Fig 1.
Schematic drawing of a position during accelerated running.
The variables described in eqs 1–3 and their interrelationships are graphically presented. Accelerations g and ahCoM are defined as by di Prampero et al. [6]. Solid circle is CoM.
Fig 2.
Example of CoM’s vertical position and curve fitting from step to step in time.
Open markers are data, solid marker indicates the breakpoint according to Nagahara et al. [10] and piecewise twice linear fit (solid lines, Eq 5a). Vertical arrow indicates the breakpoint according to linear-exponential piecewise fit (grey curves, Eq 5b). Dotted line is exponential fit (Eq 4).
Table 1.
Comparison of piecewise linear/exponential and exponential curve fitting.
Fig 3.
Curve fittings for the mean data for each step over all athletes.
Only steps with a complete data set for the variable at hand are shown and were used for the fitting procedures. Dotted line: exponential; Solid lines: piecewise linear. Horizontal (top diagram only) and vertical bars are standard deviation (n = 24). Note that the seemingly very low standard deviation, especially for horizontal velocity, is only partly due to the homogeneous group and mainly due to scaling of the diagram, which covers low velocity at the first steps to almost maximal sprinting velocity. Time = 0 is the time of the first movement of CoM during the sprint start.
Table 2.
Odds ratios for incidences of breakpoints (Pos) or continuity (Neg) as indicated by statistical comparison of the piecewise function (eqs 5a and 5b) and the exponential function (eq 4) for SvCoM, αaccCoM and LCoMsup.