Been on the bike HARD recently. For the past 6-8 days, I've been super busy at work, school, holidays, blah blah blah.... And I've only been able to ride during my commutes, 14 miles a day or so, in either my active recovery zone or aerobic zone. Trouble is, my hamstrings and calves are burning with lactic acid, and are super tight!
Ive never experienced this before... Ill be back on the bike hard again in the next few hours, but damn, this is uncomfortable!
Lactic acid does NOT last very long in the muscles... after your rides, it usually converts back into the pyruvic acid used for your aerobic energy pathways (this is the simplistic breakdown, mind you) within an hour. Not to say there isn't always some lactic acid in the bloodstream- even sitting at your desk, every living person will have some kind of lactic acid generated. But being at rest, you are vastly more aerobic than anaerobic, so you don't notice it, since the lactic acid is quickly broken down again.
What may happen is just that you're feeling some delayed onset muscle soreness (DOMS). This is from microtears in the muscle that develop from exercise and take longer to repair. In the meantime, you may feel stiffness and soreness, which people mistakenly attribute to lactic acid, when in fact, it has little or nothing to do with DOMS.
To counteract this, you'll need time off the bike, or if you have to ride, make it easy recovery. I prefer easy recovery, as they do help the blood to pump to the legs and provide the sore legs with oxygen and nutrients to enhance recovery. You could also do some massage- that always seems to help. Stretching would also help to prevent this from happening in the future. I often recommend people to do at least 20 minutes of stretching EVERY DAY. DOMS often leaves muscles in a slightly contracted state, which also causes you to feel tightness in the muscles. By stretching, you are helping the muscles to release itself from that slightly contracted state, which will prevent the feeling of tightness in the long run.
I don't have K.B.s training on the subject, but everything she says on the DOMS subject (both in this post and others) makes sense with my persional experiences. It sounds like I'm in a similar situation to you, riding six or seven days a week for more than 20 miles a day (I've averaged at least 800 miles/month since early summer, typically racking those miles up in 12-20 miles increments). I had just gotten used to DOMS because it was, essentially, permanent; I decided I needed to be a bit more careful about stretching and recovery days/rides in August when I took five days off the bike and still had essentially the same muscle soreness. I've started being more careful about streching and making sure I only push my limits while commuting a few times a week rather than every ride, and try to reserve the hard-core training for dedicated training rides. This has helped a lot, where even with the amount of riding I still do, I don't have DOMS as often, essentially only after very hard training days or weeks, and only for a day or two, not the essentially permanent stuff I had earlier in the summer. An easy and no doubt counter-productive way to deal with the discomfort is to drink lots, but I'm just a party-guy that way, and I'm sure no resposible person would condone such behavior. Anyway, that's my $0.02 on commuting and DOMS. I hope it's helpful.
To clarify..I've been commuting for two years...I've never had muscle soreness from commuting. Its not even an hour a day on the bike. Recently, I have been training, though, in addition to commuting. When I say recently, I mean a period over the past few months.
Then, after a week off from training, but resuming the recovery-paced commuting, my hamstrings, glutes, and calves are seriously sore...almost like flu symptoms, but I don't have the flu or feel ill at all...no fever... Anyways..
It might just be one of those things...lots of fluids and stretching I'm doing, with only minor benefit. Ill give it some more time...