Cardiac output during exercise in paraplegic subjects.

Area of Science:

• Cardiovascular Physiology
• Exercise Physiology
• Sports Medicine

Background:

• Spinal cord injury (SCI) significantly impacts physiological responses to exercise.
• Arm cranking is a primary mode of exercise for individuals with paraplegia.
• Understanding cardiovascular adaptations in SCI is crucial for rehabilitation and performance.

Purpose of the Study:

• To measure cardiac output using the CO2 rebreathing method during arm cranking exercise.
• To compare exercise responses between male paraplegic subjects (HP) and able-bodied (AB) individuals.
• To investigate alterations in oxygen transport capacity in high-level spinal cord injury (HP).

Main Methods:

• CO2 rebreathing method for cardiac output measurement.
• Submaximal and maximal arm cranking exercise protocols.
• Comparison of physiological parameters (VO2max, cardiac output, heart rate, stroke volume) between HP and AB groups.

Main Results:

• Maximal oxygen consumption (VO2max) was significantly lower in HP compared to AB subjects.
• Maximal cardiac output, maximal heart rate (fc,max), and maximal stroke volume were similar between HP and AB groups.
• The relationship between heart rate and VO2 (fc/VO2 slope) was steeper in HP, but not different when expressed as a percentage of VO2max.

Conclusions:

• Paraplegic individuals demonstrate a reduced capacity for oxygen transport to active muscles during arm exercise.
• Impaired vasomotor regulation below the level of spinal cord injury likely contributes to these altered oxygen transport dynamics.
• Despite differences in VO2max, cardiac function appears preserved at maximal effort in this population.