Is it healthy to exercise a muscle when it's still sore?
Is it healthy or is it damaging to exercise a muscle while it's still sore from a previous workout?
Related (if not duplicate): http://fitness.stackexchange.com/questions/7443/should-i-exercise-when-my-muscles-are-aching
In general, training while sore is perfectly fine and usually beneficial, subject to a few caveats discussed below. Almost every serious athlete frequently trains while still a bit sore from the previous workout.
The first thing to understand is supercompensation: a short while after training, your muscles end up a bit stronger. If you train again during this period, your next supercompensation period will be slightly stronger again. Repeat this cycle with proper timing over and over again and you'll gain strength in the most efficient way possible. Wait too long and the muscle returns back to a "normal" state and strength gains are slowed.
The second thing to understand is that soreness has nothing to do with the effectiveness of your workout. It's more of a side effect, which is actually not well understood. Depending on your training level and workouts, you may still be sore even when your muscles are in the supercompensation period. If this happens, you just need to put up with it and train sufficiently hard to keep the gains coming.
BTW, this is also a reason why split routines - where you train each muscle once a week - are very inefficient for the vast majority of beginner & intermediate lifters. Your muscles hit the supercompensation period in far less than a week and have started to return to normal by the time you train again. In this respect, fully body routines 2-3 times per week are going to produce strength gains much faster.
Some caveats: if you are sore to the point that it interferes with the workout (ie, you can't do the motion correctly), then you won't gain much from exercise and are better off resting. A rule of thumb to determine this is to do a thorough warm-up: if everything loosens up and you feel ok, train on. If you are still stiff and it hurts to move, rest. If you are new to a certain type of exercise, soreness levels will be much higher, so the first few weeks may require skipping more workouts than normal (don't make it a habit though). Finally, more advanced lifters who are moving a lot of weight will take longer to recover, which will impact things like workout frequency and volume.
@samuelandrew This isn't the sort of thing you'll be able to "feel", this is about the underlying physiology. The general rule is 2-3 days for most muscles.
@Samuel: there is no exact way to tell for yourself, but various studies and anecdotal evidence suggest ~48 hours is good enough for the average trainee/workout. In other words, unless you are moving HUGE weights/volume, working out the same muscles/motions 2-3 days per week on non-consecutive days tends to be ideal.
Ok, thanks. What I've been doing is upper body one day, then lower body the next, then upper body, so on and so on. do you think that's okay?
Hard to say without knowing more about you and the routine. How long have you been lifting? What exercises? How many sets/reps? In general though, upper-lower-rest can be an effective 3 day scheme for most lifters.
@YevgeniyBrikman Okay, thanks. I reckon I fall into "most Lifters" more or less.
Yevgenly very good answer. +1000 for mentioning "split routines - where you train each muscle once a week - are very inefficient for the vast majority of beginner & intermediate lifters. "
@Esqarrouth: You shouldn't *want* to be out of beginner and intermediate territory. Beginner routines are designed to give you the fastest gains possible, typically increasing the weight on the bar every single workout. The more advanced routines are slower, more complicated, and not as fun. So in a sense, that's one answer to your question: stick with a beginner routine as long as you possibly can. Only when you can no longer make progress at that rate should you do something more complicated.
@Esqarrouth: As a second answer to your question, and as a rough guide to where you are progress-wise, check out the weightlifting performance standards: http://www.exrx.net/Testing/WeightLifting/StrengthStandards.htm