Physiological Bases of Physical Limitations During Exercise

During the execution of physical activity, obese individuals suffer from considerable functional limitations which are principally related to the excess of their body mass, more than to other morbid conditions co-occuring with obesity. Important changes in body composition are associated with the rise in body adiposity, so that obese persons, and women in particular, result with a lower amount of fat-free mass and leg muscle volume per unit body mass, but with absolute larger quantities. Therefore, motor performance of obese individuals during anaerobic activity, which includes the execution of short and intense efforts, is largely reduced by the imbalance between the size of available skeletal muscle and the disproportionate accumulation of fat tissue, although the capacity of strength and absolute leg power output production are increased. Differently, activities relying upon aerobic metabolism, such as bicycle ergometer exercise or walking, are limited in obese subjects principally due to the greater metabolic energy required to move the heavier body, or single body segments involved in movements, which may ultimately exceed the limits of the aerobic capacity. The physiological mechanisms underlying these functional limitations during exercise in obesity should be considered when devising protocols of physical activity and rehabilitation aiming to cure the body mass excess.