I will add the video in case it doesn't sound clear..
Picking back up again, what is "back up" here? I also don't understand "It's on to" To what "it" reffer to?
All right, we're picking the pace of this workout back up again. It's on to some more super sets.
At 2:07
"All right, we're picking the pace of this workout back up again. " means that there had been a pause or slackening in the workout, and the announcer wants to bring the pace of the workout back to where it was before the slackening. He says "on to some more super sets," that is, we're going to do more super sets like we were doing before the slackening.
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"All right, we're picking the pace of this workout back up again. It's on to some more super sets." means that there had been a pause or slackening in the workout, and the announcer wants to bring the pace of the workout back to where it was before the slackening. He says "on to some more super sets," that is, we're going to do more super sets like we were doing before the slackening.