Health benefits of regular muscle strengthening activities highlighted in BJSM systematic review

Team focused on 16 previous studies

The findings are independent of aerobic exercise. But the analysis points to a J-shaped curve for most outcomes, with no conclusive evidence that more than an hour a week of muscle strengthening activity reduces the risk any further.

Physical activity guidelines recommend regular muscle strengthening activities for adults, mainly because of the benefits to skeletal muscle health. Examples include lifting weights, working with resistance bands, doing push-ups, sit-ups or squats, and heavy gardening (such as digging and shovelling). 

Previous research indicated that muscle strengthening activity is associated with a lower risk of death, but the optimal ‘dose’ was not known. The researchers examined databases for prospective observational studies that included adults without major health issues who had been monitored for at least two years.

The final analysis included 16 studies out of an initial cache of 29. The earliest study was published in 2012, and most studies were carried out in the USA, with the rest from the UK, Australia and Japan. The maximum monitoring period lasted 25 years.

The number of participants in the studies ranged from nearly 4,000 to nearly 480,000, and their ages ranged from 18 to 97. Twelve studies included both men and women; two only included men, while three only included women. All the studies considered aerobic or other types of physical activity as well as muscle strengthening activities.

The combination of muscle strengthening and aerobic activities may provide a greater benefit for reducing all-cause, [cardiovascular disease], and total cancer mortality [but] ... further studies are needed [Haruki Momma et al.]

The pooled data analysis showed that muscle strengthening activities were associated with a 10 to 17 per cent lower risk of death from any cause, as well as death from heart disease and stroke, cancer, diabetes, and lung cancer. No association was found between muscle strengthening and a reduced risk of specific types of cancer, including those of the bowel, kidney, bladder or pancreas.

Benefits of combining muscle strengthening and aerobic activities 

A J-shaped curve emerged, with a maximum risk reduction of between 10 to 20 per cent at approximately 30 to 60 minutes per week of muscle strengthening activities for death from any cause, cardiovascular disease, and all cancer. An L-shaped association was observed for diabetes, with a large risk reduction up to 60 minutes per week of muscle strengthening activities, after which any benefits gradually tapered off. 

Joint analysis of muscle strengthening and aerobic activities showed that the reduction in risk of death from any cause, cardiovascular disease, and cancer was even greater when these two types of activities were combined: 40 per cent, 46 per cent, and 28 per cent lower, respectively. 

Dr Momma’s team acknowledge that their study had limitations – the main one being that data from only a few studies were pooled for each of the outcomes studied. The studies they included also relied on subjective assessment of muscle strengthening activities.

The team notes that most of the studies were carried out in the US, and that the results might not be more widely applicable. The studies were all observational rather than clinical trials. Given the J-shaped associations, the potential of a higher volume of muscle strengthening activities on the reduction in risk of death is unclear, they continue. 

Conclusion

But the team concludes: ‘The combination of muscle strengthening and aerobic activities may provide a greater benefit for reducing all-cause, [cardiovascular disease], and total cancer mortality. Given that the available data are limited, further studies – such as studies focusing on a more diverse population – are needed to increase the certainty of the evidence.'

To see the full version of Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases: a systematic review and meta-analysis of cohort studies, visit: https://bjsm.bmj.com/lookup/doi/10.1136/bjsports-2021-105061