Step cadence to guide physical activity intensity in coronary heart disease

Regular physical activity at a moderate-to-vigorous intensity is associated with a lower risk of recurrent cardiovascular events and mortality in individuals with coronary heart disease (CHD). Walking is a common form of physical activity; however, there is no evidence-based recommendation for the optimal step cadence (steps per minute) to achieve these intensity levels among individuals with coronary heart disease. Thus, this study aimed to establish the agreement between manually counted step cadence and step cadence assessed by waist- and wrist-worn accelerometers during treadmill walking among individuals with CHD. Next, the study aimed to establish the association between manually counted and accelerometer-assessed step cadence with cardiorespiratory intensity, followed by the development and validation of cadence thresholds for moderate- and vigorous-intensity levels.

Participants (n = 87) performed a graded treadmill test. Step cadence was counted manually and by a waist- and wrist-worn accelerometer (Actigraph GT3x). Step cadence and oxygen consumption were measured during the final minute of walking at four speeds (3-6 km·h^{- 1}). Agreement between manual and accelerometer cadence was established using Bland-Altman analyses. Step cadence thresholds for relative (%VO₂ peak) and absolute (METs) intensity were derived using generalized estimating equations in a training cohort (70%) and validated in a validation cohort (30%).

Accelerometers underestimated the aggregated cadence compared with manual assessments, with a mean difference of -16 and -31 steps/min for waist- and wrist-worn accelerometers, respectively, with a higher level of agreement at higher speeds. Manually assessed cadence thresholds for moderate intensity were 99 (relative) and 92 (absolute) steps/min compared with 61 and 45 steps/min from waist-worn accelerometers. For vigorous intensity, manual and accelerometer thresholds were similar: 116 vs. 112 (relative) and 126 vs. 135 (absolute) steps/min. Both methods effectively identified valid thresholds for moderate and vigorous cardiorespiratory intensity.

Step cadence is a valid indicator of intensity in CHD populations, with manual and accelerometer methods showing comparable accuracy, despite accelerometer underestimation at lower speeds.

Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12623000605695 (02062023).