Fig. 7. Principal component analysis of muscle activity duration, relative onset of muscle activity and EMG burst intensity for fish swimming at 1.2 L s^–1 (red triangles) and 2.0 L s^–1 (green circles). Each point represents one measurement of muscle activity over one tail beat cycle. A description of the variable types loading heavily on each factor is given below the axis label. Further explanation of factor loadings is given in the text.