Cadence:

Investigating the relationship between cadence and intensity across the adult lifespan

Specific Aims:

Accelerometer technology has advanced quickly and more sophisticated analytical approaches have been proffered. The primary accelerometer outputs, generically labeled “activity counts,” are actually device-specific scaled digits allocated by applying a proprietary filter to the electronic signal representing detected movement. This point is important to emphasize: the allocation of activity counts to the electronic signal, and thus its interpretation, is unique to each device and cannot be translated across devices. This commercially-driven aspect of accelerometry remains a lamentable source of frustration to those who yearn for standard measures.

The exciting trend for activity classification and pattern recognition using multiple regression equations based on data variability, Hidden Markov Models, and artificial neural networks has been challenging to translate outside the controlled laboratory setting.⁵ In the pursuit of increasingly complex and technical analysis, there is a potential to overlook reasonable outputs and analyses that may be more readily intuitive, public health-oriented, and therefore directly and immediately applicable to many clinical and real-world applications. We argue that 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. A common metric that could be collected and interpreted across objective instruments, including those used in the lab and in the real world, would be invaluable. The ability to confidently interpret common cut points across instruments would be ideal.

Cadence is well known as one of the spatial-temporal parameters of gait. Like activity counts/min, cadence (steps/min) is a time-stamped variable. We previously assembled controlled studies reporting cadence and associated metabolic costs of adults; the correlation between steps/minute and MET (metabolic equivalent; an indicator of absolute intensity) level is strong (r=0.92) despite the fact that these data were compiled from diverse studies conducted on tracks, treadmills, and hallways.⁶  Most of these studies were performed at relatively faster walking speeds, leaving unanswered questions about the strength of the relationship across a broader range of locomotor speeds. The innovation of using cadence is that it is a direct, minimally processed reflection of locomotor quality [and, as we have demonstrated in our pilot study, is reasonably translatable across multiple devices (details below). Testing 14 adult participants at a more expansive range of speeds than previously studied, we confirmed that although the relationship between cadence and METs was attenuated at slower rates of step accumulation, the overall correlation was still strong (r=0.86).] The five studies^7-11 that directly measured cadence and verified absolutely-defined moderate intensity activity in adults have agreed: despite inter-individual variation, 100 steps/minute represents a reasonable heuristic value associated with moderate intensity walking. This is a remarkably consistent finding given the well-known controversy about activity count cut points, both between, and within the same technologies.¹² Using a single illustrative example, ambulatory movement detected in a continuous walk may be > 1952 activity counts based on the ActiGraph scaling,¹³ > 1535 activity counts for the Actical,¹⁴ but > 100 steps/min for both devices (and for observation and for GaitRite-assessed cadence).¹⁵ Besides this single cut point (100 steps/min) indicative of moderate intensity walking, no other cadence cut points indicative of other MET-determined levels of intensity have been rigorously evaluated.

CADENCE-Adults is an R01 study that will calibrate cadence and intensity in 260 ambulatory adults, 10 men and 10 women for each 5-year age-group category between 21-85 years (21-25, 26-30, 31-35, etc.).  We are currently conducting a similar study in 6-20 year olds (CADENCE-Kids, 1R21HD07-01A1) to identify cadence cut points associated with intensity. An R21 study was necessary with children as less preliminary data were available to support using cadence as an indicator of intensity across the developmental age ranges. For adults, however, we believe the established literature and our own pilot adult study data confirm the feasibility of wearing multiple instruments simultaneously and establishing cut points across the lifespan.

The primary aim of CADENCE-Adults is to identify objectively observed (and videotaped) and manually counted cadence (steps/min) criterion cut points associated with markers of increasing intensity across age groupings. A secondary aim is to compare different 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 mock 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.

The information derived from this R01 study will be used to calibrate adults’ cadence and intensity data. No similar data exist at this time so the approach described in this application is critical to providing a minimally processed and translatable objectively monitored metric with established cut points across the lifespan.

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