Fig. 3

Mean power in the ULF (top row) and VLF (bottom row) frequency bands; the corresponding numerical values are given for intensity dependence (figure parts a and b) in Table 1 and for time dependence (figure parts c–f) in Table 2. The main bars depict mean power and error bars show 95% confidence intervals for the means. Values are given as \(\log _{10}([\text {power}/(\text {ms}^2)]/[1/(\text {ms}^2)])\). \(^{*}\Leftrightarrow p < 0.05\), \(^{**}\Leftrightarrow p < 0.01\), \(^{***} \Leftrightarrow p < 0.001\). ULF ultra-low frequency, VLF very-low frequency, r rest, m moderate, v vigorous. \(w_1\), \(w_2\) and \(w_3\): first, second and third time windows. a Intensity dependence, ULF, b Intensity dependence, VLF, c Time dependence, m, ULF, d Time dependence, m, VLF, e Time dependence, v, ULF and f Time dependence, v, VLF