Meeting Abstract

30.4  Wednesday, Jan. 5  Running guinea fowl prefer to expire at foot down: Coordination patterns of step and ventilatory cycles MARKLEY, J.S.; University of Utah markley@biology.utah.edu

Sustained locomotion requires continuous lung ventilation. How birds coordinate cursorial locomotion and breathing is largely unknown. Locomotion and ventilation would be expected to be coordinated such that steps positively influence ventilation and that step induced ‘interfering’ flows are minimized. To address how birds breathe during running, coordination patterns between running steps and particular points in the ventilatory cycle were evaluated in guinea fowl (Numida meleagris) running at three treadmill speeds. The rate of breath flow during transitions between inspiration and expiration varied significantly with the timing of each transition relative to the step. Breaths with transitions that occurred at ‘preferred’ step fractions had shorter transition periods than breaths with transitions that occurred at ‘uncommon’ step fractions. The beginning of expiration was consistently coordinated with the timing of foot down. With this timing, intercostal and abdominal muscle activity associated with each step, would also act to induce expiration. Expiration began at foot down whether running step and ventilatory cycles were entrained at integral numbers of steps per breath or these cycles were not-entrained. However, the timing of the start of inspiration varied with entrainment ratio. Entrainment between locomotion and ventilation may be driven by coordinating the timing of key points in the breath cycle to match ‘assistive’ portions of the step cycle.