Breathwork is marketed as a fast track to calm. But a new randomized trial suggests that not every yoga breath actually settles your nervous system — and one popular energizing technique may briefly nudge it the other way.
Researchers publishing in the International Journal of Yoga Therapy put three well-known yoga breathing practices head-to-head, measuring what happened to the heart and to mood after each. The results are a useful reminder that “pranayama” is not one thing: different breaths do different jobs, and matching the technique to your goal matters more than simply “breathing deeply.”
What the Study Found
The study, published online in January 2026 by Dipak Chetry, Shirley Telles, and Acharya Balkrishna, used a randomized crossover design — meaning each of the 42 volunteers tried every technique on separate days, in random order, so each person served as their own comparison. Participants were experienced practitioners (about three and a half years of breathing practice on average), evenly split between men and women, with an average age of around 24.
On five separate days, each person completed a 15-minute session of one of five conditions: bumblebee breathing (known in Sanskrit as Bhramari), bellows breathing (Bhastrika), a rapid high-frequency breathing technique of the kind used in Kapalabhati, the “breath of fire”, plain breath awareness as an active control, and quiet rest as a do-nothing control. The team tracked heart rate variability (HRV), blood pressure, and breathing rate before, during, and after each session, and measured mood immediately before and after.
Heart rate variability is the small, beat-to-beat variation in your heart rhythm. A higher HRV — particularly a marker called RMSSD — generally reflects stronger “rest-and-digest” (parasympathetic, or vagal) activity and is associated with better stress resilience and recovery. Watching how each breath moved these numbers is a way of seeing, in real time, whether a technique is calming or activating the body.
Three patterns stood out:
- Bumblebee breath (Bhramari) slowed breathing dramatically — to roughly four breaths per minute — and was linked to a rise in low-frequency HRV power along with more pleasant, positive mood afterward.
- Bellows breath (Bhastrika) raised RMSSD, the clearest marker of vagal, parasympathetic activity.
- The rapid, high-frequency technique did the opposite: RMSSD fell, pointing to a short-term shift away from that calming vagal tone.
- Simple breath awareness lifted pleasant mood and lowered negative mood — quietly holding its own against the more elaborate techniques.
The authors concluded that bumblebee and bellows breathing appeared to increase vagally-mediated HRV, while the high-frequency practice reduced it, at least in the minutes surrounding practice.
Why It Matters
The headline isn’t that any breath is “bad.” It’s that breathing techniques are tools with distinct effects, and treating them interchangeably can work against you. A high-frequency, breath-of-fire style practice is traditionally used to energize, so a temporary dip in calming vagal tone is exactly what you would expect from a stimulating technique — helpful for a sluggish morning, but a poor choice ten minutes before bed.
This nuance often gets lost in the “just breathe to relax” messaging that dominates wellness apps and social media. The study puts numbers to something experienced teachers have long taught: slow, resonant breaths (like Bhramari’s long, humming exhale) tip the body toward rest, while fast, forceful breaths rev it up.
A few caveats keep the findings in perspective. The sample was small and made up entirely of seasoned practitioners, so beginners — whose bodies may react differently to forceful breathing — could see other results. The measurements captured only short-term, acute changes, not lasting shifts in baseline HRV. And low-frequency HRV power is influenced by more than the vagus nerve alone, so the bumblebee result is best read alongside the clearer RMSSD signal from bellows breathing. Even so, the direction of the findings lines up with a growing body of breathwork research, including a recent trial comparing breathwork with meditation.
The timing is notable, because millions of people now watch their own HRV every morning on wearables like the Oura Ring, Whoop, and Apple Watch. If your recovery score is low, this research hints that the type of breathwork you choose could matter: a few minutes of slow, humming Bhramari may support the calming side of the ledger, whereas a forceful, high-frequency session might not be the recovery tool it’s sometimes assumed to be. It also echoes earlier work showing a single breathing session can shift how the brain and body respond.
What This Means for Your Practice
The practical lesson is simple: choose the breath to match the moment. If your goal is to settle down — before sleep, after a stressful meeting, or to close a practice — reach for slow, calming techniques. If you need a lift, a short burst of rapid breathing can help, but treat it like a shot of espresso rather than a nightcap.
To wind down, try these three, drawn straight from the study’s “calming” column and its most reliable performer:- Bhramari (humming bee breath): sit tall, inhale gently, then hum on a long, slow exhale. The extended, resonant out-breath is what drove Bhramari’s near-four-breaths-per-minute rhythm and its mood boost.
- Bhastrika (bellows breath), in a gentle, controlled form: use moderate, even breaths rather than an aggressive pace so you tap its vagal, RMSSD-raising effect without over-stimulating.
- Dirga (three-part breath) or plain breath awareness: even doing nothing but watching the breath improved mood in the study — a low-effort option when you’re depleted.
Save the breath of fire (Kapalabhati) and other rapid, high-frequency techniques for daytime energy — a morning practice, a mid-afternoon slump, or the start of a workout — rather than your bedtime routine. A practical rule of thumb: if a breath makes you feel wired and alert, it belongs earlier in the day.
A simple two-minute reset you can build from the study: sit comfortably, spend 30 seconds simply noticing your breath, then take six to eight rounds of humming Bhramari with the longest comfortable exhale, and finish with another 30 seconds of quiet breath awareness. It stacks the two conditions that most consistently improved mood and calming HRV in the trial.
None of this means fast breathing is something to fear. Energizing techniques have real value — sharpening focus, building heat, and waking up a tired system — and the dip in vagal HRV seen here was a short-term response, not evidence of harm. The point is intention: knowing whether you want to rev up or wind down, and picking the breath that reliably does that job.
Key Takeaways
- A 2026 randomized crossover trial in the International Journal of Yoga Therapy tested three yoga breathing practices against controls in 42 experienced practitioners.
- Bumblebee (Bhramari) and bellows (Bhastrika) breathing raised markers of calming, vagally-mediated heart rate variability; bumblebee also improved mood.
- A rapid, high-frequency technique lowered RMSSD — a short-term shift away from calm, consistent with its energizing reputation.
- Even simple breath awareness improved mood, making it a useful low-effort option.
- Match the breath to the goal: slow, humming exhales to wind down; fast, forceful breaths to energize — ideally earlier in the day.
Source: Chetry D, Telles S, Balkrishna A. “Heart Rate Variability and Mood State Changes in Three Yoga Breathing Practices: A Randomized Crossover Trial.” International Journal of Yoga Therapy, 2026. This article is for general education and is not medical advice; talk to a clinician before starting forceful breathing practices if you are pregnant or have a heart, blood-pressure, or respiratory condition.
