I can’t add much to the sound advice already given (stretching before & after ride, build up gradually to desired commuting distance, and allow time for your body to adjust).

You don’t mention what you’re riding or the terrain of your commute. If you’re on a multi-speed bike, riding at a higher cadence in a lower gear can lessen strain on your thighs and knees.

stretch your quads before and after - get ahold of the top of your foot and lift upwards toward your buns. hold on to a wall or table or you may lose your balance. and the first answer is also correct. in michigan i cant ride during the winter months and my thighs are always sore for the first few days. you can try some squats or lunges with light weights to work those muscles, but riding will get those muscles in shape just as fast. also, good job commuting. i commute 12 miles one way and i really love the exercize and savings. keep it up!

first if you havent biked in a while/or before .. your muscles have to get used to this new function… try eating a banana to add potassium to your body.. reduces the lactic acid your muscles produce that cause fatigue and pain.. you should of started with a shorter distance and period of time and worked up the your goal over a period of a week or so.. to train your muscles…

after you bike walk for 10 - 15 minutes slowly .. to stretch the muscles..