The February issue of Science Translational Medicine reported that at the cellular level, massage reduces inflammation and promotes the growth of new mitochondria! Researchers analyzed muscle biopsies from both quadriceps before exercising to exhaustion on a treadmill, immediately after 10 minutes of massage, and after a 2.5 hour recovery period. Massage dampened the expression of inflammatory cytokines in muscle cells and promoted mitochondrial growth (the energy source of the cell).
This would explain why massage feels so good when we're sore from exercise and why exercise promotes the development of greater exercise capacity.