I know it's important to have rest days in between strength workouts, to give muscles time to rebuild and repair and actually get bigger and stronger.

My question is, if I'm still really sore two days after, say, an arm workout, does that indicate that my muscles aren't done recovering yet, and if so, does that mean I shouldn't repeat that workout yet?

I've been doing strength training on alternate days to try and get three workouts into the week, and I have no problem with just sucking it up and dealing with it hurting. But will I get better results if I space my workouts out more?

Thanks to anyone who has any ideas!

Some of the major factors in how much recovery time that will be needed is the amount of volume (for that body part) in the workout and the intensity at which you are lifting. To simplify things, we will look only at volume for now to see how the "48 hour rule" is really just a minimum rule of thumb and not gospel

Your question pertains to an arm workout. If you are doing a body part split and have an "arm day", then you are probably performing too much volume to recover in 48 hours. Also, if you are doing a body part split and have an arm workout and are looking to do arms two days later, that means that you must be neglecting other parts of the body if you are doing arms again so soon.

The 48 hours usually is sufficient for total body workouts. In those, the arm part of the workout is small and often no arm isolation at all. In upper lower, you may do a few more sets for the arms, but your volume is still not too great, so doing these twice each for upper and lower is usually not too much of a stress. In body part splits, you are often doing 3 to 4 exercises per workout for that body part. You need more time to recover because you are doing more volume. These should be done once or at most twice per week.

For example (again, to keep things simple we'll assume same weight and reps used across all sets), in a fullbody workout, you may do 1 exercise for biceps for 4 sets 3 times per week for 12 total sets. In an upper/lower, you may do 2 exercises for 3 sets, twice per week (12 total sets). In a body part split, you may do 4 exercises of 3 sets each for biceps (12 total sets). Your weekly volume is the same but the time needed to recover from that volume depends upon how condensed that volume was.

On the flip side, if you like to do one set of pushups daily, you probably don't even need to worry about days off. The volume and intensity is probably light enough to consider these as nothing
more than active recovery.

Recovery is also an individual thing, so even if you follow the volumes listed for the various splits above, there is no guarantee that you will recover in that time or you may recover sooner. Experience is the great teacher there. As far as soreness, it is not always a perfect indicator. I've known some people who are perpetually sore and I've known people who almost never get DOMS. For them, it is not a good indicator of recovery. If you are just starting out, until you get some experience and learn how your body reacts to exercise, take the cautious route. If you are sore, do a light recovery type workout instead. Do some mobility drills and callisthenics. Do another day of cardio (or extend the time if it was already part of the plan). Postpone your workout for a day. It won't hurt you. At worst, it puts you back a day on your schedule whereas pushing yourself beyond your limits can cause an injury that will put you of the gym for many days and in some cases causes people not to go back at all.

Bianca,

It will get better once your body adapts to the frequency. If you are having trouble recovering, I would cut back a bit on the weight used and work your way back up. I progress best on relatively frequent workouts (3x/week) on most exercises, I just have to make sure I don't use too much intensity or I will overtrain. The bigger problem for recovery isn't so much the muscles but the nervous system once you have been training for a while.

Listen, you have to take time off after working out. Every time you return to the gym you should be able to lift a little but more, if you are not then your muscles have not fully recovered. Now I am not talking about increasing 10 lbs each time... it could be as small as doing one extra rep or adding 1 lb to the machine/free weights.
If you are not able to do this then you have not healed and are wasting your time.

If you do, say, arms on Monday and Thursday, then your arms should not be sore on Thursday. If they are and it's not the first 2-3 weeks of your workout (when you are just getting started it takes a bit longer to recover), I would be surprised. In that case you may not be getting enough sleep or else something is wrong.

After weight training for a few weeks, I usually don't experience any soreness on, in this example, Wednesday, but for the first week or two, it's not so great.