Knee pillow, hammock angle, circulation, and cold feet

[SubaruWx]

Does a high foot end and a stiff pillow under the knees reduce circulation?

2 weeks ago, I took a short backpacking trip where Temps overnight got down to 22F. I usually sleep warm, but I don’t have the best circulation and so wear synthetic booties to keep my feet warm. I’ve been in temps colder than this before and slept warm.

This time, I woke at 3am and my lower legs and feet were dry but numb and very cold to the touch. Cold enough that I got scared. Everything else was warm. I removed my socks and booties, and alternated warming my bare feet behind my knees.

I’m trying to figure out why my feet were so cold. There were 2 major differences with this hang:

1. My foot end of the hammock was higher than normal - I normally hang the foot end 12in higher than my head, but this time it was 18-24 in higher. It felt great when I lie down, but I wonder if my feet were too high and thus had reduced circulation.

2. I have started using a vacuum bag blown up as a pillow under my knees. This eliminates all calf ridge concerns and is very comfortable, but I wonder if it reduces the flow of blood as there are a major arteries under the knees. This kind makes sense, but it seems a bit far fetched that a pillow (even a fairly stiff one) would reduce blood flow much.

It may not be one or the other, but perhaps the combination of the knee pillow and a higher foot end contributed to less warm blood flowing to my feet.

Anyone have similar experiences or wisdom to offer?

[rodfather]

Hm. Is it possible the underquilt slid down a bit due to the foot end being higher?
I usually hang the same. I like the foot end way higher along with a pillow or stuff sack full of clothes underneath my knees. I haven't been in temps that cold though.

[Twistytee]

Not sure if it’s your issue, but I notice when I cold weather camp and put a pillow under my knees, I don’t get a good seal between my top quilt and my underquilt. Cold air circulates around my hammock and creeps under my legs. I don’t have this problem when sleeping without the leg support. This was down to ~25 degrees for a low. I do t have this problem above freezing.

[SubaruWx]

Hm. Is it possible the underquilt slid down a bit due to the foot end being higher?
I usually hang the same. I like the foot end way higher along with a pillow or stuff sack full of clothes underneath my knees. I haven't been in temps that cold though.

This is possible . I use a SLD synthetic full length underquilt, and it can slip off my feet sometimes. Thus I might not have had as much insulation under my lower leg and feet. I can’t recall observing it this time, and I don’t know if this would fully account for the cold feet, but it could explain a lot.

[SubaruWx]

Not sure if it’s your issue, but I notice when I cold weather camp and put a pillow under my knees, I don’t get a good seal between my top quilt and my underquilt. Cold air circulates around my hammock and creeps under my legs. I don’t have this problem when sleeping without the leg support. This was down to ~25 degrees for a low. I do t have this problem above freezing.

Good idea, but I don’t think this was the case. The pillow was warm to touch and my calf’s were warm. It is possible that my underquilt slipped from under my feet.

[PopcornFool]

I sleep with an inflatable sit pad that I use as a knee pillow and have never noticed it affecting my circulation in any way. However, I have had problems with snug socks. I like my wool hiking socks to fit well so they don't shift and cause blisters. But they will often feel much too snug after a few hours in the hammock. The elastic pinches. If you already deal with poor circulation, tight socks probably won't help. Personally, I find it much more comfortable and warm to sleep in socks that are a bit too big (size 13-14 instead of my normal size 11-12). I always take one pair of too big socks that are my dedicated stay-dry, stay clean, sleep socks that never get worn while hiking.

[Sean McC]

… I always take one pair of too big socks that are my dedicated stay-dry, stay clean, sleep socks that never get worn while hiking.

I do the same. I have a dedicated pair of sleep socks that are thick and loose. I actually think they might be carthart. I would not want to hike in them, but they are comfy to sleep in. Though I would not want to put my dirty hiking socks into my hammock/quilt either. They get pretty nasty.

[BillyBob58]

SubaruWx,
This is a very interesting thread, and I think you are on to something. I think the key is that your "lower legs and feet were dry but numb and very cold to the touch.". Also, your knee pillow was apparently a bit stiff, not much give. So, I'd say it was likely that you were decreasing circulation below the knees. That, combined with the feet elevated more than normal(or even any at all) was likely significantly reducing the flow of warm blood to your legs and feet. To the extent that even booties could not hold in warmth that was not getting there in the 1st place.

And though it may not have applied to you this time, Twistytee made a right on point about the potential for those glorious knee pillows to interfere with TQ fit. I noticed that the very 1st time I started adding big cushy knee pillows to my GE hammocks. Not so much an issue with a sleeping bag, but that open back(often to at or below the knees) on a TQ can make things tricky. The bigger knee pillow, the trickier the fit! And if you move a bit while sleeping, look out!

For me, that situation amounts to being between a rock and a hard place. So many(but not all) of my gathered end(GE) hammocks can cause such calf ridge pain that there is no ignoring it. Most any kind of knee pillow solves that problem 100%. Plus, I'm convinced that knee pillows improve over all comfort in all hammocks(or beds for that matter) enough that I sometimes like to use them in my bridge hammocks, which are already 100% free of calf ridge, plus need no foot elevation! I was totally aware that maintaining a good TQ fit could be tricky. But I had not considered a possible reduction of blood flow below the knees. Ouch!

Here is a fun fact regarding knee pillows: Surgery beds have a thick cushy pad. But, during surgeries, especially where the patient was going to be awake( perhaps only sedated with a local anesthesia), it was pretty routine to place a big, cushy pillow under the knees except for the shortest of procedures. To not do so was to likely end up with an uncomfortable, squirming patient before we could get thru with the surgery. There was no calf ridge for these patients to worry about, but lower back pain was, and a knee pillow was still a huge benefit for them.

So, what to do? Problems such as these were why I so often leaned towards bridge or 90º hammocks for so many years. Not only did I not need a knee pillow(since there was zero calf ridge), my feet were not nearly as elevated. In fact, very oddly, with my very 1st JRB bridge hammock from back in 2007 or so, I think the directions called for hanging it with the head very slightly elevated! I was already used to hanging the foot of my hammock quite high, so that worried me. But indeed, I ended up roughly level with no slide down towards the foot end, even starting with my head slightly elevated. Plus, of course, no calf ridge, hooray! But, in my GEs, the foot end must be elevated. And except for my Superior Gear and MAYBE 1 or 2 others on a good night, I always have to find some way to deal with calf ridge with my GE hammocks. Tricky!

When I set my record low in a hammock of +6F( I know, not even below zero, what can I say? ), I used my old HH Explorer UL with a lightly augmented HH Super Shelter as insulation. No doubt the foot was elevated, as it has been my norm with GEs for many years. No knee pillow, and calf ridge quickly became a problem. I placed a torso sized cut down WM blue pad under my lower legs, and this blocked calf ridge enough for me to sleep. My head was maybe over insulated with fleece and thick JRB hood. My feet, with VB plus thin socks, inside synthetic booties, inside the foot box of a 30F TQ, were overheating and sweating a bit all night. So, even with my feet elevated, they were really too warm. I wonder how that would have worked out with a knee pillow rather than that cut down CCF pad? Would circulation have been impeded?

My head was also on the verge of too warm that night. Long ago I was taught that if the brain, the biggest hog of warm blood, is even slightly over heated, it will signal the arteries in the extremities to dilate and shunt warm blood to them. I still believe that is a fact. Confirming the old saying: if your feet are cold, put on a hat. I would add: put on a thick hood. However, this probably would not have helped in your case, due to your decreased circulation below the knees.

[SubaruWx]

Thanks all for the ideas. I have another cold(ish) trip in a few weeks, so I’ll experiment a bit and see if I can isolate the issue. I’ll try to keep a comfortable foot end height but also reduce the inflation in the pillow. I’ll also try and wear only loose socks and confirm the underquilt is properly sealed with my top quilt. Too many factors for a proper experimental design over 2 nights, but I’ll collect some data and report back.