Table 2. Basin of entrainment normalized by walking cadence and its variability.

Subject ID	Number of trials	Basin of entrainment to walking cadence ratio %	Basin of entrainment to variability ratio %
1	4	7.0	34
2	4	7.1	100
3	4	4.2	33
4	5	3.8	20
5	5	4.2	62
6	5	3.1	20
7	3	3.9	40
8	3	4.1	38
9	5	8.1	79
10	3	2.1	21
11	5	11	110
12	4	6.9	59
13	3	2.0	24
14	3	7.6	52
15	5	9.2	100
16	5	9.0	77
17	4	14	64
18	6	13	71
19	4	N/A	N/A
All subjects	80	Mean = 6.7 SD = 3.6	Mean = 56 SD = 30

The basin of entrainment was compared with the average walking period and the variability of walking cadence. Basin of entrainment to walking cadence ratio was evaluated as , where τ_before is the average walking period of last 15 strides before perturbation. Basin of entrainment to variability ratio was evaluated as , where σ_before is the standard deviation of walking period of last 15 strides before perturbation. SD means standard deviation.