The mechanics of running in children
(1998) The Journal of physiology — Vol. 509, n° 3, p. 927-940 (1998)
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- Abstract
- 1. The effect of age and body size on the bouncing mechanism of running was studied in children aged 2-16 years. 2. The natural frequency of the bouncing system (fs) and the external work required to move the centre of mass of the body were measured using a force platform. 3. At all ages, during running below approximately 11 km h-1, the freely chosen step frequency (f) is about equal to fs (symmetric rebound), independent of speed, although it decreases with age from 4 Hz at 2 years to 2.5 Hz above 12 years. 4. The decrease of step frequency with age is associated with a decrease in the mass-specific vertical stiffness of the bouncing system (k/m) due to an increase of the body mass (m) with a constant stiffness (k). Above 12 years, k/m and f remain approximately constant due to a parallel increase in both k and m with age. 5. Above the critical speed of approximately 11 km h-1, independent of age, the rebound becomes asymmetric, i.e. f < fs. 6. The maximum running speed (Vf, max) increases with age while the step frequency at remains constant (approximately 4 Hz), independent of age. 7. At a given speed, the higher step frequency in preteens results in a mass-specific power against gravity less than that in adults. The external power required to move the centre of mass of the body is correspondingly reduced.
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Citations
Schepens, B., Willems, P., & Cavagna, G. A. (1998). The mechanics of running in children. The Journal of physiology, 509(3), 927-940. https://doi.org/10.1111/j.1469-7793.1998.927bm.x (Original work published 1998)