English term (edited): stepping number

perhaps, but not sure I understand the Q

In this case we can refer to different aspects of the word "step" in the dictionary. Incase you use step it could be misleading at least for the novice English learner by taking a dictionary meaning the Noun "step" for others.Moreover present participle is used before a noun as an adjective and in this case(ing) denotes an action which is taking steps. But,using the noun "step" before the number might be correct in case one wishes to refer to one of the steps specified. For example "i jumped 58 cm. in the step number 5.

The noun step has 10 senses (first 5 from tagged texts)

1. (41) measure, step -- (any maneuver made as part of progress toward a goal; "the situation called for strong measures"; "the police took steps to reduce crime")
2. (13) footstep, pace, step, stride -- (the distance covered by a step; "he stepped off ten paces from the old tree and began to dig")
3. (7) step -- (the act of changing location by raising the foot and setting it down; "he walked with unsteady steps")
4. (2) step, stair -- (support consisting of a place to rest the foot while ascending or descending a stairway; "he paused on the bottom step")
5. (1) gradation, step -- (relative position in a graded series; "always a step behind"; "subtle gradations in color"; "keep in step with the fashions")
6. step, stone's throw -- (a short distance; "it's only a step to the drugstore")
7. footfall, footstep, step -- (the sound of a step of someone walking; "he heard footsteps on the porch")
8. tone, whole tone, step, whole step -- (a musical interval of two semitones)
9. footprint, footmark, step -- (a mark of a foot or shoe on a surface; a clue that someone was present; "the police made casts of the footprints in the soft earth outside the window")
10. dance step, step -- (a sequence of foot movements that make up a particular dance; "he taught them the waltz step")

Overview of verb step

The verb step has 2 senses (first 2 from tagged texts)

1. (23) step -- (take a step)
2. (7) step, tread -- (put down the foot, place the foot; "For fools rush in where angels fear to tread")

English term (edited): is

The selected motions included 20 paces right/left with both legs, 20 paces back/forth with both legs, 20 paces back/forth with one leg, and 20 paces right/left with one leg. There were significant age differences in all gait parameters, the trend showing decreased step numbers and extended average ground contact at each step with aging. With 60/69-year-old males and with all females, individual differences in step numbers and average contact time in both-leg pacing (back/forth and right/left) were greater than in one-leg pacing. Both-leg pacing was, therefore, considered a useful test for evaluating individual differences in dynamic balance for elderly people. Individual differences in step numbers with both-leg walking tended to lessen with age. In males aged over 70, the individual differences in step numbers and the average contact time with both-leg stepping were smaller than those with one-leg stepping.

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You are right that the English of the original is laboured and hard to comprehend in places. The above is edited into English (US and British).

Hyphenation is changed extensively, as is usage. The term "gait" (manner of walking) is useful, as is "pace" (in one of its senses, a synomym of "step"). I trust this is of help to you.

I did not understand the meaning of "20 s" in your original, and freely interpreted it as meaning "twenty repeats of a step". It could, perhaps more correctly, mean "twenty seconds of pacing". You decide :)