He can't do cardio because his knee is really messed up and where we currently live biking isn't safe. (We will be moving in the next year, and will have good access to bike trails, and he really wants to start biking once we move)

We have been doing short HIIT routines....like 10 minutes short.

HIIT? Yeeks, that used to always make me nauseous when I first started. I still don't like doing it, years later. Have him pick up a beginner strength program and/or do some other, lower-impact cardio to start out with.

What about the elliptical or swimming?

We don't have a gym membership, so it would have to be at home, and we don't have room (or the money) for any large equipment here.

The other issue that I might not have emphasized is how much he HATES exercise. The reason I started having him join me on the HIIT workouts is because they do so much in such a small amount of time. I don't see him spending a lot of time lifting, or driving somewhere to ride his bike, as he dislikes the activity so much that he isn't going to do things that take an excessive amount of time.

I promise, I'm not trying to be difficult here, I'm just trying to figure out if there is any way for him to EVER enjoy working out. I'm also wondering if anyone has heard of people NOT getting that endorphin rush? Remember, when he was in the army he did pt daily for 1.5 hours/day (so he was in good shape) and said he hated it the whole time, and always felt ill afterwards.

I've never gotten any endorphin rush from working out, personally. I do feel pretty good about myself when I hit a new record on my deadlift or something though. That's more of a feeling of accomplishment though.

Really, you just have to find something you enjoy. Swimming, running, biking, kayaking, whatever. Weight lifting (bodybuilding, powerlifting, strongman, crossfit, bodyweight routines). Martial arts, boxing....yoga... Sports? Basketball, soccer, etc?

He's just gotta try stuff until he finds something he likes. Apparently he doesn't like HIIT. Or at least it makes him sick. Have you looked into why he's feeling sick? Too much exertion, too fast can leave someone feeling sick. Working your way up might help alleviate this. Poor diet can lead to poor recovery from workouts too. I used to get really shaky, nauseous and headachy after cardio. Not enough food, too low blood sugar. I would put some sugar in a drink (not much, a tablespoon) and drink it right as I finished the workout and I'd be fine.

Having said that, I always hated even the thought of exercise. It wasn't until I found lifting that I really enjoyed it and have stuck with it.

At the end of the day, it doesn't sound like he's really all that interested which doesn't bode well.

To add to everyone else's comment, I detest cardio and most types of exercise that do not involve a barbell, so I do not do them. I don't do it anymore, but I used to really enjoy ju jitsu however. To me, unless it is lifting, I do not enjoy cardio for cardio's sake. However, activities in general, like martial arts, hiking, roller skating...whatever, will give you a caloric expenditure an not seem like cardio as the primary purpose is not burning calories. I find walking not too bad as I poodle around being nosy around mah 'hood, especially if I have a destination n mind (usually the coffee shop). One other thing I have done instead of cardio is the 'lift weights faster' thing - low weight complexes.

It really is find an activity that you enjoy.