There was actually a reason why I asked about Flute weight in my other thread. Ive been playing Flute and Fife for years. If I hold the Flute any length of time, I’ll get a soreness from the right elbow up through my bicep( I’m right handed). No secret here, its from holding the arm up for an extended period of time and like Dave Copley says the arm is around 7 Lbs and then add your Flute. I think a lot of us think you only develop arm soreness from heavy lifting or a repetitive task…not so, I think having held my arm in an unnatural fixed position such as Flute playing for an extended period caused it for me… I’m not saying everyone will get this however. On the plus side the soreness goes away quickly after I stop playing. Now when I play the Bagpipes my right arm is closer in and no pain issues, the left are is resting on the bag so no issues there either… I could be wrong, but just my 2 cents…any Health Care Providers out there that can shed light on this 
Ben Shaffer
In keeping with the board’s policy of not giving medical advice, I’ll just share my own opinions.
Playing any musical instrument for extended periods places unusual demands on the body in some way. Keeping arms extended, even in a relatively fixed position, can be considered repetitive motion. You need to vary your position as much as possible, move around, stretch frequently, and stay relaxed.
Five years ago, I developed tendonitis in my left shoulder from playing fiddle, and put it down completely. I intend to go back to it, but have gotten pretty side-tracked with this flute and whistle thing. One major upside to playing multiple instruments is that you can give your body a break when it starts whining at you, (and you SHOULD)!
It may not be the flute weight, actually; we’re talking ounces in one direction or the other. I suffered severe tendonitis in both elbows for about two years and, strangely, it was actually tension from my wrists and hands (watch the thumb!) - probably brought on by laptop use, not flute - that pulled at the elbows. It’s all pulleys and levers, the rubber bands that are tendons being aggravated at the elbow joints from much smaller muscles in my hands and wrists. Knowing that typing caused it didn’t help my flute playing any.
Agreed - no medical advice on a forum. But taking a few days’ breather won’t hurt and might save you a worsening condition later on. Arm exercises with light weights, done slowly and over time, will make the slight weight variables of different flute negligible and are good for you in any case, and - most of all - make sure your hands are relaxed when you play.
Had you been a newbie, I’d have advised building up slowly the amount of time you spend practising. Since you’ve been playing for years, that won’t apply. Have you had the problem the whole time you’ve been playing or only recently? You may want to try adjusting your right hand shape or grip. A 2 piece body would be helpful in that regard. Maybe something like relaxing your grip or lifting your fingers less far from the body? Maybe, like me, you’re just getting old, mate. This is not medical advice, just in case you wondered -
m.d.
I recently was in the market for a non-wood flute, and was able to trial both Copley and M&E. I found the M&E to be quite heavy. When I played it more than 4-5 minutes, my left hand would develop numbness/tingling. It was a shame because I actually preferred the M&E for other reasons. Perhaps this is a symptom that would have resolved with continued playing if I built strength or learned to adjust grip…or maybe it would have worsened. I ended up getting the Copley (which is nice too).
It’s a valid point that arm pain can develop from prolonged static postures. The pain can arise from holding muscle(s) in a chronically shortened position and/or with more force than necessary. Symptoms including pain can arise from fatigue and faulty posture from the head and neck on down. There are numerous reasons and every body is different. If it’s debilitating and causing you to limit playing then it may be worthwhile to see a health care practitioner such as a physical or occupational therapist, ideally a certified hand therapist or one that has experience working with musicians. There may well be a solution.
Hopefully this was generic enough with regards to medical advise… 
I wont give attempt a ‘diagnosis’ just a bit of advice --hope this is o.k…I am a UK Physiotherapist --I used to work in a shoulder clinic with a surgeon and used to get a fair bit of pain myself when I started learning about 5 years ago…
As we (i) get older things take a lot longer to get better,tissues get stiffer and postures tend to get ‘welded’ by repetitive activity …http://www.bodymap.org/index.html
Often this gets reinforced by modern life postures e.g me typing this message ,driving desk jobs etc etc.
Often in my experience insidious pain tends to be more ischeamic i.e nerves need oxygen to function well and when the muscles are overlying them are not moving or are overly tense than pain comes on . ‘Fitter’ body parts tend not to be a threat to the brain and so pain tends to be so much of a problem… It may be that the nerves from the neck and the muscles at the front of the chest/biceps are overly ‘tight’ , it may be that the problem is a combination of tension generally and shortening of one area .
Why not try generally to do some simple mobility exercises, examples here http://www.mydailyyoga.com/yoga/arm_swing.html
to really open this area , work on playing postural technique and work out the threshold i.e how long it takes for pain to come on and stop some time before this . Once you have worked out the time that your body can cope with really pay attention to see if any protection kicking in stop and stretch .What happens if you don’t and push through is that your body just learns to tense up earlier and earlier and than pain sensitivity is a possibility and chronic pain may occur …(the vast majority of the people I end up seeing). If you don’t get any joy from any of this go and see someone who can diagnose the problem.
ian
The M&E is a very heavy flute. Doug Tipple’s flutes are much ligher and my boxwood is so light it feels like plastic.
I think doing anything for a long period of time will cause problems. I played the fiddle for 3 hours the other day and though my arm was going to fall off. The fiddle holding arm, not the other one.
now if Thomas Jefferson had been on this forum, he probably would have come up with a solution like an arm rest that would support my right arm as I played 
bookcase…
Ben, is that yerself in the avatar, and if so would that be your right arm’s typical posture?
play more jigs, avoid waltzes
My Flute position when I play would be starting at the mouthpiece the Flute is angled forward and if you measure then the right tip of my shoulder to the pointer finger on my right hand it is about 9 and 1/2 ". Typically the length of the Flute angles down about 2 inches from my shoulder. My Right elbow may touch my side or go up 5 " or so depending on how I’m sitting in a chair 
may be more info than anyone would care to have!
the picture is me playing Flute in a tight corner of the kitchen table, I think I was somewhat twisted to squeeze there…As I recall I had to much junk on the table to spread out . I think the need to play a tune trumped my need to feel comfortable. Hmmm not unlike some seating arrangments at sessions
Off today, so I have a lot of time to focus on the mundane 
Time,time,time is on my side…
Then the prescription is obvious.
Just kidding.
Seriously, I dunno. Even though in your avatar pic you said you were cramped for space, on first glance your form doesn’t look out of whack to me.
lift weights
Jim,
like cans of Beer or beautiful women?
As said above, it could well be due to a build-up of tension in some area(s) of your posture. Very hard to catch and locate that increasing tension creeping in and becoming reflexive and eventually causing pain. When I notice this starting to happen, I find it useful to take out the stopper/endcap and play silently to help me concentrate on where I might be tensing up. You can also put a lump of poster putty just beyond the blown edge of the embouchure hole instead. That way, you don’t have to share your attention with tone, tuning, timing, etc - the musical side of your playing and I think it also helps to keep the eyes closed - just to further minimise distracting inputs so you can keep focusing on possible points of unwanted tension.
Garry