That's day one. This is day two2.
That god-awful pain is known as Delayed Onset Muscle Soreness (DOMS). In short, you're stiff, you ache, and every movement is an explosion of agony. God help you if you sneeze after working your abs. The pain shows up the day after you exercise and lasts for three to five days.
The part that might confuse you is that it's not lifting the weights that causes the problem. It's putting them back down. When you're lifting the weights, you're performing what's known as a "concentric contraction". The muscle is applying force while getting shorter; it's applying force in the direction of motion; it's lifting the damn weight. When you're lowering the weights, you're performing an "eccentric contraction". The muscle is contracting while being elongated; it's applying force against the direction of motion; it's hitting the brakes as you put the weight down. The mechanisms of muscles and how they work in all conditions is poorly understood, not least because it's difficult to work out in an MRI machine, but we know a few things, among them that eccentric contractions cause DOMS.
First, we know that older beliefs about the causes of DOMS are wrong. Muscle spasms and lactic acid build-up have both been ruled out. Exercise can lead to painful muscle spasms, if you dehydrate yourself and get a nasty electrolyte imbalance what with sweating. However, that condition can be thoroughly alleviated without eliminating DOMS. And lactic acid is water soluble and would wash out of the muscle in a matter of hours. For years there was a popular home remedy; drinking sugar water was supposed to dissolve the lactic acid and prevent soreness. It didn't work, not least because the sugar would be unnecessary and lactic acid wasn't the cause.
What is the cause is structural damage throughout the muscle tissue. Again, poorly understood (it's much easier to rule out a hypothesis than to confirm it), but it's not damage to individual fibers or cells, but may be the connections between the filaments, the fibers. Okay, now that we know almost nothing about what causes DOMS, how about preventing it? I know of two ways to prevent DOMS. They're guaranteed to work, and they're the only things that do.
- Never work out.
- Always work out.
There. Isn't that simple?
I'm serious. Make sure your muscles never face an unusual challenge. That means you never challenge them, or you always challenge them. Either way, no unusual challenges. Personally, I work out six days a week. You don't have to be quite that extreme. I think three days a week would be sufficient.
Still, that's not going to help you at the start of a workout. You're going to be sore; it's unavoidable. However, there are ways to minimize it. Start soft. Be extremely pessimistic in your estimates of what you can handle. Then cut that in half. Then work up from there as slowly as you feasibly can. You'll be sore, but not as sore as if you start challenging yourself right away. By the time you get to the point where you're actually challenging your muscles, you'll have worked through the sore period and won't have any more.
Another thing, don't be afraid to work out when you're sore. It'll make you feel better. So long as you're not working at 99%, you're not going to be injuring yourself.
1 - That's a popular meme. You see it a lot. It's from the wonderful blog, Hyperbole and a Half.
2 - Unsurprisingly, I found that image in a blog post talking about strength training.