A warm up is the process whereby an athlete goes through a range of exercises in order to get their body ready for competition or training. Warm up exercises move from low intensity to high intensity and from general movements to sport specific movements. Warm ups prepare the body for physical activity by: increasing the heart rate, the respiratory rate, the cardiac output, and the blood flow to the muscles being used. It causes the liver to release glucose into the blood and opens muscle cells so that blood glucose can easily enter the muscle for energy production. Warm ups also increase the body temperature, which increases joint mobility, decreases the risk of injury and speeds up the chemical reactions which produce ATP. In warming up a netball player, movements might start with a slow jog, which slowly increases to a fast run. The athlete then might add changing direction to the running, and then introduce a netball for catching and throwing activities, which could begin at slow movements and work up into faster movements. Finally the warm up would include mini games to reproduce the specific movements needed in netball.
Cool downs are essentially the opposite of a warm up. They involve movements that help speed up recovery and enable the body to slowly adjust its systems and bring the body back down to rest. These movements move from medium intensities to low intensities and from sport specific movements to general movements. Often a cool down involves passing a ball around, while jogging and progresses to a walk before stretching. The goal of a cool down is to allow the body to remove: left over lactate and pyruvic acid, carbon dioxide and water. This helps prevent fluid pooling in the used muscles, as muscular contraction helps transport blood and the lymphatic system back towards the heart. If the heart continues to pump blood to the muscles being used and the muscles are resting, then the fluid does not return to the heart at the same rate that it arrives, which leads to pooling.
The benefits of stretching in a warm up or cool down are often debated. There is much evidence to suggest that stretching before physical activity does NOT help prevent injury. Dynamic stretching has been shown to be useful in a warm up as it replicates movements that may occur during the physical activity, but these movements should be sport specific. Stretching as part of the cool down helps lengthen the muscle and can assist in avoiding some stiffness experienced after physical activity.
Before aerobic training a warm up should go for 10 min and aim to increase the heart rate to the 70% MHR aerobic threshold slowly. Movements should progress from lower intensities to the higher one and from general movements such as a jog or star jump to more specific movements such as running with a ball at their feet for soccer. Movements could also include a small 5-on-5 mini game. After the physical activity the cool down should go for 5-10 minutes, depending on the duration of the session. Exercises could include a jog around the field passing a ball and then go into some walking in various directions and then some stretching of the leg muscles for the soccer players.
Before resistance training a warm up should go for 10 min and aim to increase blood flow to the group of muscles being used and prepare them for heavy lifting. This preparation is done, not just by doing an aerobic warm up, but also doing the specific movements required throughout the training session. This could include some lightweight bench presses for a chest session, and some push-ups to get the muscles ready to lift the heavier weights.