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.