[b said:
Quote[/b] ]Being able to do things in life like running up a flight of stairs to get a forgotten article or dashing out to the car in the parking lot during a downpour without having to pant is something I can't sacrifice...not to mention the satisfaction of whipping up on high school and college kids less than half my age on the basketball court.
you dont have to go to THAT extent of sacrificing cardio for maximal gains.
lower the cardio a little. Instead do two cardio sessions per week. One can be your HIIT, and the other your 30min at 80% MHR. On the other days, there is no need to be sedentary either.... go for a brisk 30min walk if you like.
You will not loose the level of conditioning you currently have at all by lowering the cardio!
As for fat gain, thats totally dependent upon your diet.
perfroming HST will up your metabloic requirements. Two cardio seesions per week plus 3 HST sessions will mean if you want to gain muscle, you will probably have to eat a little more than you are doing at the moment (read the 'eating for size' article for diet guidance).
But having said that, obviously if you eat more calories than you need, you will gain some fat. so you have to be careful and monitor your progress on a fortnightly basis.
Invest in a set of scales, a measuring tape and a set of skin fold calipers. Using these three, you can detremine whether you are gaining weight, and how much of that weight gain is fat and how much is lean.
If two weeks goes by and you have not gained a shred of weight, then add a couple of hundred calories to your daily diet.
If two weeks goes by and you have gained 2lbs, but the skinfold/waist measurements tell you that over 1.7lbs is fat, you need to lower your calories by a couple of hundred or look at your training (you might not be adequately providing growth stimulus etc).
If after two weeks you have gained 2lbs and the skin fold tells you that 1lb was lean, that is perfect (its unlikley you will do better than that).
just keep a good record detailing everything, average daily calories for that week, HST details, amount of cardio performed. If you do that, pretty soon you will have a good idea of what makes you tick.