The purpose of this examination was to explore the effects of stride length (SL) perturbations on walking gait, relative to preferred walking (PW) and running (PR), via lower extremity range of motion (ROM) variability. ROM variability at the hip, knee, and ankle joints, in the sagittal and frontal planes were used in evaluating motor control of gait, where increased gait variability has been previously implicated in fall susceptibly.
Nine participants (5 male, 4 female; mean age 23.11±3.55 years, height 1.72±0.18m, mass 72.66±14.37kg) free from previous lower extremity injury were examined. Kinematic data were acquired using a 12-camera system (Vicon MX T40-S; 200Hz). Data filtering and interpolation included a low pass, 4th order, Butterworth filter (15Hz cutoff) and cubic spline. Five gait trials were completed for PW and PR, with subsequent SL manipulations computed as a percentage of leg length (LL). SL perturbations included 60%, 80%, 100%, 120%, and 140% of LL.
Kinematic analysis involved one stride (two steps) during each gait trial, assessing ROM at the hip, knee, and ankle from heel contact to toe-off for each limb, in the sagittal and frontal planes. Variability was expressed using coefficient of variation (%). Comparisons were made using 3×7 (joint × stride condition) mixed model ANOVAs, with repeated measures on stride condition (α = 0.05), using SPSS 20.0.
Differences in lower extremity ROM variability were detected among stride conditions in the frontal and sagittal planes (F[3.185,76.451] = 3.004, p = .033; F[4.595,110.279] = 2.834, p = .022, respectively). Greater ROM variability was observed at, and in excess of SLs of 100%LL relative to PW in the frontal plane (PW: 9.2±4.2%; 100%LL: 11.8±3.6%, p = .014; 120%LL: 13.5±5.8%, p = .046; 140%LL: 13.8±6.5%, p = .016), and between SLs of 80%LL and 120%LL in the sagittal plane (4.9±3.0%; 7.8±4.7%, p = .046, respectively). From this, PW appeared to occur within SLs of 60%LL to 80%LL, while SLs exceeding 100%LL resulted in increased lower extremity ROM variability. This may have consequences for fall susceptibility at increased stride lengths during walking. PR did not reveal significant variability differences (p>.05) compared to walking conditions in either the sagittal or frontal plane (7.5±5.0%; 12.8±7.7%, respectively), suggesting that running represents a separate, but stable gait pattern. In the sagittal plane, ROM variability was significantly lower at the hip (3.9±1.5%), relative to the ankle (8.4±1.6%, p<.001) and knee joints (7.4±2.6%, p = .001), suggesting that gait control may be more active at the ankle and knee joints. Future investigations should examine kinetic changes in gait when altering stride length.