Beyond Cut Points: Accelerometer Metrics that Capture the Physical Activity Profile

作者：Rowlands Alex V^*; Edwardson Charlotte L; Davies Melanie J; Khunti Kamlesh; Harrington Deirdre M; Yates Tom

来源：Medicine and Science in Sports and Exercise, 2018, 50(6): 1323-1332.

DOI：10.1249/MSS.0000000000001561

• INTENSITY GRADIENT
• AVERAGE ACCELERATION
• GENEACTIV
• BODY FATNESS
• PHYSICAL FUNCTION

Purpose: Commonly used physical activity metrics tell us little about the intensity distribution across the activity profile. The purpose of this paper is to introduce a metric, the intensity gradient, which can be used in combination with average acceleration (overall activity level) to fully describe the activity profile. Methods: A total of 1669 adolescent girls (sample 1) and 295 adults with type 2 diabetes (sample 2) wore a GENEActiv accelerometer on their nondominant wrist for up to 7 d. Body mass index and percent body fat were assessed in both samples and physical function (grip strength, Short Physical Performance Battery, and sit-to-stand repetitions) in sample 2. Physical activity metrics were as follows: average acceleration (Accel(AV)); the intensity gradient (Intensity(GRAD) from the log-log regression line: 25-mg intensity bins [x]/time accumulated in each bin [y]); total moderate-to-vigorous physical activity (MVPA); and bouted MVPA (sample 2 only). Results: Correlations between Accel(AV) and Intensity(GRAD) (r = 0.39-0.51) were similar to correlations between Accel(AV) and bouted MVPA (r = 0.48) and substantially lower than between Accel(AV) and total MVPA (r >= 0.93). Intensity(GRAD) was negatively associated with body fatness in sample 1 (P < 0.05) and positively associated with physical function in sample 2 (P < 0.05); associations were independent of Accel(AV) and potential covariates. By contrast, MVPA was not independently associated with body fatness or physical function. Conclusion: Accel(AV) and Intensity(GRAD) provide a complementary description of a person's activity profile, each explaining unique variance, and independently associated with body fatness and/or physical function. Both metrics are appropriate for reporting as standardized measures and suitable for comparison across studies using raw acceleration accelerometers. Concurrent use will facilitate investigation of the relative importance of intensity and volume of activity for a given outcome.

• 出版日期2018-6