When you start a cardio session, do you set a time goal, like "I'm going to use the elliptical for one episode of Veep?" Or do you set a distance goal, such as, "I will stay on this treadmill until I run five miles, no matter how long it takes?" Neither approach is wrong, but if you can figure out when it's best to go for time vs. distance, you'll get more out of your training and see better results.
"There's no one answer to anything," says Kai Karlstrom, a T4 manager in Chicago. "Incorporating a combination of time and distance goals as well as a variety of activities into your training program is the most effective approach."
When to watch the clock:
If your goal is to gain speed or burn more calories, workouts based on time, such as tempos or a lunchtime quickie, are essential. "Physiologically, you should only be able to train in a certain heart-rate zone for a certain amount of time. If you match those zones are with your set interval or workout times, you can maximize your results," said Karlstrom.
For example, doing long, slow workouts will help you burn fat, whereas short, hard intervals will blast more calories (short, slow workouts pretty much get you nowhere). Also, if your schedule is packed and you only have 20 minutes to exercise, by all means, set a goal of getting the most productive workout possible in that time period, whether it means taking a tough class or pushing yourself on the machines. If you aim for a distance and fall short, you might leave feeling disappointed or stressed, rather than triumphant, as you should.
When to go the distance:
If you have a specific distance goal to reach in the long-term (like a road race), you're better off not leaving it up to chance. "If you want to finish a 10K, for example, and you can only run two miles right now, you need a plan that will take you from two to six miles, rather than 20 to 60 minutes," said Karlstrom. One recent study in Medicine & Science found that kids who were told to run a set distance covered more ground than those who were told to run for a certain amount of time, perhaps because minutes are less tangible than a finish line.
The bottom line:
To achieve progress and avoid a plateau, make sure every workout serves a specific purpose, said Karlstrom. "If you're aiming for a particular distance, try to cover the same mileage in less time each week so you know you're pushing the pace. And if you're gunning for a time, aim to log more miles, lift more weights, or gain more flexibility, each session."