Table 1.
Summary of key methodological issues from a review of 183 youth accelerometer studies from 2005–2010.
| All youth studies ( n=183) % (n) | Preschool studies (n=21) % (n) | Children studies (n=94) % (n) | Adolescent studies (n=68) % (n) | |
|---|---|---|---|---|
| Year of publication | ||||
| 2005–2006 | 20.8 (38) | 30.0 (6) | 14.9 (14) | 26.5 (18) |
| 2007–2008 | 32.8 (60) | 30.0 (6) | 35.1 (33) | 30.9 (21) |
| 2009–2010 | 46.4 (85) | 40.0 (9) | 50.0 (47) | 42.6 (29) |
| Actigraph model | ||||
| 7164 | 67.8 (124) | 71.4 (15) | 66.0 (62) | 69.1 (47) |
| GT1M | 17.5 (32) | 9.5 (2) | 23.4 (22) | 11.8 (8) |
| Model not specified (e.g., ‘Actigraph’) | 14.8 (27) | 19.0 (4) | 10.6 (10) | 19.1 (13) |
| Epoch (seconds) | ||||
| 2 | 2.2 (4) | 0.0 (0) | 4.3 (4) | 0.0 (0) |
| 5 | 4.9 (9) | 9.5 (2) | 6.4 (6) | 1.5 (1) |
| 10 | 5.5 (10) | 0.0 (0) | 9.6 (9) | 1.5 (1) |
| 15 | 7.7 (14) | 42.9 (9) | 2.1 (2) | 4.4 (3) |
| 30 | 7.7 (14) | 4.8 (1) | 4.3 (4) | 13.2 (9) |
| 60 | 62.3 (114) | 42.9 (9) | 66.0 (62) | 63.2 (43) |
| Missing | 9.8 (18) | 0.0 (0) | 7.4 (7) | 16.2 (11) |
| Non-wear time within a day (consecutive minutes of ‘0’ counts)a | (n=181) | (n=92) | ||
| 10 | 17.1 (31) | 9.5 (2) | 17.4 (16) | 19.1 (13) |
| 15 | 1.7 (3) | 0.0 (0) | 3.3 (3) | 0.0 (0) |
| 20 | 22.1 (40) | 9.5 (2) | 20.7 (19) | 27.9 (19) |
| 30 | 5.0 (9) | 0.0 (0) | 3.3 (3) | 8.8 (6) |
| 60 | 5.0 (9) | 14.3 (3) | 6.5 (6) | 0.0 (0) |
| 180 | 0.6 (1) | 0.0 (0) | 0.0 (0) | 1.5 (1) |
| Missing | 48.6 (88) | 66.7 (14) | 48.9 (45) | 42.6 (29) |
| Definition of a valid day (number of valid wear hours) | ||||
| <6 | 2.7 (5) | 9.5 (2) | 3.2 (3) | 0.0 (0) |
| 6 | 3.8 (7) | 14.3 (3) | 4.3 (4) | 0.0 (0) |
| 6.7 | 0.5 (1) | 4.8 (1) | 0.0 (0) | 0.0 (0) |
| 8 | 11.5 (21) | 9.5 (2) | 10.6 (10) | 13.2 (9) |
| 8.1 – 9.9 | 4.9 (9) | 4.8 (1) | 8.5 (8) | 0.0 (0) |
| 10 | 29.0 (53) | 14.3 (3) | 21.3 (20) | 44.1 (30) |
| 10.1 – 11.9 | 0.5 (1) | 0.0 (0) | 1.1 (1) | 0.0 (0) |
| ≥ 12 | 3.3 (6) | 0.0 (0) | (2) | 5.9 (4) |
| 10 on weekdays, 8 on weekend days | 2.2 (4) | 0.0 (0) | 4.3 (4) | 0.0 (0) |
| 12 on weekdays, 10 on weekend days | 1.1 (2) | 0.0 (0) | 2.1 (2) | 0.0 (0) |
| 10 on weekdays, 60% mean weekend WT | 0.5 (1) | 0.0 (0) | 1.1 (1) | 0.0 0) |
| Ratio or % (e.g., 80% of average WT, 70/80 ruleb) | 5.5 (10) | 4.8 (1) | 6.4 (6) | 4.4 (3) |
| Counts criteria (e.g., <10,000 and >20,000,000= invalid day) | 3.3 (6) | 0.0 (0) | 5.3 (5) | 1.5 (1) |
| Accelerometer worn during predefined moments and valid hours | 2.7 (5) | 9.5 (2) | 3.2 (3) | 0.0(0) |
| not used (e.g., school hours only) | ||||
| Unclear or other | 2.7 (5) | 0.0 (0) | 3.2 (3) | 2.9 (2) |
| Varied by purpose of analysesc | 1.1 (2) | 4.8 (1) | 0.0 (0) | 1.5 (1) |
| Missing | 24.6 (45) | 23.8 (5) | 23.4 (22) | 26.5 (18) |
| Minimum number of wear days to be included in analyses | ||||
| 1 | 1.1 (2) | 0.0 (0) | 2.1 (2) | 0.0 (0) |
| 2 | 6.6 (12) | 4.8 (1) | 9.6 (9) | 2.9 (2) |
| 3 | 28.4 (52) | 19.0 (4) | 29.8 (28) | 29.4 (20) |
| 4 | 26.8 (49) | 23.8 (5) | 26.6 (25) | 27.9 (19) |
| 5 | 7.1 (13) | 0.0 (0) | 5.3 (5) | 11.8 (8) |
| 6 | 1.1 (2) | 4.8 (1) | 1.1 (1) | 0.0 (0) |
| 7 | 4.4 (8) | 9.5 (2) | 4.3 (4) | 2.9 (2) |
| 10 or more | 1.1 (2) | 4.8 (1) | 1.1 (1) | 0.0 (0) |
| Varied by purpose of analysesc | 5.5 (10) | 9.5 (2) | 3.2 (3) | 7.4 (5) |
| Missing | 18.0 (33) | 23.8 (5) | 17.0 (16) | 17.6 (12) |
| Number of weekend days to be included in analyses | ||||
| 0 | 57.9 (106) | 61.9 (13) | 51.1 (48) | 66.2 (45) |
| 1 | 23.0 (42) | 14.3 (3) | 30.9 (29) | 14.7 (10) |
| 2 | 2.7 (5) | 4.8 (1) | 2.1 (2) | 2.9 (2) |
| Varied by purpose of analysesc | 0.5 (1) | 0.0 (0) | 1.1 (1) | 0.0 (0) |
| Missing | 15.8 (29) | 19.0 (4) | 14.9 (14) | 16.2 (11) |
| Cut point for MVPA (counts/min)d | (n=178) | (n=21) | (n=92) | (n=65) |
| 400 (Krishnaveni)49 | 0.6 (1) | 0.0 (0) | 1.1 (1) | 0.0 (0) |
| 614–2274 (Freedson youth 3METs, 6–18 yearse)36 | 29.2 (52) | 9.5(2) | 29.3 (27) | 35.4 (23) |
| 1160 (Treuth, 3METs)33 | 1.7 (3) | 0.0(0) | 2.2 (2) | 1.5 (1) |
| 1400–3500 (Freedson youth, 4METs, 6–18 yearse)36 | 2.8 (5) | 0.0 (0) | 3.3 (3) | 3.1 (2) |
| 1680 (Pate)46 | 2.2 (4) | 19.0(4) | 0.0 (0) | 0.0 (0) |
| 1952 (Freedson adult, 3 METs)48 | 5.6 (10) | 4.8 (1) | 4.3 (4) | 7.7 (5) |
| 2000 (European Youth Heart Study)44–45 | 9.6 (17) | 0.0 (0) | 10.9 (10) | 10.8 (7) |
| 2172 (Welk)35 | 1.1 (2) | 0.0 (0) | 2.2 (2) | 0.0 (0) |
| 2460–3564 (Sirard, 3–5 years)39 | 4.5 (8) | 38.1 (8) | 0.0 (0) | 0.0 (0) |
| 2500 (Metcalf)50 | 1.1 (2) | 0.0 (0) | 2.2 (2) | 0.0 (0) |
| 3000 (Treuth, 4.6METs)38 | 6.7 (12) | 0.0 (0) | 7.6 (7) | 7.7 (5) |
| 3200 (Puyau)42 | 12.9 (23) | 19.0(4) | 13.0 (12) | 10.8 (7) |
| 3581/3600 (Mattocks, 4METs)37 | 1.7 (3) | 0.0 (0) | 2.2 (2) | 1.5 (1) |
| Energy expenditure equation (Trost)40 | 2.8 (5) | 0.0 (0) | 2.2 (2) | 4.6 (3) |
| More than 1, used own cut point | 7.3 (13) | 4.8 (1) | 7.6 (7) | 7.7 (5) |
| Used counts only (no cut points) | 6.2 (11) | 4.8 (1) | 8.7 (8) | 3.1 (2) |
| Missing | 3.9 (7) | 0.0 (0) | 3.3 (3) | 6.2 (4) |
| Cut point for sedentary time (counts/min)f | (n=90) | (n=20) | (n=38) | (n=32) |
| 9 (Krishnaveni)49 | 1.1 (1) | 0.0 (0) | 2.6 (1) | 0.0 (0) |
| 100 (Treuth, Evenson)38,41 | 28.9 (26) | 5.0 (1) | 26.3 (10) | 46.9 (15) |
| 151 (Pate)46 | 3.3 (3) | 15.0 (3) | 0.0 (0) | 0.0 (0) |
| 199 (Mattocks)37 | 4.4 (4) | 0.0 (0) | 5.3 (2) | 6.3 (2) |
| 299 (Rowlands)51 | 3.3 (3) | 0.0 (0) | 7.9 (3) | 0.0 (0) |
| 499 (European Youth Heart Study)44–45 | 13.3 (12) | 0.0 (0) | 21.1 (8) | 12.5 (4) |
| 799 (Puyau)42 | 17.8 (16) | 0.0 (0) | 21.1 (8) | 25.0 (8) |
| 999 (Metcalf)50 | 2.2 (2) | 0.0 (0) | 5.3 (2) | 0.0 (0) |
| 1099 (Reilly)47 | 8.9 (8) | 30.0 (6) | 5.3 (2) | 0.0 (0) |
| 1204–1259 (Sirard, 3–5 years)39 | 7.8 (7) | 35.0 (7) | 0.0 (0) | 0.0 (0) |
| Freedson ( <1 – 1.9 METs)36 | 3.3 (3) | 5.0 (1) | 2.6 (1) | 3.1 (1) |
| More than 1, used own cut point | 2.2 (2) | 5.0 (1) | 0.0 (0) | 3.1 (1) |
| Missing | 3.3 (3) | 5.0 (1) | 2.6 (1) | 3.1 (1) |
WT = wearing time
MET = Metabolic Equivalent Task
a
Only studies where accelerometer was worn for a whole day were included.
b
Using the 70/80 rule, a valid day can be defined as the period during which at least 70% of the study population has recorded accelerometer data, and 80% of that observed period constitutes a minimal day for inclusion in data analysis.
c
In instances where the cohort and stage of study were the same but methods varied, these were noted as ‘method varying by analysis or purpose’
d
Only studies reporting results on moderate or MVPA were included in this summary. Studies only reporting on sedentary or vigorous were not included. Values represent lower threshold.
e
Includes Dowda,52 Trost,25 and Freedson36 references, and reference without the MET value specifically stated.
f
Only studies reporting results on sedentary behaviors were included in this summary. Studies using counts only were not included. Values represent upper threshold with lower threshold being “0”.