Gendered exercising

I have a relatively limited sample size, I'll admit, but I've just realized how very female-oriented exercise videos seem to be. My previous work out videos were along the lines of "Bellydancing for Weight Loss" or "Fat-Burning Dance Party", so I wasn't particularly surprised that there were basically no men featured. But the new one that's kicking my ass does have a female trainer, but she's off the Biggest Loser tv show, which I'd gotten the impression was pretty balanced, gender-wise. (I don't actually watch the show; I hadn't initially realized who she was. I originally chose the video because it got really outstanding comments on Amazon.) The exercises are not at all female-oriented--they're stuff like pushups and crunches and punching invisible stuff and the evil side lunges with arm raises from hell. They're just straight up cardio and strength training, no froufy stuff at all. But the people in the video are still all women.

So why is it that exercise videos seem to be feminine by default? I mean, I use them because I know that if I add the hurdle of having to leave the house to go to the gym, I won't ever actually exercise. And I'm spoiled and refuse to run in foul weather. Surely many guys would like to exercise in their own homes. Is it because they were initially marketed towards stay-at-home moms and seem feminine because of that? Is it because women are more obsessed with fitness? Do men interested in exercise prefer either totally solitary pursuits (weight lifting or running with no one talking at them) or team sports, while women prefer the illusion of exercising with a group who nonetheless can't actually judge you? Is it the stereotypical "men don't like directions" thing? Why is this such a gendered activity?