How do I actually improve my HRV — what works?

The four interventions with the strongest evidence for improving HRV in men, ranked by effect size and quality of evidence: (1) consistent aerobic exercise at zone 2 (150–180 min/week), the largest sustained HRV improvement; (2) slow resonance frequency breathing (5–6 breaths per minute), acute and trained effects documented in RCTs; (3) alcohol removal, one of the fastest HRV recoveries, often visible within 2 weeks; (4) sleep quality improvement, particularly increasing deep sleep, the overnight window where vagal tone is restored.

The mechanism underlying aerobic exercise's HRV effect is increased vagal tone through enhanced baroreflex sensitivity, regular zone 2 training literally trains the baroreflex to be more responsive, increasing the beat-to-beat variation that is HRV. Cold exposure and meditation generate acute HRV shifts but have limited evidence for sustained autonomic retraining. Supplements marketed for HRV (ashwagandha, magnesium) show modest effects in some trials, but nothing close to the effect size of aerobic training.

Honesty Scale: Zone 2 aerobic training, Solid (1). Resonance breathing, Solid (1) for acute effect, Promising (2) for sustained autonomic training. Cold exposure, Early (3) for HRV. Ashwagandha, Early (3) for HRV-specific effects.

What to do: Build to 150 minutes of zone 2 training per week before adding any other intervention. Practice 5-minute resonance breathing sessions (5.5-second inhale, 5.5-second exhale) daily, this is the one behavioral tool with genuine RCT evidence for HRV improvement (Lehrer et al., Applied Psychophysiology Biofeedback, 2003).

For the full picture, read Your Whoop Is Worried. Here Is What It Actually Found.