The purpose of a warm-up is to prepare the body for the more intense movements to come. It should slowly increase your heart rate thereby increasing blood flow to the working muscles. This provides the muscles with the oxygen and nutrients necessary for contraction. Doing a proper warm up before exercising can greatly reduce the risk of injury.
A warm up should be movement specific. This is why it is important to plan ahead. If your plan involves working the lower body, the warm up should work the total body but significantly more time should be dedicated to dynamically stretching and working the lower body. If your exercise session involves the upper body, it is important to warm up and dynamically stretch the shoulders, neck, chest, back, and torso.
The cool-down should be used for static stretching or PNF to return the muscles trained to their original resting length. During exercise muscles are constantly contracting, in other words, constantly shortening in order to lift a weight for example. We want to return the muscle to its resting length so it remains flexible which will reduce risk of injury. A cool-down will also help prevent or reduce muscle soreness.
Static: Holding a stationary pose for 20 seconds at a time
Ballistic: Passive stretch that has an added bouncing component. An example would be holding a hamstring stretch while rocking to try and touch your toes.
PNF (Proprioceptive neuromuscular facilitation): PNF is an advanced version of static stretching. PNF involves contracting the muscle you want to stretch for 6 seconds and the relaxing to perform a static stretch for 20 seconds. This is meant to help the muscle move through a greater range of motion. Checkout the VIDEO by the ‘Stretch Coach’ Brad Walker on the fundamentals of PNF stretching.
Dynamic: This type of stretch takes a muscle through a full range of motion from contraction to relaxation. Effective way to stretch to prepare for sport training or exercise. Example would be performing high-knee or butt-kick running exercises. These exercises actively prepare the muscle for more intense exercise versus a static stretch and PNF which are primarily performed to lengthen the muscle.