We Don’t Need Optimal Sleep
"It's the f*cking pre-workout." Andy Galpin, Ph.D., unfiltered on supplements, evening workouts, and why sleep perfectionism backfires.
One of the best things that’s happened to me in 2026 is falling in love with sauna and cold plunging. I’ve always enjoyed contrast therapy, but for the past six months, I’ve been doing sauna and cold plunge at least a few times a week.
I love the ritual of it. I love how it smells inside a sauna, especially during an aufguss. I love the tingly rush as I warm up after being icy cold. I love the music. I love that I always have an excellent conversation—with a new friend (or myself)—while I’m sweating it out. I love the feeling of walking out calmer than I walked in.
I’ve also become convinced that I sleep better on the days I do contrast therapy—which is exactly the kind of thing I’d side-eye if someone else told me that. I’d love to believe there’s a measurable physiological benefit. But have I simply built myself a very expensive placebo?
I talked to exercise physiologist Andy Galpin, Ph.D., to find out.
Andy spent 13 years leading an exercise-science lab at Cal State Fullerton before becoming Executive Director of the Human Performance Center at Parker University. He’s coached Olympic gold medalists and world-record holders, hosts the podcast Perform (such a good, nerdy listen—check it out if you don’t already subscribe), co-founded the sleep technology company Absolute Rest, and has published dozens of peer-reviewed papers.
We got on Zoom to talk about sleep—and the Deep Rest Reset, his new 14-day sleep program with neuroscientist and philosopher Sam Harris, Ph.D., in the Waking Up meditation app. (Join me in the 10–20 minutes a day challenge; sign-ups close tomorrow.) Andy founded a sleep company, and he told me to ignore my sleep score. From there we got into supplements, evening workouts, what women in midlife actually need from cardio, and a whole lot more. Geek out with us.
Our conversation has been lightly edited for clarity and flow.
Liz: I’ve gotten really into sauna and cold plunging over the last six months. I feel like I sleep more deeply on those nights. Am I crazy?
Andy: No. If you swapped out the sauna and the cold plunge and told me you cut your toenails every night and you sleep better, I’d say, Okay, if you’re sleeping better, you’re sleeping better.
Here’s how sleep works.
