Effects of limb-length discrepancy on gait economy and lower-extremity muscle activity in older adults

Background: The amount of limb-length discrepancy necessary to adversely affect gait parameters in older adults is unknown, with information being largely anecdotal. This investigation was conducted to determine the effects of limb-length discrepancy on gait economy and lower-extremity muscle activity in older adults. Methods: Forty-four men and women ranging in age from fifty-five to eighty-six years with no evidence of limb-length discrepancy of >1 cm participated in the study. Subjects walked on a treadmill at a self-selected normal walking pace with artificial limb-length discrepancies of 0, 2, 3, and 4 cm applied in a randomly selected order. Indirect calorimetry was used to measure oxygen consumption and minute ventilation. Electromyography was used to measure muscle activity of the right and left quadriceps femoris, plantar flexors, gluteus maximus, and gluteus medius. Heart rate, the rating of perceived exertion, and frequency of gait compensation patterns were also measured. Results: There was a significant increase in oxygen consumption and the rating of perceived exertion with 2, 3, and 4-cm artificial limb-length discrepancies; a significant increase in heart rate, minute ventilation, and quadriceps activity in the longer limb with 3 and 4-cm artificial limb-length discrepancies; and a significant increase in plantar flexor activity in the shorter limb with a 4-cm artificial limb-length discrepancy compared with the same parameters with no artificial limb-length discrepancy. Conclusions: Both oxygen consumption and the rating of perceived exertion were greater with a 2-cm artificial limb-length discrepancy than they were with no artificial limb-length discrepancy. There appears to be a breakpoint between 2 and 3 cm of artificial limb-length discrepancy in older adults with regard to the effects on most other physiological parameters. A 3-cm artificial limb-length discrepancy is likely to induce significant quadriceps fatigue in the longer limb. Elderly patients with substantial pulmonary, cardiac, or neuromuscular disease may have difficulty walking with a limb-length discrepancy as small as 2 cm.