I used to be a gym rat back in my 20s, but with two kids under 5 and a demanding job, I physically cannot get to the weight room anymore. I keep seeing ads for these streaming fitness apps (like P90X, Insanity, etc.) that claim "total body transformation." Are these programs actually effective for strength, or are they just glorified aerobics? I don't want to lose weight; I want to gain muscle back.