Complete fitness course and Buy Swingshot from trainer were missions in Ratchet & Clank. Ratchet and Clank ran into a Qwark bot in Metropolis while looking for Captain Qwark. Clank confused the robot for the real Qwark after it offered them to take his fitness course, for which they would receive a reward from his personal fitness trainer upon completing it.
To reach this area, turn left at the Gadgetron vendor, at the start of the landing area, and head for the nearby Qwark bot.
The fitness course consists of three parts, none of which contain any enemies, though hazards in the form of explosive crates and the danger of falling off are still present. Begin with climbing the nearby steps, followed by a series of two wall jump sections to reach the top, from where you can zip line down to the next area. This large structure presents you with the challenge of moving platforms, that alternatively slide in and out of the wall. They are still relatively slow and easy to traverse, however. Take note of an apparent dead end, where two tall blocks appear, prompting you to wall jump to the top quickly enough before they retract back into the wall.
After another series of moving blocks and wall jumps, you will have reached the top. Here you will find a second zip line, which will promptly lead you to the end of the course, where the fitness trainer awaits. She demands 1,000 bolts before she hands over the price, which means the end of the "Complete fitness course" and start of the "Buy Swingshot from trainer" missions. Afterwards, you can use the nearby versa-targets to reach a third zip line to return to the start.