I wanted to just drop a quick word in here about pain. This isn't aimed at any particular poster here, but is inspired by a few messages posted in this thread. First let me say that I am not a medical professional, I'm just some guy posting something on an internet message board and that's how this post should be taken. In other words, do your own research and assume your own liability.
Somewhere along the line, people got the idea that they should never feel pain. If something causes pain, you must cease it immediately. Part of that seems to be that if you are engaged in a rigorous activity and feel pain and/or discomfort, you need to stop. You've over exerted yourself. This is entirely not true.
Keep in mind, I'm not talking about pain or discomfort that signals injury. We all know what that feels like. It usually a sharp, immediate pain. Any sharp, immediate pain needs to be assessed immediately. I'm talking about the dull ache of fatigue or soarness that we get.
When you're working out, running, biking, swimming, whatever; that pain is a backseat driver telling your brain to stop. It's telling you to slow down. It's the pain that wants you to do nothing. It's saying you're overexerting yourself and need to stop. The thing is, this pain is normal, natural and a sign that you are actually making progress. As I posted previously, this pain shows up way to early. It wants you to stop at the first sign of fatigue.
That pain is actually the 'gatekeeper' to your physical reserve. Back in caveman days, this pain would tell you to mellow out so you could keep your tank full for when the sabertooth tiger attacked, the forest people chased you, or you had to battle Chocodiles.
That pain is still there, but we don't need it to guard our reserves anymore. So when it pops up, we shouldn't listen to it, other than to realize that we are now tapping into our physical reserve, which is exactly what we want. The more we use that reserve, the larger it will become. This is endurance building.
When you are working out, that pain means we are doing something right. We are in the cardio zone where our heartrate is being worked up, our muscles are being challenged. The longer you work through that pain, the more your endurance builds.
And yeah, anytime you go from 0 activity to a lot, you are going to get tendons and muscles in your knees and ankles that swell and get sore. Those are also temporary conditions. Use RICE (Rest, Ice, Compress, Elevate) to take care of that. That will go away as those pieces become stronger. There are low impact ways to build strength in those muscles, google it. Lots of info out on the interwebs.
Pain can indicate a failure, but in a cardio workout pain mainly is an indication that you're stretching yourself, which is actually what you want.
+1, couldn't agree more. You will feel pain (the non injury type) throughout your exercise if you're doing it hard enough to make gains in strength and endurance. Your brain will be screaming at you to stop. All normal. Muscle soreness post workout (often delayed by 24-48 hours) is completely normal as well, and it is indicative of muscle damage/repair - the mechanism by which you grow muscle tissue and get stronger.