You have reached the end of the course. This page sums up the three levels in a few lines each, then gives you 12 questions drawn from all of them. Pass this quiz and every earlier lesson quiz, and you can print a course certificate.
Take your time. Each answer explains every option, so the quiz also works as a review.
Level 1: Foundations
- Your heart does not tick like a clock. The gaps between beats keep changing, and breathing in speeds the heart up a little while breathing out slows it down.
- HRV is how much those gaps change from beat to beat, usually given in milliseconds.
- At rest, HRV mostly reflects the vagus nerve Vagus nerve The main nerve of the parasympathetic nervous system, running from the brainstem to the heart, lungs and gut. Its fast signals to the heart drive most beat-to-beat HRV. More about Vagus nerve , the fast brake on your heart (Laborde and colleagues, 2017).
- Higher is not always better. Extra beats, sensor errors, irregular rhythms and overreaching can all push HRV up (Shaffer and Ginsberg, 2017).
- Every number comes from the gaps between beats, and bad beats must be removed first.
Level 2: Reading your numbers
- RMSSD RMSSD Root mean square of successive differences: an HRV metric built from how much each heartbeat interval differs from the next. It mainly reflects vagal activity. More about RMSSD follows beat-to-beat change, SDNN SDNN The standard deviation of all NN intervals in a recording, in milliseconds. It measures overall variability, and its value depends strongly on how long the recording lasts. More about SDNN the overall spread, and lnRMSSD lnRMSSD The natural logarithm of RMSSD. Taking the log evens out the spread of RMSSD values, which makes day-to-day changes easier to compare and analyze. More about lnRMSSD is the log of RMSSD. Never compare numbers from different metrics.
- Age shifts typical HRV more than anything else. Your own trend is the most useful comparison.
- Devices disagree because they measure different things in different ways. Compare trends, not values.
- Measure at the same time and in the same position every day.
- A baseline Baseline Your own usual HRV level and range, built from weeks of readings taken the same way. Comparing a reading with your baseline says more than comparing it with other people. More about Baseline takes two to three weeks. Watch your 7-day average, not single days.
Level 3: Using HRV well
- Age and genes set your range. Alcohol, illness, sleep, training, stress and the menstrual cycle move you inside it. HRV is sensitive but not specific (Altini and Plews, 2021).
- HRV-guided training works at least as well as a fixed plan in small trials. A low reading means an easy day, not a lost week.
- Stress lowers HRV while it lasts. Slow breathing makes HRV larger during the exercise, which is not the same as a higher resting HRV.
- HRV cannot diagnose, detect or rule out disease. The standards for measuring it were set in 1996, and the warning that it is easy to misread still holds (Task Force, 1996).
The one rule to keep
Symptoms matter more than any number. Chest pain, fainting, palpitations, breathlessness or feeling unwell for a long time need a doctor, whatever your HRV says. Lesson 14 lists the red flags.
Your certificate
Your progress stays in this browser. When you have passed every lesson quiz, including this one, your course certificate is ready to print. If some lessons are still open, the certificate page lists them with links.
Thank you for taking the course. For more reading, start with what affects HRV or normal HRV by age.