Objectives Accurate, objective measurement is important for understanding adolescents' physical activity (PA) behaviour. When using accelerometry to objectively measure PA, a decision must be made regarding how frequently data is recorded (i.e., epoch length). The purpose of this study was to examine i) PA bout length, and ii) the effect of variations in accelerometer epoch length on PA estimates during physical education (PE) and leisure time in adolescent boys. Design Cross-sectional study. Methods Year 9 boys (N = 133; mean age ±SD = 14.36±0.48 years) wore accelerometers during two PE lessons, and for a period of seven consecutive days. Data were reintegrated from 1s into longer periods of 2, 5, 10, 30, and 60 seconds. ANOVAs were used to test for differences in PA estimates between epochs in leisure time and PE. Results The mean length of vigorous PA (VPA) bouts was 3.5±2.0 seconds for PE and 2.5±1.7 seconds for leisure time, and mean length of moderate PA (MPA) bouts was 2.3±0.5 seconds for PE and 2.9±0.5 seconds for leisure time. During PE, estimates of MVPA, MPA, and light PA (LPA) increased as epoch increased from 1 second to 60 seconds, while VPA and sedentary behaviour estimates decreased. During leisure time, estimates of all PA intensities decreased as epoch increased from 1 second to 60 seconds, with the exception of sedentary behaviour, which increased as epoch length increased. Conclusion The context in which PA occurs can influence PA bout length measurement and the effect of variations in epoch length on PA estimates. Researchers measuring PA with accelerometry should be conscious of the possible influence of context on PA estimates.
References
[1]
Andersen RE, Crespo CJ, Bartlett SJ, Cheskin LJ, Pratt M (1998) Relationship of physical activity and television watching with body weight and level of fatness among children: Results from the Third National Health and Nutrition Examination Survey. JAMA 279: 938–942. doi: 10.1001/jama.279.12.938
[2]
Janssen I, LeBlanc AG (2010) Systematic review of the health benefits of physical activity and fitness in school-aged children and youth. Int J Behav Nutr Phys Act 7: 40. doi: 10.1186/1479-5868-7-40
[3]
Strong WB, Malina RM, Blimkie CJR, Daniels SR, Dishman RK, et al. (2005) Evidence based physical activity for school-age youth. J Pediatr 146: 732–737. doi: 10.1016/j.jpeds.2005.01.055
[4]
Nader P, Bradley R, Houts R, McRitchie S, O'Brien M (2008) Moderate-to-vigorous physical activity from ages 9 to 15 years. JAMA 300: 295–305. doi: 10.1001/jama.300.3.295
[5]
Sallis JF (2000) Age-related decline in physical activity: A synthesis of human and animal studies. Med Sci Sports Exerc 32: 1598. doi: 10.1097/00005768-200009000-00012
[6]
Freedson PS, Miller K (2000) Objective monitoring of physical activity using motion sensors and heart rate. Res Q Exerc Sport 71: 21–29.
Edwardson CL, Gorely T (2010) Epoch length and its effect on physical activity intensity. Med Sci Sports Exerc 42: 928–934. doi: 10.1249/mss.0b013e3181c301f5
[9]
McClain JJ, Abraham TL, Brusseau TA, Tudor-Locke C (2008) Epoch length and accelerometer outputs in children: Comparison to direct observation. Med Sci Sports Exerc 40: 2080–2087. doi: 10.1249/mss.0b013e3181824d98
[10]
Bailey RC, Olson J, Pepper SL, Porszasz J, Barstow TJ, et al. (1995) The level and tempo of children's physical activities: An observational study. Med Sci Sports Exerc 27: 1033–1041. doi: 10.1249/00005768-199507000-00012
[11]
Baquet G, Stratton G, Van Praagh E, Berthoin S (2007) Improving physical activity assessment in prepubertal children with high-frequency accelerometry monitoring: A methodological issue. Prev Med 44: 143–147. doi: 10.1016/j.ypmed.2006.10.004
[12]
Blaes A, Baquet G, Van Praagh E, Berthoin S (2011) Physical activity patterns in French youth - from childhood to adolescence - monitored with high-frequency accelerometry. Am J Hum Biol 23: 353–358. doi: 10.1002/ajhb.21142
[13]
Vanhelst J, Béghin L, Duhamel A, Bergman P, Sj？str？m M, et al. (2012) Comparison of uniaxial and triaxial accelerometry in the assessment of physical activity among adolescents under free-living conditions: the HELENA study. BMC Med Res Methodol 12 26: 1–6. doi: 10.1186/1471-2288-12-26
[14]
Nilsson A, Ekeland U, Yngve A, Sjoestroem M (2002) Assessing physical activity among children with accelerometers using different time sampling intervals and placements. Pediatr Exerc Sci 14: 185–190.
[15]
Rowlands AV, Powell SM, Humphries R, Eston RG (2006) The effect of accelerometer epoch on physical activity output measures. J Exerc Sci Fit 4: 52–58.
[16]
Ward DS, Evenson KR, Vaughn A, Brown Rodgers A, Troiano RP (2005) Accelerometer use in physical activity: Best practices and research recommendations. Med Sci Sports Exerc 37: 582–588. doi: 10.1249/01.mss.0000185292.71933.91
[17]
Sirard J, Slater M (2009) Compliance with wearing physical activity accelerometers in high school students. J Phys Act Health 6: 148–155. doi: 10.1249/01.mss.0000322355.38394.38
Esliger DW, Copeland JL, Barnes JD, Tremblay MS (2005) Standardizing and optimizing the use of accelerometer data for free-living physical activity monitoring. J Phys Act Health 2: 366–383.
[20]
Freedson PS, Pober D, Janz KF (2005) Calibration of accelerometer output for children. Med Sci Sports Exerc 37: 523–530. doi: 10.1249/01.mss.0000185658.28284.ba
[21]
Freedson PS, Sirard J, Debold E, Pate R, Dowda M, et al. (1997) Calibration of the Computer Science and Applications, INC. (CSA) accelerometer. Med Sci Sports Exerc 29: 45. doi: 10.1097/00005768-199705001-00256
[22]
Trost SG, Loprinzi PD, Moore R, Pfeiffer KA (2011) Comparison of accelerometer cut points for predicting activity intensity in youth. Med Sci Sports Exerc 43: 1360–1368. doi: 10.1249/mss.0b013e318206476e
[23]
Troiano RP, Berrigan D, Dodd KW, Masse LC, Tilert T, et al. (2008) Physical activity in the United States measured by accelerometer. Med Sci Sports Exerc 40: 181–188. doi: 10.1249/mss.0b013e31815a51b3
[24]
Gabriel KP, McClain JJ, Schmid KK, Storti KL, High RR, et al. (2010) Issues in accelerometer methodology: The role of epoch length on estimates of physical activity and relationships with health outcomes in overweight, post-menopausal women. Int J Behav Nutr Phys Act 7: 53–62. doi: 10.1186/1479-5868-7-53
[25]
Tabachnick BG, Fidell LS (2007) Using multivariate statistics. New York, United States: Pearson Education Inc.
[26]
Cohen J (1988) Statistical power analysis for the behavioral sciences: Lawrence Erlbaum.
[27]
Berman N, Bailey R, Barstow TJ, Cooper DM (1998) Spectral and bout detection analysis of physical activity patterns in healthy, prepubertal boys and girls. Am J Hum Biol 10: 289–297. doi: 10.1002/(sici)1520-6300(1998)10:3<289::aid-ajhb4>3.0.co;2-e
[28]
Welk GJ, Corbin CB, Dale D (2000) Measurement issues in the assessment of physical activity in children. Res Q Exerc Sport 71: 59–72.
Dencker M, Svensson J, El-Naaman B, Bugge A, Andersen LB (2012) Importance of epoch length and registration time on accelerometer measurements in younger children. J Sports Med Phys Fitness 52: 115–121.
[31]
Vale S, Santos R, Silva P, Soares-Miranda L, Mota J (2009) Preschool children physical activity measurement: Importance of epoch length choice. Pediatr Exerc Sci 21: 413–420.
[32]
Gutin B (2008) Child obesity can be reduced with vigorous activity rather than restriction of energy intake. Obesity 16: 2193–2196. doi: 10.1038/oby.2008.348
[33]
Carson V, Rinaldi RL, Torrance B, Maximova K, Ball GDC, et al. (2014) Vigorous physical activity and longitudinal associations with cardiometabolic risk factors in youth. Int J Obes 38: 16–21. doi: 10.1038/ijo.2013.135
[34]
Holman RM, Carson V, Janssen I (2011) Does the Fractionalization of Daily Physical Activity (Sporadic vs. Bouts) Impact Cardiometabolic Risk Factors in Children and Youth? PLoS ONE 6: e25733. doi: 10.1371/journal.pone.0025733
[35]
Sayers A, Mattocks C, Deere K, Ness A, Riddoch C, et al. (2011) Habitual levels of vigorous, but not moderate or light, physical activity is positively related to cortical bone mass in adolescents. J Clin Endocrinol Metab 96: E793–E802. doi: 10.1210/jc.2010-2550
[36]
Matthews C, Hagstr？mer M, Pober D, Bowles H (2012) Best practices for using physical activity monitors in population-based research. Med Sci Sports Exerc 44: 68–76. doi: 10.1249/mss.0b013e3182399e5b
[37]
Trost SG (2007) State of the art reviews: Measurement of physical activity in children and adolescents. Am J Lifestyle Med 1: 299–314. doi: 10.1177/1559827607301686
