Fig. 2. Sample recordings from alligator 2 (body mass 1.22 kg) of change in pitch (top trace) associated with EMG activity (second trace) in the diaphragmaticus during ventilation and during a dive. The V below the EMG trace indicates muscle activity in the diaphragmaticus associated with inspiration. During this time the alligator's head was level with the water and its body was at a positive 45° angle as illustrated by the schematic alligator above the left side of the pitch angle trace. It should be noted that during this particular ventilation cycle very little change in the pitch angle can be seen. The D below the EMG trace indicates muscle activity in the diaphragmaticus associated with a dive. The vertical bars that mark the beginning of a dive and the subsequent return to the original pitch angle after surfacing from the dive delimit a dive–surface cycle. The maximum pitch angel for this dive–surface cycle was reached at around –45° when the alligator's head was parallel to the surface of the water and its body assumed the indicated angle as illustrated by the schematic (upper right side of the inclinometer trace). In order to compare muscle activity over the course of a dive–surface cycle of different lengths, the cycle was divided into 100 equal bins and the average integrated muscle activity for each bin calculated. A sample of how this was done for a cycle is shown below the EMG trace in this figure. The calibration bar, 1 s.