Functional ambulation performance testing of adults with Down syndrome

The purposes of this study were (1) to determine temporal distance (TD) gait measures and the Functional Ambulation Performance Scores (FAPS) of adults with Down syndrome, (2) to determine the reliability of TD gait measures and FAPS of adults with Down syndrome and (3) to compare gait measures of adults with Down syndrome (DSA group), and adults without developmental disability (NDDA group). The FAPS is a quantitative representation of gait performance derived from TD gait measures.

Forty-one people participated in the study: 21 (9 males, 12 females) in the DSA group (mean age 41 years, range 23-51 years); and 20 (9 males, 11 females) in the NDDA group (mean age 40 years, range 20-56 years). All participants were in good health and were community ambulators. TD gait measures and FAPS were obtained for four trials from each participant: two immediate test-retest and two 2-week test-retest. One trial consisted of two passes at a comfortable, self-selected velocity on a 4.57-m sensor-embedded walk mat connected to a computerized analysis system (CIR Systems-GAITRite™). Reliability was assessed by the ICC(2,k). Direct comparisons were made between the two groups for FAPS and TD gait measures.

DSA overall ICC(2,k) for the FAPS = 0.92; mean normalized velocity, left and right step length/leg length ratio, and left and right step time ranged from 0.91 to 0.93. For these measures DSA immediate test-retest ICC(2,k) ≥ 0.91; 2-week test-retest ICC(2,k) ≥ 0.76. Mean gait measures were lower for the DSA group than for the NDDA group for FAPS (DSA = 90.3 ± 10.4; NDDA = 98.2 ± 2.4), step length/leg length ratio (DSA = 0.75 ± 0.10; NDDA = 0.78 ± 0.04), and step time (DSA = 0.53 ± 0.08 s; NDDA = 0.55 ± 0.05 s). Mean gait measures were higher for the DSA group than for the NDDA group for mean normalized velocity (DSA = 1.46 ± 0.43 LL/s; NDDA = 1.42 ± 0.14 LL/s) and base of support (DSA = 12.04 ± 3.74 cm; NDDA = 9.72 ± 2.89 cm).

Mean TD gait measurements were similar for both groups except for BOS; however, the variability was greater in the DSA group as reflected in generally larger standard deviations. The eight-point lower mean FAPS for the DSA group compared to the NDDA group indicates different gait proficiencies between the two groups. For the DSA group, the FAPS, mean normalized velocity, step length/leg length ratios, and step time ICC(2,k) results were ≥ 0.91 for immediate test-retest and ≥ 0.76 for 2-week test-retest (good range ≥ 0.75). The results suggest that these measures can be used as indicators of gait performance for adults with Down syndrome.