Aerobic and resistance training
A previous review examined the effect of concurrent training on exercise performance and revealed the following important point: When aerobic exercise preceded strength training, any muscle strength impairments were limited to the muscle groups used in the aerobic training. For example, when cycle ergometry (a lower-body cardiovascular activity) was performed first in the concurrent sequence, it was shown to noticeably impair lower-body resistance training performance (as measured by the submaximal incline leg press). However, starting the session with cycle ergometry, whether it was performed at high or moderate intensity, had no limiting effect on upper-body strength performance (as measured by the bench press).
Another looming question in the discussion of concurrent training has been whether one particular workout sequence elicits a more pronounced postexercise calorie “afterburn.” This afterburn is scientifically known as excess postexercise oxygen consumption, or EPOC. Briefly, EPOC refers to the calories expended above resting (or pre-exercise) values following an exercise bout. This caloric expenditure, which has its most prominent effect within the first 2 hours following the exercise session, represents the oxygen consumption above resting level that the body uses to return to its pre-exercise state. (See November–December 2004 IDEA Fitness Journal for a more thorough discussion.)
A recent investigation by Drummond and colleagues examined the combined effect of resistance and aerobic exercise and compared the effects of different sequences of these two modalities on EPOC. The study also addressed the question of whether concurrent training sessions have a more meaningful impact on afterburn than sessions of aerobic or resistance exercise alone.
Study Subjects
The subjects in this study were 10 physically active males (mean age = 26 years) who had been jogging and strength training at least 2 days a week for the previous 6 months. Before beginning testing, all the subjects completed 1-repetition maximum (1RM) assessments on the resistance exercises to be performed in the study, to establish the precise workout intensity to be used. In addition, the men performed a maximal aerobic capacity (VO2max) test to establish the appropriate intensity for the aerobic sessions.
Pre-Exercise Procedures
Prior to all four testing sessions, the subjects refrained from any physical activity for 48 hours. Each man recorded and duplicated his diet for the day before and the morning of each test, eating dinner at 5:00 pm on the day prior to testing, and eating breakfast, complemented by a nutrition bar, at 6:00 am on the testing day. Nutritional intake and timing were controlled because of the important role nutrition plays in exercise performance (a factor in exercise afterburn). On arrival at the exercise physiology laboratory, each subject lay in a supine position for 30 minutes in a relaxed atmosphere, and resting metabolic rate (RMR) data were collected. Data from the first 5 minutes were discarded.
Testing Conditions
To prevent any type of order bias, the exercise sessions were arranged using a methodical technique referred to as “double- randomized Latin square crossover design.” At the end of each testing session, EPOC values were collected in precisely the same manner (described below). The four experimental conditions included the following:
Resistance-Only Session. The subjects completed 3 sets of 10 repetitions at 70% of their 1RM, with a 105-second rest between sets and exercises. Each subject performed the following seven exercises in this order: (1) bench press, (2) leg press, (3) barbell biceps curl, (4) triceps extension, (5) hamstring curl, (6) latissimus pull-down and (7) knee extension. Five minutes after completing the resistance training exercises, subjects were placed in a supine position, and their EPOC was recorded for the first 60 minutes and then at two 15-minute intervals, at 75 minutes and 105 minutes.
Run-Only Session. Each subject ran for 25 minutes on a treadmill at a stride pace of 70% VO2max. Five minutes after completing the treadmill run, each subject’s EPOC was measured as described above.
Run-Resistance Session. The men performed a 25-minute run at 70% VO2max, as in the run-only session. Five minutes after completing the run, they performed exactly the same resistance training bout as in the resistance-only session (at the same intensity and in the same order). Once again, 5 minutes after the resistance training exercises were completed, EPOC data were collected.
Resistance-Run Session. In this testing condition, the resistance training session was completed first; then, following a 5-minute break, the 25-minute cardiovascular run on the treadmill was performed. EPOC data were collected for each subject, following the same procedure used for all other conditions.
Results
The subjects’ EPOC levels returned to pre-exercise values within 40 minutes of all four exercise sessions, confirming previous research that demonstrated that the prominent effect of exercise afterburn occurs within the first 2 hours of exercise. Perhaps the first 10 minutes of EPOC reveal the most meaningful data from this well-designed study. (See “Comparison of the First 10 Minutes of EPOC for the Four Testing Conditions,” above).
It is interesting to note that EPOC, measured in milliliters of oxygen per kilogram of body weight per minute (ml/kg/ min), was significantly higher after the resistance-only and run-resistance sessions than after the resistance-run and run-only sessions. Although the researchers did not calculate actual calories expended or provide the data necessary to do so, they did record RMR (baseline = about 3.5 ml/ kg/min). Ten minutes after exercise, EPOC was about 66% above the RMR for subjects in the resistance-only and run-resistance sessions, as compared with about 45% and 34% for those in the resistance-run and run-only sessions, respectively. At 20 minutes postexercise, EPOC for the men in the resistance-only session was 28% above RMR, as compared with 17% for the men in the run-only session.
Practical Application
This study provided answers to at least two questions regarding the effect of concurrent training on EPOC:
1. The combined run-resistance or resistance-run sequence did not elicit an exaggerated EPOC response compared with the single-modality training.
2. At the exercise intensities incorporated in this study, resistance-only and run-resistance sessions had the most meaningful effect on EPOC within the first 10 minutes postexercise. Some of the mechanisms that elevate EPOC following resistance exercise include resynthesis of the phosphagen energy system (ATP-PC), lactate removal and peripheral blood circulation and muscle temperature recovery.
Previous research has clearly shown that intensity is the factor that affects EPOC most profoundly. Therefore, a follow-up study in which subjects perform aerobic exercise and resistance training sessions at different intensities (e.g., 75%, 80%, 85% of maximum) might be very enlightening to this debate about sequence.
Many questions on concurrent training are now being scientifically investigated and answered. However, while taking all of the research results into consideration, fitness professionals also need to consider that variety in training is important for maximizing physiological change and preventing psychological boredom. Mixing up the exercises and exercise order will assuredly be a convincing formula for long-lasting exercise success.
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