Question High Altitude Athletes.... Less efficient at depth?

[Sure Squintsalot]

So, I live at around 5,500 ft above sea level, never smoked, and have decades of regular, long aerobic exercising at altitudes above 7,000 ft. Even with a 100 cu ft tank, I average about 25% less bottom time than most lifetime sea-level smokers on a 72 cu ft tank, whose only exercise is regular walks from the sofa to the fridge.

I thought I was an outlier until I ran into a retired, and quite fit high altitude mountaineer who's also experienced the same frustrations. I get back in the boat with less than 30 bars and Heinrich and his buddies will have over a 100 (then light up as soon as their suits are off). Sure, two data points do not make a trend, nevertheless, should I move to the coast and start smoking 3 packs a day?

Is there something about being aerobically unfit that is well suited for scuba diving? Can a diver with borderline emphysema stay down far longer than a Peruvian gold miner?

 

[RobPNW]

There’s a significant number of things that determine your air consumption under water other than fitness.

 

[lowwall]

So, I live at around 5,500 ft above sea level, never smoked, and have decades of regular, long aerobic exercising at altitudes above 7,000 ft. Even with a 100 cu ft tank, I average about 25% less bottom time than most lifetime sea-level smokers on a 72 cu ft tank, whose only exercise is regular walks from the sofa to the fridge.

I thought I was an outlier until I ran into a retired, and quite fit high altitude mountaineer who's also experienced the same frustrations. I get back in the boat with less than 30 bars and Heinrich and his buddies will have over a 100 (then light up as soon as their suits are off). Sure, two data points do not make a trend, nevertheless, should I move to the coast and start smoking 3 packs a day?

Is there something about being aerobically unfit that is well suited for scuba diving? Can a diver with borderline emphysema stay down far longer than a Peruvian gold miner?

Gas usage is simply average volume of a breath x average frequency (breaths per minute).

You are used to breathing deep and fast to get sufficient oxygen when exercising at altitude. This is not necessary at depth where each breath is crammed chock full of O2 molecules. But your brain doesn't have a PPO2 sensor, so you are going to breathe like you are used to unless you consciously counter it.

What you don't want to do is decrease volume by regularly taking shallow breaths. That will result in rising CO2 levels which can lead to all sorts of nasty side effects from headaches to panic.

Which brings us to frequency. Think of it this way, if each breath is the same volume, you have a fixed number of breaths before you run out of gas. If you take a breath every 8 seconds, your dive will last twice as long compared to someone who takes a breath every 4 seconds.

I suggest decreasing your breathing frequency by consciously taking long, slow exhales. This very effectively clears CO2 while increasing time between breaths. Unless you are working very hard or slow to 2 breaths a minute, you will always have more than sufficient oxygen for your metabolic needs thanks to the high partial pressures of O2 you get at depth. Especially with the extra red blood cells you have as a high altitude athlete.

 

[lowwall]

There’s a significant number of things that determine your air consumption under water other than fitness.

Only volume x frequency determines air consumption.*

However several factors can influence one or the other of these, mostly frequency. The biggest one is how much you are using your muscles as metabolizing O2 leads to higher CO2 concentrations which triggers a feeling that you have to breath.

Extra work can come from such things as being nervous and tensing up your muscles, excessive kicking to counteract non-neutral buoyancy, extra drag from poor trim or bulky equipment, and poor positioning if there are currents.

* Ok, obviously depth too. Some folks just like to be a little deeper or shallower than everyone else and that will affect gas usage.

 

[VikingDives]

So, I live at around 5,500 ft above sea level, never smoked, and have decades of regular, long aerobic exercising at altitudes above 7,000 ft. Even with a 100 cu ft tank, I average about 25% less bottom time than most lifetime sea-level smokers on a 72 cu ft tank, whose only exercise is regular walks from the sofa to the fridge.

I thought I was an outlier until I ran into a retired, and quite fit high altitude mountaineer who's also experienced the same frustrations. I get back in the boat with less than 30 bars and Heinrich and his buddies will have over a 100 (then light up as soon as their suits are off). Sure, two data points do not make a trend, nevertheless, should I move to the coast and start smoking 3 packs a day?

Is there something about being aerobically unfit that is well suited for scuba diving? Can a diver with borderline emphysema stay down far longer than a Peruvian gold miner?

Most divers have problems they don't realize. Breathing, buoyancy and trim are three of the most common deficits. Being overweight is another. If you want to meet me out at Blue Hole sometime, we can do a dive together. It might be an easy fix (or three).

 

[Vicko]

Athletes often have higher SAC, simply because they are trained to breath deeply and frequently, especially runners.. However athletes that dive a lot have much lover SAC because they have higher tolerance of Co2, so they breathe less.

 

[inquis]

Your lungs have grown/adapted to compensate for the lower number of molecules in a normal breath at altitude. This will give you a higher consumption rate than YOU would have if you lived at sea level, all else being equal. However, comparing to anyone else is folly. You can almost certainly improve, but there will always be someone with a better (and a worse) rate. It's not a competition (except possibly with yourself).

 

[johndiver999]

A lot of good comments, but also relevant is your body mass and muscle mass and basal metabolism. A large person with considerable muscles is going to burn more calories (and oxygen) than a much smaller person. Also of relevance - that I have observed- aerobic athletes are very good at pumping out a high work load and they do that by increased respiration - that feels normal and easy to them. So these athletes can blow through a lot of air, without being stressed if they allow the work load to increase a fair bit.

Lastly, making air consumption a competition, even with yourself is unwise. A diver can make small changes to consciously reduce air usage, but trying too hard is dangerous.

 

[Sure Squintsalot]

A lot of divers, especially Germans, are lifetime smokers. Why should unfit, obese, older, lifetime smokers be able to dive more than, say, 8 minutes on a full tank?

For what it's worth, I can't say that, including myself, the scuba community at large (see what I did there?) are paragons of healthy lifestyles. Might that lifestyle be uniquely suited to recreational diving?

 

[lowwall]

A lot of divers, especially Germans, are lifetime smokers. Why should unfit, obese, older, lifetime smokers be able to dive more than, say, 8 minutes on a full tank?

For what it's worth, I can't say that, including myself, the scuba community at large (see what I did there?) are paragons of healthy lifestyles. Might that lifestyle be uniquely suited to recreational diving?

I can't tell from your profile, but are you familiar with the concept of partial pressures? There's a good discussion here: Partial pressure - please put in simple words . But basically, the deeper you go, the greater the number of oxygen molecules in each breath.

This surfeit of oxygen wipes away the physiological need for increased breathing rates given the low to moderate physical exertion demands of recreational scuba. It does this essentially without regard to the relative fitness and lung efficiency of the diver. It's really an enormous difference, the number of oxygen molecules per given volume increases 22% going from your 5,500ft to sea level. It increases 200% going from sea level to 20m (67'). This is why I suggested above that you can safely slow your breath rate (by extending exhalations) if you want to decrease your gas consumption rate.

The other advantage (or rather removal of disadvantage) diving gives to older and/or obese divers is that we become weightless when immersed in water. All the effort that we expend to fighting gravity goes away. Fat even has a partial advantage to the extent that it keeps the diver warmer.

The net result is the physiological differences between people that lead to large performance differences on the surface are minimized while diving; at least at the low effort levels which, frankly, you should strive for in most aspects of recreational diving.