The SKyRoCKeT Study: Surface-Knit and Reformulate CADENCE-Kids for Translation. - 7. Project Summary/Abstract Physical activity (PA) is associated with a number of short- and long-term health outcomes in children, adolescents, and young adults (collectively, young people). In particular, an inverse dose-response relationship exists between moderate-to-vigorous PA (MVPA) and cardio-metabolic risk factors. Accurately quantifying young people’s daily MVPA is essential for effective surveillance, research, clinical, and public health applications. Yet, technical expressions of intensity in terms of energy expenditure (i.e., oxygen consumption or metabolic cost expressed in metabolic equivalents or METs) and/or percent of age-predicted heart rate maximum may be uninterpretable to all but those trained in human physiology. A more practically accessible yet still objective metric is needed to track and influence young people’s healthful levels of PA. The SKyRoCKeT Study (Surface-Knit and Reformulate CADENCE-Kids for Translation) will build on the R21 CADENCE-Kids study and recruit a sex- and age-balanced sample of 360 young people 6-20 years of age to: 1) Innovatively surface-‘knit’ the age dimension through a continuous, unbiased-by-age, and physiologically-coherent age-cadence-log(MET) flexible surface approach without artificially-generated jumps between age ranges and with enhanced precision of cadence-intensity threshold estimates. This single surface will coherently transition between ages, borrow inter-age information, and be data-driven; 2) Reformulate CADENCE-Kids by providing granular, age-specific cadence-intensity thresholds, calculated with enhanced precision for MVPA. Data will be objectively collected using a similar treadmill protocol to the R21-funded pilot study, with incrementally faster paces. A full running bout will now also be included for everyone when possible. We will concurrently collect cadence with direct observation as well as with multiple contemporary wearable technologies. Collecting cardio-respiratory fitness and habitual PA data, we will develop additional, innovative algorithms to predict relative intensity defined by lab-based indicators of oxygen uptake (%VO2peak, %VO2R), heart rate (%HRR, %HRmax), and rating of perceived exertion to facilitate computation of individually calibrated thresholds applicable to the free-living or habitual PA living condition. We will also investigate additional differences in surfaces and cadence-intensity thresholds by sex and body mass index standard deviation scores. Height- and/or leg-length-specific (hyper)surfaces will be explored as more precise alternatives to the age dimension; and 3) Propel science forward innovatively through translation to outdoor over-ground walking. We hypothesize that treadmill-set cadence-intensity thresholds will reliably translate and allow eliciting predictable metabolic costs during outdoor over-ground walking emblematic of free-living ambulatory behaviors. The SKyRoCKeT Study is an innovative critical step to provide coherent, interpretable, objectively monitored step-based intensity metrics of widespread use to inform national PA guidelines, interventions, assessments, analyses, school-based health education curricula and programs, and public health messages for young people.