Physiological Responses to Sit-to-Stand and Six-Minute Walk Tests in Heart Failure: A Randomised Trial

Background Short-duration sit-to-stand tests are utilised in rehabilitation settings to alleviate logistical challenges associated with the six-minute walk test (6MWT). We assessed the utility of the 30-second sit-to-stand (30-STST) and 60-second sit-to-stand (60-STST) tests as surrogate measures of the 6MWT. Method On separate days, 16 male participants (71 [7] years) with stable heart failure with reduced ejection fraction (36.9 [4.9] %) completed two 6MWT and the 30-STST and 60-STST. Pulmonary gas exchange (oxygen consumption, carbon dioxide production [V˙CO₂], ventilation [V˙E], respiratory exchange ratio, ventilatory equivalent for CO₂ [V˙E/V˙CO₂] and partial pressure of end-tidal CO₂ [PETCO₂]) was measured using a portable metabolic system. Non-invasive haemodynamics (cardiac output, stroke volume, arteriovenous oxygen difference) were measured using impedance cardiography. Mean arterial pressure, heart rate, oxygen saturation and dyspnoea (0–10 scale, arbitrary units) were also monitored. Mixed-effects models (Bonferroni corrected) accounting for time (pre-exercise rest, end-exercise) and test (6MWT, 30-STST, and 60-STST) were used to assess the relation between results observed during each testing modality. Results While PETCO₂ (mean difference [95% confidence interval], −4.9 [−8.9 to −0.8] mmHg), and dyspnoea (1 [0-2] arbitrary units) differed between the 6MWT and 60-STST, no other differences were observed between these tests. In contrast, oxygen consumption (−0.5 [−0.6 to −0.3] L.min⁻¹), V˙CO₂ (−0.5 [−0.7 to −0.4] L.min⁻¹), V˙E (−18.3 [−26.0 to −10.0] L.min⁻¹), PETCO₂ (−5.1 [−9.6 to −0.7] mmHg), cardiac output (−2.4 [−4.9 to −0.3] L.min⁻¹), heart rate (−20 [−33 to −7] beats/min) differed between the 6MWT and the 30-STST, however, no other differences were observed between the 6MWT and the 30-STST. Conclusions Cardiopulmonary, non-invasive haemodynamic and dyspnoea responses differed between the 30-STST and the 6MWT. However, the lack of test-specific differences between the 6MWT and the 60-STST highlights the strong physiological stimulus elicited by this short-duration test modality. The 60-STST has promising utility as a functional measure of heart and lung capacity within cardiac rehabilitation programs.