I've been near to sedentary for a long time and have recently started cycling to hopefully regain some form of fitness and lose some weight. I'm currently 172lbs and I'm 5'7". My fitness feels to me to be about as bad as it can get, I started cycling 2.5K daily (close to nothing, I'm aware) and have just upped it to 5K a day. Here's my concern; my thighs/legs in general start to ache an absolute ton after even a couple of minutes of cycling. It doesn't seem like any kind of long term endurance makes them ache, they just start to hurt almost immediately, and it gets really, really tiresome when I'm on ANY kind of incline. It's like even the slight strain of pedalling the bike is making my muscles feel as though I'm doing some kind of hardcore resistance exercise, it's terribly annoying. I know a lot of people who are recently restarting some kind of exercise complain that they feel just awful, but I'm really concerned that something else is going on here. The distances I'm going are low, it's not like I'm hugely overweight and I'm only 23. Does anyone have any information/advice to impart?