Review and special article
Physical Activity and Physical Fitness: Standardizing Assessment with the PhenX Toolkit

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Abstract

The focus of the PhenX (Phenotypes and eXposures) Toolkit is to provide researchers whose expertise lies outside a particular area with key measures identified by experts for uniform use in large-scale genetic studies and other extensive epidemiologic efforts going forward. The current paper specifically addresses the PhenX Toolkit research domain of physical activity and physical fitness (PA/PF), which are often associated with health outcomes. A Working Group (WG) of content experts completed a 6-month consensus process in which they identified a set of 14 high-priority, low-burden, and scientifically supported measures. During this process, the WG considered self-reported and objective measures that included the latest technology (e.g., accelerometers, pedometers, and heart-rate monitors). They also sought the input of measurement experts and other members of the research community during their deliberations. A majority of the measures include protocols for children (or adolescents), adults, and older adults or are applicable to all ages.

Measures from the PA/PF domain and 20 other domains are publicly available and found at the PhenX Toolkit website, www.phenxtoolkit.org. The use of common measures and protocols across large studies enhances the capacity to combine or compare data across studies, benefiting both PA/PF experts and non-experts. Use of these common measures by the research community should increase statistical power and enhance the ability to answer scientific questions that previously might have gone unanswered.

Introduction

During the past 60 years, data have continued to accumulate, demonstrating numerous health benefits of a physically active lifestyle throughout the life span and the health advantages of being physically fit.1, 2, 3 Further, PA/PF increasingly are being recognized as important exposure variables when evaluating gene–environment interactions to determine risk for major chronic diseases. However, there is general agreement that most studies investigating the combined role of genetics and PA/PF on health and performance outcomes have been severely limited because of inadequate sample size.4, 5, 6 The ability of researchers to combine data across studies could increase the statistical power to associate phenotypic, environmental, and genetic data with disease outcomes, enhancing the opportunity to identify meaningful results that previously might have gone undetected. Also, standardized measurement methodologies facilitate replication of study findings and the comparison of data collected during studies of various population subsets.

A portfolio analysis of grants funded by the National Cancer Institute highlighted the need for guidance and resources for physical activity assessment. Grants funded between September 2004 and January 2009 that measured physical activity as an exposure, outcome, or covariate were reviewed for details about assessment method. The 87 grants identified were sorted by study design and use of physical activity measure (exposure, outcome, or covariate). These grants used 33 different self-report measures and at least six different accelerometer-based devices and pedometers.

In several cases, instruments that were not suited to the needs of the study design were used (Heather Bowles, PhD, National Cancer Institute, personal communication, 2010). For example, a surveillance instrument intended to characterize the activity level of a population might be used inappropriately to assess change in activity in a clinical trial with physical activity as a primary outcome. This diversity of methods presents a serious challenge for contrasting or combining study data in a uniform manner. This paper describes the development and content of the PA/PF domain within the Phenotypes and eXposures (PhenX) Toolkit. PhenX is a source for standardized measures across a variety of content areas and is described in general before focusing on the details of the PA/PF domain.

Section snippets

The PhenX Toolkit

The PhenX Toolkit was developed as a source of high-priority, low-burden, and evidence-based measures for use by a wide variety of researchers.7, 8 Although investigators are likely to be knowledgeable in selecting and implementing measures in their own content area, they quickly may become overwhelmed by the myriad of measures available in other fields. Further, once a measure is identified, the appropriate implementation of that measure also must be understood.

The PhenX Toolkit provides

Results

The WG identified 14 measures (Table 1) that can be classified as metrics of PA/PF, mediators or moderators of activity, and a precursor to fitness assessment. Under metrics of physical activity, measures selected were a short physical activity screener, a comprehensive reported measure, and a comprehensive objective measure, as well as an objective measure of walking and a reported measure of sitting. Metrics of fitness included performance-based measures of integrated fitness (endurance,

Discussion

In the process of selecting measures and protocols for the PA/PF domain in the PhenX Toolkit, a number of issues needed to be addressed. It quickly became apparent that for a number of well-established measurement tools used to assess PA/PF in published studies with a health orientation, data documenting validity, reliability, and sensitivity to change were limited or lacking. This was especially true when the goal was to evaluate the physical activity of individuals instead of groups.

Even for

Other Physical Activity Measurement Resources for Use by Investigators

In addition to the PhenX Toolkit, several other resources for assisting investigators with their measurement of physical activity recently have been made available. In July 2009 an NIH-sponsored workshop titled “Assessment of Physical Activity Using Wearable Monitors: Best Practices for Monitor Calibration and Use” was held, with the proceedings published as a supplement to Medicine and Science in Sports and Exercise.31 This report provides a comprehensive discussion of many of the measurement

Conclusion

Although the inclusion of PA/PF measures and protocols in the PhenX Toolkit will aid investigators in combining data across genomewide association studies, these measures have the potential for a broader application by researchers in multiple disciplines. Investigators planning genetic, clinical trial, or epidemiologic studies in disciplines ranging from cancer to diabetes to cardiovascular health, or even obesity, can benefit from the inclusion of PhenX PA/PF measures. As healthcare

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