2nd Percentile SAC Rate

[GameChanger]

Hi Joebob, I am 6'1" and weigh near 300 pounds. Large fat 62 year old dude. Generally active taking mountain walks with my dog in the mornings. I last dived in June last year. I am off to Bali for 3 weeks next week then off to Bohol Cebu 2nd half of October thru 1st week of November.

Now I have posted in the average sac rate thread and yes I am quite good on air but use diving and breathing techniques. I have been diving since 1986 and before covid hit for the previous decade I was doing around 200 - 250 dives a year on diving vacations. I will often do 12 days straight diving with 3 - 4 dives a day. By the end of these vacations I am so zoned in I get people tugging on my fins thinking unresponsive diver cause I move like a corpse. When I was new to diving I certainly used far more air than my dive buddies.

Perhaps go back to a single 100 tank and just try to do dives where you really do not move around, let the water currents carry you.
In Bali we will be doing some fast drift dives... In this video you see lots of divers flailing around except the diver at the back barely moving his fins. He is the one in control and perhaps using less gas.
I think your lungs work just fine. It's diving techniques that you need to learn to reduce gas consumption.

I get lots of people who have never dived with me thinking this fat guy will be done in 20 minutes.

The current in that video reminds me of a wall dive site in Cozumel, MX called Barracuda.

 

[Joneill]

The current in that video reminds me of a wall dive site in Cozumel, MX called Barracuda.

Also just like Tiputa Pass in Rangiroa.

 

[Lorenzoid]

I am in a 6mm wetsuit right now. The last 10-15 dives have been with doubles, but before that was all single tank. It might be interesting to switch back for a few dives to see if there is a big difference. I could see a scenario where it would have gone down more over time if I hadn't switched to doubles. My single tank setup is a jacket style though.

Sure, as an experiment, try going back to the single-tank setup, do some relaxing dives where you're not swimming hard, and take a few data points. If you report back that it didn't make much difference we will all be stumped, and maybe your original question about a health condition is worth considering.

As for the doubles, when I first read your post I was going to suggest trying a larger tank, because my SAC seems to be lower when I know I have way more gas than I need to do a dive. It's all about relaxing. As soon as I stop caring about gas consumption, my consumption decreases. On that note, maybe do a bunch of dives in the single-tank setup without calculating your SAC or otherwise caring about anything but enjoying the dive (I find singles more fun than doubles anyway). THEN, after some later dive, do a calculation.

 

[Kendall Raine]

I am in a 6mm wetsuit right now. The last 10-15 dives have been with doubles, but before that was all single tank. It might be interesting to switch back for a few dives to see if there is a big difference. I could see a scenario where it would have gone down more over time if I hadn't switched to doubles. My single tank setup is a jacket style though.

I agree with all the advice offered in this thread, but, that said, 1.2-1.6 is very high. Suspect a big part is newness to diving along with diving steel doubles after so few dives(?!). Since you're diving wet (in Washington?) thermal issues could also contribute.

If after trying to lighten your equipment package, accumulating 100 dives, and focusing on respiration you're still >.8 you might consider a pulmonary function test. My guess is technique, gear and experience will solve the issue but physiology is a possible contributor.

 

[kaylee_ann]

It has been a long time since I looked at that thread, but IIRC correctly, I participated by strongly cautioning against drawing any conclusions from it. It is bound to present an unrealistic range of results.

• It is on ScubaBoard, a forum highly overrepresented by experienced divers. Another SB forum found that the majority of participants use a BP/W setup for their BCD, and about the time of that survey, an industry survey of the scuba retailers showed that BP/Ws represented 1% of BCD sales. In my area, the vast majority of dive shops do not stock BP/Ws.
• The survey called for voluntary participation. I don't recall if I participated, but I hope I didn't, for the very reason exemplified by the opening post. When people voluntarily participate in a survey, the ones who participate tend to be at the extremes, and if one extreme is clearly bad, then that extreme gets little partitication.
• As results get published while people are still participating, later participants tend to skew their responses in the direction of the majority.

So I do not believe that any survey of ScubaBoard participants on any topic will come anywhere close to reflecting the range of behaviors in the diving public.

and i'm sure everyone's entirely truthful about their actual SAC rate, rather than hiding that it's high.../s

 

[kaylee_ann]

Forget about your SAC rate for now and just enjoy the dives. It will come.

This- if you're anxious, your respiratory rate will increase.

 

[arew+4]

And one more thing, that helped my boys dramatically,

In, two, three,
Out, two, three, four.

Focus on it when ever nothing else is stealing your attention. Eventually you'll get to the point where you check back in and find your still at that tempo.

 

[Blackcrusader]

and i'm sure everyone's entirely truthful about their actual SAC rate, rather than hiding that it's high.../s

Keylee Ann I am going to log each dive's start ending pressure on my vacation starting next week. First dives are in an area of slow currents or no current diving. Going to take it easy and not do any deep dives for the first couple of days although by the 4th dive the 1st morning dive might be down to 40m depth for a sunrise dive to see bumphead fish. After I return I will post what my SAC rate was for the trip.

 

[kaylee_ann]

Keylee Ann I am going to log each dive's start ending pressure on my vacation starting next week. First dives are in an area of slow currents or no current diving. Going to take it easy and not do any deep dives for the first couple of days although by the 4th dive the 1st morning dive might be down to 40m depth for a sunrise dive to see bumphead fish. After I return I will post what my SAC rate was for the trip.

Awesome! Interested to see how your rate will vary based on activity, depth etc

 

[Blackcrusader]

Awesome! Interested to see how your rate will vary based on activity, depth etc

Yeah me too after a long break from diving. Normally I use the first day of diving to really just settle back into my gear and get my breathing technique sorted. By the second day I am normally back in my zone. If I can start with my first dives being a sac rate of around 10l/min and then dropping down to my normal 8l/min in gentle diving I will be happy. I have not had covid so hoping I also don't get it on my vacation. Best thing for me is to find tiny critters to photo where I need to be motionless with no bubble trails.