Ciaran Flanigan is making a case that's become increasingly well-supported: cold plunge therapy isn't just recovery theater for elite athletes. It's a legitimate physiological tool with measurable effects on mood, immunity, and longevity — accessible to anyone willing to get uncomfortable for a few minutes.
The numbers he cites are striking. A 500 percent increase in norepinephrine after cold exposure. A 30 percent reduction in sick days for regular practitioners. These aren't fringe claims anymore. They're appearing consistently across the research literature, and they align with what we're seeing from other voices in this space.
The norepinephrine finding is where I'd focus your attention. Huberman has covered this extensively — that cascade of catecholamines triggered by cold isn't just a stress response. It's a training stimulus. You're teaching your nervous system to modulate between activation and calm. The sympathetic spike is real. The parasympathetic recovery that follows is where the adaptation happens.
What Flanigan describes as "hitting the brakes on inflammation" maps directly onto research around cold-induced vasoconstriction and the flushing of metabolic waste. When blood retreats from the periphery to protect vital organs, and then rushes back as you rewarm, you get a vascular pump effect. Athletes have known this intuitively for decades. The science has simply caught up.
Here's where I'd push back gently on the framing. Cold exposure is consistently presented as straightforwardly good — more is better, colder is better. But the research on timing complicates this. If you cold plunge immediately after strength training, you blunt the anabolic signaling. The inflammation you're suppressing isn't just waste — it's part of the adaptation cascade. For recovery purposes, cold is excellent. For muscle-building purposes, you may want to wait two to four hours after your training session before getting in.
The 37 degrees Fahrenheit recommendation Flanigan mentions is aggressive. Rhonda Patrick and others have found significant benefits at temperatures between 50 and 60 degrees Fahrenheit. You don't need to suffer maximally to get the physiological response. The threshold matters far less than consistency of practice.
Start at 55 to 60 degrees Fahrenheit. Two to three minutes. Three times per week. That's the evidence-supported minimum effective dose. Build the habit before you chase the intensity. If you have access to heat — sauna, hot tub — alternate. Ten minutes of heat, two to three minutes of cold, repeat. That contrast protocol is where the vascular pump effect peaks, and it's the entire premise behind what we're building at Contrast Collective.
The 30 percent reduction in sick days from the Dutch cold shower study is remarkable — but what's often missed is the mechanism. It wasn't that cold showers killed pathogens. It was that regular cold exposure trained the autonomic nervous system to respond more efficiently to all forms of stress, including immune challenges. The benefit wasn't direct. It was systemic. You're not hardening against cold specifically. You're building a more responsive, adaptable nervous system that handles every stressor — physical, psychological, immunological — with greater precision. Cold is the training ground. Life is the competition.