Coach Aaron Geyser reduces recovery to two essential mechanisms: transitioning from sympathetic to parasympathetic dominance faster, and increasing what he calls "the contrast of blood flow." That's it. Everything else — the cold plunges, the heat sessions, the foam rolling — is just a vehicle for those two outcomes.
It's a deceptively simple framework. And the more I sit with it, the more I think it's exactly right. Most people approach recovery by asking "what should I do?" Geyser is asking a better question: "what is recovery actually trying to accomplish?" Once you have that answer, the tactics become obvious.
The vasoconstriction-vasodilation cycle from cold plunges is well-documented. Your blood vessels constrict in the cold, then dilate aggressively when you exit. That oscillation — that contrast — is doing real work. It's moving metabolic waste out and nutrient-rich blood in, essentially flushing the system. Geyser's sleep improvement after cold exposure fits neatly with the mechanism: drop your core temperature in the evening, and you're amplifying the natural circadian temperature decline that allows for deep sleep onset.
Rhonda Patrick's research on sauna shows the heat side of this equation with equal clarity. Regular heat exposure increases plasma volume and improves vascular compliance — the same adaptations you get from aerobic exercise, without the mechanical stress. Four to seven sauna sessions per week in the Finnish studies correlated with a 50 percent reduction in cardiovascular mortality. The cardiovascular system becomes more elastic, more responsive. The contrast Geyser describes isn't just about cold — it's about the full oscillation between thermal states.
The individual variability point is where practitioners most often disagree. Geyser acknowledges it openly: "if you think it benefits you, continue to do it." That's not scientific imprecision — it's intellectual honesty. The research on cold timing, for instance, is genuinely contested. Cold immediately after strength training may blunt the hypertrophy signal by suppressing the inflammatory cascade that drives adaptation. For endurance athletes training 17-plus hours per week, that trade-off shifts completely. What suppresses muscle gain in a powerlifter may be exactly what a triathlete needs to show up fresh the next day.
If you're doing more than 10 hours of training per week, five minutes of cold exposure in the evening is worth building into your routine. Not as a test of toughness. As a sleep intervention. Pair it with heat earlier in the day — sauna or even a hot bath — to get the full oscillation effect. Let the contrast do the work.
Here's what Geyser doesn't explicitly say but the mechanism implies: every time you complete a cold plunge, you're training your autonomic nervous system to recover faster from stress — not just physical stress, but any stress. The parasympathetic rebound after cold exposure is a rehearsal. You're teaching your nervous system the pattern of returning to calm. Do that consistently, and the same shift happens faster after a hard conversation, a difficult meeting, a day that didn't go as planned. The cold plunge isn't just recovery from training. It's recovery practice for life.