A friend of mine recently asked me how she should be warming up for target deep dives. She’s relatively new into the sport and is currently a ~35m diver, diving in very particular conditions: A very cold Canadian quarry with a steep 1-shot thermocline at around 10m. 

The last time I was diving at that location, the water changed from around 18-degrees to 4-degrees in the space between 9 and 10m. 

Like I said.. A very steep thermocline. My advice to her was to either; 

Do 1 no-contractions hang shallower than the thermocline and stay in the warmer water – Or –  Take 3-5:00 extra relaxation time at the surface and skip the warm-up. 

Thinking beyond just this one example, my advice would be very similar to almost any diver, in any location, at any level.

Of course, in warm water there’s no need to ‘avoid’ thermoclines during your warm-ups, and before someone gets on my case about “not warming-up is an advanced technique for advanced freedivers”… Yes, for most divers, 1-2 warm-up dives is probably a better idea than just going for your target on dive number one.

However, the principles of my advice will remain the same for almost everyone. We need to think about what warm-ups can do for us, and what they can’t. Taking that into account will help all of us come up with our best warm-up procedure. 

What warm-ups can’t do

I think the best place to start is with what warm-ups can’t do and maybe dispel some myths about the effects of warm-up dives. 

To the best of my ability, I cannot find any objective or subjective evidence that doing warm-up dives will improve our dive response. I cannot find evidence that warming up improves our blood shift, or that blood shift is cumulative. I cannot find any real evidence that warming up improves the “spleen effect”… 

Basically, I firmly believe, (and haven’t seen evidence to change my mind) that warm up divesm do not improve our physical ability to perform a deep dive (or a DYN/STA for that matter). They don’t increase our physical ability to hold our breath, and they do not physically protect our lungs from barotrauma.

They do not “kick in” your dive response as we are often taught to believe.  

If done correctly, a perfect warm-up will have a neutral effect on our physical abilities. Take a warm up too far and this will become a negative effect.

So what are they even good for?  

What warm-ups can do

Despite the “fact” (I use that term lightly FYI) that they do not improve our physical ability, I do believe that they can be extremely beneficial for our mental ability

For most freedivers, a good dive can be an extremely relaxing thing. Hanging at neutral buoyancy feels great and can quickly slow down our internal rhythm, kind of like a condensed  meditation. For many of us it’s really hard to fully let go of the general thoughts that consume our normal everyday lives. A warm up dive can be the catalyst to let go. 

A warm-up or two can easily get us into the perfect state of relaxed-yet-focused that we need to be in just before anything ‘big’. This ideal mental state is what extends our breatholds and reduces physical tension protecting us from injury and blackout. 

Some of us (no-warm-up divers) can achieve this state before our first dive, and some of us can’t. Warm-ups are for those who can’t, which isn’t something to be ashamed of or particularly concerned about. If you need warm-ups, do them. Just make sure to do them right. 

Getting it right

For me, getting the warm up right means maximizing what it can do, and forgetting about the things that it can’t do. 

As mentioned, all a warm-up serves to do is help us achieve a correct mental state. We are using breath-holds to lull us into a sleepy, calm, and focused mindset – Ready for our deepest dives. To achieve this, we want to do the most comfortable and enjoyable warm-up dives possible. 

In simple terms: Shallow hangs, without pushing (no contractions). Simply enjoy your dive(s). A comfortable 1:00 warm-up is far more useful than a 2:00 one that you need to push for. A gentle 10m hang is better than an exhale dive to 25m that unnecessarily stresses the lung tissues.

Warm-up dives need to be easy and calming. Every tiny bit of effort whether it’s mental, physical, or technical, takes away from the effectiveness of a warm-up. Unless they are as easy as possible, they are potentially doing more harm than good. 

What to avoid

I think the first and most obvious thing to avoid is becoming hypoxic, even mildly, during your warm-ups. To do a big dive we rely heavily on O2 that’s stored in our blood and tissues and becoming hypoxic, even just a little, means that we’ve eaten into those stores which don’t recover immediately. 

I recently safetied a small depth competition, and there was 1 hypoxic ‘event’ in the whole comp: An LMC that luckly didn’t require assistance. The diver in question, surfaced from their last warm-up dive (nearly 20:00 before the dive) with blue-lips. Even 20:00 isn’t enough time to fully recover from a hypoxic warm-up. 

Secondly, I would avoid any lung compression. Warm-ups do not decrease our risk of squeezing, but they can increase it. Doing FRC or RV (any of the various degrees of exhale diving) is, in my opinion, very risky. All it does is put unnecessary stress on the lungs, without any benefit to our bloodshift or alveolar flexibilty. 

A warm up dive should never take you below your residual volume. This means <30m on inhale, and <10m on FRC (if you decide FRC warm ups is the way to go for you). My deepest dive to-date with warm up was an 80m VWT dive, and my warm up for that was an inhale hang at 12m. 

Thirdly, we need to avoid any significant nitrogen exposure. The last competition I participated in was the ‘Dahab-Apnea Spring Comp’. During the briefing a ~70m diver asked for a 50m warm up line. Doing such a deep (speaking in %%) dive right before a competition dive is pretty crazy. 

This can only be detrimental to physical performance and serves no value at all. I could go on about increased squeeze or BO risk, but the obvious one here is DCS. Of course, it’s probably not going to be a problem doing 50 & 75 in a single ‘session’, but due to the 0-benefit nature of doing a 50m warm-up dive (don’t forget mild hypoxia, and lung compression problems), I can’t see the nitrogen exposure as a risk worth taking.

Finally, just don’t complicate things for yourself. I’ve seen divers who descend to 10m, exhale some air, and then continue to 15 to hang. I’ve seen divers who do a 15m dive for exactly 150% of their target dive time, and then a 20m for exactly 200% of their target dive time. Some hang until first contraction and then wait 00:30 before coming up. The arguments for doing these things are usually; increased bloodshift, better dive response, decrease risk of squeeze, less this, more that… ETC

With all due respect, these arguments are wrong. These kinds of warm-ups are doing nothing for the body, and are very far from ‘as relaxing as possible’ rendering them less effective than they can be. 

The only measurement that matters in a warm up is: How good it felt. 

How do I know I’ve gotten it right?

Well to be honest.. You never really do (but it doesn’t actually matter).  

This is in my opinion the single most advantageous part of doing no-warm up dives. You really can’t f*** it up. 10-15:00 of lying on the surface with your eyes closed is really-really simple. Not much can go wrong here. 

However, for those of you who do warm up.. 

Your body knows what to do, and it’s the weeks of training that lead to the dive you’re about to do that will decide whether or not you’re capable of doing it. 1-3 warm-up dives aren’t going to magically increase your preparedness for a deep-dive, but like I’ve pointed out, they can ruin it.

I guess the easiest way to say it is that you can’t not do enough. Your warm-ups can’t be too short, too shallow, and they for sure can’t be too easy. As long as they make you feel relaxed and focused, then you’ve done as much as you possibly can: You’ve done the perfect warm-up. 

At the end of it all the success of a dive lies in the hands of your training, not in your warm-up. 

Just a quick note about the featured image: Not only is this probably my favourite photo of me freediving, It’s actually the last time I’ve ever warmed up for a proper deep dive. It was a ~2:15 dive to 15m before a 67m CWT-b personal best.