Strut-n-Rut has the same thought I had.......you don't need to hold your arm straight out in mid air on the deer(unless of course he's staring a hole thru you! <img src=icon_smile_shock.gif border=0 align=middle><img src=icon_smile_big.gif border=0 align=middle>)

You can simply hold tight with your back muslces against the wall, and lower your bottom limb until it rests on your thigh......you'd be surprised how long you can hold the bow back without having to hold it UP also.
I drew on a nice buck a few years ago just as his head went behind the only tree on the trail in front of my stand......A big white oak.
I figured it was a slam dunk until he stopped with just his head and shoulders sticking out on my side.
There was a kid playing on a motorbike way up at the top of the field edge, and the buck was locked up watching what that stinkin kid was doing.
I was afraid to let down he was so close, but managed to get the bottom limb resting on my thigh.
I'm not kidding when I say I think I held that bow back for 5-6 minutes......adrenaline helps.
When he finally committed and took 2 more steps the pin was back up and on him with very little movement and it was over........when I released , I realized just how tired my back muslces were, but I NEVER would have gotten that buck trying to hold the bow straight out.
Your back muscles will take much more strain than your much smaller arm muscles, so use them if you have to.

On a trip to South Africa not all that long ago, I drew on an Impala while he was facing dead away from me at a water hole. My thinking was I would draw while he wasn't looking, hold for a bit, and he would turn and give me a shot.

I drew, and held, and held, and held, sweat began to run down my face, down my back, from under my arms, until I finally had to let down. I simply couldn't hold with any confidence any longer. I imagine I held it for maybe 2 minutes.

Being able to let the bow down easily and quietly made all the difference.

I let down, caught my breath, while he continued to drink with his butt in my face. When he pulled his head up (maybe 2 minutes later) I redrew and took a broadside shot at 20 yards. His horns and skin now adorn my small but oh-so-quant trophy room! <img src=icon_smile_big.gif border=0 align=middle>

Likewise, on a hunt last month in Argentina, I drew as a large herd of Blackbuck antelope moved towards me. Crouched down on my knees near a small patch of cover, I was at full draw, holding, as they moved in my direction. I held for approximately 1 minute before taking my blackbuck at approximately 5 yards. Yep, 5 yards.

If you've ever seen blackbuck run and hop, you would understand why there's no way to draw with them close if you are on the ground. I a herd, there's too many sets of eyes to see you and they scatter way too fast. Being able to draw as they were incoming and hold til they were in position was key to my success on that antelope.

Bow hunting takes exercise and a certain amount of physical strength, where rifle hunting takes considerably less. Exercise in between your practice sessions. Some basic exercises with dumbbells like one-arm bent over rows, etc. can really help with a smooth and quiet draw, the ability to hold at full draw longer, and the ability to aim better and more stable.