They suggest that the null findings may be due to imprecisions related to physical activity assessment. These might mask a weak or modest association. They point out that some household activities, like washing clothes and scrubbing floors, may have been classified as more vigorous than they actually are. Given that over 58 percent of women in the study reported engaging in at least 30 minutes of vigorous activity per day, the authors suggest that the inclusion of these various household activities may have led to overestimated amounts of absolute vigorous activity. They also note, however, that "household activity may be of particular significance to women," and should be included as part of a physical activity assessment to gain a more accurate picture of total physical activity.
Still, the authors conclude, "our results do not support the hypothesis that physical activity confers significant protection against the overall development of colon cancer in women. Our findings point towards the need for conducting further research, particularly among women, that uses well-formulated, accurate measures of physical activity and distinguishes between different types of physical activity (i.e. recreational, occupational, and household activity) in relation to colon cancer risk."