I just got my first recumbent yesterday, a used Vision R40, and after my first ride my legs were sure feeling it. Then I started wondered if I'm riding with proper recumbent form. I've seen some people on this forum talk about "spinning" and make mention of not "mashing" the pedals, although I'm not exactly sure what they mean.
What is proper riding form and what is a good way to tell if the pedals are at the proper distance in front of the rider?
Spinning is maintaining a higher cadence with not so much force on the pedals. You use the speed of your pedaling to maintain your bike's speed. Mashing is using a lot of force with a lower number of revolutions to maintain forward speed.
As for proper fit, I sit in my seat and place the center of my foot on the pedal. My leg sits straight when I'm in that position, but has a comfortable bit of flex at my full pedal extension when I'm cycling. Not sure if I described that adequately.
In addition to what aenlaasu wrote, spinning involves trying to power around the entire pedal stroke. That means the old wipe-the-shoe motion at the dead spots of the circle and sometimes pulling a bit on the pedal that's coming up. In mashing, you just push down on one pedal at a time; so whatever speed you acquire, you get it in pulses.
I usually set my seat by placing my heel on the pedal and it should just reach the pedal without straining. When clipped in, I like to see about a 15 degree bend in my knee at it's straightest point. Good way to check this is to ride by a reflective window in a store front, and you can see it. ( Or have someone video tape you as you ride, from the side).
Don't make the mistake I made an think you can mash the gears to power your way up hills on a recumbent the way you used to on a road bike. You'll pay for it. I did. I quickly learned, the hard way, to not do this. Gear down and spin your way up and over hills.
You use differant sets of muscles on a recumbent then you do on a road bike. For starters you are probably feeling pretty sore in your quads just above your knees. You also may feel sore in the glutes higher toward your lower back and maybe some soreness in your lower back. At some point you will notice some sore muscles in your abdomine as well. But you likely do not feel much soreness in your calves. This will take a little bit to get used to as you use these muscle groups that you did not use so much on a road bike or did not use as much as you will on your recumbent. It took me about 1,000 miles to develope what they call 'bent muscles. It may take you less or even more to do the same.
This is all good advice. And there's one other thing to consider: getting your "bent legs".
When I first switched to a 'bent two years ago, I didn't have any fit or pedaling speed problems, as I've been riding seriously for 35 years and have always been pretty obsessive about proper fit and keeping a high cadence. But, I also have a tendency to ride hard, probably more than I should. Quite often at the end of my early 'bent rides, I'd get off the bike and barely be able to stand, my legs would be so wobbly. And I wasn't riding any harder than I had been on my df, it was just that my legs hadn't adjusted to the different pedaling action of a recumbent. So don't be worried if your legs are more sore or tired than you're used to. This too shall pass.