Hemodynamic and cardiorespiratory responses to various arm cycling regimens in men with spinal cord injury.

Study design: Repeated measures within-subjects crossover study.
Objectives: High intensity interval exercise (HIIE) elicits higher oxygen consumption (VO2) and heart rate (HR) versus moderate intensity continuous exercise (MICE) in men with spinal cord injury (SCI). No study has compared hemodynamic responses to HIIE versus MICE in SCI. In this study, we determined hemodynamic and cardiorespiratory responses to different bouts of arm cycling in men with SCI. Setting: Human Performance Laboratory, San Diego, CA.
Methods: Five men (age and injury duration = 42.6 ± 16.1 yr and 9.9 ± 7.6 yr) with SCI participated in the study. VO2peak and peak power output were initially assessed. Subsequent visits included MICE, HIIE, sprint interval exercise (SIE), and a no-exercise control (CON). Energy expenditure was matched across modes and equal to 100 ± 10 kcal. During the bouts, cardiac output (CO), stroke volume (SV), HR, and VO2 were measured.
Results: Heart rate, SV, and CO increased in response to all exercise bouts and were higher during exercise versus CON. During HIIE and SIE, heart rate approached 90% of maximum, and stroke volume increased by 40% which was higher (p < 0.05) versus MICE and CON. In addition, exercise led to a two (MICE) to threefold increase in CO (HIIE and SIE) although it was not different from CON. VO2 during SIE and HIIE was higher (p < 0.05) versus MICE. Conclusions: Similar to results in non-disabled populations, HIIE and SIE elicit near-maximal values of SV and CO.