The primary purpose of this study was to evaluate the variability of sedentary behavior (SB) throughout a 7-day measurement period and to compare SB between weekdays and weekend days. Second, this study aimed to determine the minimum number of days of SB measurement that is comparable to 7-days of measurement. Secondary to the primary purpose, this study aimed to determine the role demographic variables play in the variability of SB. METHODS: Accelerometry data was previously collected in the Clinical Exercise Physiology Program at Ball State University from 708 participants (260 males, aged 57±13 years, BMI = 30±6 kg/m2; 448 females, aged 52±12 years, BMI of 29±8 kg/m2) who wore an accelerometer at least 4 days. To determine if differences exist between individual days, SB data (<100 cpm) from 293 participants (99 males, 194 females) with 7-consecutive days of accelerometry data, were compared using a two-way repeated measures ANOVA. The larger 4-day cohort was used to compare SB on weekdays and weekend days using a univariate ANOVA. To determine the minimum number of SB measurement days compared to the typical 7-day period, a stepwise regression was performed with the 7-day sub-cohort. RESULTS: No differences in SB were found between individual days (p>0.05) when using the 7-day cohort. However, when using the 4-day cohort, weekdays were found to be more sedentary than weekend days (p<0.05). Using the 7-day cohort, 2 weekdays and 2 weekend days of SB measurement were found to be comparable to 7 days of measurement (R2 of 0.91). CONCLUSION: No differences in SB were found between individual days of the week, however more time, on average, was spent in weekdays (66%) compared to weekend days (64%). 4 days of SB measurement were found to be comparable to 7, meaning the typical 7-day measurement period may not be necessary. / School of Physical Education, Sport, and Exercise Science