TY - JOUR
T1 - Beyond cut points
T2 - accelerometer metrics that capture the physical activity profile
AU - Rowlands, Alex V.
AU - Edwardson, Charlotte L.
AU - Davies, Melanie J.
AU - Khunti, Kamlesh
AU - Harrington, Deirdre M.
AU - Yates, Tom
PY - 2018/6/30
Y1 - 2018/6/30
N2 - 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 (AccelAV); the intensity gradient (IntensityGRAD 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 AccelAV and IntensityGRAD (r = 0.39-0.51) were similar to correlations between AccelAV and bouted MVPA (r = 0.48) and substantially lower than between AccelAV and total MVPA (r ≥ 0.93). IntensityGRAD 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 AccelAV and potential covariates. By contrast, MVPA was not independently associated with body fatness or physical function. Conclusion AccelAV and IntensityGRAD 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.
AB - 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 (AccelAV); the intensity gradient (IntensityGRAD 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 AccelAV and IntensityGRAD (r = 0.39-0.51) were similar to correlations between AccelAV and bouted MVPA (r = 0.48) and substantially lower than between AccelAV and total MVPA (r ≥ 0.93). IntensityGRAD 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 AccelAV and potential covariates. By contrast, MVPA was not independently associated with body fatness or physical function. Conclusion AccelAV and IntensityGRAD 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.
KW - average acceleration
KW - GENEActiv
KW - adiposity
KW - exercise test
KW - physical activity
U2 - 10.1249/MSS.0000000000001561
DO - 10.1249/MSS.0000000000001561
M3 - Article
SN - 0195-9131
VL - 50
SP - 1323
EP - 1332
JO - Medicine and Science in Sports and Exercise
JF - Medicine and Science in Sports and Exercise
IS - 6
ER -