Cardiovascular and oxygen uptake kinetics during sequential heavy cycling exercises

Area of Science:

• Exercise Physiology
• Cardiovascular Physiology

Background:

• Understanding the dynamic response of oxygen uptake (VO2) and cardiac output (CO) is crucial for exercise physiology.
• The relationship between VO2 and CO kinetics during repeated bouts of heavy exercise needs further elucidation.

Purpose of the Study:

• To investigate the relationship between the rapidity of oxygen uptake (VO2) and cardiac output (CO) increases during heavy exercise.
• To examine the impact of prior heavy exercise on VO2 and CO kinetics.

Main Methods:

• Six subjects performed repeated heavy exercise bouts on a cycle ergometer above the ventilatory threshold.
• Oxygen uptake (VO2) was measured breath-by-breath, and cardiac output (CO) was determined using impedance cardiography.
• Exercise bouts were separated by 10-min recovery at 35% peak VO2.

Main Results:

• VO2 and CO responses were significantly related and faster during the second heavy exercise bout compared to the first.
• Prior heavy exercise increased the amplitude of the fast component of VO2 without altering its time constant.
• A decrease in the slow component of VO2 was observed following prior heavy exercise.

Conclusions:

• The amplitude of the fast component of VO2 is more sensitive to prior heavy exercise than its time constant.
• Prior heavy exercise influences the dynamic response of VO2 kinetics during subsequent exercise bouts.
• These findings contribute to understanding exercise adaptation and cardiovascular regulation.