When you keep exercising continuously, you can increase your heartbeat and breathing, which is good for your body. Moving at your fastest speed is hard to keep doing for a long time. A medium speed would increase your heartbeat and breathing, and it's easier to keep going without stopping. Working together with a partner when you are exercising, make activities more fun. You can encourage each other to keep trying hard. Sometimes it's easier to be successful and complete a challenge when you are working together with a partner.