Can I train if my muscles sore?
Generally speaking - I wouldn't recommend it. The soreness in your muscle is typically a result of two things:
- Mechanical damage (micro-tears in actin-myosin pairs that make your muscles contract); or
- Damage from hydrogen ions and mounting acidity as a result of high-intensity exercise in largely anaerobic condition
(many people mistakenly think of soreness as a result of accumulating lactate - this is really not the case, though, as lactate gets cleared out of muscles pretty quickly)
Exercising sore muscles then inflicts additional damage on muscle fibers and slows down the recovery process. Furthermore, muscles that have not fully recovered after a heavy lift are not strong enough to withstand another heavy lift - and you may be setting yourself up for an injury.
There really is no extra benefit from pounding the sore muscles - it doesn't speed up synthesis (quite the contrary), doesn't create any special metabolic conditions to stimulate further growth (that metabolic condition - the presence of hydrogen ions and subsequent promotion of Growth Hormone and testosterone synthesis - is a delicate balance - if you "overstimulate" your muscles, the mounting acidity becomes damaging and leads to catabolism, instead) and it doesn't make you a better athlete by any means. Recovery and rest is essential to progress - so don't take it lightly.
You can partially speed up the recovery and get rid of soreness by mild massage and light exercise that resembles "warm-up" (with really light weights) - just to get the blood flowing and nutrients delivered - but exercising in its real sense would be counterproductive. Instead - just wait until the soreness goes away