Fig 2. The relation between SF and HR for each speed series based on Model 1.

From bottom to top V_90%, V_100%, V_110%. The central line in the boxplot represents the median, the edges of the box are the 25th and 75th percentiles, and the whiskers extend to ±1.5 of the interquartile range. The outliers (+) beyond this range belong to a single participant. An optimum of 83 strides·min^-1 was calculated using the parameters of Model 1.