After both acute exercise and physical training, i.e., regularly performed exercise, increased glucose tolerance or unchanged glucose tolerance in the face of lower plasma insulin concentrations may be seen during oral (OGTT) and intravenous (IVGTT) glucose loading (85,89,116,148). Conversely, physical inactivity during bed rest or resulting from spinal cord injury decreases glucose tolerance in the face of increased insulin concentrations (39,88,107). The deterioration in glucose tolerance during bed rest can be diminished by exercise (39,88). These findings indicate a direct relationship between physical activity and insulin action and also suggest an inverse relationship between physical activity and glucose induced insulin secretion.
