Only one in 20 British adults are meeting the correct type of recommended exercise guidelines, warns new research.
Women, older people and those living in deprived areas are most likely to be physically inactive, according to the shock findings based on a study of more than 250,000 people in England.
Whilst a lot of people do aerobic exercise such as running or cycling, far fewer do the equally important strengthening exercises that include weights.
"Under the most stringent definition of strengthening activity, we found around one in 20 adults met current guidelines, a stark contrast to the estimate that two in three adults are physically active based solely on aerobic activity," explained Dr Gavin Sandercock, of the University of Essex.
"Just 7.3% of men and 4.1% of women achieved the recommendations for strengthening activity."
These may include lifting weights, hill walking, push ups and and heavy gardening, for instance, rather than cycling, swimming or running.
"It can be hard for people with busy lives to get into the gym to do traditional weight training where it is often more convenient to go out for a quick bike rid or run," says personal trainer Daniel Harrison of Unique Personal Training.
"But in order to maintain our health and fitness it is important to combine strength exercises as well as getting out heart rates up.
"There are lots of everyday activities are actually weight-bearing and can be incorporated into our daily lives. Spring cleaning your house and moving the furniture can be both a cardio and weights workout, or carrying your shopping back from the supermarket instead of driving.
"If you have young children, then carrying them around or pushing their buggies in the park is a great form of strength and cardio exercise."
Dr Sandercock's study found that women and older adults aged 50 to 65 were less likely to meet guidelines for aerobic, strengthening and combined aerobic plus strengthening activity.
"The prevalence of meeting activity guidelines was lower in adults from more deprived areas," he said.
"Adults with lower academic qualifications were less likely to meet activity guidelines than those educated to degree level or higher."
The 2011 UK physical activity guidelines were the first to recommend at least twice-weekly bouts of strengthening activity as part of at least 150 minutes of moderate-to-vigorous physical aerobic activity per week.
They were based on high-quality evidence for the additional health benefits, explained Dr Sandercock.
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His team analysed data from the Active Lives Survey which provides detailed information on how over 16s engage with sport and physical activity.
The findings backed existing estimates from The Scottish Health Survey and Health Survey for England.
He said: "We found that, regardless of the definition used, fewer adults met the current strengthening activity recommendations compared with the number meeting aerobic activity guidelines.
"While more than two thirds (67%) of adults reported the equivalent of at least 150 min/week, fewer than a quarter (23%) of the sample actually met the current UK physical activity guidelines specifying twice-weekly muscle-strengthening activity."
When including only activities that met the description provided in current guidelines, just 5% of adults met the recommendations.
Dr Sandercock explained: "We included strengthening activities only if performed in bouts of ten minutes or more. Stipulating a minimum bout duration reduces estimates of how many adults meet aerobic activity guidelines."
He added: "Compared with aerobic activity, fewer adults engage in strengthening activity regardless of how it is defined.
"When strengthening activity is included, the proportion of English adults meeting current physical activity guidelines could be as high as one in three but possibly as low as just one in 20.
"A harmonised definition of strengthening activity, that is aligned with physical activity guidelines, is required to provide realistic and comparable prevalence estimates."
The study was published in the journal PLOS One. Additional reporting by SWNS.