Well I've started the cobra press-up type exercises, so I'll see how they work out for me. Quick question on technique though ; how high should I press? If I straighten my arms, but leave my shoulders pushed back, my hips just about stay on the floor. Should I push through until my shoulders are fully forward as this would leave my hips hanging (albeit with a stretched back)?

As for the back extensions, what sort of regiment should I be doing for them, i.e. weight/reps/sets/range of motion etc?

Just in case it's relevant, I've included my current training below:

Monday - Gym (all exercises are three work sets of five reps):
Squat - 175kg
Calf raise - 140kg (three sets of twelve)
Dips - Bodyweight + 20kg
Standing barbell shoulder press - 67.5kg
Pec dec - 125lbs
Abs - 20kg incline ab curls or leg raises (three sets of eight)

Tuesday - Hockey Training (90 minutes, mix of sprints, steady states and standing about)

Wednesday - Gym
Chins - Bodyweight + 10kg
Low rows - 87.5kg
Power shrugs - 130kg
Bicep curl - 47.5kg
Wikipedia reference-linkRotator cuff work (a mix of exercises and weights)
Side bends - 45kg (three sets of eight)

Thursday - Hockey Training

Saturday - Hockey Match