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Weighing up the evidence: Exercise. How much is enough?

Does performing physical activity just once or twice a week still deliver health benefits?

How often is enough? After the excesses of Christmas, many New Year’s resolutions are made in an attempt to atone for these extravagances. According to a YouGov survey in 2022, 49 per cent of adults made a New Year’s resolution to do more exercise or improve their fitness.

There is little doubt that being physically active is associated with a range of health benefits. The NHS recommends undertaking at least 150 minutes of moderate intensity activity a week or 75 minutes of vigorous intensity activity, which is spread evenly over four to five days a week, or every day.

Adhering to this guidance has clear health benefits as demonstrated in a 2020 study which included 479,856 adults who were followed for a median of nearly nine years. The results showed that undertaking the recommended amounts of physical activity reduced the risk of all-cause mortality by 40 per cent, and the risks of cardiovascular disease and cancer by 50 and 40 per cent respectively.

In the UK, levels of physical activity are on the increase with 63 per cent of adults reporting that they achieved the recommended levels of exercise. Yet despite the clear benefits to exercising, why is this figure not higher?

Time constraints

One of the greatest barriers that is consistently reported in surveys is having sufficient time to exercise – and it seems that this also applies to the very healthcare professionals whose job it is to promote staying active. Time constraints, together with high levels of burnout and stress, are perceived as barriers to exercise by both doctors and nurses, for example. No doubt the same is true for pharmacists.

A further limiting factor for healthcare professionals is the long hours worked, which can make it impossible to spread exercise across the week. So, with a widespread belief that there is insufficient time to attain the recommended levels of exercise, could the health benefits be achieved by working out for just one to two days a week? 

Compressing exercise time

There is some evidence to show that squeezing exercise into just two days a week is beneficial.  For example, a recent meta-analysis of four studies with 426,428 participants, found that the risk of cardiovascular disease was 27 per cent lower among people exercising for just two days per week compared to those who were inactive. Similarly, there was a 17 per cent lower risk of all-cause mortality – but the study relied on what people self-reported and such information is prone to bias.

This limitation was overcome in another recent study that used accelerometer-derived data worn on the wrist for seven days. A total of 89,573 people were categorised into three groups:

  • Active ‘weekend warriors’: those for which more than half of their total exercise was undertaken over one to two days
  • The regularly active: those exercising throughout the week
  • An inactive group: those who undertook less than 150 minutes of exercise per week.

One of the most interesting observations from the study was how nearly half (42 per cent) of all participants were actually weekend warriors, getting their exercise over one to two days. However, when researchers compared the cardiovascular outcomes for the three groups, it was clear that the health benefits for both weekend warriors and those deemed to be regularly active, were broadly similar.

For example, the risk of a myocardial infarction was 19 per cent lower for those completing 150 minutes of exercise spread over the week and 22 per cent lower for the weekend warriors. Similar reductions in risk for the two active groups were seen for heart failure and stroke.

The accelerometer-derived study demonstrates that exercising for just one or two days each week, provided that it is up to the recommended level of 150 minutes, reduces the risk of a broad range of adverse cardiovascular outcomes by a similar level compared to exercising most days of the week.

So, the next time a patient tells you they don’t have enough time to exercise, suggest that they only really need to work out on one to two consecutive days every week to achieve worthwhile health benefits.

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