What factors affect underwater swimming endurance and how to improve it?

Question

I have a good 45 minute cardiovascular workout just before swimming. Although I’ve got my breath back when I go in I imagine my body is still depleted in some way?

What factors affect my (or anyone’s) ability to conduct sustained swimming under water? And what can I do to improve my performance? Is the change in performance more likely to be due to age or to the prior cardiovascular workout?

Edit

A little back ground

I’m now 57 and I do an hour’s cardio workout of quite vigorous intensity twice a week with heart rate up to 170 bpm for the last 5 years. I also play short tennis once a week and do a reasonable amount of walking. So I’m active and reasonably fit. In my early forties I was doing a desk job, didn’t go to the gym and was not that fit, but I was still able to swim a 25m length under water (just) most of the time that I really tried. Now I find that I can only do 20m before coming up for air. That said I swim after going to the gym so I’m not “fresh”, although my breathing has returned to normal when I’m in the pool.

I suppose what I should do is try the swimming first as a proper comparative test for myself, age v fitness. But this made me wonder what factors would affect my performance. Some things I have noticed are that hyperventilating (but not going to mad!) seems to help so perhaps not being fresh is important, as I have only ever been able to do the underwater length once per pool visit, but I’m not sure why?

Update - I am now able to swim this under water length without difficulty provided I spend 7 minutes breathing quickly before trying. Not enough to make me feel dizzy but the blood must be well oxygenated.

Answer 1

The main limitation here is that the oxygen you inhale before you submerge, is consumed by your muscles as you swim. The more energy you use, the faster your oxygen depletes, and this is what causes the "damn, I need to go up top and breathe again" feeling.

The best way to improve your underwater distances, is to learn the best techniques; that is to say, the technique that is most energy efficient.

Performance is expected to drop with age, but since you haven't told us your age, I wouldn't default to using that as an explanation. Where I swim, there are seniors who will out-swim me with a broken hip, simply because they know their shit.

If you have the opportunity, join a swimming class for intermediate/advanced swimmers, and they'll show you the ropes. Competetive swimmers rely heavily on having the most optimal technique in terms of each stroke's distance-to-oxygen-cost ratio, and they'll clear over half the length of the pool after the dive, with leg-drive only.

Answer 2

Primarily lung capacity is the issue here, but the rate at which your body uses oxygen is determined by your overall fitness level, muscle mass and technical efficiency.

As a competitive swimmer with 30+ years experience, I know from experimenting that I can swim further/longer underwater by using a relaxed, steady pace (long, controlled breastroke pull and kick) than by trying to rush to the other end of the pool. This is because your body uses more oxygen when working harder.

Having more muscle mass is a big factor too. I like the analogy that bigger muscles is like having a bigger engine in your car: it goes faster but uses way more fuel. For your body during aerobic activity, fuel = oxygen (plus glycogen etc).

I would definitely try swimming first and compare the results. In some respects doing other cardio will have depleted your muscle energy stores which is likely to reduce your efficiency in the pool, but on the flip side it may improve oxygenation of your blood (which is why athletes warm up before competitions to "get the blood pumping"). Ideally perhaps do a short 10-15 minute cardio warm up and then get in the pool and see.

I will say that in terms of improving underwater endurance, really you need to keep practicing swimming, maybe using some breath control exercises like swimming front-crawl and only breathing every 5, 7 or 9 strokes instead of the more typical 3. Doing other cardio like running or cycling, while it helps with general fitness, won't necessarily improve your underwater endurance because this is actually anaerobic (without oxygen) ability, hence why training restricted breathing exercises will help more.