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 af fect gait parameters in older adults is unknown, with information being lar gely anecdotal. This investigation was conducted to determine the effects o f limb-length discrepancy on gait economy and lower-extremity muscle activi ty 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 wal king pace with artificial limb-length discrepancies of 0, 2, 3, and 4 cm ap plied in a randomly selected order. Indirect calorimetry was used to measur e oxygen consumption and minute ventilation. Electromyography was used to m easure muscle activity of the right and left quadriceps femoris, plantar fl exors, gluteus maximus, and gluteus medius. Heart rate, the rating of perce ived exertion, and frequency of gait compensation patterns were also measur ed. Results: There was a significant increase in oxygen consumption and the rat ing of perceived exertion with 2, 3, and 4-cm artificial limb-length discre pancies; a significant increase in heart rate, minute ventilation, and quad riceps activity in the longer limb with 3 and 4-cm artificial limb-length d iscrepancies; and a significant increase in plantar flexor activity in the shorter limb with a 4-cm artificial limb-length discrepancy compared with t he same parameters with no artificial limb-length discrepancy. Conclusions: Both oxygen consumption and the rating of perceived exertion w ere greater with a 2-cm artificial limb-length discrepancy than they were w ith no artificial limb-length discrepancy. There appears to be a breakpoint between 2 and 3 cm of artificial limb-length discrepancy in older adults w ith regard to the effects on most other physiological parameters. A 3-cm ar tificial limb-length discrepancy is likely to induce significant quadriceps fatigue in the longer limb. Elderly patients with substantial pulmonary, c ardiac, or neuromuscular disease may have difficulty walking with a limb-le ngth discrepancy as small as 2 cm.