Garmin Mk3i to improve SAC rate

[bvbellomo]

I've been a big fan of Garmin watches for running for about 10 years, have a horrible SAC rate, and use a Sherwood Vision which is an older dive computer I am considering replacing. I am tempted to spend a weekend in a quarry with a Mk3i to get some data on my heart rate - the assumption being that the higher my heart rate, the worse my gas consumption, and that a Mk3i can give me nice graphs of both together. For example, can keeping my arms statue-still lower my heart rate? Does it raise when I fin hard? Does it matter if I frog kick or flutter? Is it higher with a camera? Does having a thicker wetsuit raise or lower my heart rate in cold water? My heart rate varies a lot by day and time and how I slept, ate, etc - it 73bpm right now and true resting is less than 60bpm. I didn't do any exercise today except weight lifting, but I had a big dinner with alcohol. Is my assumption right or can I use more air with a low heart beat and less with a higher rate? I could probably do a similar analysis with the Garmin watch I already have and the Sherwood with a little more work.

So my question is mainly for people with the MK3i. Have you ever tried to do something like this? Do you collect heart rate data on your dive? Do you find it useful?

 

[Pavao]

I do have a Garmin.
But I’m sorry man, this is pretty much pointless, a measure of your heart rate will only confirm that it should be lower, but you already know this.

Stress level and exertion is what is causing a higher sac rate, more diving will get you more comfortable underwater and good diving techniques will lower exertion, both of these will have a tremendous effect on your sac rate

For example, can keeping my arms statue-still lower my heart rate? Does it raise when I fin hard?

Of course. Is your heart rate lower when sitting on the couch or when you’re jogging?
This is why proper buoyancy is so key, and proper buoyancy is a combination of proper weighting, trim and propulsion. Frog kicks are symmetrical in comparison to flutter, this means a proper frog kick takes advantage of the glide fase, which is a montionless stage of the kick, motionless means less exertion.

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I once did a series of repetitive dives in a cave completing a circuit, at various fixed points I’d write down the time and pressure, I did it in a cave because it’s static and could replicate the dive with the exact same conditions. Did dives in a normal pace and then did it again going extremely slow. The slower dives were about 40 minutes longer in duration, yet I used less gas, even though I stayed longer underwater at the same depth as the other dives, I had a lower overall gas consumption due to lower levels of exertion.

I hope this helps.

 

[Underwater Tourist]

you are way way overthinking it imho

ask your buddy to film you for 10 minutes without you knowing, and then post the footage.

99% of the time poor sac = sub optimal inwater technique