Strength training periodization theory is in part based on biological studies of the general adaptation syndrome proposed by Selye (29). Periodization involves systematic training variation accomplished by alternating training volume and intensity, with the objective of optimizing performance and recovery (13,26). Strength training periodization is used for specifically training athletes (5,14). However, use of periodization is not exclusively for elite athletes. Periodization has been applied successfully in various populations with different levels of physical fitness and training experience and for rehabilitation purposes (1,7,8).
The classical method of linear periodization (LP) divides typical strength training into different periods or cycles: macrocycles (9-12 months), mesocycles (3-4 months), and microcycles (1-4 weeks), increasing intensity gradually while training volume is reduced between and within these cycles as training progresses (27). Another form of periodization used is undulating or nonlinear, previously described by Poliquin (25), which is characterized by more frequent alterations in intensity and volume (21). This model was adapted by Rhea et al. (27) receiving the name of daily undulating periodization (DUP), in which modifications in volume and intensity are made daily (12).
Several studies have focused on comparing periodized vs. nonperiodized programs and showed the superiority of periodized training for increasing strength (15,18,22). To date, one study by Rhea et al. (27) was found, which compared linear vs. DUP (nonlinear) periodization for strength gains in previously trained individuals, and results showed that DUP had a higher efficiency in maximizing strength in relation to classical LP. In this study, the authors programmed LP with microcycles lasting 4 weeks each.
Many combinations of training duration, volume, and intensity can be used in an attempt to maximize strength gains. As Rhea et al. (27) stated, more research needs to be done to determine what specific combination of variables will elicit maximum gains in strength. Thus, it is necessary to compare different periodization models to evaluate the best periodization model for strength gains in elite athletes, trained, and sedentary individuals. Typically, 3 training zones (4-6, 8-10, and 12-15 repetition maximum [RM]) have been used on a weekly basis in studies comparing nonlinear periodization with nonvaried programs (18,21,22) and with LP programs (27). However, in the present study, only 2 training intensities and volumes were performed in the same week of the DUP program. This was done to examine the efficacy of less frequent changes in volume and intensity in an DUP program. Therefore, the goal of the present study was to compare the efficacy of LP with microcycles lasting 1 week and DUP with 2 training volumes and intensities in the same week of training for maximal strength gains and body composition changes, in experienced weight-trained men.
Experimental Approach to the Problem
The main objective of the present study was to compare the strength gains between LP and DUP weight training programs over 12 weeks of training. In the present study, the volume and intensity of both periodization programs were equated, as recommended by Rhea et al. (27,28). Only one study (27) was found, which compared LP and DUP for strength gains in previously trained individuals. In this previous study by Rhea et al. (27), microcycles lasted 4 weeks in the LP program. The main difference between the Rhea et al. (27) study and the present study is that microcycles in the present study for the LP program lasted 1 week, guaranteeing more load variation in the program. Thus, the study compared strength gains between DUP and LP programs with microcycles lasting 1 week in the LP program. The dependent variables in the present study were strength and body composition and the independent variables were the 2 periodization models (LP and DUP). Tests for body composition and maximum strength were performed pre training (T1), after 8 weeks of training (T2), and after 12 weeks of training (T3).
Forty men aged 18-25 were recruited and randomly assigned into 2 groups: (a) a group that performed 12 weeks of LP strength training (n = 20) and (b) a group that performed 12 weeks of DUP strength training (n = 20). The inclusion criteria were a minimum 1-year experience of strength training and on questioning no use of ergogenic supplements. According to the American College of Sports Medicine (ACSM) (1), the individuals were considered “trained.” Training experience and habitual physical activity were determined by the use of a questionnaire and interview. In the 12 months prior to the study, all subjects had strength trained at least 4 times per week using 3 sets of 8-10 RM for the exercises performed. If the subjects missed 2 training sessions, they were removed from the study. The training period for all subjects started after July vacation, in the beginning of August, when university classes began. All participants signed an informed consent document approved by the “Universidade Federal de São Carlos” Research Ethics Committee for Human Use (Protocol No. 114/2006). The present research procedures were in accordance with guidelines for use of human subjects set forth by the ACSM. The 2 training groups showed no significant differences for the pretraining characteristics presented in Table 1 (p ≤ 0.05).
Body composition was determined using skinfold thickness with a Lange skinfold caliper. The equation of Jackson and Pollock (16) for men (18 to 61 years old) was used to estimate body density. In this equation, the sum of chest, abdominal, and thigh skinfolds is used. The same investigators performed all tests. Body fat percentage was estimated by Siri's (30) equation. Body fat percentage was used to estimate fat mass (kilogram) and fat-free mass (kilogram).
One RM tests of the free weight barbell bench press, leg press 45° (Cybex International, Medway, MA, USA), and standing arm curl were used to determine maximal strength. The 1 RM tests were performed in the same day with a minimal 10 minutes of rest interval between the tests in the following order: bench press, leg press 45°, and arm curl. After a general warm-up (10 minutes of low-intensity treadmill running), subjects performed 8 repetitions with an estimated 50% of 1 RM of the exercise being tested using each subject's previous training experience, and after 1 minute of rest, 3 repetitions with an estimated 70% of 1 RM were performed. After 3 minutes, subsequent trials were performed for 1 repetition with progressively heavier weights until the 1 RM was determined within 3 attempts, using 3- to 5-minute rest periods between trials (23). The range of motion and exercise technique were standardized according to the descriptions of Brown and Weir (4). To make sure the pretraining 1 RMs were stable prior to beginning training, the pretraining 1 RMs were determined on 3 separate days with 2 days between them. A high interclass correlation was found between the second and the third 1 RM trials (bench press r = 0.99, leg press 45° r = 0.99, and arm curl r = 0.99). The greatest 1 RM determined from the last 2 trials was used as the baseline measure. Student's t-tests showed no significant differences between the LP and DUP groups (p ≤ 0.05), for pretraining maximal strength values in any of the 3 exercises tested.
Participants trained 4 times per week, and each training session lasted around 50 minutes. The average duration for complete repetitions was of 3-4 seconds (both concentric and eccentric phases of the movement). Training was divided into A (Monday and Thursday, days 1 and 3) and B (Tuesday and Friday, days 2 and 4) in accordance with the recommendations of ACSM (1) for advanced lifters to train 4-6 days per week (Table 2). For both groups, abdominal crunches (3-4 sets of 20-30 repetitions in 2 sessions per week) were included. The exercise order was strictly followed by both groups, as presented in Table 2. For all listed exercises, 3 sets until voluntary concentric failure were performed; and the number of repetitions and rest intervals between sets and exercises were followed according to the intensity prescribed for a training session. The rest intervals between sets and exercises were 12 RM, 45 seconds; 10 RM, 1 minute; 8 RM, 1 minute and 20 seconds; and 6 RM, 1 minute and 40 seconds. All sessions were supervised individually by an experienced strength training professional.
Volume and intensity were modified differently for each group (Table 3). However, mean volume (total repetitions performed) and intensity over the entire 12 weeks of training were equal for the LP and DUP groups. The difference between groups was the time and sequence in the training volume and intensity.
In the LP program, training intensity was increased each microcycle (1 week) and the volume was decreased. In the present study, LP group followed the volume and intensity pattern as presented in Table 3, each microcycle lasted 1 week. In the first week, participants performed 3 sets of 12 RM; in the second week, 3 sets of 10 RM; in the third week, 3 sets of 8 RM; and in the fourth week, 3 sets of 6 RM. This pattern of volume and intensity was repeated 3 times in the 12 weeks of training.
Different from the LP program, in which the intensity and volume changed each week, in the DUP, program intensity was modified in the same week, so that participants trained with different 2 different volumes and intensities in the same microcycle. For the DUP program in weeks 1, 3, 5, 7, 9, and 11, participants trained on days 1 and 2 with 3 sets of 12 RM and on days 3 and 4 with 3 sets of 10 RM. In weeks 2, 4, 6, 8, 10, and 12, participants trained on days 1 and 2 with 3 sets of 8 RM and on days 3 and 4 with 3 sets of 6 RM (Table 3). For LP and DUP groups, a recovery week occurred between the fifth and sixth week in which the subjects performed only 2 training sessions in this week (Monday, training session A, and Friday, training session B), with 2 sets of 12 RM in each exercise. Periodizations applied were based on previous studies published in the literature (3,18,21,28).
All data are presented as mean ± SEM. The Kolmogorov-Smirnov normality test and a homoscedasticity test (Bartlett criterion) were used to test the normal distribution of the data. All variables presented a normal distribution and homoscedasticity, so a repeated measures analysis of variance (ANOVA) (2 groups by 3 time points) was used to test for significant differences between training groups. The Tukey post hoc test was applied where indicated by an ANOVA. To test for significant differences between groups in pretraining variables, Student's t-test were used. In all calculations, the alpha level was set at p ≤ 0.05. Test-retest reliability for maximal strength was determined using an intraclass correlation coefficient (9). The software package used for all analyses was Statistica 6.1 (Stat. Soft, Inc., Tulsa, OK, USA).
The mean of all subjects was 98% compliance with the training programs. For anthropometric variables including body composition, no statistically significant changes were observed in the LP or DUP groups after 12 weeks of training.
There was a statistically significant increase in bench press strength for both groups, at T3 compared with T1 (Table 4). Linear periodization showed an increase of 15.16 kg (p = 0.041), equivalent to 18.2%. Daily undulating periodization showed a higher percentage increase of 22.4 kg, equivalent to 25.08% (p = 0.002). There were no statistically significant differences between T1 and T2 or between T2 and T3, for LP and DUP groups in bench press. With regard to the leg press 45° maximal strength, the LP group exhibited a significant increase of 65.5 kg (p = 0.012), corresponding to 24.71%, at T3 compared with T1. However, for DUP group, a higher percentage increase of 40.61% was observed (p = 0.001), corresponding to 93 kg, at T3 compared with T1. Additionally, DUP group showed a significant increase of 12.23% (28 kg, p = 0.028) at T2 compared with T1 and 25.48% at T3 (65.5 kg, p = 0.001) compared with T2.
In arm curl maximal strength, LP group demonstrated a significant increase of 14.15% (6.1 kg, p = 0.041) at T3 compared with T1. Similarly to the other exercises evaluated, DUP group demonstrated a higher percentage increase, 23.53% (10 kg, p = 0.023) at T3 compared with T1. A significant increase of 20% (8.5 kg, p = 0.049) was also found in T2 compared with T1 for the DUP group. Although the DUP group exhibited a higher percentage increase in strength for the bench press, leg press 45°, and arm curl from T1 to T3, no statistically significant differences were found between LP and DUP groups.
The main objective of the present study was to compare strength gains and body composition alterations after 12 weeks of LP and DUP training. Results showed that both the LP and DUP programs caused significant increases in maximal strength of both the upper (bench press, arm curl) and lower body (leg press) in men with at least 1 year of strength training experience. However, the DUP program produced a higher percentage increase in strength, in the upper and lower body, compared with the LP program. Although the DUP group showed an increase in strength that was of a higher percentage, no statistical differences were found between groups.
Daily undulating periodization has been shown to induce similar increases in maximal strength as a multiple set nonvaried program and an LP program, although the percentage increases were slightly higher with DUP (2). Comparisons of DUP with a single set training model indicate greater increases in maximal strength in both untrained women (22) and women collegiate tennis players (18). While a comparison of DUP with a multiple set training model also indicates greater increases in maximal strength in women athletes with DUP (19). Collectively, the present and previous studies indicate that DUP is an efficient training program to increase maximal strength and does increase strength to a greater extent than nonvaried programs.
Tan (31) and Rhea et al. (28) both indicate the need for studies comparing DUP and LP methods. To the authors' knowledge, 2 previous studies have compared maximal strength increases due to LP with DUP. Rhea et al. (28) compared LP and DUP programs during 15 weeks of training. Both programs trained using 15-25 RM and were meant to increase local muscular endurance. However, both programs showed significant increases in maximal knee extension strength (9.1% with LP, 9.8% with DUP) with no significant difference between programs shown. Although the goal of this previous study was to increase local muscular endurance, it agrees with the present study's results of similar increases in maximal strength with DUP and LP programs.
The second study compared DUP and LP programs using 4-8 RM resistances (27). After 12 weeks of training, the LP program increased maximal strength 14.4 and 25.7% in bench press and leg press, respectively, while the DUP program resulted in maximal strength gains of 28.8 and 55.8% in the bench press and leg press, respectively. The increase in the leg press was significantly different between groups, while the bench press changes were not significantly different between groups. These results were similar to the present study in that both studies show greater percent gains in maximal strength with DUP compared to LP. Rhea et al. (27) reported that during weeks 10-12, participants involved with DUP anecdotally reported symptoms of fatigue and excessive muscle soreness, which was not observed in the present study. The reasons for the reporting of fatigue and muscle soreness in the Rhea et al. study (27) and not in the present study are unclear. Both studies included a recovery week after the fifth week of training and performed 3 sets of each exercise. However, a greater training volume was performed during the present study due to the inclusion of more exercises in the training programs and 1 more training session per week (4 vs. 3 sessions per week). Thus, it is unclear why symptoms of fatigue and muscle soreness were reported in the previous study due to DUP.
In the present study, the DUP showed a higher percentage increase in maximal strength for the bench press, leg press 45°, and arm curl after 12 weeks of training (DUP 25.08, 40.61, and 23.53% vs. LP 18.2, 24.71, and 14.15%, respectively). Another interesting aspect was that after 8 weeks, the DUP group showed significant increases in the leg press 45° and arm curl maximal strength, which was not shown by LP group. Additionally, the DUP group also showed a significant increase in leg press 45° maximal strength from 8 to 12 weeks of training, which was not shown by the LP. These results indicate that DUP may increase maximal strength to a greater extent during the initial training period and result in more consistent strength gains as training progresses. These observations are supported by the results of previous studies (18,19,27).
The initial strength gains (1-8 weeks) due to strength training are primarily neural adaptations after this period strength gains are also influenced by increases in muscle mass (6,10,20). The significantly greater increases in maximal strength with DUP compared to LP during the first 6 weeks of training previously shown (27) and in the present study, indicate that DUP may induce quicker neural adaptations than LP.
In the present research, no significant alterations in body composition (fat-free mass, body fat percentage, and fat mass) were found after 12 weeks of training with either DUP or LP. It is clear that resistance training of sufficient duration can increase fat-free mass and decrease percentage of body fat. For example, both DUP and nonvaried 3-set programs show significant changes in fat-free mass and percent body fat after 4 months of training (18,19). Thus, 12 weeks of training may have been of insufficient duration to change body composition significantly in subjects with at least 1 year of weight training experience. A limitation of the present study and many previous studies examining body composition changes due to weight training is the use of skinfolds to estimate body composition. Skinfolds may not be sensitive enough to determine changes in body composition during relatively short training periods.
In conclusion, the present study and previous studies indicate that DUP is an effective training program to increase maximal strength in both untrained and trained individuals. Additionally, DUP may induce significantly greater increases in strength during the initial weeks of training compared with LP and nonvaried programs. Due to the limited amount of research comparing DUP with other training programs, further research needs to be performed to confirm all these conclusions.
Strength training induces improved adaptations in performance, such as strength gains, increase in power, and muscle twitch velocity. These adaptations are accompanied by physiological alterations (10,11). As an example, the endocrine system may play a considerable role in muscular adaptations to strength training, and it is well established that program variations have an impact on hormonal adaptations (6). By reason of more frequent stimulus variations in DUP, it may be hypothesized that this type of periodization exerts higher stress on the neuromuscular system, so that there could be greater adaptations, leading to higher increase in muscle strength (27).
This as well as previous studies support that DUP is an effective training program to increase maximal strength in untrained and trained individuals. Daily undulating periodization may induce even greater increases in maximal strength than nonvaried and LP programs in some populations. DUP using 2 instead of 3 training zones or ranges per week as used in previous studies is an effective training program to increase maximal strength. Strength and conditioning professionals can use DUP programs to bring about optimal gains in maximal strength.
The authors would like to thank CAPES/PROSUP for financial support.
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