.
Vertical jump significantly improved for all 3 groups between PRE and MID. However, no other changes were noted, and no between-group differences were observed. No between- or within-group changes were observed in vertical jump power. Upper-body power as assessed by the MBT revealed significant PRE to POST improvement for only PL. No between-group differences were noted.
The subjective assessment of the training programs can be observed in Table 3. No significant differences were noted between the groups in any of the subjective measures assessed. All 3 groups indicated that they felt stronger and more powerful than at the beginning of the study, and each group indicated that their specific training program provided the best opportunity for them to increase their strength and power. In addition, all groups remarked that they were able to maintain the prescribed intensity and volume of training, and that recovery between each training session was sufficient.
The results of this study indicate that the greatest gains in strength and vertical jump height during a 15-week off-season strength and conditioning program in college football players occurred within the first 7 weeks of training, and the magnitude of strength improvement did not differ between the training programs. These results likely reflect the rapid strength gains made by the subjects returning from an extended detraining or active recovery period. After the end of the regular season, all returning players (e.g., subjects) were recommended to participate in an active rest period. No formal strength and conditioning program was employed, but the subjects were encouraged to remain physically active. This phase of the yearly training cycle is designed to allow the athlete to recover from the competitive season (11), but it also provides time for the collegiate athlete (especially at the Division III level) to focus on his or her studies and to prepare for final exams. The active rest period in this study was approximately 10 weeks (it also coincided with the semester break). Although resistance training may have occurred during this period, it was not monitored, and, from anecdotal experience, it was not performed at the intensity or consistency generally seen during official team training sessions. Previous studies have demonstrated significant strength losses occurring from similar detraining periods (8). The significant strength improvements noted in the initial stage of the off-season training program likely reflect the rapid return to previous strength levels as a result of neural adaptation (6), which would have given an advantage to the groups where high force and power exposure were the greatest owing to the need for maximal recruitment of motor units. The concept of a rapid strength return after a detraining period in resistance trained subjects has been termed “muscle memory,” and this was first demonstrated in women by Staron and colleagues (27). The results observed during the initial 7 weeks of training in this study seem to support this concept even in highly trained men.
As the training program progressed, additional changes in strength may have provided a greater reflection on the effectiveness of the different training paradigms being examined. However, with another microcycle of active rest (the week of spring break) and only 7 additional weeks of training, the ability to stimulate physiological adaptations may be limited, considering the resistance training experience of these athletes. Previous research has indicated that short-term strength improvements in experienced, resistance trained athletes may be more a function of neurological change vs. change in lean tissue mass (9). A greater duration of training seems necessary to impact changes in lean tissue mass to generate greater strength improvements in these athletes (9).
Performance in upper- and lower-body power measures differed between the groups. Significant improvements in vertical jump height were seen between PRE and MID in all 3 groups. However, no additional improvements were seen in any group from MID to POST. Furthermore, vertical jump height at POST was not significantly different than PRE for any group, suggesting that lower-body power performance was reduced at that time point. The final 7 weeks of training also coincided with a 5-week plyometric, speed, and agility program that was performed during spring football. Spring football at the level of this college (Division III) is performed without any physical contact, and with a finite amount of practice times permitted. As a result, the 4-d·wk−1 off-season resistance training program was maintained throughout the 15 weeks. It is possible that the cumulative training stresses of resistance, plyometric, speed, and agility training resulted in a potential overtraining syndrome that minimized performance gains, especially in the lower body. Moore and Fry (21) have reported that the combination of off-season training and spring football practices in American college football players can result in nonfunctional overreaching, in which short-term performance decrements are seen.
A significant PRE to POST MBT improvement was seen in PL only. It is likely that the greater intensity of training used by PL in the latter stages of the training program provided a greater stimulus for power development than the nonlinear style of training used by PNL or NP. Although PNL incorporated power training from the beginning of the training program, the single session of power training for the lower body per week may not have been sufficient to provide an adequate training stimulus. The training program for NP did not provide any higher-intensity training typically seen during power cycles. Previous research has demonstrated that power performance may even decline if force outputs during training are not sufficient (22).
Research on the efficacy of periodization models has primarily investigated previously untrained or recreationally trained individuals. These studies (10,26,28-30,33) have established that manipulation of training intensity and volume provides a greater advantage for strength and performance gains than training programs that do not use any variation strategies. However, these results have been extrapolated to be efficacious for competitive strength/power athletes even though there are only 2 studies known to have actually examined periodization strategies in competitive athletes. One study investigated collegiate women's tennis players with no prior resistance training experience (18), and the other study examined collegiate football players (16). Both studies indicated that nonlinear periodization strategies were superior to either no periodization (18) or to a high-intensity single-set training program (16). This study seems to be one of the first investigations to examine the efficacy of different variations of off-season periodized or nonperiodized training programs in experienced, resistance trained, competitive strength/power athletes, but within the context that these athletes were beginning their training after a prolonged period of active rest.
Only 3 studies are known that have compared linear with nonlinear periodized training programs (2,5,26). All 3 studies examined recreational lifters exercising 3 d·wk−1 for 9-12 weeks. Although 2 studies were unable to see any significant difference in strength gains between linear, nonlinear, and nonperiodized training programs (2,5), Rhea et al. (26) have demonstrated that nonlinear training was more effective in eliciting strength gains than a traditional, linear resistance training program. The mechanisms underlying these differential findings are not clear, but differences in training volume between the studies were apparent. In the studies that have shown no significant differences between training paradigms, training volume was equated (2,5). However, Baker and colleagues (2) still used a higher volume (5 sets per exercise in the core exercises) of training than Rhea et al. (3 sets per exercise for all exercises) (26). Similar to Rhea and colleagues (26), training volumes between the groups in this study were not equated. It was believed that this represented a realistic comparison of 3 different training regimens that are used to train competitive strength/power athletes within the context of this sequence of time. Regardless, no significant between-group differences were seen. Although these results support the work of Baker et al. (2) and Buford et al. (5), it is likely that a longer duration of training is necessary to differentiate differences in training paradigms in experienced resistance trained athletes (9).
There are a variety of training paradigms that can be used to train competitive athletes; however, no specific training design has proven to be more efficacious than the other. The results of this study do not provide clear evidence to support either periodized linear, planned nonlinear, or nonperiodized training programs during a 15-week off-season resistance training program in college football players. However, it is important to place this study in the appropriate context regarding the time frame in which it was conducted. Subjects began this study after a period of active rest in which they were likely detrained. Any of the resistance training programs would likely have stimulated rapid strength improvements. In addition, this study used a single nonlinear training model. There are many possible nonlinear training sequence models that emphasize different training characteristics of strength and power that can be used to train athletes (17). Incorporation of a different nonlinear model may have resulted in different adaptations. The results do not provide a clear indication as to the most effective training program for strength and power enhancement in already trained football players. Although recovery of training-related performance was achieved after only 7 weeks of training, further gains were not observed. These data indicate that longer periods of training may be needed after a long-term active recovery period and that active recovery may need to be dramatically shortened to better optimize strength and power in previously trained football players.
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Keywords:© 2009 National Strength and Conditioning Association
American football; athletes; power; strength training