I find that if I work out frequently my muscles don't get very sore after working out, but if I do slightly more intense workouts less frequently my muscles stay sore for at least two days. With the less frequent workout schedule I do less work overall, but it's effects are more noticeable on my muscles. Which workout routine is actually building more muscle?
How most anaerobic work outs work, as I understand them, is that they cause minor tears to the muscle this causes the process of healing to occur and strengthens the muscle adding mass to and strength to it in the process. The soreness comes from that, your body healing the small tears, so if you are getting sore less often when you are working out more frequently is probably due to the fact that your body has the necessary tools already sitting there to heal the tears, that or its getting tougher to cause the tears.
To build mass quickly higher intensity, lower rep exercises help, a day to rest that body part is the minimum, though some people continually hit the same body part with different exercises, not recommended because of the chance for injury. You can work out every day but just switch it up, one day upper body, one day legs. If you want to really focus your work outs, one day chest and biceps, one day shoulders and triceps, one days legs, giving each body part two days rest regardless of the intensity of the work out.
If you go for lower reps make sure you are using proper form, bad form and heavy weight is a recipe for injuries. Also, to reduce the soreness warm up, stretch, get your body ready for what ever you are about to throw at it, stretching helps avoid injury
One rest day between workouts is generally fine. Not taking rest days for up to five or six days in a row can work too, if you're careful. Two rest days between workouts is less common and may be less effective but but can work.
Soreness is not a good indicator of whether you should work out again.
Strength and conditioning coach Kelly Baggett espouses a bodybuilding-style approach for short-term gains:
If you really wanna gain 10 quick pounds, high volume and high frequency training will certainly do it. You probably won't make any strength gains but for short term optimization in hypertrophy you might try something like the old 3 on 1 off routine that every bodybuilder and their brother did in the 80's: Chest, shoulders and tris one day, back, traps and bis the next, and legs the next. Take a day off and repeat. Do about 12 sets of 8-12 reps per muscle group and eat at least 20 calories per pound of bodyweight. That will put some quick muscle size on you but long term it's an exercise in futility for the average person and here’s why:
The adaptations to increased volume that contribute to growth take place relatively quickly. Your body will initially adapt to this volume with a fast increase in muscle size over the course of about 6 weeks. However, once you’ve hit the point where your muscles have adapted, you will hit a wall. In order to continue to improve you need to either train with even more volume or increase the tension (load) from your existing volume. You’re already performing 20-24 sets per muscle group per week – what are you supposed to do, increase this to 40 sets? Then 60? Then 100? Additionally, even with 24 sets per week your system will be too worn down to ever really put any weight on the bar. These factors make the chronically high volume option a poor choice for ongoing gains.
He advocates a mixed strength/hypertrophy approach for the long term, however. He calls this Heavy/Light training:
You hit a muscle group at least twice during the week. One workout is designed to stimulate strength gains with balls to the wall all out training where the focus is on setting strength PRs. Then a few days later you hit the muscle again but with a lighter workout designed to stimulate some hypertrophy without draining all your strength. Then you wait a few more days and hit the heavy workout once again for more strength PRs.... You optimize recovery for heavy intense workouts so you can make progressively dramatic increases in strength and you also use enough frequency and volume per body-part to optimize growth.