I see a lot of confusion, misuse, and misapplication of terms in the media about fitness. Recently, I was asked about “burst training”, have seen the term “strength” misapplied, and am frustrated by the increased use of “metabolic.”
To be clear, there are five components of physical fitness: cardiorespiratory, muscle strength, muscle endurance, flexibility, and body composition. Muscle strength is one’s ability to life a maximal weight for one repetition. Muscle endurance is the ability to repeat contractions or sustain a contraction. Big difference. Strength training, then, is (by definition) lifting heavy weights for few repetitions–usually fewer than 5. “Metabolic circuits” are, by definition, NOT strength training activities. Arguably, they are also not training for the cardiovascular system. Great perhaps for general fitness, but not much for strength or cardiorespiratory fitness (imho). Great for the time-constrained. I believe the promotion of “metabolic circuits” or complexes for fat-burning is hype.
Resistance training (note, this is a more correct term for lifting things heavier than nothing repeatedly) of any kind burns calories, though relatively few. The effectiveness on resistance training is in increasing the amount of lean tissue in the body, which increases one’s basal metabolic rate (i.e., the calories that one burns at rest) and in increasing the “after-burn” the calories that are continued to be burned post exercise. The key here is volume–how much weight is lifted for how many sets of how many repetitions. It doesn’t matter so much whether the weight is lifted in single repeated sets or complexes (e.g., metabolic circuits, super sets, etc.–there are a lot of catchy terms for these). Lift weights and restrict your caloric intake, and you will lose fat.
The concept of burst training or metabolic circuits is largely based upon Tabata training (8 repeats of 20-second high-intensity bursts followed by 10-s recovery–4 minutes) which is performed on a stationary bike (or possibly a treadmill). This has been shown to affect VO2max, but repeated air squats or burpees are not that same.
If you want to build strength and muscle mass, lift weights accordingly. If you want to improve your cardiorespiratory fitness (i.e., VO2max), perform aerobic activities at an appropriate intensity level (ideally, mixing high intensity interval training with long duration training) to adequately tax the cardiorespiratory system. If the goal is general fitness and you are are constrained by time, consider exercise complexes (metabolic circuits, if that is what you want to call them), but understand that impact on your fitness will be limited.
If you want to build strength, muscle endurance, VO2max, and lose fat, your best bet is to structure you available training time accordingly. Increase you number of training sessions rather than trying to condense everything into fewer, longer sessions at the gym.
Fitness professionals like to use marketing and branding to sell their services. For the most part, nothing is really new. Science is teaching us how to better manage exercise, but, otherwise, there isn’t much new. Fancy words are sometimes just lipstick on a pig. There are no short-cuts. There are no secret lists of foods to eat/not eat or special exercises. There are just the principles of good nutrition, overload, specificity, and progression. Maximize your efforts at getting fit and minimize the hype.
Set your goals and achieve them!