4-2-6 breathing (inhale 4, hold 2, exhale 6, hold) leans on making the exhale longer than the inhale — the idea has real scientific backing, but the literature is more divided than advertised on this exact recipe.

noli's read

Several single-session studies support the idea that a longer exhale relative to the inhale raises heart-rate variability (HRV) more than a 1:1 ratio — for instance Bae et al. 2021 (n=28) and Laborde et al. 2021 (n=64 athletes) report this effect, persisting for a few minutes afterward. But a 2024 replication study found no effect of a 1:2 versus 1:1 ratio on HRV at 6 breaths per minute, and a review of 9 studies on the topic finds split results: 3 studies find no ratio effect, 1 favors an equal ratio, 1 favors a longer inhale, and only 4 favor a longer exhale. A 12-week trial of regular practice, meanwhile, found no significant difference between extended exhale and equal-ratio breathing on anxiety or long-term HRV. In other words, the short-term effect shows up in several studies but not all, and nothing proves a specific ratio like 4-2-6 durably beats plain equal-ratio slow breathing. Verdict: mixed — a longer exhale has real single-session support, but far from unanimous, and no demonstrated benefit over time.

the sources

1. 1Zaccaro A et al. 2018