People should be set more realistic exercise goals because small amounts of activity are significantly better than none for improving health , experts have said.
Two articles published in the British Medical Journal (BMJ) suggested that the weekly target of 150 minutes of "moderate intensity activity" currently recommended for adults is beyond the reach of some, especially older people.
Rather, people and public health bodies should focus on the benefits of small increases in daily physical activity.
More than a third (35.6%) of adults worldwide are not sufficiently active, despite proof that too much sitting increases the risk of chronic diseases.
Those who do not get enough exercise are particularly susceptible to diabetes, heart disease and some types of cancer.
The proportion of time spent being inactive has been shown to rise from 55% (7.7 hours) at 20 to 29 years, to 67% (9.6 hours) for those aged 70 to 79.
Philipe de Souto Barreto at the University Hospital of Toulouse argued that benefits can be achieved by people doing less than the recommended amount of physical activity.
Less than one hour of moderate physical activity a week led to a reduced risk of death from all causes of 15%, according to one study of over 250,000 adults aged 50 to 71 in the US.
Those getting 20 minutes or more of vigorous physical activity less than once a week saw a reduction of 23%.
A review of another six studies found that people walking for 1 to 74 minutes a week had a 19% decrease in the risk of all-cause mortality compared to those doing nothing.
Professor Barreto said that policies to promote physical activity should focus on those who are "fully sedentary" and the main goal should be "to make small incremental increases in physical activities in their daily life rather than reaching current recommendations".
Older adults in particular find it difficult to meet moderate and vigorous exercise levels, according to a second article by Professor Phillip Sparling and colleagues at the Georgia Institute of Technology.
They wrote that focusing on the 150 minute recommendation "may mean that the benefits of lesser amounts of exercise are overlooked" and called for more realistic increases in light activities.
While the 150 minute a week standard should not be abandoned, a broader approach may help older sedentary patients towards the recommended levels of activity, the experts argued.
Responding to the studies, Professor Kevin Fenton, director of health and well-being at Public Health England, said: "Everyone needs to be active every day - bouts of 10 or more minutes of physical activity have proven health benefits, but getting 150 minutes or more of moderate activity every week is the amount we need to positively impact on a wide range of health conditions.
"This includes reducing the risk of heart disease and type 2 diabetes."