Researchers asked 4,681 people without diabetes, whose average age was 43, to do leg and bench presses to measure their muscle strength, and to perform treadmill tests to assess their cardiorespiratory fitness. During an average follow-up period of more than eight years, 229 participants, or almost 5 per cent, developed diabetes.
Compared to people who scored lowest on muscle strength tests at the start of the study period, those with moderate muscle strength were 32 per cent less likely to develop diabetes. Higher levels of muscle strength, however, didn’t appear to impact future diabetes risk.
“You don’t need to be the Hulk to help reduce your risk of diabetes,” said study co-author Dr Angelique Brellenthin of Iowa State University in Ames.
“Performing even a small amount of resistance training, which is a main contributor to muscular strength, may provide big benefits,” Brellenthin said. “Bodyweight squats, lunges, push-ups and planks are great for beginners.”
The study focused on type 2 diabetes, the most common form of the disease, which is linked to obesity and ageing and happens when the body can’t properly use or make enough of the hormone insulin to convert blood sugar into energy.
Moderate muscle strength was associated with a lower risk of diabetes even after researchers accounted for a person’s aerobic fitness levels as well as risk factors that can contribute to diabetes risk, such as family history, smoking, drinking, obesity and high blood pressure, researchers report in Mayo Clinic Proceedings.
Before adjusting for these other factors, people with high muscle strength did have a somewhat lower diabetes risk compared to the weakest participants. But after accounting for these factors, that advantage disappeared.
“Muscles are highly metabolically active and high users of glucose,” or blood sugar, said Dr Tahseen Chowdhury of Royal London Hospital in the UK.
“Greater muscle mass and volume will tend to use more glucose, but also tend to be more sensitive to the effects of insulin which increase muscle uptake of glucose,” said Chowdhury, who wasn’t involved in the study.
The study wasn’t a controlled experiment designed to prove whether or how muscle strength might directly impact the development of diabetes. It also wasn’t designed to determine which types of workout might be best for diabetes prevention.
“The best way to prevent diabetes is to avoid a high-calorie diet and to have regular aerobic physical activity at moderate to high intensity for at least 30 minutes for 5 to 6 days a week,” said Dr Stefano Volpato of the University of Ferrara in Italy.
“Resistance training exercises are useful to increase muscle mass, but results of this study are too preliminary to recommend this type of intervention to prevent diabetes,” Volpato, who wasn’t involved in the study, said by email.
Because the risk of diabetes increases with age, it’s possible that results would look different for adults over 65, said Dr Alan Sinclair, director of the Foundation for Diabetes Research in Older People at Diabetes Frail Ltd and a visiting chair in diabetes care at Kings College London.
“The study would have been more interesting and relevant if the mean age of subjects was over 65 years where lowered muscle strength means much more than diabetes risk – it also means something about walking ability, risk of falls, risk of frailty, and loss of independence,” said Sinclair, who wasn’t involved in the study.
Even so, “the study emphasises the importance that maintaining a moderate degree of muscle strength can provide some protective value against diabetes developing,” Sinclair said.