Background: Physical activity guidelines state that adults should engage in at least 150 min of moderate to vigorous physical activity (MVPA) per week to benefit health. A high proportion of adults in England fail to reach this target. Accurate knowledge of MVPA guidelines could influence the amount and quality of MVPA engaged in by adults. This study aimed to determine knowledge of the MVPA guideline within a large sample of working adults in England and identify individual and workplace-related predictors of knowledge. Methods: 10,992 adults completed an online survey which included questions on demographics, knowledge of the MVPA guideline and workplace predictors for physical activity. Multinomial logistic regression identified predictors of underestimating, overestimating or not knowing the MVPA guideline relative to accurately reporting the guideline for males and females separately. Results: Respondents were 37 % male, 95 % White, 63 % with a degree or higher, and had a mean age of 38.9 +/- 11 years. The MVPA guideline was accurately reported by 15 % of adults while 13.8 % overestimated, 8.9 % underestimated and 62.3 % failed to provide any estimate of the guideline. Low education predicted underestimation (females: OR = 0.36, 95 % CI 0.17, 0.80) and not knowing (males: OR = 0.37, 95 % CI 0.14, 0.96; females: OR = 0.36, 95 % CI 0.19, 0.69). Ethnicity was a significant predictor for females only (OR 3.55, 95 % CI 1.46, 8.63; OR 4.03, 95 % CI 1.58, 10.27; OR 3.73, 95 % CI 1.67, 8.33). Employer support for physical activity was a significant predictor of accurate knowledge of the MVPA guideline for both males (underestimation: OR = 0.63, 95 % CI 0.40, 1.00; 'don't know': OR = 0.71, 95 % CI 0.51, 1.00) and females (overestimation: OR = 0.72, 95 % CI 0.53, 0.97; underestimation: OR = 0.66, 95 % CI 0.47, 0.92; 'don't know': OR = 0.60, 95 % CI 0.47, 0.76). Conclusions: Knowledge of the MVPA guideline within working adults in England is low. Employers should play a role in using targeted strategies to increase knowledge as employer support-related factors may influence knowledge of the MVPA guideline. Employers who assert strategies to promote physical activity and encourage employees who have responsibility for promoting health to educate their colleagues may help improve the MVPA knowledge of their employees.
