Dr. Rhonda Patrick: So I do want to kind of shift gears because cold-water immersion is an area that you have done research in. And I'm personally interested in the neuroendocrine effects of cold-water immersion. A lot of physically active people are interested in using cold-water immersion for recovery, for enhancing— sorry, for blunting inflammation of the muscle. But you've shown, and maybe you can talk about your study about, you know, doing cold-water immersion immediately after resistance training can blunt some gains.

Dr. Luc van Loon: Yeah.

Dr. Rhonda Patrick: Do you think the timing of cold-water immersion can affect, you know, whether or not you're going to blunt those gains?

Dr. Luc van Loon: Because you want to keep doing those cold showers?

Dr. Rhonda Patrick: Yes, I'm doing those as well.

Dr. Luc van Loon: So, yeah, I mean, I think, I mean, with looking at heart rate variability and stuff like that, I mean, I've been experimenting with that myself as well with the cold showers and the ice baths. But, of course, from a muscle perspective, nothing makes sense on recovery after exercise that cold would actually be helpful. So, we did a study where we used the intrinsically labeled protein so we could track where the protein goes acutely, but also more long-term. And after exercise, We put one leg in cold water and one in thermoneutral water. And we saw that the leg in the cold water did not get the same stimulation of muscle protein synthesis. And basically, less of the protein would actually go to the leg, less perfusion, less stimulation of muscle protein synthesis.

So, from at least for the first 6 hours, it seems evident that acute recovery— Recovery in the light of muscle protein synthesis, glycogen restoration is actually compromised by the lower temperature. Part of that is because you inhibit perfusion, but also, of course, all the enzyme and all the process activity in the muscle is also reduced by a lower temperature because that is just what happens. I was surprised that I thought like, hey, maybe then you compromise that acute recovery phase, but then you maybe catch up later on. when you warm up. So that if you do this over 2 weeks, it doesn't make any difference. So we continued doing that for, if I'm not incorrect, over 2 weeks with 6 training sessions. And so it is 6 training sessions with only up to about 15 minutes of cooling.

I thought that could never have an effect over those full 2 weeks. And if there is an effect, we would not be able to pick it up. But we did. And over those 2 weeks, total protein synthesis in that leg that received cooling compared to the other was actually less and actually measurably lower. So that 6 times 15 minutes cooling over 2 weeks, 14 days, 24 hours, had a negative impact on the stimulation of muscle protein synthesis. My only conclusion is that the reconditioning is therefore not optimal. Now, if you still want to do the cooling, now the shower is only short, but would it be Good to do it at different times? I think so. Why is everybody then still doing the cold-water immersion after exercise?

I think it came from sports where you basically hurt the muscle, where there's massive inflammation, where there's blunt force trauma on the muscle that actually you basically support the muscle in recovery, not the recovery, not the reconditioning, but basically minimize the damage. And then people started using it for other sports as well. But I think for resistance training or for endurance training, it's— you shouldn't be using it, at least not acutely after the exercise session.

Dr. Rhonda Patrick: You said something that I picked up on. You said for 6 hours. Do you think that if you do cold-water immersion and you wait 6 hours after resistance training, that you would still affect muscle protein synthesis?

Dr. Luc van Loon: Pure speculation. I think it would be less so.

But then the other question is then for your, your other benefits, whatever they are, of course, there's also a lot of discussions on that. Do you need to do that 15, 15 minutes? Is it better to do it the other day? At least the first few hours, I think, are essential for the muscle. I would stay away from the cold there. Is it okay to do it then in the evening or the next day? I would favor that as opposed to the other one.

Dr. Rhonda Patrick: So, waiting for recovery days. You mentioned endurance training, but, you know, there are studies showing that cold-water immersion can enhance performance in endurance athletes and also enhance neuromuscular function. You're talking about that.

Probably not as These people aren't, you know, the resistance training is really stimulating muscle, so I'm wondering if you could do it perhaps on an endurance training day, maybe wait a few hours again.

Dr. Luc van Loon: I think we would have found exactly the same thing if we had done endurance training. So this was resistance training. I think if we had done endurance training, you would also have less of your amino acids that you ingest go to the muscle. I mean, a lot less of all this kind of work has been done after endurance training, but It seems to follow all the same principles. It's just the different sets of proteins that are being expressed to a greater or lesser extent after endurance versus resistance exercise.

But they're also responsive to nutrition, and so they should also be responsive to blood flow to the muscle. So I think it doesn't make a difference for endurance or resistance-type exercise. The studies that I've seen is they either show no effect, and if they show effect, it's studies where it's not endurance exercise. It's actually high-intensity intermittent type exercise where there's also a huge damage effect and inflammation. And I think there it can have a benefit to dampen that down, and then acute performance afterwards is less compromised. But that's something else than optimizing your training reconditioning. Right. Yeah.

Dr. Rhonda Patrick: So you're talking more at the elite level where they're really like the rowers or the, you know, these runners that are that are, you know, they're incurring more damage on their muscle. So if the cold-water immersion is causing vasoconstriction, it's preventing the muscle perfusion, right? The question is, how long does that last? So the norepinephrine is the hormone that is regulating that, as you know, and that does go up even after just, you know, 2 minutes in cold. So the question then goes, well, Well, how long does that last? So, like, you know, is it an 8-hour response? Do you think it would be 8 hours that it's going to be affecting?

Dr. Luc van Loon: I have no idea. In this case, I mean, temperature, at least skin temperature, was already quite normal quite fast.

But the response over 6 hours was still visible. So, I mean, these studies are hard to do because then if you actually would do it this way, I would like to take a biopsy at 2, 4, 6, 8, 12, 14, 16, 18, 22, and 24 hours. And of course, nobody wants to participate. Not even the older subjects in our studies are going to sign up for that. Or at the very least, it would be interesting to do a cold-water immersion where it's not immediately after resistance training. It's, you know—

Dr. Luc van Loon: Oh yeah. That would be great. 6 to 8 hours, maybe the next day.

If we would do that 2-week intervention study where you actually have the 3 sessions And the, and the, the, no, the 6 training sessions, and you have the 6 cooling sessions, and then you have the 6 cooling sessions on the days that you don't have the training. So you have 3 treatments, 6 training sessions with cooling, 6 sessions with cooling on the other day, and only the 6, 6 training without the cooling.

Dr. Rhonda Patrick: Yeah, that's a huge study, but I mean, I'll be interested to see what comes out after 2 weeks.

Dr. Rhonda Patrick: Yeah. I guess the question is, is that, you know, If you're doing resistance training and you wait 6 to 8 hours after that training, will that cold-water immersion blunt your gains? You said maybe a little bit, maybe not.

Dr. Luc van Loon: It will likely be less if you do it on the opposite day.

Dr. Rhonda Patrick: So waiting just on a recovery day is what you think is best.

Dr. Luc van Loon: But that's the whole thing. We always focus on muscle. But everything has to be optimal. I mean, it's the same as, oh, you can take creatine and you get stronger legs and you have a higher workload. But then if you're a high jumper and you gain 1.2 kilos simply also by most of it actually water retention, it's not going to improve your high jumping. So it's more than only muscle, of course. Of course. Yeah.