Training Load: How to Tell If You're Doing Too Much

Your watch shows "high load" in red, your legs feel heavy, and you're wondering whether to ease off. Or it says "optimal" even though you've slept badly for a week. Which one should you trust?

The load number is useful, but it doesn't measure fatigue. It's an estimate of what your workouts cost your body. To know whether you're doing too much, read it alongside how you feel, and look at the trend over time.

What training load actually measures

External load is what you did: distance, duration, elevation gain. Internal load is what it cost your body. Two people who do the same 15 km (9.3 mi) outing don't pay the same price. One finishes feeling fine, the other is wiped out for two days. Internal load is what matters when you're asking whether you're doing too much.

Session RPE, no sensor needed

For example, a 60-minute workout rated 6 out of 10 gives 360. A 90-minute run rated 4 also gives 360. These aren't the same workout, but they weigh the same on your week. You don't need a watch for this. It's useful for swimming, gym sessions, or the day your battery is empty.

What your watch calculates

The two brands start from different foundations. A load of 400 on Garmin and a load of 400 on Polar don't mean the same thing. If you switch watches, start over: compare your load to your own past numbers, not to a friend's.

Why magic thresholds don't hold up

The acute:chronic ratio

This ratio divides your recent load by the load from previous weeks and looks for a "sweet spot." The idea is appealing: a green light or a red light.

In 2020, a critique published in the International Journal of Sports Physiology and Performance (Impellizzeri and colleagues) concluded that no evidence supports using it to reduce injury risk. It also argues that the ratio splits a continuous measure into arbitrary zones and assumes a cause-and-effect link that nobody has demonstrated. A ratio that looks good isn't a guarantee, and a ratio that looks bad isn't an alarm.

The 10% rule

Another common guideline is not to increase your weekly distance by more than 10%. A 2014 study followed 873 novice runners wearing GPS watches for a year. In that group, 202 got injured. Runners who had increased their distance by more than 30% over two weeks did not have a significantly different overall injury rate from those who had increased it by less than 10%.

This study looked at beginners, and it doesn't mean you can do anything you want. It means a fixed rule isn't enough to protect you. Keep the 10% as a rough guideline for caution, and pay more attention to how your body responds. To build a week without rushing, these 3 runs a week are a good starting point.

From normal fatigue to overtraining

Feeling tired after a heavy week is normal. It means you've stressed your body enough to trigger adaptation. The problem starts when the fatigue doesn't go away even with rest.

The 2013 consensus statement from the European College of Sport Science (ECSS) and the American College of Sports Medicine (ACSM) describes overtraining as "prolonged maladaptation": your body can no longer adapt to what you're asking of it. Signs include lasting fatigue, falling performance, and mood disturbances.

What counts is duration. One hard week, with heavy legs and a bad workout, isn't overtraining. Weeks where your pace slips, you sleep poorly, and you no longer want to train deserve to be taken seriously. The line between overreaching and overtraining is blurry, so don't look for a label. Look for the trend.

Signals to check against your watch

Research supports tracking load over time. The list below comes mostly from coaching practice. One signal tells you nothing on its own. It's the combination that matters:

• Sleep: you fall asleep poorly or wake up without energy, several days in a row.
• Mood and motivation: you keep putting off workouts, or you feel irritable.
• Legs: they stay heavy for several days after a normal effort.
• Resting heart rate: it's higher than usual on several mornings in a row.
• Pace and heart rate: at the same pace, your heart rate is higher, or at the same heart rate, you're going slower.

If your load climbs, two or three of these signals show up, and they last, your recovery isn't keeping up. If your load is high but you sleep well, feel motivated, and your pace holds, nothing points to a problem.

What you can do after your next workout

1. Rate your effort within five minutes of finishing, from 1 to 10, and multiply by the duration.
2. Note how you feel when you wake up: sleep, energy, mood, in a few words.
3. Compare to your own trend: this week's load against previous weeks, using the same method.
4. Back off if several signals last: one fewer workout or easier sessions, rather than "making up" for it by pushing harder.
5. Change only one thing at a time: volume or intensity, not both.

KILYO reads your watch workouts and tracks how they change: a volume jump from one week to the next, a pace that holds or doesn't, a heart rate that rises for the same effort, a loss of consistency. It then adjusts your plan accordingly.

Written with the help of AI.