This KB article I wrote may also help:
Sometimes you’ll notice that when climbing an ascent in a group, or even alone, your avatar will stand up out of the saddle and sprint up the hill, while others in your group remain seated but still keeping up with your power, speed or pace.
Why does _your _avatar stand while others are seated? (or vice versa, others stand up and sprint, while you remain seated, keeping pace with them)
This is not a bug at all; it’s just how Zwift visualizes your rider’s power on the segment.
We’ve noticed through extensive testing that this appears to be related to a _rapid _change in either cadence, or power, within a very short period of time. In other words, if you’re doing 22mph @87rpm cadence, and hit the bottom of a hill and decide to sprint up that hill, you’ll increase your cadence from 87rpm to say, 95rpm and your speed will jump from 22mph to 28mph to start that sprint. Zwift sees that and rises your avatar up out of the saddle to visualize that increased effort.
A rider next to you may achieve the same result, but instead of a rapid jump from 22mph to 28mph, they take theirs gradually through the gears, going from 22mph… 24mph… 26mph… and slowly increase their cadence to bring up that speed, so they stay seated.
There’s also a change when you exceed 459W of power, such as an all-out, full-gas sprint. Your rider will stand up and get out of the saddle to charge down the road as fast as your legs can carry.
So if you want to jump up, gear down and increase your cadence fast, and you’ll rise up (and your workout will be more cardio or aerobic than if you stay seated). If you want to stay seated, just ramp up your power and cadence gradually and you’ll remain in the saddle (resulting in a more anaerobic or muscle-building workout).