Aerobic activities such as running, cycling, and rowing, are correctly considered to be the most effective exercises for burning calories at a high rate of energy expenditure. For example, running at 6 miles per hour (mph) burns approximately 10 calories per min (kcals/min), running at 9 mph burns approximately 15 kcals/min, and running at 12 mph burns approximately 20 kcals/min. Regardless of one's fitness level, most of the calories used during endurance exercise are derived from aerobic energy sources.
Although less likely to be considered a major calorie burning activity, strength training actually provides several processes for energy expenditure. These include anaerobic energy during resistance exercise performance, aerobic energy during resistance exercise performance, recovery energy right after a strength training session (excess post-exercise oxygen consumption or EPOC), and muscle tissue remodeling energy during at least three days following a strength training session. The cumulative effect of these resistance exercise energy components results in a much higher calorie requirement than is generally understood.
Anaerobic Energy
Resistance exercise requires a relatively high percentage of anaerobic energy production due to the typically high training intensity, heavy muscular loading, brief activity bouts, and localized blood flow occlusion. Scott and colleagues8 found that a set of higher-load resistance exercise performed to muscle fatigue used significantly more anaerobic energy than aerobic energy. For example, a set of bench presses with 70% of maximum resistance (1RM) required approximately 6 calories of anaerobic energy and 1 calorie of aerobic energy. They also determined that a set of lower-load resistance exercise performed to muscular fatigue used significantly more anaerobic energy than aerobic energy. For example, a set of bench presses with 45% of 1RM resistance required approximately 7 calories of anaerobic energy and 2 calories of aerobic energy. According to these research results, a set of bench presses performed to muscular fatigue uses 7 to 9 calories depending on the percentage of 1RM resistance used. However, a study by Robergs and associates,7 in which participants performed bench presses for 5 consecutive minutes, predicted higher energy expenditures of 10 to 16 calories per minute depending on the percentage of 1RM resistance used.
Aerobic Energy
As presented in the preceding section, aerobic sources provide approximately 15% to 25% of the energy used during a set of bench presses performed to muscular fatigue. Of course, all energy expenditure must ultimately be restored through the aerobic system (oxygen uptake). Therefore, aerobic energy expenditure accounts for a large percentage of the calories used during the recovery periods between successive exercise sets. In a study of circuit strength training, male subjects who performed 1 set of 14 resistance machine exercises in 20 minutes averaged approximately 8 calories of energy expenditure per minute.5 A similar study by Wilmore and associates11 reported approximately 9 calories of energy expenditure per minute during a 22.5-minute circuit strength training session. Research by Haltom and colleagues3 revealed that a shorter-rest (20-second) strength training circuit used almost 9 calories per minute, and that a longer-rest (60-second) strength circuit used almost 7 calories per minute. Hempel and Wells5 found that oxygen uptake for men performing a 20-minute strength training circuit averaged 21 ml/kg/min, or 6 METs. Although this is a relative low oxygen uptake and energy expenditure compared to aerobic activities such as running, it does not take into account the recovery energy and muscle tissue remodeling energy associated with resistance exercise.
Recovery Energy
Resistance training is characterized by relatively high heart rates, ventilation rates, and lactate levels, that result in relatively large recovery energy expenditure (EPOC) following the exercise session.1,3,6 As presented above, Haltom and colleagues3 examined two 16-station circuit strength training protocols that used either 20-second or 60-second rest intervals between successive exercises. The shorter-rest workout, which was completed in 13 minutes, used 190 calories during the exercise session and 52 additional calories during the 1-hour immediate post-training period, for a total gross energy expenditure of 242 calories. The longer-rest workout, which was completed in 23 months, used 240 calories during the exercise session and 37 additional calories during the 1-hour immediate post-training period, for a total gross energy expenditure of 277 calories. Based on these findings, recovery energy expenditure during the hour following a circuit strength training session may be 15% to 27% of the calories used during the workout.
Muscle Tissue Remodeling Energy
Due to the muscle microtrauma associated with high-intensity strength training, tissue remodeling processes may significantly increase resting energy expenditure for three days after a workout.10 Research by Hackney, Engels, and Gretebeck2 revealed a 9% increase in resting energy expenditure for 72 hours following a high-volume session of resistance training (8 sets of 8 exercises). A similar study by Heden and associates4 reported a 5% increase in resting energy expenditure for 72 hours following a low-volume session of resistance training (1 set of 10 exercises). Given these results, an individual with a resting energy expenditure of 2000 calories per day may use an additional 100 to 180 calories per day for muscle tissue remodeling processes. Tissue remodeling is largely responsible for the higher resting energy expenditure in strength trained muscle (9 calories per pound per day) than in non-strength trained muscle (6 calories per pound per day).9, 12
Summary
Resistance exercise involves four processes for energy expenditure, including: (1) anaerobic energy used during the exercise performance; (2) aerobic energy used during the exercise performance; (3) recovery energy used during the hour after exercise performance; and (4) muscle tissue remodeling energy used during (at least) three days following the training session. Consequently, the cumulative energy expenditure associated with resistance exercise is considerably higher than generally ascribed, especially the performance of circuit strength training.
Wayne L. Westcott, Ph.D., is professor of exercise science at Quincy College in Quincy, MA. He has written 28 books on strength training, and is an active member of the New England Chapter of ACSM.
References
1. Burleson M, O'Bryant H, Stone M, et al. Effect of weight training exercise and treadmill exercise on elevated post-exercise oxygen consumption. Med Sci Sports Exerc. 1998; 30:518-22.
2. Hackney K, Engels H, Gretebeck R. Resting energy expenditure and delayed-onset muscle soreness after full-body resistance training with an eccentric concentration. J Strength Cond Res. 2008;22:1602-9.
3. Haltom R, Kraemer R, Sloan R, et al. Circuit weight training and its effects on excess postexercise oxygen consumption. Med Sci Sports Exerc. 1999; 31:1613-8.
4. Heden T, Lox C, Rose P, et al. One-set resistance training elevates energy expenditure for 72 hours similar to three sets. Eur J Appl Physiol. 2011; 111:477-84.
5. Hempel L, Wells C. Cardiorespiratory cost of the Nautilus express circuit. Phy Sportsmed. 1985; 13:82-97.
6. Melby C, Scholl C, Edwards G, Bullough R. Effect of acute resistance exercise on postexercise energy expenditure and resting metabolic rate. J Appl Physiol. 1993;75:1847-53.
7. Robergs, R, Gordon T, Reynolds J, Walker T. Energy expenditure during bench press and squat exercises. J Strength Cond Res. 2007; 21:123-30.
8. Scott C, Leighton B, Ahearn K, McManus J. Aerobic, anaerobic, and excess postexercise oxygen consumption energy expenditure of muscular endurance and strength: 1-set of bench press to muscular fatigue. J Strength Cond Res. 2011;25:903-8.
9. Strasser B, Schobersberger W. Evidence of resistance training as a treatment therapy in obesity. J Obes. 2011;2011:482564.
10. Westcott W. Resistance training is medicine: Effects of strength training on health. Curr Sports Med Rep. 2012; 11:209-16.
11. Wilmore J, Parr R, Ward P, et al. Energy cost of circuit weight training. Med Sci Sports Exerc. 1978; 10:75-8.
12. Wolfe R. The unappreciated role of muscle in health and disease. Am J Clin Nutr. 2006; 84:475-82.