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 1^st length and to the lower LF amplitude of each spectral window (which were all achieved in the 1^st 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.