Muscle mass questions.

[Hoppa]

I have been lifting for about 3 years now and im pretty happy with my size.
I don't want to grow anymore as i feel i am losing speed and agility for football.
Is there any way in which i can continue to increase/maintain my strength without continuing to have massive gains?
Would higher reps/lower weight help?

Also, my pecs are developing a lot faster compared to the shoulders/traps so it looks pretty stupid. I am working them out once a week.
Should i stop benching and focus on other pec exercises?

[Big H]

Try using a 5x5 routine with progressive weightlifting. Start with a weight you can do for 5 reps and 5 sets, if you can properly execute all the reps of the lift then the following week up the weight by 2.5 or 5 lbs. This is the best way I found for gaining strength while maintaining muscle mass. You want to use heavy weight and do it with high intensity, you should be reaching positive failure at the end of each set (meaning you gotta work for the last rep).