Effects of limping on normal exercise response.
Ten subjects performed two identical exercise tests on a motor-driven treadmill while walking normally or while limping. The two tests were separated by a rest period sufficient to permit return to a base-line state and the sugjects were randomly assigned to a normal-limp or limp-normal exercise sequence. Work rate was varied progressively by increasing treadmill grade in 5-degree increments to a maximum of 20 degrees, while limping was induced by insertion of a 0.5-cm wooden spike under the heel of the dominant foot. At all work rates, limping produced consistent increases in all variables studied, except for tidal volume where a decrease was seen. At the highest work rate these differences tended to disappear. Even considering the greater O2 consumption induced by limping, there were still significant (P less than 0.01) increases in both respiratory rate and ventilation at all but the highest work rate, accompanied by an insignificant fall in tidal volume. This suggests that these changes were not induced by the alterations in the internal or external work of walking and that limping somehow alters the regulation of exercise hyperpnea.