It’s certainly possible to burn 800+ calories per hour for a couple hours. Normal, actually, for someone doing athletic training. (E.g., anyone training semi-se

It’s certainly possible to burn 800+ calories per hour for a couple hours. Normal, actually, for someone doing athletic training. (E.g., anyone training semi-seriously for any kind road race is doing this at least once a week.) But I’d pretty surprised if you did it without training to build up to it. You could have developed the aerobic capacity through other activities, but I’d have thought various muscles would be unprepared and would be giving you rather strong pain signals. If you nevertheless pushed through that, I’d think you’d be SORE AF today and barely able to move. Or maybe your activity confused the calorie model your Apple Watch uses. Not that it isn’t great exercise.