I believe it would be heavier weights and less reps
but go to a gym and ask a trainer
or read online
You have to hit the gym. Consistence and technique are key.
If you just want weight, go for simple carbs instead of protein. Lots of rice and bread and sugar and soft drinks. You'll definitely gain weight, but you'll be terribly unhealthy and pasty-looking, and possibly diabetic.
If you want muscle mass, keep your protein levels high and do fewer reps with more weight, but you'll need to work out more than just your biceps! You might need to wear some support for your back; ask a doctor or orthopaedist.
Also, maybe get your thyroid checked; if you're fairly sedentary and not gaining weight at 4000 calories a day, you may suffer from hyperthyroidism. If you don't I really, really, really envy you...
As an ex gym rat I recommend max weight per rep. No more than 8 reps per set. For football on off season bulk up this is what I used to do:
280 - 8 Reps
300 - 6 Reps
320 - 4 Reps & If you can go for the last set but if you cant 3 sets is good.
340 - 2 Reps
Depending on your amino and creatine take in you might plato in. 1 month up to 3 months.
When you do plato switch your work out to light weight fast reps for at least 2 weeks at least but I recommend 3 weeks. Keep your creatine intake the same until you get to the 3rd month then cycle off for 3 weeks and start all over.
Also after the first month you can add a Nitric Oxide Booster, try Body Fortress it the best for the price, buy it at Wal-Mart online.
I don't know how weak your spinal cord is and what this means, but I would see a sports doctor before you put any major stress on it.
But cultivating a physique does not come overnight. Stay away from steroids, eat a well balanced diet and don't quit. Good Luck.
you've got some learning to do lad, there is a lot more to gaining muscle mass than drinking shakes and doing biceps curls.
The Shake Weight and sit-ups