Problem #1: We don't actually know if increased time would necessarily rip our arms off. Remember, the arm movement results from receiving signals from the brain AND receiving chemicals from the rest of the body to allow our muscles to contract and expand AND receiving oxygen from our blood. It is possible that to someone standing in the anomaly, the movements would simply be small, jerky, and followed by long pauses.
Actually, scratch the math, I'm just going to continue with what I think would actually happen if you
put your arm inside the anomaly. You can read it like xkcd,
but without the illustrations, and done by an amateur:
Blood flow: Our arm is connected to the body on several levels. First of all, we have the blood flow from our pulmonary system coming inside and out. The blood crossing the boundary would suddenly speed up, leaving the arm very oxygen deprived. When it exits the anomaly however, because it exits at a faster rate, it come come back to normal. So is it it for our problems with oxygen? No it isn't, and it has to do with the blood you already had in your arm before you enter the anomaly.
Depending on how fast you put your arm in, it might, or it might not be a problem. Assuming it is, the blood you already have in your arm would speed up, coming to the exit faster than it can handle it. The result would be an artery blockage, directly before and after the exit of the anomaly. As you can imagine, it would be very unpleasant. Maybe your veins will even burst, and you just have muscle cramps, I do not know. It is likely that this blockage will get fixed with time, as our arteries can handle a faster blood flow than we have.
My sucky illustration:
http://s1308.photobucket.com/user/Horrible_illustrations_for_ER/media/arteryblockage_zps3000cbeb.png.htmlThe result, is that after a few seconds, your arm would become very oxygen deprived. Have you ever tried holding a book for several minutes straight up? At some point, your arms will go numb all lower down by themselves. The severity of it might vary depending on how much the anomaly speeds the time up, but it will go numb on some level.
Conclusion: Enter the anomaly slowly. Don't linger. Don't just put your arm in, enter entirely.
Muscles: You're likely to have a lot of problems here, but luckily, some of them can be avoided. First of all, you need oxygen, and you won't be getting it much, so it will be really uncomfortable. In addition, to function, the muscles need some chemical (C something I believe?) to be able to break and make bonds. I don't know where you're getting that from, and how much you have (anyone knows anatomy?), but assuming they come from the rest of your body, you will very soon find it not only hard to give commands to your numb arm, but it will also be very slow at executing those commands due to the difficulty of breaking and making those bonds. That slowness might actually be good for you, depending how you look at it. But it be bad for your muscles.
Now for the serious, but luckily avoidable, problem. Unless you're very precise as to what you're doing, you are likely to have your arm stop somewhere shown on the first diagram. Meaning, either in the middle of your biceps, or of your triceps. That is bad. If you move the muscle at all while in that position, the muscles will stretch like they are supposed to. However, the parts of a muscle on the anomaly part, will stretch a lot faster. That will result in a rapid increase in tension as one part of a muscle struggles, but cannot, pull the other part with it. That is likely to result in strains, sprains if you do it over a filament, or even serious ripping. Worse, you will likely experience mind-boggling pain, and do something like bend down, or flinch your arm away, or shake uncontrollably (Will save?). By doing that, you will only make the problem worse, and may cause serious damage to yourself. Still not sure about ripping your arm off, your body just doesn't have enough power to do that, but you are likely to break something.
How to avoid it? Don't use that muscle that is at the intersection of the zones. At all. Enter with your arms put your arms to the side, or not moving. Don't bend or unbend your knees when stepping in. When steeping in, step with only one foot, but make sure the intersection does not touch the pelvis area. Then follow the illustration. The last one is shown because as parts of your body enter, you will probably curl together, as your head goes down so as not to snap your neck, etc... Doesn't actually have any negative effects beyond embarrassment.
Illustration for how to enter:
http://s1308.photobucket.com/user/Horrible_illustrations_for_ER/media/crossing_zps20ff3796.png.html(Problem with this method: you enter the anomaly relatively fast. So in short, this method sucks. I only thought of it now. Actually, what is probably a better way, is to lie on a stretched/cart, and be hauled in really slowly, so you don't have to move at all.)
Conclusion: Don't use the muscles half in the anomaly. Enter it entirely. Don't linger.
Brain Reception: Your brain is likely to be overloaded with information, as the nerve cells send back the usual messages to the brain. However there may be a lot more of them coming because of the time change. That might not be a problem at all depending on how fast the signals travel in our body, and how much the time is increased. Probably not a big problem. If unlucky, your brain will go into panic mode, thinking something is wrong. In that case, I don't think anyone knows what will happen. Fever, fight or flight, heart rate, shock,
, et cetera...
Your movements are likely to be very jerky, as the brain sends out signals at a slower rate than they are followed. As someone who has no knowledge of how specifically the signals are transferred and followed. I have no idea on the consequences of that beyond that.
Concusion: ?? Suck it up?
But it should be fine once we enter the anomaly. If we do so, at least. I'm tired. If I missed something, don't berate me. Also fun things to think about as we enter: Eyeballs. Inside organs shifting as we enter. Digestive system.