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Circuit Training vs Periodized Resistance Training in Women
Ryan Overturf, B.S. and Len Kravitz, Ph.D.

Study Reviewed:
Marx, J.O., Ratamess, N.A., Nindl, B.C., Gotshalk, L.A., Volek, J.S., Dohi, K., Bush, J.A., Gomez, A.L., Mazzetti, S.A., Fleck, S.J. Hakkinen, K., Newton, R.U. & Kraemer, W.J. (2001). Low-volume circuit versus high-volume periodized resistance training in women. Medicine & Science Sports & Exercise. 33 (4), 635-643.

Introduction
Although the popularity of resistance exercise is soaring, the scientific comparisons of “total-body” resistance training programs are in the formative stages. As well, with women, the physiological training adaptations beyond 12-week resistance training interventions are fundamentally unknown. In this 24-week study reviewed, the physiological adaptations of a single-set circuit training design were compared to a periodized multiple-set program in an untrained group of women. Following a brief overview of periodized training design, a review of the methods, results and findings of this landmark investigation will be presented and discussed.
Periodization Overview
Periodization is an approach to resistance training programming that includes systematic alternating cycles of weight lifted (intensity) with total repetitions or volume (repetitions x sets) (Fleck, 1999). The roots of this exercise program design date back to the 1950’s and early 1960’s where European coaches, trainers and sports scientists were coaching some of the greatest athletes of that period. The coaches and trainers determined that no matter how fit the athletes were, they just couldn’t continue to train harder and harder. So the trainers did something quite revolutionary with their athletes’ training schedules. They methodically had the sportspersons complete resistance training phases that included high-volume, low-intensity resistance workouts, and then alternated these cycles with low-volume, high-intensity training phases. Eventually this scheme of resistance training filtered to the United States in the 1970’s, where it had its rudimentary beginning. Over the last 10 years, different forms of periodization have attained notable popularity in the U.S. (Marx et al, 2001).
The theoretical roots of periodization come from the Canadian scientist, Dr. Hans Selye, who first presented the General Adaptation Syndrome (G.A.S.) theory (Kraemer, 1998). This theory suggests that the body adapts to training in three different phases. The first phase is characterized as the alarm stage. This is the introduction of the resistance training program where the exerciser experiences allot of soreness and stiffness due to the ‘shock’ of the exercises on the body. The second phase of the G.A.S. is the resistance phase. In this phase, the body is adapting to the demands of exercise and is becoming stronger. The third phase is referred to as “exhaustion” or fatigue, caused by training too hard or too long without sufficient recovery. Overtraining is a practical occurrence of what might be occurring in the third phase of the G.A.S. To avoid the exhaustion phase of the GAS, there must be some type of orderly change in the stimulus.
The Physiology of Periodization
Most individuals have approximately 50% of slow-twitch and fast-twitch fiber types, although this varies comparatively between people, and also within a person’s body (McArdle, Katch & Katch, 1996). The physiological and metabolic characteristics of slow-twitch endurance fibers, and fast-twitch explosive strength muscle fibers are thoroughly discussed in nearly all current exercise physiology texts.
Contrariwise, the physiological explanations why periodization programs work so effectively are just beginning to be understood by exercise scientists. One accepted explanation is that the systematic training approach of periodized programs provides a satisfactory overload to specific muscles fiber types while other fibers are getting necessary recovering (Kraemer, Fleck & Evans, 1996). Thus the recovery is inbuilt in periodization training design. The alternating cycles of high-volume, low-intensity with low-volume, high-intensity provide a satisfactory stimulus/recovery for the different types of muscle fibers, minimizing the possibility of experiencing the exhaustion phase of the G.A.S.
Is There ‘One’ Best Periodization Program?
Because of differences in gender, body types, body composition, muscle fiber percentages, age, health, fitness level and genetics, there is no single best periodization program that suits everyone. Traditional models of periodization describe a progression from high-volume and low-intensity work towards decreasing volume and increasing intensity during the different cycles. If this reduction in volume is in incremental steps during the training cycles, it is referred to as stepwise periodization. On the contrary, with undulating periodization, training volume and intensity are increased and decreased on a regular workout basis, but not in the traditional pattern of always increasing intensity and decreasing volume, as the training period progresses (See IDEA Personal Trainer, Volume 11, 2000, for more information on periodization).
The Purpose of the Study
The purpose of this recent investigation was to determine the training adaptations associated with low-volume circuit-type weight training versus a periodized high-volume resistance training program on muscular fitness and performance in women. As a secondary interest, the researchers also examined changes in basal anabolic and catabolic hormones.
The Subjects
Thirty-four women with an average age of 23 years were chosen to participate in the 6-month study. All of the women were considered active, but untrained in resistance exercise. The participants were nonsmokers, eumenorrheic, and not taking any medications. Prior to the study, each woman was determined to have no medical or endocrine disorder that would affect the findings of this investigation.
Assessments of Muscular Performance
Testing was conducted on three different occasions throughout the 24-week period: before the initiation of training (T1), after 12-weeks of training (T2), and at the end of the six month training period (T3).
Muscular Strength. One-repetition maximum (1-RM) was used to determine muscular strength for the upper and lower body in each participant. The subjects were tested on a Universal weight machine in both the bench press and leg press exercises, following standardized 1-RM testing procedures.
Muscular Endurance. On the same Universal machine, each subject’s muscular endurance was determined by selecting a load at 80% of their 1-RM and measuring the maximum number of repetitions for bench press and leg press. Abdominal endurance was also tested using the 1-minute sit-up test.
Anaerobic Power. Each subject performed a Wingate anaerobic power test on a cycle ergometer. The Wingate test is used to determine peak muscle power, which indirectly reflects an individual’s anaerobic capacity. This test involves pedaling against a constant resistance (which is adjusted according to a person’s gender and body weight) at maximal effort, for 30 seconds. Peak power was established as the highest 5-second segment of average power output in that 30-second period. For maximal speed evaluation, a 40-yard sprint test was employed.
Assessments of Hormone Concentrations
Each female subject was instructed to not participate in any type of vigorous activity for 48 hours prior to the targeted onset of menses. This reduction in intensity would decrease the confounding hormonal activity. Venous blood samples were taken between 8 a.m. and 10 a.m. and during the early follicular phase of the menstrual cycle (to reduce any possible variations in hormone concentrations). The hormone concentrations that were measured were serum testosterone, insulin-like growth factor-1 (IGF-1), human growth hormone (GH), and cortisol concentrations. Similar to the muscular assessments, hormone concentrations were assessed at T1, T2, and T3.
Assessment of Body Composition
Each subject’s body composition was determined at T1, T2, and T3. Body composition was estimated by a standard hydrostatic weighing technique using a load cell. A load cell is a platform connected to four posts, which uses force transducers with a digital read-out to assess a subject’s body density. This method gives a more precise measurement for hydrostatic weighing, compared to the commonly used spring-based autopsy scale. Residual volume (the volume of air remaining in the lungs after a forced maximal exhalation) was measured using an oxygen dilution method.
Training Protocols
The 34 subjects were matched for physical characteristics and then randomly assigned to one of the following three groups: low volume, single-set circuit (SSC), periodized high-volume multiple-set (MS), or non-exercising control group (CON). All workouts were individually supervised by certified personal trainers who provided spotting, motivation, advice, and encouragement to the subjects. The control group did not participate in resistance training, but they did perform their normal recreational activities during the 24-week study.
SSC Protocol. The subjects in the SSC group trained on 3 alternating days each week. Their workouts were done in a single-set fashion with 1 to 2 minutes of rest between exercises. During the sets, the women performed 8-12 repetitions until momentary muscular failure. If the individual was able to perform 12 or more repetitions for a set without assistance, the resistance was increased for the following session. To reduce training boredom, the subject’s alternated between two different circuits in the same exercise order throughout the 6-month period.

SSC Exercises:
Circuit A: Leg press, Bench press, Leg curl, Seated row, Standing calf raise, Arm curl, Sit-up, Pullover, Military press, Hip abduction/adduction

Circuit B: Knee extension, Chest fly, Leg curl, Lateral raise, Seated Calf raise, Triceps pushdown, Back Extension, Upright row, Rotator cuff exercises, Lat pulldown

MS Protocol. Those in the MS group trained 4 days per week and completed 2-4 sets of each exercise. The researchers chose four days of training to allow the subjects to perform a higher volume of work and to give them some variation in their program design. The Monday and Thursday exercise sessions (see Table 2) were performed at an intensity level which varied between light (12-15 reps), moderate (8-10 reps), or high (3-5 reps). Tuesday and Friday sessions (see below) were performed using a moderate intensity of 8-10 reps. This is an undulating periodization design scheme. During the exercise sessions, if the subjects could perform more repetitions than their target zone, the weight was increased for the next set or the following training session. The tempo of each set was modified with the submaximal resistance workouts incorporating more explosive movement speeds. The researchers did not state the time of the concentric and eccentric phases. Between each set, the subjects had a rest period of 1-2 minutes on light and moderate days, and 3-4 minutes on heavy days.

MS Exercises:
Monday/Thursday Exercises: Hang clean, Squat, Bench press, Push press (similar to a shoulder press), Leg curl, Sit-up, rotator cuff exercises

Tuesday/Friday Exercises: Upright row, Dumbbell military press, Arm curl, Triceps pushdown, Lat pulldown, Seated row, Sit-up, Side bend, Lateral hip flexion, Leg Curl, Calf raise, Lunge

Results
The present study demonstrates that a 6-month high-volume, periodized multiple-set resistance training program will have a greater effect on muscular fitness/performance and body composition when compared to a low-volume, single-set circuit program (See Tables 3 & 4). The MS group had a much greater increase in 1-RM for bench press (47% vs 12%) and leg press (32% vs 11%) when compared to the SSC group. For the muscular endurance tests, the MS group out-performed the SSC group in bench press (24% vs 10%) as well as leg press (65% vs 19%). The MS group also exhibited higher percent increases for sit-ups performed in one-minute (42% vs 13%), Wingate peak power (27% vs 4%), vertical jump power (40% vs 10%), and time improvement in the 40-yard dash (6% vs 1%), than the SSC group. At the end of the 6 months, the MS group showed a greater decrease in percent body fat (25% vs 10%) and a higher increase in fat-free mass (8% vs 2%) than the SSC group. The CON group did not show any significant change in muscular performance or body composition.
Resting serum hormonal data showed a significant increase in serum testosterone and IGF-1 for both the SSC and MS groups at the end of the study. Serum cortisol levels decreased significantly in the MS group, but not in the SSC group. Finally, both groups displayed no significant changes in serum GH levels during any point of the research period. Serum hormone levels did not change in the CON group at any point.
Bottom Line Application
The results of this study show that both a single-set circuit training program and a periodized, multiple-set program will increase muscular performance in untrained women, thus both have validated usefulness in resistance training design. However, just as the researchers hypothesized, the MS group had a higher magnitude of change in muscular performance over the 6-month training period. Those in the MS group demonstrated larger increases in all categories tested: upper and lower body maximal strength, muscular endurance, muscular speed and power. The women in the MS group also showed measurably better physiological changes related to decreases in percent body fat, increases in lean body mass, decreases in serum cortisol, and increases in serum IFG-1 and testosterone levels. The authors note that these hormonal changes help to explain the superior changes in lean body mass and decrease in percent fat observed in the MS group. Previous studies that have investigated these two “total body” training programs have ranged from eight to 14-weeks in duration. These shorter durations clearly do not provide enough time for the identification of training adaptations. In this study, 1-RM strength increased to a higher level for both leg press and bench press exercises, especially during the 2nd three months of training.
Although the researchers in this study utilized a 4-day per week periodization design, we realize many clients cannot attain that type of frequency of workouts. Therefore, in Table 5 we have created four different 3-day per week periodization schemes (employing the undulating periodization theme and exercises of this article). These could be performed weekly, by weekly or monthly, depending on the individual goals of your client.
As personal trainers, it is important to observe from this study’s results how the volume of exercise and the training variation play a vital role in the modulation of the exercise stress and recovery patterns, which ultimately leads to greater muscular adaptations. This investigation appreciably substantiates the use of periodization programs with your clients. From a research perspective, these findings emphasize the importance of other longer-term training studies (&Mac179; 6 months) to fully differentiate adaptations between total body resistance training programs. Finally, as reviewers of this article, we would like to congratulate the primary investigator, James O. Marx. and his colleagues for conducting a truly groundbreaking study in the field of resistance exercise for women.

Additional References:
Fleck, S. J. (1999). Periodized strength training: A critical review. Journal of Strength and Conditioning Research, 13, 82-89.

Frankel, C. C. & L. Kravitz. (2000). Periodization. IDEA Personal Trainer, 11, 15, 17.

Kraemer, W. J., S. J. Fleck, and W. J. Evans. (1996). Strength and power training: physiological mechanisms of adaptation. Exercise and Sports Science Reviews, 24, 363-397.

Kraemer, W. J. (1998). Periodization in Resistance Training. IDEA Personal Trainer, 9, 27-34.

McArdle, W. D., Katch, F. I., and V. L. Katch. (1996). Exercise Physiology: Energy, Nutrition, and Human Performance 4th edition. Williams & Wilkins.
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