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

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.

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 [P_ETCO₂]) 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.

While P_ETCO₂ (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), P_ETCO₂ (-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.

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.