CADENCE-Adults is an R01 study that will calibrate cadence (steps/min) and intensity in 260 ambulatory adults, 10 men and 10 women for each 5-year age-group category between 21-85 years, effectively covering the adult lifespan. Cadence is one of the temporal-spatial parameters of gait. Cadence multiplied by stride length equals speed. Capture and expression of objectively monitored physical activity in terms of cadence represents an overlooked opportunity to represent free-living patterns of ambulatory intensity. There is merit in being able to translate technological and analytical advances into more accessible terms, especially if public health goals are to be realized. Cadence represents a minimally processed and translatable metric that could be collected and interpreted across objective instruments, including those used in the lab, in the clinic, and in the real world. The primary aim of CADENCE-Adults is to identify objectively observed (video-taped) and manually counted cadence (steps/min) criterion cut points associated with markers of increasing intensity across age groupings. A secondary aim is to compare multiple instruments' abilities to accurately detect criterion values for cadence at different speeds and thus better inform our confidence in comparing this metric across instruments. To achieve these aims, cadence and oxygen uptake data will be collected during a treadmill assessment of incrementally faster paces and also using portable metabolic testing of common free- living activities to test the primary hypothesis: Activity intensity (oxygen uptake) will increase in a linear or nonlinear (curvilinear) fashion as cadence increases such that we will be able to develop statistical models for predicting markers (cut points) of intensity from cadence. We are uniquely positioned at the Pennington Biomedical Research Center to successfully conduct CADENCE-Adults as designed in a 5-year time period. We have conducted pilot testing demonstrating the feasibility of this project, established recruiting methods, and are fully experienced in exercise testing, accelerometry, and management of large complex data sets. We expect that cadence cut points established in CADENCE-Adults will be used both to assess ambulatory intensity, but also to inform program design focused on increasing not only the volume of physical activity (e.g., steps/day) but also its intensity (e.g., cadence) in user-friendly metrics. No similar data exist a this time so the approach described in this application is both innovative and critical to providin a minimally processed and translatable objectively monitored metric with established cut points across the lifespan.