Deep breathing oxygenates your muscles and calms your nervous system to help your body relax. Deep, full, slow breathing increases blood flow to muscle tissues to help muscles recover more quickly from exercise, and to remove lactic acid and other toxins that can build up in muscle tissue and cause post workout soreness, stiffness and pain For more click  http://www.easymix.co.nz/knowledgebank/health/Monique-Rana-The-power-of-the-breath-while-stretching