AFAICT, the model used doesn’t ever allow the jumper to push against the ground. Since it also limits the time spent getting up to speed, that limits the amount

AFAICT, the model used doesn’t ever allow the jumper to push against the ground. Since it also limits the time spent getting up to speed, that limits the amount of energy one can load into the system. They also use l1 (distance between top of swing and seat) = 2m. I think that’s way too short for a swing. The modeled height of the seat from the ground is also small, at 40cm. The final expression isn’t simple, but even keeping that height the same, the first term is l1 sin Φ, and that grows with l1. I didn’t check, but suspect v also grows if l1 increases. If so, the other terms also go up if l1 increases. They also don’t model what Olympic swingers would do. I expect they would start by standing on the swing, grabbing the ropes high, and pulling hard, bringing their lower body almost horizontal, at a height at least a meter above the starting position, and then almost let go of the ropes, dropping down on the falling seat. Just before jump-off, they might even try to hang below the seat as far as possible, like they do in ring or on the horizontal bar in gymnastics.