Figure 4. The duty times of the masseters of all experimental animals. The (over all experimental days; n = 7) averaged 5% (A), 20% (B), and 50% duty times (C) for the superficial (open) and deep (solid) masseter regions as recorded for all 6 animals. Standard deviations are shown above the bars. Significant differences between muscle regions are indicated by single (p < 0.05) or double asterisks (p < 0.01).