(SD1 is standard deivation of the group as a whole, SD2 is mean standard deviation of individuals. Meaurements seem to be in cm/s.)
All fast: 171 cm/s (SD1 22, SD2 7) Step Length 63 cm (SD1 13, SD2 3) Cadence 169 Steps/minute, (SD1 29, SD2 6)
All Normal: 119 cm/s (SD1 19, SD2 7) Step Length 100 cm (SD1 11, SD2 3) Cadence 134 Steps/Minute (SD1 17, SD2 6)
All slow: 86 cm/s (SD1 19, SD2 6) Step Length 48 cm (SD1 11, SD2 3) Cadence 110 Steps/Minute (SD1 17, SD2 5)
7-11: Fast 179 cm/s (SD1 21, SD2 8.) Step Length 62 cm (SD1 5, SD2 3) Cadence 175 Steps/Minute (SD1 25, SD2 7)
12-18 Fast: 179 cm/s (SD1 18, SD2 5) Step Length 78 cm (SD1 7, SD2 2) Cadence 138 Steps/Minute (SD1 12, SD2 3)
7-11 Normal: 119 cm/s (SD1 18, SD2 5) Step Length 54 cm (SD1 6 SD2 2) Cadence 132 Steps/Minute (SD1 12, SD2 5)
12-18 Normal 129 cm/s (SD1 15, SD2 6) Step Length 67 cm (SD1 6, SD2 3) Cadence 116 Steps/Minute (SD1 11, SD2 4)
7-11 Slow: 83 cm/s (SD1 17, SD2 6) Step Length 48 cm (SD1 7, SD2 3) Cadence 105 Steps/Minute (SD1 16, SD2 5)
12-18 Slow: 99 cm/s (SD1 17, SD2 5), Step Length 60 cm (SD1 7, SD2 3) Cadence 99 Steps/Minute (SD1 12, SD3)
If we look at this data, we can see that a Normal 7-11 y/o walks 54 cm per step, & their velocity is 119 cm/s, which makes sense, since the step is not the full stride.
Thus, if it takes them 1 second to move 119 cm, but 1 step moves them only 54 cm, then presumably the single step takes as much time to do as 54 cm's size as a portion/percentage of 119 cm! So....
119 / 54 = 2.2037037. Thus, divide 1 second by 2.2037037 for how much time for the 54 cm 1 step! 0.453781513 seconds!
As an alternative, it was mentioned above most people (Adults especially) have step-length-to-height ratios of 0.40 to 0.45.
We can try applying this to youths.... (
Link for average heights used.) For simplicity & brevity's sake, we'll use the lowest ratio.
11 yrs F: 144 cm * 0.40 = 57.6
12 yrs F: 149.8 * 0.40 = 59.92
11 yrs M: 143.5 * 0.40 = 57.4
12 yrs F: 149.1 * 0.40 = 59.64
More or less the same. The ratio is probably more applicable to adults, or maybe Standard Deviations has to do with it. Not entirely sure.