The ability of heart rate or perceived exertion to predict oxygen uptake varies across exercise modes in persons with tetraplegia

Abstract

Study design: Descriptive study. Objectives: To examine grouped and intra-individual relationships between 1) exercise intensity and heart rate (EI-HR); 2) EI and oxygen uptake (EI-VO2); 3) VO2 and HR (VO2-HR); and 4) perceived exertion and VO2 (PE-VO2) in persons with tetraplegia (C4/5–C8) during different modes of exercise. Setting: Community in Winnipeg, Canada. Methods: Participants exercised at 3 graded intensities during arm ergometry (ERG), wheeling indoors on cement (MWC), or hand-cycling outdoors (HC). EI (Watts, km/hr) and VO2, HR and PE were recorded. Results: 22 persons completed ERG, 14/22 also completed MWC and 5/22 completed ERG, MWC and HC. Regression analysis of grouped data showed a significant relationship between EI-VO2 but not for EI-HR or HR-VO2. Intra-individual analyses showed a strong correlation (r or ρ > 0.7) for VO2-HR for 16/22 during ERG. In the participants completing multiple exercise modes, a strong VO2-HR relationship was present in 12/14 in ERG, but in only 6/14 in MWC. The 5 persons exercising with all 3 modes had a strong HR-VO2 relationship in 5/5 for ERG, 2/5 in MWC and 1/5 in HC. A strong relationship for PE-VO2 was observed in a higher proportion of participants (versus HR-VO2) during MWC (9/14) and HC (2/4). Conclusion: Within the same individual, the HR-VO2 relationship varies across modes, despite exercising over similar ranges of steady-state VO2. HR appears less able to predict VO2 compared to PE. Based on these new findings, systematic investigation of the HR-VO2 relationship across modes of exercise in tetraplegia is warranted.