Written by: Vojko Strojnik, Ph.D.

The goal of warm-up is to prepare the body for increased exertion. Many processes in the body are temperature dependent, therefore raising body temperature is one of the main goals of warm-up. Most of the body's enzymes work more efficiently at higher temperature, higher than we typically have during inactivity. For movement, those enzymes involved in energy production are the most important. Transfer of oxygen in the body also improves with higher temperature. Tendons become more stretchable and therefore can store more energy, and at the same time are more resilient to injuries. Joint cartilage thickens because of the movement, which lessens forces in joints.

Warm-up can be active or passive. Active warm-up is better because it is associated with systematic (hormonal) changes in the body. Active warm-up is performed to induce the decomposition of chemical energy in the muscles, where most of this energy is used for production of heat and only about 25% for movement. In addition, with active warm-up the blood moves into active muscles to provide better conditions for muscular work.

What is the recommended method for raising body temperature? The optimal level of warm-up is the intensity that brings about 60-70% of maximum oxygen usage (which can be determined with the help of a heart rate monitor). Ideally, the warm-up should trigger perspiration in approximately 7 minutes. We usually warm up with the same activity that will follow in the main part of the workout. Runners will warm up by running, cyclists by cycling, swimmers by swimming, since the same activity will prepare precisely those muscles involved in the main workout phase.

The warm-up routine to raise body temperature can be followed by a routine to increase flexibility and activation. The addition of such a routine is recommended in those instances where the main workout requires movements with large amplitudes and high intensities, such as those workouts focusing on strength and speed. Flexibility can be increased in warm-up with dynamic methods that include fluent movements with larger amplitudes. Examples of gradual activation include gymnastics exercises and weight lifting.

The warm-up phase usually lasts for about 15 minutes. During longer breaks, you will need to either warm up again or extend the warm-up routine.

Do not overdo the warm-up, either by the extent or the intensity, since it may cause rapid fatigue or exhaustion of energy stores. On the other hand, warm-up should not be too short. Five minutes is the shortest recommended warm-up time.

It is also possible to warm-up passively, in a sauna, in warm water, or in the sun. Although the body temperature increases, this warm-up is not comparable to active warm-up. It does not trigger appropriate hormonal changes that support activity, and blood flow is directed under the skin as a cooling response instead of to the muscles. Therefore, the functional readiness of the body for strain after passive warm-up is less than after active warm-up.