Many environmental factors can have either a positive or a negative impact on exercise. Humidity is a general term for various descriptions of the water vapor in the air and is usually seen as having a negative impact on physical activity. This is due to the effect it has as a barrier to cooling the body. The temperature of air is one factor that determines the amount of water vapor that it can hold. The colder the air, the less water vapor it is able to carry. Absolute humidity is the amount of water vapor per mass of dry air in a given volume at a certain air temperature. Relative humidity is the water vapor content of the air relative to its content at saturation. ...