Update :Well although my damage seemed to have gone away, it hadn't completely and came back if I played a lot.
I went to see a physio and she showed me that it was a lot more than my arm that the problem was located in.
The whole left side of my body was a lot more tense than the right, but both were tensed up.
Try touching your toes, does this hurt a lot?
Try sitting on the edge of a table with your feet dangling. Stick your right leg out horizontally, bend your toes TOWARDS your body, then lower your head towards your leg. This will hurt a bit.
Do the same thing with the left leg. Does this hurt a lot more?
The regime the physio gave me was this :
Do the sitting on the edge of a table (use some padding like towels to avoid sore arse, stick your leg out horizontally, pull the foot towards you and lower your head towards your leg.
Repeat 5 times for each leg.
Lie on your back with your knees bent and your feet on the lfoor. Spread your arms out horizontally. Slowly, tip both legs over to one side, stretch your opposite arm out (e.g. leaning left, stretch right arm), turn your head towards this arm, try to make as straight a line as possible down your body (from your leaning legs up to your arm.
Do the same in the other direction
Repeat to total of 5.
Lie on your back with both knees bent so th at the feet are flat on the loof. Breathe in and hold your tummy. Tighten the buttocks so as to flatten the spine towards the floor by rocking the pelvis Relax and allow the pelvis to return to the starting position as you breath out.
Repeat to 5.
Lie on your back with both knees bent so that the feet are flat on the floor. lift up knees to the chest and gently pull them so as to stretch the base of the spine and "massage" the back. Circle each knee at the same time in opposite directions guiding the movement with your hands.
5 times baby
Kneel square on all fours. Breath in and round the back. Breath out and hollow the back. Relax and repeat.
This cat lives only 5 times
5 Push ups
lie on your tummy with your handss directly underneath your shoulders and your elbows tucked in. Push up with your arms so as to arch the base of your spine. Keep the pelvis and tummy down and your buttocks relaxed. Hold the position for a few sections. Relax
6 Always trust in the concept of breathing into pain and allowing it to go as you breath out.
7. These excersises should centralise and reduce intensity of pain. Pain may temporarily increase. This should only be temporary and is the result in changes in tissues.
8. If the pain becomes isgnificantly more distal (away from the midline) and greater in intensity you are doing too much excersise and need to rest the body. However, never stop using your mind to help focs and release pain.
9. Do not force through pain. If in any doubt, or pain persists, contact a physio.
10. Drink 2 litres a day of water/liquids (water is best, dont listen to any adverts).
I do this set of excercises twice a day.
Another important point is focus on your playing, lighten up your touch as much as possible. Once you have reached the lightest touch you can, shut the hell up because you can go lighter with less force and more precision.
Having been recovering from a case of tendon strain (not really sure what to call it, RSI seems to strong, and it wasnt carpal tunnel although I did get a few of the symptoms of it) I would like to share a few things that helped me.
Most importantly, rest. Don't do anything with the hand, this means NOTHING. Imagine it doesnt exist. Type one handed, eat one handed, pull things out of your pocket with the wrong hand. Try and get a wrist brace, which will help you, but also remind you not to use the hand. If you do get one and it feels uncomfortable, take it off for a bit.
As you start to feel less pain, twinges (anything, dont think its "just nothing") start doing some stretchs :
1.Hold your palms face up, put your thumb at the base of your little finger, keep your fingers held together for 5 seconds, then stretch them apart for 5 seconds.
Repeat 5 times a session, as often as you remember each day (say 5-6 times a day, hours apart)
2.Palms up again, touch the tips of your fingers against the top of your palm (as if you made a fist then straightened out your knuckles, but not your fingers)
then try and spread your fingers as far apart as possible for 5 seconds in similar fashion to the first excersize.
3. Same as 2 but with your thumb placed at the base of your pinkie, a mix of 1&2
4. place your opposite hand (the one thats not injured) ontop of your injured hand (palms down).
Push up with the injured hand, keep it in place with the good hand.
Repeat with good hand underneath, injured pushing down. And with injured hand on it's side.
5. Palms forward (as if pushing a wall). Gently pull hand backwards (not too far!) with your good hand
6. Clench a fist for a few seconds then "throw" it out, releaving it completely.
7. Grab your elbow with your hand (on the opposite hand fool :P) and place the arm (the one with the elbow your holding) ontop of the one holding it, and gently stretch the arm by pulling towards the hand your holding it with.
E.g. hold left elbow with right hand, place left arm ontop of right arm, tug gently with your right hand.
8. Place your arm behind your head and bend it (so its pointing at the floor) use the opposite hand to tug it down gently
(7 & 8 are viewable on the Petrucci video, I put them here for those who dont own it)
Once you have made a noticeable recovery shred away for 20 hours a day at the speed you could before.
If you want to never play again.
Pick up your guitar and try playing just one or two notes. Any pain? If so stop. If not stop.
Each day increase the amount of notes you play by two. I did two weeks of playing from 2 notes to 16 increasing each day.
Dont play them fast either!
As you build up what your playing slowly, take a piece of music with even playing and slow it down (I'm talking semi quavers at 40bpm here). (I chose technical difficulties) and just play a bar more each two or three days.
Remember any pain means stop. No pain doesn't mean its ok to carry on playing either.
It's all about discipline, which most of your guitar playing heros have or will tell you is a key element to playing. (Remember Vai's mini lesson saying to play one fret for 5 minutes using any method you want as a form of discipline).
Eventually you will start to notice improvement, it WILL take a long time, longer than you would want.
If you feel the need to see a physio, do so.
The most important thing to do, is to pause when doing things and notice when you are tense, then relax your body and start again. Even if you tense up straight away; pause, untense and start again.
Work on your posture. Sit up straight.
Don't play every day. Relax.
When playing, take CONSTANT breaks. Like every 10 minutes or so break for 5.
As you start to being able to play more you will eventually be able to play cleaner and faster than you could before. Due to the insane precision you should have been excersising when playing at tempos like 40bpm.
Take it from me, take it easy.