Strength training (or resistance training) does much more than build strong muscles and bones. Research in the past few years has confirmed that lifting weights changes human metabolism in ways that improve health and well-being. Resistance training improves resting metabolic rate and cardiorespiratory fitness. Indeed, some authors call this type of training an exercise therapy program (Strasser & Schobersberger 2011). That’s a powerful swing of the pendulum from days when pushing barbells and mastering squats were seen primarily as ways to boost strength, muscular endurance and bone density.
This article synthesizes the major metabolic effects of strength training, as confirmed in recent research. We also outline mechanisms leading to metabolic gains and discuss how these positive changes relate to your training clients and your fitness practice.
RMR, EPOC and Strength Training: Background
- Resting metabolic rate (RMR) is a measure of the calories we burn at rest. RMR accounts for 50%–75% of daily caloric expenditure (Aristizabal et al. 2015). Maintaining the body’s vital functions, such as heart rate, breathing and brain function, demands quite a lot of energy.
- Excess postexercise oxygen consumption (EPOC) refers to the increased rate of oxygen uptake (i.e., energy expenditure) after dynamic exercise. Specifically, EPOC is the energy the body consumes to restore its pre-exercise condition.
Strength Training Research With RMR and EPOC
WEIGHTLIFTING, RMR AND SUPPLEMENTS
One project (Aristizabal et al. 2015) recruited 61 recreationally active adults (ages 18–35) who had done no strength training for a minimum of 1 year prior to the study. The 9-month (96-workout) experiment periodized the training into three 12-week mesocycles. These cycles included multiset (3- to 5-set) training with light-intensity sessions (12–15 reps, 60–90 seconds of rest between sets); medium-intensity sessions (8–10 reps, 1–2 minutes of rest between sets); high-intensity sessions (3–6 reps, 2-3 minutes of rest between sets); and power sessions (whole-body exercises at 30%–45% of 1-RM, 3 minutes of rest between sets). Exercises consisted of bench press, squat, hang clean, biceps curl, heel raise, abdominal exercises, lat pulldown, lunge, upright row, push press and weight-plate lift.
Participants were divided into 3 groups. During the 9 months, all of them did the same training sessions, but each group received a different type of supplementation (whey protein, soy protein or carbohydrate). RMR increased in participants by approximately 5%. There were no group differences in RMR increases due to the supplementation.
EPOC AND EXERCISE INTENSITY
One unique study compared EPOC values after three workouts with similar energy expenditure (Greer et al. 2015):
- strength training (60% of 1-RM to fatigue) with seated pectoral fly, squat, lat pulldown, cable triceps pushdown and heel raise in a circuit (1-minute rest between sets), repeated over 45 minutes
- moderate-intensity steady-state aerobic training at approximately 39% of aerobic capacity, stopping when participants had burned the same number of calories as they did in the RT workout
- high-intensity interval training (HIIT), 30 seconds at 90% of aerobic capacity, followed by 120–180 seconds of relief at a light intensity until caloric burn matched the RT workout
The HIIT and resistance trials showed similar EPOC values at 12 and 21 hours after the workouts, significantly higher than the results for the steady-state aerobic trial. EPOC for the resistance/HIIT groups was 15% above baseline at 12 hours and 12% above baseline at 21 hours. In practical terms, the study calculated that weightlifting/HIIT burned an impressive 300 more calories in 24 hours than the steady-state aerobic training.
How Weight Training Influences RMR and EPOC
Muscle mass and thyroid hormones have a profound effect on RMR. Apart from building lean body mass, strength training may trigger metabolic changes in muscle that influence thyroid hormones, though more research is needed in this area (Aristizabal et al. 2015).
Research shows that strength training can disrupt muscle differently than aerobic training does. Strength training leads to muscle protein synthesis and repair, which are energy-demanding metabolic processes. Higher exercise intensities produce more EPOC because they cause more muscle disturbance (Greer et al. 2015).
To boost RMR, it’s a good idea to use periodized programs in which participants cycle progressively through various aspects of training and there are systematic changes in intensity and volume (Aristizabal et al. 2015). For maximum EPOC, use compound exercises that recruit as much muscle mass as possible at higher intensities relative to a person’s fitness level (Greer et al. 2015).
The study found a clear dose-response relationship between the number of sets and hypertrophy, the scientific term for muscle growth. In counting weekly sets per muscle group, the researchers found that significant hypertrophy occurred with the following: <5 sets (+5.4%); 5-9 sets (+6.5%); and >10 sets (+9.6%). This hypertrophy spectrum provides personal trainers with training guidelines that can be adjusted to suit clients’ preferences and fitness levels.
For more information on strength training and its influence on different diseases and conditions, see “Metabolism and Strength Training” in the online IDEA Library or in the May 2019 print edition of Fitness Journal. If you cannot access the full article and would like to, please contact the IDEA Inspired Service Team at 800-999-4332, ext. 7.