The Simple Calculation That Will Help You Get Fit Without Getting Injured

When athletes get injured, they often blame doing too much. And it’s true: Overuse injuries are real. But a 2016 review of research into a wide variety of sports found that it’s actually the athlete who’s less conditioned—not the one who puts in consistent, hard training—who’s more likely to sustain non-contact, soft-tissue injuries.

That’s because training develops physical qualities (like strength and fitness) that protect against injury—if it’s done right. “The trick is to get to that point, to that robustness,” says study author, exercise scientist, and elite-athlete coaching consultant Tim J. Gabbett, Ph.D. And that means maintaining an appropriate “training load,” i.e.: how much stress the volume, intensity, and frequency of your workouts (among other things) put on your body.

“Load allows you to cope with more load,” says Gabbett. “Most athletes intuitively know this: If they can train consistently it actually builds robustness, it doesn’t build fragility.” Yet mistakes still happen.

According to Gabbett’s findings, the athletes most likely to get injured are often those who do significantly more than they’re used to, creating excessive and rapid spikes in their training load. For instance, a weekend warrior-type cyclist who tries to tackle a century ride without proper preparation, a new runner who jumps into a marathon training plan, or an experienced athlete who returns to their regular training after taking significant time off.

So how do you avoid unnecessary spikes? Calculate and track your training load.

How to Calculate Your Training Load

To track your training load, Gabbett recommends comparing your acute load—what you’ve done this week—with your chronic load—the level of training you put in and maintain regularly.

The simplest way to do this is by tallying up one metric, like miles ran, minutes spent exercising, or reps times weight lifted. For instance, if you want to measure your training load by miles ran and you did three 3-mile runs this week, your training load would be nine units. The number you get is less important than how it changes week to week.

To more accurately calculate your training load, you could also take intensity into consideration. After each workout, grade it on a scale of perceived effort from 0 to 10, where 0 is at rest, 3 is moderate, 5 is hard, and 10 is all-out. Multiply this number by the number of minutes spent doing that workout to get units of load. This method also allows you to include a variety of activities into your calculation.

For example, a 30-minute hard run would be 30 x 5 or 150 units. An hour of moderate yoga would count as 60 x 3 or 180 units. And 45 minutes of very hard lifting might be 45 x 8 = 360 units. You’ll get the best results with this method if you’re honest and consistent in your calculations.

How to Detect—and Correct For—Dangerous Spikes

To monitor for training-load spikes, add up your load units for the current week and divide the total by your average load during the previous three to six weeks. (Use a longer span of time if your training has changed significantly during that period.)

Gabbett has found that a ratio of .8 (slight decline) to 1.3 (slight increase) seems to be the “sweet spot”—the level where you are gaining fitness but not at much risk for injury. An acute:chronic ratio greater than 1.5 puts you at a high risk of injury.

To protect yourself against injury, monitor your increase in volume as you plan and do your workouts. It’s hard to judge the difficulty of a workout in advance, however, so the full load calculation has to happen at the end of the week. If you find your ratio is greater than 1.5, don’t panic. “There are going to be occasions, in some sports, where you can’t avoid going over 1.5,” says Gabbett. Be aware that you’re pushing it, monitor your body carefully, and maybe back off a bit in the subsequent week before building again.