Scuba diving calories!

skinnyrev2b

So, I started MFP again and have been accurately logging my (weighed) food intake, water intake and, after taking advice from the boards, not been eating the full calories MFP says I've earned from exercise. (I've been typically been eating 25-50% of them depending on my food choices for the day - still trying to work out what fills me up for the least amount of calories/greatest protein gain). However I had to laugh when entering my exercise for today:
Walking the dog (4mph pace for 30 mins) = 180 calories - ok, fair enough - got some hills in there so that sort of makes sense.
Circuits (30 day Shred for 28 mins) = 250 calories - um, think this is a little high
Scuba (120 mins) = 1000+ calories!!! No. I'm sorry, but no way! Maybe in the Maldives on a mad current dive swimming against it (though why you'd try is beyond me) but two hours teaching in the pool (I'm an instructor) - no way! Just goes to show how easy it would be to over eat based on MFP's skewd calculations!

mtaratoot

I posted something similar to another thread, but it was four years old. I'm posting here, too, since it's a newer thread and because this thread title is a better fit. It's about MFP's calculation of calories burned SCUBA diving.

I too was VERY surprised that MFP said 90 minutes of SCUBA diving expended 736 calories. This is about the same as an hour of vigorous lap swimming. That can't be. I was on a stationary bike doing a HIIT workout the other day for 32 minutes, my pulse was up to and over the peak range during the strenuous part, and the machine told me I expended 300 calories. I can believe the machine in this case. It's really hard for me to accept that 90 minutes of diving is the same energy expenditure as an hour of high intensity interval training of vigorous freestyle swimming. Today I did a vigorous but steady-state cardio workout on a stationary bike for 49 minutes and recorded 490 calories and another 26 minutes on another bike for 250 calories. I worked WAY harder than diving.

That said, I try to use very little effort when diving. Aside from extending dive time by using less breathing gas, it's advised NOT to do strenuous activity during a dive or in the 24 hours afterwards. This recommendation is to reduce the chances of decompression sickness (DCS). In the case of my most recent dives, I actually was working a bit. I'm a dive volunteer at a non-profit aquarium. Many of our tasks do take effort -- but nothing like swimming laps or getting to peak heart rate on a cardio machine. In fact, I have experienced increased breathing rate when doing vigorous scrubbing. What that happens, I get "behind my breath" because even though I have a very nice regulator, it can only provide so much air. If feels a little panicky when it happens. Been there, done that. I just relax and breathe a minute or two and things get better; I have never panicked enough to head for the surface. Yeah; there's plenty of air up there, but it's best to work out problems where you are. For tech divers using rebreathers at depth, it's EXTREMELY dangerous to have increased breathing rates due to partial pressure of gasses. At very deep pressures, oxygen can become toxic, so partial pressures are decreased for deep rebreather tech dives. Even just a little exertion can, and has, become fatal. I'm not a tech diver, so this doesn't affect me. But I still like to breathe!

So, I searched around at the Divers Alert Network (DAN) website to see if they had published any data on caloric effort from diving. No luck. I will continue to search for some hard data, but am not sure I will find any. I wonder where the estimates on MFP came from. Anybody know?

While it's true that water conducts heat much faster than air, and while our water is 45 - 50 degrees F., I wear a drysuit with a warm undergarment. Even in 45 degree water, I stay fairly warm unless I'm not doing ANY activity. One of our vacuuming chores is very low energy, and during those dives, my fingers can get a little cold sometimes. Effort or not, there's usually dampness on the exterior of my undergarment up against the inside of the drysuit. Perspiration happens. It's nothing like what I sweat out on the cardio machines. No way. With my old undergarment, I would sometimes get cold on a second dive as the garment wasn't as efficient at moving moisture away from my skin. The new undergarment is awesome; thanks Bare! I do need to add a little extra lead because it's so thick, but that's an easy fix.

Looking a bit deeper (pun intended), I find it interesting that there are 14 different choices in MFP for bicycling (seven each for actually riding and for stationary bikes). There's ONE entry for SCUBA, free diving, and snorkeling combined. These are fairly different activities.

I think that it would be possible to link caloric effort to air consumption. When I download data from my dive computer, the Oceanic software calculates a Surface Air Consumption (SAC) rate. It normalizes the breathing gas used at any depth to what a diver most likely would have used on the surface. All else being equal, an experienced diver with good buoyancy control will have a lower SAC rate than a new diver. Even though some of that extra air will be going in/out of a BCD or drysuit, that new diver will be almost certainly be doing more work, and therefore burning more calories. For a given diver, especially an experienced one with efficient movements, the SAC rate increases as effort increases. An example; three weeks ago I did a 54 minute dive that wasn't very energetic. I slowly moved along the bottom following another diver and watching for large fish with pointy teeth. My SAC rate was 0.505 cuft/min. A second 50 minute dive was more energetic; hovering around 12 feet deep near the tunnel watching for those friendly fish while a working diver cleaned the acrylic. My SAC rate for that dive was 0.627 cuft/min. My dives this week were more energetic than that; I was the one cleaning the acrylic as well as the windows and lights underneath the tunnel. That under-tunnel job usually gets my breathing up. My SAC rates were 0.653 and 0.686 cuft/min. When I get on that stationary bike or elliptical or treadmill, I can GUARANTEE I'm breathing quite a bit more than two thirds of a cubic foot of air per minute. I'm huffing! It would be interesting to get a really long second stage hose and ride a stationary bike while breathing from a bottle of air to see what my SAC rate would be. I'm actually curious enough I may see about borrowing a giant hose and/or hookah setup to check it out.

Is there any way that the MFP estimate can be improved? Or what else am I missing that uses calories while diving? I know when I've overshot the boat in current and had to WORK to get back, that could burn more calories, but that's a minority of diving. I also know when I'm on a multi-day doing four or five dives (50 - 70 minutes each) per day for five days, I am ravenous. And there's always plenty of food to put in. Climbing back on the boat is perhaps the most energetic part of those dives, again unless current comes into play.

Diving in the 1970s was a different animal without BCDs and basically keep kicking or sink. I wonder if the MFP estimates are from old Navy trials that probably should be revised to meet today's diving standards.

DAN was recently at the aquarium I volunteer at to continue a study on heart health of divers. Because most of us are a little older and dive in drysuits, it was a good environment for them to work in. I wonder if any of their data would be useful, or maybe if they'd come back and to a caloric expenditure study. I should ask.

skinnyrev2b

Hi there. I totally agree (I popped over and 'liked' your post last night when it showed up on the forum). Whilst I've never really got in to the science of calorie burn, I am a tech diver as well as recreational. Therefore I try to keep my SAC rate at about 10-12 l/m, even when teaching (which can get stressful). Thus even though I'm breathing denser air than at surface, and have been carrying round some heavy gear before and after, as well as coping with significant temperature changes, I would consider the calories burned to be comparable to walking (anecdotally speaking).
I suspect MFP have extrapolated from swimming - I can imagine an inefficient snorkeler could expend as much effort as a moderate swim. But just because it's in water does not mean they're all interchangeable!
I guess there's so few of us that it's not worth changing the calculation; or more likely, there's still not enough science to justify any change.
My OH suggests there's been a study done by DAN recently - so maybe I'll take a look and get back to you.

girlinahat

As a former diver I can totally agree that the calories seem ridiculous. When I was diving (UK, waters of 8-19 degrees C, drysuit, on air or nitrox, depths 30-40m) the basic daily activity consisted of – getting to site, having a bacon butty, hauling kit from the car, getting into the drysuit halfway then needing a pee, getting the boat in the water/getting on the hardboat, loading kit from pile into boat, putting on drysuit fully, needing a pee, getting on boat, sweating as we drove to the dive site, trying to find the wreck, hauling the shot over the side of the boat towards the wreck.
Kitting up, buddy check, fall in water, sink, adjust, turn on torch.

The actual dive consisted of me vaguely waving my legs in a leisurely fashion while I ambled around the site, looking for nudibranchs, too many spider crabs, the odd blenny and trying to remember which bit of the wreck was which, and the odd check on my buddy. Then at the end of the dive, either hope we found the shot (unlikely), or set of a DSMB and get to the surface, and probably a surface swim to the boat.

Haul out of the water, have a cup of tea, then off to the next site and surface interval, repeat.

Everything in reverse including getting the boat out of the water, as fast as we could so we could get to the pub for a beer that tasted magnificent, and scoffing food.

I can imagine that the entire day could use that many calories, but not the dive itself. I would be interested in knowing whether depth, pressure and breathing compressed air on demand have an effect. Would comparisons with pilots at altitude work? The discussion on air consumption may be telling – if the average surface air consumption (at the actual surface) is said to be 25L/min then as the majority of divers are experienced in REDUCING this (I used to calculate on the basis of 16L/min although my actual was around 10-12L/min) would this not indicate LESS calories used?

mtaratoot

I sent a request to DAN this morning. I bet they'll get back in touch next week. If they have NOT done this study, maybe they have some insights or will consider doing a study. I'd participate!

SonyaCele

I'm pretty sure I burn more calories walking to the dive boat than I do on the dive itself.

skinnyrev2b

Particularly with a twin set!!! (LOL). Tbh, that's usually trolleyed in and put on at the water's side. But you get my point.
Good call on contacting DAN mtaratoot.

hroderick

i think it would be better based on air used than time

Meaganinsardinia

I am exhausted after diving! I thought the calories were right. Looking forward to finding out.

mtaratoot

I got a reply from DAN this morning. Good stuff. The person that contacted me was Peter Buzzacott. He was an author on a peer-reviewed paper on this topic, and they are going to be doing some more research. The paper was in Diving and Hyperbaric Medicine, Volume 44 #2, June 2014; pages 74 - 78. The other authors are Neal Pollock and Michael Rosenberg.

The authors looked at almost 1000 recreational dives in a variety of situations. Divers were 32 - 52 years old. They used gas consumption to estimate exercise intensity. Their results were an average of 5 (+/-1) MET for the dives. They report that mean +2SD (7 MET) captured "the vast majority of dives monitored." They recommend divers have a 7 MET capacity in ensure ample reserves. I did happen to notice the BMI of the divers averaged 27; many divers ain't svelte.

They cite a previous study by DAN where "normal swimming in a modest to benign dive environment" was around 4 MET; they recommended 6 MET capacity as a safety margin.

Peter also pointed me to a resource at the Harvard Medical School that METs associated with various activities. They list diving as a 7.0 MET activity.

What does this all mean? More research is needed! I think it means that we are generally overestimating the exertion during a dive, but that it's a REALLY GOOD idea to have at least 7.0 MET capacity to engage in diving just as a safety precaution.

Azdak

mtaratoot wrote: »

I got a reply from DAN this morning. Good stuff. The person that contacted me was Peter Buzzacott. He was an author on a peer-reviewed paper on this topic, and they are going to be doing some more research. The paper was in Diving and Hyperbaric Medicine, Volume 44 #2, June 2014; pages 74 - 78. The other authors are Neal Pollock and Michael Rosenberg.

The authors looked at almost 1000 recreational dives in a variety of situations. Divers were 32 - 52 years old. They used gas consumption to estimate exercise intensity. Their results were an average of 5 (+/-1) MET for the dives. They report that mean +2SD (7 MET) captured "the vast majority of dives monitored." They recommend divers have a 7 MET capacity in ensure ample reserves. I did happen to notice the BMI of the divers averaged 27; many divers ain't svelte.

They cite a previous study by DAN where "normal swimming in a modest to benign dive environment" was around 4 MET; they recommended 6 MET capacity as a safety margin.

Peter also pointed me to a resource at the Harvard Medical School that METs associated with various activities. They list diving as a 7.0 MET activity.

What does this all mean? More research is needed! I think it means that we are generally overestimating the exertion during a dive, but that it's a REALLY GOOD idea to have at least 7.0 MET capacity to engage in diving just as a safety precaution.

Definitely a good start. The biggest challenge with measuring any occupational or leisure activity is standardizing the terms/movements so that you are comparing apples to apples. You can measure 1000 dives, but if you are doing the 3-4 MET dive, calories burned will be significantly different from a 6-7 MET dive. And how continuous is the movement?

Sounds like the authors numbers are more reliable than the Compendium. Knowing how a lot of the data in the Compendium is derived, I don’t have a lot of faith in those numbers.

But this gives you some ballpark numbers. Good thing to bring to the group.

mtaratoot

Another follow-up.

I'm just back from a five-day dive trip in the California Channel Islands. I can't believe how much I ate. We did four dives per day except the last day when we could only sneak in three and still get back to port in time. I didn't gain weight even though I figured it would be ok if I gained a little. I ate WAY more than I ever do. Like more than double. Total dive time over five days was 806 minutes.

This wasn't particularly energetic diving. I like to go SLOW. We didn't have a terrible amount of current. We had some. We did have some surge in some places, but if you just relax, it isn't a big deal. Navigation for most of the dives (all but two) was pretty easy if you pay attention. I dove NITROX on ten of the 19 dives. Deepest dive was not much below 100 feet, and most dives were in the 60 to 80 foot range for max depth. A couple were much shallower. I wore a drysuit, and I varied my undergarments to match water temperature. I was only cold on the first dive.

So maybe the physiology of diving does oxidize as many calories as the literature claims.

Causalien

I thought the calories are correct too. Water here is very cold and requires the thickest dry suit. I find that the cold really shaves away your calories. After a day of div9ng and eating, I usuallt come home to find myself about 2 lb lighter.

But ya, if I were to dive in my shorty in shallow tropical warm water with not much to do, it doesn't feel like I expand much calories. It usually feels like I get hungrier the colder I get as I dive longer.

Bentforkx

According to the AlertDiverOnline, a skilled diver with good bouyancy control, swimming no more than 0.5 knots should be working around 3 METs. Swimming against a 1.2 knot current could be working up to around 10 to 12 METs.
Based on about 1,000 recreational dives they suggest about 5 METs of energy is expended on average.
1 MET (metabolic equivalent) = 1kcal/kg/hour = the amount of energy spent sitting still. I am assuming the kilograms do not include your weight belt....
So as an ex PADI instructor myself, I would assume sitting at the bottom of the pool should be a relatively low MET rating.

http://www.alertdiver.com/Physical-Fitness-for-Diving

ps, edit was to correct my reference, sorry

Causalien

In arctic conditions requiring drysuit. It is estimated that between 6000 to 9000 kcal per day is necessary to survive. Which is consiatent with my own observed weight loss of 2lbs after a full day of div8ng assuming that 3500 kcal ~= 1lb

mtaratoot

My typical working dive is in 48 degree water. I'd hardly call that arctic conditions, but far from tropical. I dive dry. I have a warm enough undergarment that I stay warm with the possible exception of my fingers if I'm moving slowly. If we are doing a lot of scrubbing, especially if it's not that far below the surface (six to 12 feet), staying relaxed is key to maintaining buoyancy. I still usually find dampness on the exterior of my undergarment after a dive (inside the drysuit but away from my skin). We have some wetsuit divers on my team. I guarantee they expend more energy for thermoregulation than I do.

I think that DAN study is probably the best data we have for now.

My personal experience does suggest it's more energetic than it seems. This is just based on what I eat on days that I dive and what the scale responds with.

I think modern equipment could probably measure energy expenditure, or at least pulse rate and maybe gas exchange, and get better estimates at least for some dives. I'd wear a heart monitor if it would provide new data, but I think the only real way to estimate gas exchange is just my SAC rate (surface air consumption equivalent). I know that varies from around 0.5 cubic feet per minute (CFM) for non energetic dives to near 0.8 CFM for active working dives.

I wonder if I could go back into my spreadsheet, identify dive days, maybe even assign a dive difficulty rating (purely subjective or SAC rate), compare with my caloric intake the days before and after and compare with non-diving weeks. I probably won't, but it might be interesting.

mjbnj0001

Interesting. So much more is known now than when I was an instructor in the 70s/80s. Based in NJ, we were cold water divers for the most part, and this includes ocean, deep lakes (e.g., Lake George NY) and quarries. Wetsuits, as drysuits were still not as common (and frankly, my custom-tailored wetsuit kept me generally pretty toasty). I was "one with the water" and very efficient (very low air consumption, for instance), but frankly, I could eat a horse daily and still lose weight. This is on average; all conditions, types of dives, destinations, etc. In fact, the habit of being careless about calories consumed became a problem when my sedentary day job (computer programming) became the dominant part of my career and I stopped teaching. I was teaching in-pool 3 nights/wk, 40+ weeks a year, and in the open water 10+ months/year, with also my own recreational diving year-round. Sadly, I've developed some age-related conditions and can no longer scuba dive. I miss it. I still snorkel, which is usually a more vigorous activity.