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Cardiovascular responses in paraplegic subjects during arm exercise
M T Hopman1, B Oeseburg, R A Binkhorst
1Department of Physiology, University of Nijmegen, The Netherlands.
Summary
Paraplegics exhibit lower maximal performance during arm exercise due to reduced stroke volume (SV) and active muscle mass. However, their cardiovascular system compensates during submaximal exercise with a higher heart rate (HR) to maintain cardiac output (Qc).
Area of Science:
- Cardiovascular Physiology
- Exercise Science
- Sports Medicine
Background:
- Individuals with spinal cord injuries (SCI) often experience altered cardiovascular function.
- Arm exercise is a primary mode of aerobic activity for individuals with paraplegia.
- Understanding cardiovascular responses is crucial for optimizing exercise protocols and health outcomes in paraplegia.
Purpose of the Study:
- To compare cardiovascular responses during maximal and submaximal arm exercise in paraplegics versus able-bodied controls.
- To investigate the factors limiting maximal exercise performance in paraplegics.
- To elucidate the compensatory mechanisms during submaximal exercise in paraplegia.
Main Methods:
- 11 male paraplegics (T6-T12 complete SCI) and 11 matched controls performed maximal and submaximal arm-cranking exercise.
- Cardiac output (Qc) was measured using the CO2 rebreathing method.
- Maximal oxygen uptake, heart rate (fc), and stroke volume (SV) were assessed.
Main Results:
- Paraplegics had lower maximal oxygen uptake and higher maximal heart rate (fc,max) than controls.
- At equivalent submaximal oxygen uptakes, stroke volume (SV) was lower and fc was higher in paraplegics.
- Cardiac output (Qc) was similar between groups at the same submaximal oxygen uptakes.
Conclusions:
- Maximal arm exercise performance in paraplegics is limited by smaller active muscle mass and reduced SV, despite higher fc,max.
- Submaximal exercise in paraplegics involves compensatory increases in fc to maintain Qc.
- Impaired venous blood return and reduced ventricular filling pressure likely contribute to lower SV in paraplegics.