Resting heart rate can hint that something has changed, but it cannot tell a runner whether they are overtrained. A rise of several beats over your normal for a few days can point to illness, poor sleep, heat or stress as much as training, and in research on heavy training blocks, resting heart rate has even fallen. The clearer warning signs are a drop in performance that rest does not fix, along with changes in mood, sleep, motivation and how often you get sick.
This post is part of our pillar on training by recovery.
What can resting heart rate tell a runner?
Your resting heart rate is useful in one way: as a trend against your own baseline. Measured the same way each morning, or overnight by a wearable, it can flag a day or a run of days that look different from your normal.
What it reflects is broad. Many things can move it:
- A cold or other infection coming on
- Short or broken sleep
- Heat, dehydration or a late heavy meal
- Alcohol
- Work, exam or life stress
- A hard session or race the day before
That is why a raised number is a reason to ask questions, not a verdict about your training.
What can resting heart rate not tell you?
It cannot diagnose overtraining, and it can miss real fatigue. In a randomized study of 21 trained triathletes, a three-week overload block cut performance in the overload group by about 9 percent, and performance rebounded above baseline after a taper. In that tired group, resting heart rate was more likely to go down than up, and weekly averaged heart rate variability rose rather than fell. Single HRV readings taken once a week missed the change.
So a low or normal resting heart rate does not prove you are fresh, and "my heart rate went down, so I am fitter" is not always true. For more on reading the related signal, see HRV for runners.
What is the difference between overreaching and overtraining syndrome?
The joint consensus statement of the European College of Sport Science and the American College of Sports Medicine lays out a spectrum:
- Functional overreaching. A short-term drop in performance after a hard block, without lasting psychological or other symptoms. With recovery, performance comes back and often improves. This is part of normal hard training.
- Non-functional overreaching. The balance between training and recovery has slipped too far. Performance stays down longer, and other symptoms often appear. Recovery tends to take weeks to months rather than days.
- Overtraining syndrome. A prolonged maladaptation that can take months to resolve. The consensus is clear that telling it apart from non-functional overreaching is very hard. Doctors make that call based on how the athlete recovers over time and after ruling out other causes.
The same statement notes that no single marker, including hormones, blood tests, performance tests or questionnaires, meets every requirement to be a reliable test. There is no number on your watch that says "overtrained."
What are the real warning signs for runners?
Look for patterns across several of these, lasting more than a week or two:
- Performance: paces that used to be steady now feel hard, and an easy week does not bring them back
- Effort: easy runs feel moderate, and you cannot reach your usual effort in workouts
- Mood: irritability, flatness, loss of enjoyment, or dreading runs you used to like
- Motivation: wanting to skip training, or forcing yourself out the door most days
- Sleep: trouble falling or staying asleep despite being tired
- Illness: colds and sore throats that keep coming back
- Soreness: heavy legs or aches that do not clear between sessions
Your own reports matter here. A systematic review of athlete monitoring found that self-reported measures such as mood, stress and perceived fatigue tracked training load more sensitively and consistently than common objective measures, including resting heart rate.
What should you do if you see these signs?
- Cut intensity first. Turn hard sessions into easy running or rest for several days. See whether to run a hard workout on a low recovery day.
- Do not make up missed work. Doubling back is how a dip becomes a hole. Read why you should not make up a missed workout.
- Protect sleep. Aim for a consistent schedule and enough hours before adding training back.
- Eat enough for the work you do. Under-fueling can produce many of the same signs. The International Olympic Committee consensus on relative energy deficiency in sport describes health and performance problems in both female and male athletes whose intake is too low for their training.
- Reduce the other stress you can. Training load is only part of your total load.
- Return gradually. When you feel normal again, bring back easy volume before intensity.
When should a runner see a doctor?
See a doctor if:
- Fatigue, poor performance or low mood last more than two or three weeks despite easier training
- You have chest pain, fainting, a racing or irregular heartbeat, or unusual breathlessness during or after running. Stop running and get seen promptly.
- A raised resting heart rate comes with fever or other illness symptoms
- You notice missed or irregular periods, repeated bone injuries, or a sense that you cannot eat enough for your training
- Low mood affects daily life. A doctor or mental health professional can help.
The consensus statement stresses ruling out illness, infection, low iron, low energy intake and other medical causes before calling anything overtraining. That work belongs to a doctor, not a coach or an app.
How your HealthAI coach applies this
You check in on sleep, soreness and energy in the health portal, and your coach reads those check-ins alongside the runs you log. When the pattern turns, such as poor sleep and high soreness for several days or workouts that feel much harder than they should, your coach eases the next hard session and adjusts the rest of your two-week plan. HealthAI does not sync with any watch yet, so if you track resting heart rate, add the trend to your check-in note in plain words. Your coach will not diagnose overtraining, and lasting fatigue or any heart symptom goes to a doctor. Plans start at $30 a month, and you can see plans here.
Your coach builds this around your training data. Start at HealthAI.coach.
Sources
- Meeusen R et al., Prevention, diagnosis, and treatment of the overtraining syndrome: joint consensus statement of the European College of Sport Science and the American College of Sports Medicine. Medicine and Science in Sports and Exercise, 2013. doi:10.1249/MSS.0b013e318279a10a
- Le Meur Y et al., Evidence of parasympathetic hyperactivity in functionally overreached athletes. Medicine and Science in Sports and Exercise, 2013. doi:10.1249/MSS.0b013e3182980125
- Saw AE et al., Monitoring the athlete training response: subjective self-reported measures trump commonly used objective measures: a systematic review. British Journal of Sports Medicine, 2015. doi:10.1136/bjsports-2015-094758
- Mountjoy M et al., 2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine, 2023. doi:10.1136/bjsports-2023-106994