Like all forms of exercise- If you are doing something new and using new muscles- Take it steady. Now as to the Pedalling in circles. I do a Spinning class and we have a session in which we climb a hill at a sensible pace and with pressure on the wheel. We are made to pedal normally for 30 seconds and then change to 30 seconds only pulling up on the pedals. This helps build up the muscles and over a few sessions the period of pulling up is extended. I only realised that this was having an effect on my riding when I started to pull the foot off the pedals on the up stroke on a ride. I now have the cleat tension up somewhere near the max to stop this happening and my ankle muscles have improved from trying to twist the foot out of what sometimes feels like a vice.