Curve fittings for the mean data for each step over all athletes.

<p>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.</p

Example of CoM’s vertical position and curve fitting from step to step in time.

<p>Open markers are data, solid marker indicates the breakpoint according to Nagahara et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.ref010" target="_blank">10</a>] and piecewise twice linear fit (solid lines, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.e005" target="_blank">Eq 5a</a>). Vertical arrow indicates the breakpoint according to linear-exponential piecewise fit (grey curves, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.e006" target="_blank">Eq 5b</a>). Dotted line is exponential fit (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.e004" target="_blank">Eq 4</a>).</p

Schematic drawing of a position during accelerated running.

<p>The variables described in eqs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.e001" target="_blank">1</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.e003" target="_blank">3</a> and their interrelationships are graphically presented. Accelerations <i>g</i> and <i>a</i>_<i>hCoM</i> are defined as by di Prampero et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.ref006" target="_blank">6</a>]. Solid circle is CoM.</p

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 S<i>v</i>_<i>CoM</i>, α_{<i>accCoM</i>} and L_{<i>CoMsup</i>}.

<p>Odds ratios for incidences of breakpoints (Pos) or continuity (Neg) as indicated by statistical comparison of the piecewise function (eqs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.e005" target="_blank">5a</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.e006" target="_blank">5b</a>) and the exponential function (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159701#pone.0159701.e004" target="_blank">eq 4</a>) for S<i>v</i>_<i>CoM</i>, α_{<i>accCoM</i>} and L_{<i>CoMsup</i>}.</p

Comparison of piecewise linear/exponential and exponential curve fitting.

<p>Comparison of piecewise linear/exponential and exponential curve fitting.</p

Intensity distribution for the sprint training groups during all training sessions.

<p>Best sprint from pre-training testing was set as reference (100%) for 90SUP and 90UNSUP, while best sprint within each training session was set as reference (100%) for 100UNSUP.</p

Between group changes (mean and 95% CIs) versus controls for underlying performance variables between pre- and post-training.

<p>The differences vs. control group are assessed by estimated marginal mean. Minus (-) indicates lower values post-training compared with the control group (assessed by estimated marginal means). HR = heart rate, BLa^- = blood lactate concentration, SL = step length, SR = step rate</p><p>* = significantly different (Bonferroni adjusted) from CON (<i>p</i> = 0.01).</p><p>Between group changes (mean and 95% CIs) versus controls for underlying performance variables between pre- and post-training.</p

Physical and training characteristics at inclusion.

<p>Values are mean ± SD. BM = Body mass, Tot. vol. = Total training volume. Training values are based on self-reported weekly averages during the intervention period. There were no significant differences among the groups for any of the variables, except for body mass (*100UNSUP < 90UNSUP, <i>p</i> = 0.04).</p><p>Physical and training characteristics at inclusion.</p

Sex difference (%) for performance in running and jumping disciplines from age 11 to 18.

<p>Data are mean and 95% CIs for 60 m (panel A), 800 m (panel B), long jump (panel C) and high jump (panel D) for top 100 Norwegian male and female performers in each discipline.</p

Performance development from age 11 to 18 in running and jumping disciplines.

<p>Data are mean ± SD for 60 m (panel A), 800 m (panel B) long jump (panel C) and high jump (panel D) for top 100 Norwegian male and female performers in each discipline.</p