Should you train by time or distance?

Our expert settles the conundrum of cardio.

When you start a cardio session, do you go with a time goal in mind, setting out to use the Elliptical for 30 minutes, or for one episode of Veep? Or do you set a distance goal, intending to stay on the treadmill until you cover 5 miles, no matter how long it takes? Neither is wrong. But if you can figure out when it’s best to use both, you’ll get more out of your training and see better results.

“There is no one answer to anything,” said Kai Karlstrom, a T4 Manager in Chicago. “Incorporating a combination of time and distance goals, as well as a combination of activities, into your training program is the most effective approach.”

When to watch the clock:

If your goal is to gain speed, or to burn more calories, workouts based on time, such as tempos or lunchtime quickies, are essential. “Physiologically, you should only be able to train in a certain heart rate zone for a certain amount of time. So if you know what those zones are, and you properly match up your effort levels with your set interval or workout times, you can maximize your results,” said Karlstrom. For example, doing slow, long workouts will help you burn fat, and short, hard intervals blast more calories, but short, slow workouts pretty much get you nowhere. Also, if you have a packed schedule and know that 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 and/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, you’re better off not leaving it up to chance. “For example, if you want to finish a 10K race, and you can only run two miles right now, then you need a plan that will specifically take you from two to six miles, rather than 20 to 60 minutes,” said Karlstrom. One recent study in Medicine & Science in Sports and Exercisefound 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 the minutes were 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 measuring your workout by distance—say, running 5 miles each week—try to cover the same mileage in less time each week, so you know you’re pushing the pace. And if you’re working within a time frame, like 30 minutes per workout, aim to log more miles, or lift more weight, or gain more flexibility, each session.”