Figure 4. Graphical representation of the trends of the spectral windows values of LF (%) due to breathings (□), voluntary adjustments (◊), and strokes (Δ), in relation to swimming speeds (dashed line) of each length. Voluntary adjustments and strokes are significantly and inversely correlated with speed. Percentages were obtained as follows: firstly, 100% was assigned to the higher forward speed value of the 1st length and to the lower LF amplitude of each spectral window (which were all achieved in the 1st length). Then, speed values and spectral window amplitudes of the remaining 7 lengths were transformed in percentage according to their reduction or increase compared to the 100% value.