I like to train my cardio a lot so I run 2 sprint sessions and 3 7 mile runs a week, but desperately need to gain weight for my basketball which I take very serious. If I try to gain weight can I still maintain my fitness ?

P.S. I'm 9 stone and need to get to about 10 and a half.

Sure you can. The most-successful way I've done so is called the Zig-Zag Method.

Basically, you train with the intent of gaining mass, so you must increase your caloric intake and your intake of anabolic supportive nutrition. But the trick is in HOW you do so.

If you just start eating more without changing your workout habits, you're very likely to store fat as well as gain muscle. What you must do is adjust your metabolic rate on a gradual scale.

You can accomplish this by cycling your nutrition plan on a weekly basis. For example, starting on Monday, you could ingest more nutrients and calories than you're accustomed to, which will fuel your growth. You could keep this up for 3 days. On Thursday and Friday, you would go back to ingesting the same amount of calories as you're accustomed to. Keep this up for a couple months and I guarantee you'll see results.

You will have ingested enough calories to gain lean mass (as long as the food you eat is nutritionally sound), but you will have gradually "stepped-up" your metabolism to accommodate your increase in caloric intake.

This is the missing link that most amateur athletes are completely unaware of in their training... they focus entirely on the caloric intake because that's what the talking heads jam down their throats, but in all honesty, caloric intake is only one factor among many.

Fuel your growth with supportive nutrition, spark your growth with periodized weight training, and balance your growth with an awareness of your basal metabolic rate by Zig-Zagging your nutrition plan.

You will succeed.