Related Experiment Videos
Elevated intra-abdominal pressure limits venous return during exercise in Varanus exanthematicus.
Suzanne L Munns1, Lynn K Hartzler, Albert F Bennett
1Department of Ecology and Evolutionary Biology, University of California, 321 Steinhaus Hall, Irvine, CA 92697, USA. smunns@uci.edu
The Journal of Experimental Biology
|October 23, 2004
Summary
Treadmill exercise in monitor lizards increases cardiovascular and respiratory functions. However, elevated intra-abdominal pressure during exercise compresses abdominal veins, limiting venous return and potentially maximal oxygen consumption.
Area of Science:
- Comparative physiology
- Reptilian cardiovascular and respiratory systems
Background:
- Understanding physiological responses to exercise in reptiles is crucial for ecological and evolutionary studies.
- The Savannah monitor lizard (Varanus exanthematicus B.) serves as a model for investigating reptilian exercise physiology.
Purpose of the Study:
- To investigate the effects of treadmill exercise on cardiovascular and respiratory parameters in Varanus exanthematicus at 35°C.
- To determine the role of intra-abdominal pressure in modulating venous return during exercise and recovery.
Main Methods:
- Physiological measurements of cardiovascular (venous return, heart rate, arterial blood pressure) and respiratory (minute ventilation, breathing frequency, oxygen consumption) systems during treadmill exercise.
- Experimental manipulation of intra-abdominal pressure via saline infusion in resting lizards to assess its impact on venous return.
Main Results:
- Treadmill exercise significantly increased lung ventilation, gular pumping, intra-abdominal pressure, mean arterial blood pressure, and venous return.
- Venous return decreased at high activity levels, with peak values for mean arterial pressure and venous return observed during recovery.
- Elevated intra-abdominal pressure in resting lizards reduced venous return when it exceeded central venous pressure, indicating venous compression.
Conclusions:
- Increased intra-abdominal pressure during locomotion in lizards compresses abdominal veins, potentially limiting cardiac output and maximal oxygen consumption.
- The physical compression of abdominal veins by elevated intra-abdominal pressure is a significant physiological constraint during strenuous activity in monitor lizards.