Table 2.
Variable | Young | Older | Odds Ratio | ||||
---|---|---|---|---|---|---|---|
Recover (n = 31) |
Fall:Step (n = 11) |
Recover (n = 8) |
Fall:Step (n = 18) |
Fall:No-Step (n = 10) |
For Falling a |
||
At Slip Onset: | |||||||
XCOM | (%ft len) | 0.5 ± 7.4 | −6.5 ± 7.7 d | 2.7 ± 8.6 | 6.9 ± 9.0 | 10.1 ± 10.4 | 0.81 |
dXCOM/dt | (m/s ) | 0.10 ± 0.01 | 0.09 ± 0.02 | 0.09 ± 0.01 | 0.09 ± 0.01 | 0.09 ± 0.02 | 1.56 |
Stability | (%) | 8.9 ± 4.1 | 4.5 ± 4.7 d | 9.4 ± 4.7 | 11.6 ± 4.5 | 13.0 ± 5.0 | 0.92 |
At Mid-Slip:b | |||||||
XCOM | (%ft len) | −10.6 ± 10.5 | −19.0 ± 5.5 | −15.3 ± 9.1 | −11.8 ± 12.9 | −9.0 ± 8.7 | 1.20 |
dXCOM/dt | (m/s ) | −0.11 ± 0.08 | −0.12 ± 0.05 | −0.20 ± 0.07 f | −0.18 ± 0.06 f | −0.16 ± 0.06 | 1.45 |
Stability | (%) | −14.6 ± 9.7 | −20.1 ± 6.1 | −25.3 ± 8.3 e | −21.4 ± 7.8 e | −18.9 ± 0.06 | 1.49 |
At 1st Step Initiation: c | |||||||
XCOM | (%ft len) | −15.8 ± 16.7 | −26.3 ± 16.2 | −22.4 ± 25.2 | −16.0 ± 25.9 | – | 1.23 |
dXCOM/dt | (m/s ) | −0.06 ± 0.10 | −0.07 ± 0.07 | −0.14 ± 0.09 e | −0.10 ± 0.10 e | – | 1.11 |
Stability | (%) | −13.2 ± 13.7 | −19.3 ± 10.0 | −23.2 ± 12.7 | −16.8 ± 13.8 | – | 1.27 |
At 1st Step Touchdown: | |||||||
XCOM | (%ft len) | 39.0 ± 23.8 | 6.5 ± 31.5 i | 20.7 ± 21.1 f | −15.3 ± 27.8 f,i | – | 6.67 j |
dXCOM/dt | (m/s ) | −0.01 ± 0.06 | −0.01 ± 0.03 | −0.05 ± 0.04 | −0.02 ± 0.05 | – | 0.93 |
Stability | (%) | 7.5 ± 8.6 | −0.8 ± 9.3 h | −0.6 ± 5.5 f | −4.7 ± 5.2 f,h | – | 4.55 j |
XCOM = center of mass (COM) anteriorly-directed position relative to heel of posterior foot in ground contact; dXCOM/dt = COM forward velocity relative to support surface of posterior foot in ground contact; Stability = distance of COM state from model-predicted boundary for backward balance loss (<0 indicates unstable); g = 9.81 m/s2; ft len = foot length; bh = body height.
Factor by which the odds of falling change for a decrease of 1 SD in the variable across all subjects.
Excludes 9 Young Recover, 4 Young Fall:Step, and 1 Older Recover subject who stepped before the posterior foot reached the slip midpoint.
Step initiation could not be identified in 1 Young Recover, 1 Young Fall:Step, and 3 Older Fall:Step subjects.
p < .05 vs. Young Recover and Older Fall:Step (interaction of age group and slip outcome).
p < .05
p < .01 vs. Young (main effect of age group).
p < .01
p < .001 vs. Recover (main effect of slip outcome).
p < .001 for Odds Ratio ≠ 1.