A heart rate variability reading that jumps from one morning to the next does not necessarily mean your training went wrong. Buchheit's 2014 review in Frontiers in Physiology puts the typical day to day variation of the natural log of RMSSD, a common HRV measure, at about 10 to 20 percent. That is the noise you have to see through before asking whether slow breathing for recovery does anything.
Slow breathing apps and coaches promise faster recovery, calmer nerves and better HRV. Some of that is well supported, some of it is borrowed from other settings. Here is what the studies show after hard training.
What HRV is and why slow breathing moves it
Heart rate variability describes how much the time between heartbeats fluctuates. RMSSD, the measure used in most of the studies below, captures beat to beat changes that mainly reflect vagal activity, the calming branch of your autonomic nervous system. Your heart speeds up slightly as you breathe in and slows as you breathe out, so the pattern of your breathing shapes the signal.
Lehrer and Gevirtz explained in 2014 why a pace near six breaths per minute stands out. At about 0.1 Hz the swings in heart rate are largest, and heart rate and blood pressure run roughly 180 degrees out of phase, so the baroreflex, your blood pressure feedback loop, amplifies the swing. The authors call strengthened baroreceptor function the best supported mechanism. They also say that other proposed routes, such as effects through vagal afferents to the brain, rest on preliminary work, and that a link to metabolic efficiency must remain speculative.
What the large review shows
Laborde and colleagues screened 1,842 abstracts and included 223 studies in a 2022 systematic review and meta-analysis. Vagally mediated HRV rose during slow breathing, right after a single session, and after multi session programmes. That is a solid finding about the signal itself. The abstract does not say that recovery from training improves.
What happened after hard training
Two recent trials looked at exactly that question, and neither gave a win to slow breathing.
In 2025, Kasap and Aydin ran a randomised crossover study with 40 physically active sports science students (25 men, 15 women, average age about 21). Each did three 15 minute interval sessions on a spin bike at 85 to 95 percent of maximum heart rate, with at least 48 hours between sessions. In the rest periods they breathed spontaneously, in a 4-4-4-4 box pattern, or at six breaths per minute with a 5-5 rhythm. Final heart rate was 159.05 beats per minute with spontaneous breathing, 164.65 with box breathing and 154.77 at six breaths per minute. Box breathing was higher than six per minute by 9.87 beats, but six per minute did not differ significantly from spontaneous breathing. Time to return to baseline heart rate was 703, 753 and 676 seconds, with no significant difference. Perceived exertion on the 6 to 20 scale was 15.25, 17.27 and 15.25. HRV itself was not measured.
In January 2026, Raidl and colleagues published a randomised trial with 34 participants. Everyone did four weeks of supervised sprint interval training. One group added ten minutes of slow paced breathing after each session and every evening before bed. Performance gains did not differ between groups, and nocturnal heart rate was 3.1 beats per minute higher in the breathing group (95 percent confidence interval 0.47 to 5.72). The authors concluded that daily slow paced breathing gave no additional performance or physiological benefit.
A 2017 systematic review by Jiménez Morgan and Molina Mora covered heart rate variability biofeedback, which trains breathing with live feedback, in athletes. Six of seven studies reported improved psychophysiological variables that helped performance. All studies were small, with 1 to 30 participants, only three of seven used the standard protocol, follow up ran up to ten weeks, and the authors call the evidence limited.
The honest limit
Raising HRV during a breathing session is not the same as recovering faster. The two training trials above looked at heart rate, perceived exertion, performance and nocturnal heart rate, and found no benefit. One used young, active students and did not measure HRV at all. The other's abstract does not state the participants' training level.
The positive performance findings come from small biofeedback studies. The mechanism paper says clearly which parts are speculation. And HRV is a noisy tool: Buchheit reports that heart rate recovery has a typical error of 25 to 35 percent, and that changes must exceed this noise to mean anything. None of the studies above shows that a ten minute breathing session after training restores muscle or improves the next session.
How to actually use it
If you enjoy it, try five seconds in and five seconds out for five to ten minutes, seated, after your cooldown. Treat it as a way to unwind, not as a recovery booster.
Skip strained patterns. In the 2025 trial, box breathing between intervals ended with a higher heart rate and a perceived exertion score of 17.27 against 15.25.
If you track HRV, measure at the same time under the same conditions each morning. Buchheit notes that averaging three to four days cuts the noise, and that a change of about 3 percent in resting vagal HRV is the smallest worthwhile one.
Judge your recovery by how you feel and perform across a week, not by one number. For the nasal side of recovery, see our article on nasal breathing for athletes and nasal breathing while running.
Stop and get checked if slow breathing makes you dizzy, if you notice palpitations, or if you have chest pain or lasting shortness of breath.
FAQ
What is the best breathing for recovery after exercise?
None of the studies above showed a breathing pattern that speeds up physical recovery. Slow breathing reliably raises HRV during the session. In the 2025 trial, six breaths per minute did not differ significantly from normal breathing in time to return to baseline heart rate.
Does slow breathing increase HRV?
Yes, in the 2022 meta-analysis vagally mediated HRV rose during, right after and after programmes of slow breathing.
Is HRV a good recovery indicator?
It can help when read as a trend. A single morning value has a day to day variation of about 10 to 20 percent.
Slow breathing reliably moves your HRV and may help you unwind, but the two trials after hard training do not show faster recovery. Use it for calm, and judge recovery by the week, not the reading.
This article is for general information and does not replace medical advice. If you have palpitations, dizziness or chest symptoms, please have them checked by a doctor.
Sources
- Buchheit M (2014). Monitoring training status with HR measures: do all roads lead to Rome? Frontiers in Physiology 5:73. PMC
- Lehrer PM, Gevirtz R (2014). Heart rate variability biofeedback: how and why does it work? Frontiers in Psychology 5:756. PMC
- Laborde S, Allen MS, Borges U, Dosseville F, Hosang TJ, Iskra M, Mosley E, Salvotti C, Spolverato L, Zammit N, Javelle F (2022). Effects of voluntary slow breathing on heart rate and heart rate variability: a systematic review and a meta-analysis. Neuroscience & Biobehavioral Reviews 138:104711. doi.org/10.1016/j.neubiorev.2022.104711
- Kasap M, Aydin GR (2025). Box breathing or six breaths per minute: which strategy improves athletes post-HIIT cardiovascular recovery? PLoS ONE 20(11):e0336615. doi.org/10.1371/journal.pone.0336615
- Raidl P, Wessner B, Laister S, Csapo R (2026). No evidence for the efficacy of slow-paced breathing as a recovery strategy after sprint interval training. International Journal of Sports Physiology and Performance 21(2):302-311. doi.org/10.1123/ijspp.2025-0138
- Jiménez Morgan S, Molina Mora JA (2017). Effect of heart rate variability biofeedback on sport performance, a systematic review. Applied Psychophysiology and Biofeedback. doi.org/10.1007/s10484-017-9364-2