The extent of bleeding will depend on the vascularity of the tissues involved, and may also be increased if injured during exercise. It is important to stop bleeding into tissues as the blood will act as an irritant, increase inflammation, and must be cleared from the tissues before the healing process can properly commence. Cells starved of nourishment from the blood due to injury will soon die. These dying cells stimulate the release of histamine causing the blood vessels to dilate, thereby bringing increased blood supply and extra nutrients to help repair and rebuild the damaged tissues. During this phase of increased but slower and more viscous blood supply, the capillary walls become much more permeable and quantities of protein and inflammatory substances are pushed into the area causing swelling.
Various reactions continue at a rapid rate, all contributing to the healing process.
Muscle spasm may also occur causing the muscle to contract either voluntarily or involuntarily, helping prevent further movement. However, this may have adverse effects by further restricting blood flow and also placing more pressure on nerve endings, leading to increased pain. By applying ice or cooling immediately after an injury involving damage to soft tissues, the level of swelling and amount of blood allowed to leak out may be substantially limited. This may be repeated every 2 hours during the first two days after injury. It is important not to keep the ice on any longer than 10 minutes as the body then reacts by increasing blood flow to warm the area and therefore exacerbating the swelling.