Is it helpful to occasionally go for a long walk, or are short bursts of movement spread throughout the day better?

Short bursts of movement spread throughout the day are clearly no less valuable than one long session. Research involving tens of thousands of non-exercising adults showed that people who accumulate roughly 4.5 minutes of brief, vigorous activity each day, such as climbing stairs briskly or carrying a heavy shopping bag, already had a 20% lower risk of cancer than people who did none of this at all. For cancers related to physical inactivity the risk reduction was as high as 31%. Nearly all of those activities lasted at most one minute at a time.

The longer such a block lasts, the greater the apparent health benefit. Blocks of 5 to 10 minutes of moderate-to-vigorous activity were linked, in another large cohort study project, to a 52% lower risk of death and a 41% lower risk of a serious cardiovascular event, compared with blocks shorter than one minute. Blocks of 1 to 3 minutes fell in between, with reductions of 34% and 29% respectively. There is therefore a clear 'more is more' pattern in duration, as long as the intensity is sufficient.

One long walk per week is therefore not the ideal strategy if you are largely sedentary for the rest of the day. Research shows that prolonged sitting, particularly blocks longer than 30 to 60 minutes, raises the risk of cardiovascular disease, diabetes and premature death. This applies even if you are otherwise active. The practical lesson: get up every half hour and, if you do not exercise regularly, work as many short but vigorous movement breaks into your day as possible.

For blocks shorter than ten minutes the evidence is somewhat less fully developed than for longer sessions, because randomised studies have only examined longer blocks. All major cohort studies are observational, meaning there is a strong association but no proof that the activity itself causes the lower risk. Nevertheless, the effects are consistent and large enough to take seriously.