Many gyms are open for business in New York, but the high-octane in-person group classes they are known for are not. Virtual exercise groups, however, are sweating it out in big numbers. For example, Akin Akman, a Nike master trainer, is drawing thousands of online students with his popular Aarmy workouts, which combine high-intensity cardio, circuit weight lifting and stretching.

Before the pandemic, Mr. Akman, a former tennis player and SoulCycle instructor, taught packed classes at Aarmy’s headquarters near NoHo. Now he is there, with just a few other instructors, driving and inspiring students in an empty space, through a video camera. Recruits, as he calls them, undergo mental conditioning too, which can come in handy during this trying time. “‘How do I approach a challenge in my life?’ is what sparks my coaching instinct,” said Mr. Akman, a sometimes underwear model who has worked with the likes of Jake