Exertion, the overhead and decompression

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JonG1

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Location
Glossop UK
# of dives
2500 - 4999
Given the nature of the environment it is not uncommon for an ohe to require exertion pre and post dive, often following a decompression exposure, possibly a saw tooth profile and involving a multitude of heavy items to get to and from the dive base.

My questions are around how best to manage the risks of post dive exercise and it's correlation with an increase in incidence of dcs.

Do you adjust gf, inc helium, use surface o2, do you try and clear the environment ahead of peak bubbling (is there even a consensus on time frame?) do you break kit down and increase the number of trips, or hump heavier to get out quicker (ahead of peak bubbling for example).
 
I'd add water and air temperature as another variable.

Even in warm water (22C), I'm a strong proponent of surface deco for big dives. I try for 15 minutes of relaxing at the surface per hour of deco incurred. I don't have any rationalization for that duration other than anecdote. Generally this works well for a team debrief. I'll stay on the loop of pure O2 until I'm as "stripped" as I can get. All bailout bottles, deco bottles, suit gas, heat battery, scooter, reels, pockets, half my harness unclipped, etc. If the air is cold, I'll leave my heat on (having stepped up wattage as surfacing time approached.

I then exit water with just my ccr on. Drop it on the gound/car/tailgate/bench and then drink some water and relax for a bit. Depending on how shallow the water is with my gear still in it, I'll strip out of my suit and grab the gear in a few small trips, starting with lightest gear and ending with scooter(s). This means it's often in excess of an hour between surfacing and picking up anything heavier than an AL80.

It's a long process but I view it as part of finishing the day safely. On a boat with generally shorter dwell/surface time, I'll stay on loop longer and undress before pulling up drop line with deco and bailout bottles if conditions allow.
 
If I can get ahead of the post surfacing bubbles I just do it. I.e. if I leave bottles and scooters in the water next to my RIB I try to grab it all as soon as I can immediately post surfacing then relax. If I can't just be done with it I try to spread it out as much as I can and make the loads modest.

I already pad my deco. 50/75 plus as much time on surface loop O2 (fO2 > 90%) as I can rationalize.
 
It depends on the dive and length of deco.

Short deco dives (less than say 2hrs of deco) I'll get out of the water. Usually by the time I've unclipped deco/ stage bottles, scooter, etc, I feel like its time to get out. Longer than that, and I'll chill on the surface for a good 20 mins or so before turning on the gravity machine.

On real long decos (5hrs+), I try not to carry anything out of the water (including my rebreather). Ideally dives like that are supported and the support team can help wrangle gear up to the truck. Worst case, I'll walk my rig back to the truck after a nice surface deco, grab something to drink, jabber jaw a bit, and relax in the water before schlepping tanks and scooters.
 
The main issue for our nearest OHE is challenging access they are mines generally not hugely deep max 40m but most are 18-25m.

Getting in and out though involves hills, slate adits and slopes that require hand lines sometimes over the slate debris from rock fall or the cutting sheds.

I aim to get my RB out straight away before peak bubbling then do multiple trips for the rest.
Last week it took nearly an hour to clear tree fall from the entrance, which was a ball ache.
 
The main issue for our nearest OHE is challenging access they are mines generally not hugely deep max 40m but most are 18-25m.

Getting in and out though involves hills, slate adits and slopes that require hand lines sometimes over the slate debris from rock fall or the cutting sheds.

I aim to get my RB out straight away before peak bubbling then do multiple trips for the rest.
For sumps with deco I pad the dive like crazy. 50/70 GFs, surface O2, snacks and drinks after getting out. But at some point you gotta work pretty hard to get the stuff out of the cave (and/or back to the car) and further delays run the risk of darkness, trip & fall, or hypothermia. So DCS becomes less of a concern vs just getting out out.
 
Yeah I pad the stops and also puff on the loop on the way out with a decent fraction.
 
I like taking my sweet time swimming back while staying on O2. Then relax for about 10 mins on the surface before exiting the water. Then it's just a slow lazy process with no rushing to collect stages, deco bottles, scooter.
 
O2 prebreathe on the CCR while I'm putting everything on, if on OC, I get on my O2 bottle once ready to go and breathe it on the way down until I drop it off. There's been some research that alludes to that helping, but it certainly doesn't hurt. On OC I'm way too lazy to change gases from my bottom mix though, but even if I did change I'm not sure it would actually change any of the deco obligation.

Make sure to take air breaks on deco to keep your lungs clean to get bubbles out and make sure to move while on deco. All joints moving around, kicking around the basin, basic calisthenics/stretches, etc.

Surface deco on the loop/O2 for as long as possible while breaking everything down.

Use a cart whenever possible.

In cave country I will usually get out, get to the truck, get out of my suit, get some water/munchies, then go back and get things one by one.
 
I did a 4 hour run at manatee a couple weeks back. 30 minutes of deco, all in the Friedman habitat followed by about 15-20 minutes surface deco before climbing out. Maybe another 10 before we started hauling anything. 25-30 total rest minutes after surfacing. Still got some significant discomfort in my left shoulder that persisted for a few days. I think sawtooth profiles in particular call for more surface deco than the in water deco time might indicate. That timeframe has worked for countless long ginnie dives and even a couple long downstream Emerald dives, but it doesn't cut it at manatee. Something I'll have to take into account going forward.
 
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