cyclists riding on a road in a rural setting with a field in the background — Trevor Raab

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For many cyclists, a wearable fitness tracker is just as essential as clipless pedals or a jersey with generous pockets. And while many smartwatches track basic metrics like distance, pace, duration, and heart rate, only certain types, including Garmin, Coros, Polar—and now the Apple Watch Series 6 and later—calculate training load, too.

Training load, a means of quantifying your training, can be a powerful metric, as long as you understand what the numbers mean and how to use them effectively.

We talked to experts to find out exactly what training load measures and some important dos and don’ts when it comes to incorporating into your day-to-day.

What does training load actually mean?

“Training load is a way of quantifying a volume of training that an athlete has accumulated over some amount of time, taking both volume and intensity into account,” says Cody Stephenson, head of education at Training Peaks, and former cycling coach and exercise physiologist.

According to the International Journal of Sports Physiology and Performance, training load has two measurable aspects: external load and internal load. External load includes metrics like how much weight you lifted or how many miles you rode. But those numbers alone can’t paint an accurate picture of how hard you worked.

“A hundred miles on a mountain bike is a heck of a lot different than 100 miles on a road bike,” says Rob Pickels, a USA Cycling-certified coach, exercise physiologist, and consultant with Forever Endurance.

Internal load, on the other hand, looks at variables like heart rate and metabolism, or processes that occur in your body. “[Internal load metrics] don’t care how far you went on your bike, just how hard you worked,” says Pickels.

How does your device measure training load?

While methods for measuring training load vary across devices, the algorithms will put more weight on the workouts you completed in the last seven days.

If you log your workouts on Training Peaks, you’ve probably noticed the platform gives you two scores for training load: acute training load (ATL), a score that’s based on your training load over the past seven days and chronic training load (CTL), which is based on your training load over the past 42 days.

The reason for the focus on the previous week: Fatigue from any workout completed in the last seven days has a much greater negative effect on your body than the workouts you’ve done (and subsequently recovered from) less recently. “Workouts, when they first happen, are bad for you. They make you a worse athlete, they make you more tired,” explains Stephens. But once your body has had a chance to recover, that training stress translates to adaptations that make you stronger and faster.

Garmin bases training load metrics on excess post-exercise oxygen consumption (EPOC), or how much time your body spends consuming more oxygen than it normally would after you’re done exercising. Garmin calculates your EPOC scores for the prior seven days and compares it to your typical EPOC scores, gathered over a longer period of time, to give you a numeric score or a range (high, optimal, or low) for your training load.

Both Coros and Polar rely on your heart rate during your workout and the duration of your workout to determine training load, a method known as training impulse (TRIMP). It’s worth noting that these measurements have some limitations for activities like strength training, where a session can create significant muscle fatigue without necessarily keeping your heart rate elevated.

Apple takes heart rate, pace, duration, and perceived effort into account to classify your training load on a scale from “well below” to “well above,” based on the stress of your workouts over the last seven days compared to what you’ve done over the previous 28 days. While Apple will calculate your training load without any manual input from you by default, it gives you the option to edit your effort level after each workout.

How can cyclists use training load metrics to optimize their fitness?

“There are no good or bad training loads. There’s only whether or not a particular training load is appropriate for you,” says Pickels.

Here are some tips to help you understand the context in which your training load exists and how you can use that information to support your training (without getting too obsessed with the numbers).

Establish a Baseline

Your training load metrics alone don’t mean much, if anything, unless you have something to compare them to. “Ninety for me and 90 for you are potentially different,” says Pickels.

The numbers are meaningful when you can zoom out and see which direction they’re trending. And to do that, you first have to establish a baseline. Many athletes can establish a baseline within a four to six weeks of consistent tracking, even if you’re starting with a completely blank slate, as long as you’re consistently using the same tracking system (more on that later).

That said, depending on how your training is structured and your athletic history “you might not truly understand the numbers for even longer than that because you haven’t been through the full range of experiences,” says Pickels.

Once you know how your body is responding to your baseline training, or chronic training load, you can adjust your acute training load up or down as needed to meet your goals, says Stephenson. For example, you might notice that you’re more tired than usual. If your training load metrics indicate that you’ve been pushing harder than usual in the past few weeks, that could be a cue to back off before you get sick or injured.

So while training load metrics might not tell you exactly what workout you should do on a given day, they can be great for helping you identify big picture trends so that you can dial in your periodization.

Be Consistent With How You Measure

“There is no perfect metric out there,” says Pickels. That said, you can learn a lot from the training load metric you do use—as long as you use the same one every single time. Only by comparing apples to apples, you can identify big picture trends in your training. And it turns out, those “apples” don’t necessarily need to encompass the latest, greatest technology.

Stephenson recalls coaching a small group of athletes to compete in the 200-mile Unbound race and relying solely on rate of perceived exertion (RPE) and distance to plan their training. “I told them, ‘Just tell me how much you ride every day and tell me if it was easy, medium, or hard. And then I just estimated a training stress score (TSS) for every workout by multiplying intensity by duration,” says Stephenson. “It’s definitely a valid way to calculate chronic training load, especially if the coach or the athlete is reporting their numbers accurately.”

You run into problems when you’re looking at external metrics like watts one day and TRIMP the next. For example, Training Peaks defaults to measuring your cycling training load according to wattage. But say you have multiple bikes, and only one has a power meter. You might be using heart rate data to determine your training load for some workouts and wattage for others, depending on which bike you’re riding.

You’ll get training load calculations for all of these workouts, but they won’t be very meaningful, because they’re comparing two different metrics, says Pickels.

Be Honest With Yourself

Unlike other devices on the market, the new Apple Watch software lets you edit the RPE of a given workout to determine your training load, which can be a huge plus. For example, two workouts might look identical if you looked only at duration plus wattage or heart rate. But if you were tired, stressed, underfed, or dehydrated going into the workout, it would take a lot more out of you—and the ability to integrate that subjective experience into the objective data can be very valuable in determining an accurate training load.

But only if you report honestly. “I could see people skewing the RPE harder or easier for different reasons,” says Pickels. For example, you might have felt exhausted during an interval session. But instead of rating it as the 9 out of 10 effort it was, when you see lower wattage than you expected, your ego can inadvertently interfere—which means you record it as an 8.

On the other hand, if you hate wind, you might give a windy ride a higher RPE than a hilly ride where you worked equally hard, just because you found the gusts mentally challenging.

Overestimating your RPE can artificially inflate your training load, while underestimating it can make it appear that you did less work than you actually did. And if you’re using those numbers to map out your future training, you’re setting yourself up for undertraining or worse, overtraining.

Look at the Big Picture

For better or for worse, many cyclists have a tendency to get hung up on numbers. “And if you give them a number that goes up with training, they want to make that number higher,” says Stephens.

But if you’re training strategically, including a periodized training plan and tapering before key races, you need to see a dip in your training load at certain points in your training cycle. If you never allow your numbers to decline, “you can overtain yourself into oblivion,” says Stephenson.

Instead of focusing on metrics to the point where it’s counterproductive, Stephenson suggests coming back to your why. If the goal is to be as fit as possible on race day, it’s vital that you allow your training load to decline so you can shed fatigue and toe the line with fresh legs.

Similarly, your training load may not look the same from year to year, life circumstances like job stress, family commitments, travel, and illness, or what Pickels calls “life load,” can lead to inconsistent performance. That’s when it makes sense to shift your focus away from the numbers so you can potentially re-evaluate your training from a wider perspective, says Pickels. “You need to be able to see the entire forest, instead of just the trees,” he says.

Pam Moore

Contributing Writer

Pam Moore is an occupational therapist-turned-intuitive eating coach, certified personal trainer, and award-winning freelance writer with bylines in outlets including The Washington Post, Time, SELF, Outside, Runner's World, and others. Listen to her podcast, Real Fit, or subscribe to her newsletter, Real Nourished, at

pam-moore.com

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