Among the fitness questions we receive, some are perennial favorites. Like this one: Which is better for scorching up calories: cardio workouts or weight training?
The short answer is you need to do both. Quit your groaning. It's not as hard as it seems. The calorie-burning debate gets complicated quickly. You are probably burning more calories when you are actually moving a heavy weight than when you are doing aerobic exercise. But you are taking breaks, so over 30 minutes the actual number of calories burned doing strength training will be less.
Time factors into the contest another way, too. You are limited in the amount of strength training you can do. Experts will advise you weight-training no more than two to three times per week, to give the body time to repair microscopic muscle tears produced by training that are key to gaining strength. But you can do cardiovascular exercise every day. Ideally, you want a combination of moderate to vigorous aerobic exercise and moderate-intensity strength training. But if vigorous aerobic exercise and vigorous weight training went head-to-head for calories burned, vigorous aerobic exercise would win. A guide is used by the Centers for Disease Control and Prevention, among other august authorities, to classify hundreds of physical activities by energy expenditure. The expenditure is measured in METs, or metabolic equivalents. The more METs an activity requires, the harder the activity and the more calories burned. Doing circuit training (a series of exercises using different muscle groups, with minimal rest in between) requires eight METs, the same as running at a speed of 5 mph. To increase to 6 mph (a 10-minute-mile pace), you need 10 METs. Heavy weight lifting, by contrast, requires only six METs; light weight lifting, three. In other words, you have to work very hard at a non-cardiovascular exercise such as weight lifting to get to the same MET level reached by less-intense cardiovascular exercise. And only cardio will take you into the highest calorie-burning realm.
However, the cardio-vs.-strength debate overlooks two factors that are a key to weight loss and weight maintenance. One is calorie intake. You can burn as many calories as you like with exercise, but if you eat them back, you won't lose weight. Most people will eat to compensate for calories burned unless they are very careful. The second factor is that all movement matters. It is the total volume of exercise over the day that is most important. Both planned exercise and lifestyle activities count. So you can't take just one dose of exercise and do whatever you want for the other 23 hours. To combine cardio and strength training, you can either look at your week or your workout as a place to mix it up. If you exercise six days a week, you could use three days for 60-minute cardio workouts and three days for 30 minutes of cardio plus 30 minutes of strength training. Or you could order the combo platter.
If a new client wanting to lose weight came, he would recommend "circuit-style strength training" because it keeps the heart rate elevated, increases caloric afterburn and builds muscle. The exercises can be all strength exercises (switching muscle groups from chest to back or arms to legs) or a combination of strength and cardio exercises (a set of pull-downs followed by a lap around the track or three minutes on a bike). To burn more calories during exercise, you need to increase oxygen consumption [another measure of energy expenditure], which means you have to work harder.
So the debate is over. Shake hands, people. It's a tie. Cardiovascular exercise and strength training can go have a small, low-fat, low-sugar, moderate-protein smoothie together and chuckle about the days when they were adversaries competing for our attention.