Fig. 1.

Classification of Physical Activity. Acute physical activity refers to an individual bout of activity that can be part of the normal process of conducting daily business (normal daily physical activity) or it can be exercise which refers to a planned session of physical activity such as walking, jogging, bicycling, swimming, weight lifting or stretching intended to be part of a chronic physical activity program with the goal of improving health. Chronic physical activity is a regimen of exercise carried out over time with the goal of improving physical or psychological health. Exercise training is a chronic physical activity regimen of sufficient intensity, duration, and frequency to increases physical fitness. Sub-exercise training is a chronic physical activity regimen that is not of sufficient intensity, duration, or frequency to improve physical fitness, but may reduce psychological stress and improve psychological health.