Diaphragm does not produce ammonia or lactate during high-intensity short-term exercise.

The research experiment confirms that unlike limb muscles, the diaphragm does not produce ammonia or lactate during high-intensity short-term exercise, using six healthy trained ponies for testing.

Methodology

• The research involved six healthy, trained ponies. These animals were selected for the purpose of studying the physiological processes of the diaphragm during intense exercise.
• Phrenic venous catheters were implanted in the ponies 5-9 days before the experiment. The purpose of this was to allow the researchers to take blood samples during the exercise period.
• Four minutes of high-intensity exercise at 32 km/h and at a 7% grade was enforced on the ponies. This level of exertion was equivalent to high-intensity short-term exercise for the animals.
• At rest, the heart rate was recorded with an average rate of 47 beats per minute and the oxygen extraction by the diaphragm was 26.5%. These were the base measures before engaging in the exercises. With exercise, the heart rate rose substantially, on average to about 218 beats per minute and the diaphragmatic oxygen extraction tripled to around 80.9%.
• Simultaneous blood samples were taken from the abdominal aorta and the phrenic vein during rest and during the period of high-intensity exercise. These samples were then analyzed for blood-gas components as well as lactate and ammonia concentrations using standard procedures.

Results

• The exercise led to an increase in the respiratory frequency and pleural pressure change to approximately 138 breaths per minute and 30 cmH2O, respectively. This indicates high stress on the respiratory muscles due to the exercise.
• Notwithstanding a substantial dip in the oxygen tension in the phrenic-venous blood of the exercised ponies (to around 15.5 Torr), the phrenic-venous lactate and ammonia concentrations did not exceed their equivalent arterial values. This shows that the diaphragm muscle did not manufacture extra lactate or ammonia during the exercise.
• The study confirmed that, contrary to limb muscles, the diaphragm does not engage in net production of ammonia and lactate during high-intensity short-term exercise despite the increase in workloads.

Conclusion

• The research reveals that unlike the limb muscles, which readily increase ammonia and lactate production under high workloads, the diaphragm primarily meets its energy needs through aerobic metabolism, even during high intensity exercises.