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.