Instead of tracking everything in the hopes of learning something useful, focus on a few crucial stats that will help you leverage your data, make key changes, and see real results.
Stats to Track
Heart Rate Variability
Your heart rate variability (HRV)—the change in time between each heartbeat—will tell you when you’re good to train and when you need to back off, says Janet Hamilton, a coach and exercise physiologist with Running Strong, an Atlanta-based distance-running coaching program.
The more relaxed, free from fatigue, and “trainable” you are, the greater the variability between heartbeats. Frequent changes indicate that your heart is responding well to even the slightest changes within your body and is ready to recover and work again. Meanwhile, low HRV signals that your body is under too much stress and not ready for intense workouts. This consistency suggests that your heart may be fatigued and is more or less maintaining status quo among your body’s systems.
For the most accurate and consistent data, measure your HRV every morning before you get out of bed. Smartphone apps like Ithlete ($7.99) and Elite HRV (free) sync to a companion heart rate monitor to take the measurement. If you don’t want to invest in an HRV tracker, you can measure your resting heart rate every morning before you get out of bed, says Chris Hauth, former Olympic swimmer, Ironman world champion, and founder of AIMP Coaching. If you notice your resting heart rate increasing, invest more time in recovery.
Workout Volume and Intensity
Monitoring your daily and weekly workout volume (exercise frequency and duration) and intensity (pace) can help ensure that you are pushing when you need to and truly tapering when the time comes. Meanwhile, stalled progress can signal plateaus or potential burnout. While your ideal volume and intensity will depend on your goal, you can safely increase your weekly mileage or speed by 5 to 10 percent per week, Hamilton says. “Some will increase for 20 percent, and then hold for two to three weeks.”
Rate of Perceived Exertion
Tuning in to your rate of perceived exertion (RPE), or how hard you feel like your body is working, is another great way to know when it’s time to kick things up a notch. Or, on the flip side, back off a bit—especially when used in tandem with volume and intensity.
Seeing how your RPE jibes with training volume gives you an even better sense of when to increase or decrease volume and intensity. Endurance athletes in particular are notorious for going too hard on their long-slow training days, which often robs them of that workout’s intended purpose, Hamilton says.
Rank your RPE according to the Borg scale, which runs from six (zero effort) to 20 (max effort). Long-slow training sessions should land around nine to 11. Use the measurement to guide your training efforts—harder tempo runs should rank much higher on the scale (and feel much tougher), while longer recovery runs should rank lower, giving your body time to recover from difficult efforts.
Stats to Skip
Unless you think you may be undereating, counting calories isn’t an ideal strategy for athletes, says Ariana Fotinakis, a certified personal trainer with the Trainerize online training app. First off, those numbers might not even be accurate. A study of 12 popular fitness trackers showed their daily estimated caloric expenditures were off by as much as 590 calories in either direction. Second, the macro- and micronutrients you’re getting as you ask your body to do more are far more important than the sheer calorie count.
Use your energy level as a barometer for whether you’re fitting enough of the right types of foods in your diet to fuel your uptick in effort during training.
Training Heart Rate (Sometimes)
Glancing down at your heart rate monitor can be a simple and easy way to gauge how hard you’re working. Unfortunately, the DIY approach to target heart rate training can be tricky. Your average Google search will yield target heart rate zones that are typically calculated using age-predicted max heart rate equations. That means they don’t necessarily factor in the fitness levels of endurance athletes.
In other words, you run the risk of making training choices based on less than accurate numbers. Heart rate zones and lactate threshold can be effective training tools when specifically geared to your body. But to use this metric effectively, it’s best to work with an exercise physiologist to find your true maximum heart rate or follow a plan to come up with your own training zones. That might mean something like a 20-minute threshold test, where you find the pace you can sustain for that time while still giving max effort, and use that number to determine your target zone.
Trying to lose weight while training is detrimental to your training. You just can’t hit PRs when you’re in a caloric deficit, Fotinakis says. If you legitimately feel like you have weight to shed, try to do so before you dive into training. It’s also important to remember that you may gain weight during your taper. This extra weight is mostly due to a combination of carbo-loading and lower mileage and intensity. Together, they help your liver and muscles top off their glycogen reserves—and every molecule of glycogen holds on to H2O. The result: You toe the start line with more energy and hydration on board.