If you’re training for a race, chances are you have a strict training regimen: five days on, two days off, with specific goals each day.

But your body varies day by day, so why not your regimen? Some days you might be exhausted, while others you feel in top shape. This variation in energy levels leads to one important question: “Who do you listen to—your schedule or your body?”

The short answer: keep a routine, but let your body have a say.

If you want a responsive training plan, start reading your body’s performance capacity directly. Make your heart rate variability (HRV) part of your training routine and it can help you adjust your workouts so that harder training days align with your body’s readiness, not your calendar.

HRV is a Sign of Your Training Capacity

HRV is the constant variation, in milliseconds, between your heartbeats. It is a strong indicator of your body’s training capacity, as it reflects activity in your autonomic nervous system (ANS).

Your HRV indicates how your ANS is balancing its packed daily to-do list.

On one hand, your fight-or-flight system is using energy to maximize short-term performance, demanding resources to respond to mental and physical stressors (e.g., daily stress or a workout). On the other hand, your rest-and-digest system needs energy to prioritize long-term survival, demanding resources to maintain homeostasis, repair your body, strengthen muscles, and support your immune system.

You need both to prepare for athletic feats (fight-or-flight) and to recover afterward (rest-and-digest).

HRV reflects that balance as a holistic measure of your total load. The more you demand of yourself daily, the less you have in the tank to train effectively.

Consider HRV to be your training fuel gauge:

  • If your HRV is lower than your average, energy demands are already high from one branch of your ANS. Maybe your fight-or-flight is engaged from chronic stress, or your rest-and-digest is actively fighting a cold. Pushing now is asking your body to expend resources it might not have, putting you at risk of overtraining and stressing your body beyond what it can handle.
  • If your HRV is higher than your average, you’re ready to get moving. Your ANS is prepared to respond productively to stress—flexibly moving between fight-or-flight action and rest-and-digest recovery. Pushing now allows you to capitalize on your body’s recovery capacity, helping it bounce back from a hard workout.

Things to Keep in Mind

If you’re trying to balance your training and recovery days, it can be difficult to know where the line is until you’ve crossed it. You don’t want to write workout checks your body can’t cash.

By monitoring your HRV, you can clearly see when your body has the bandwidth for intense workouts.

Look for these patterns relative to your baseline:

  • A small drop in HRV is normal as you recover from training, alternating between physical stress and recovery.
  • A large drop in HRV is an early warning sign that you may be overworking your system. A hard training session, especially on top of accumulated fatigue, will lower your HRV.
  • A consistently low HRV, outside of your normal range, is a sign that you’re not allocating enough time to recovery.

Start Training with HRV Today

If you’re looking for that extra edge, try incorporating HRV into your workout routine. It can take some of the guesswork out—letting you know when your body is ready to amp up the intensity, or not.

  • Establish a baseline: HRV values naturally fluctuate. Give yourself at least 2 weeks to establish a clear baseline before you take the numbers at face value.
  • Know your own numbers: Your values are exactly that: yours. For resting heart rate, there is a target number in the 40’s that athletes can all strive for. But HRV is different. There is no gold standard range for HRV; it is highly personal, and there are elite athletes who have high and low ranges.
  • Use your HRV to define push days: When your HRV is high relative to your baseline, it’s a good indicator you can train hard and are likely to recover quickly. On days when your HRV is low, be purposeful about your recovery, both mental and physical.
  • Pair your HRV with sleep data: Hard training days signal to your body that it should prioritize deep sleep for tissue repair. Keep an eye on how that impacts more brain-based sleep stages like REM, which are necessary for optimal mental performance as well.
  • Look long term: Watch for patterns in your HRV throughout the month, and keep in mind that your daily HRV values may fluctuate as your fitness and resilience improves.