A long-term follow-up study found that people who did about 90 to 120 minutes of strength training a week had about a 13 percent lower risk of death from all causes than those who did not do strength training.

An online media outlet, Gigazine, reported on July 19 local time that a Harvard T.H. Chan School of Public Health research team analysed links between strength training and mortality using data from three studies that tracked U.S. healthcare workers over a long period.

The study covered about 150,000 people. Participants reported every few years how much time they spent on strength training and aerobic exercise such as walking, cycling and swimming. The follow-up period ran up to 30 years, and about 36,000 people died during that time.

The analysis found that the effects of strength training were pronounced within a certain range. The group that did 90 to 120 minutes a week had about a 13 percent lower risk of death from all causes than the group that did none. Deaths from cardiovascular diseases, including heart disease and stroke, were about 19 percent lower, and deaths from nervous system diseases such as dementia were about 27 percent lower.

The association with cancer deaths differed somewhat. The study found that only less than 60 minutes of strength training a week was linked to a decline in cancer mortality. It also found that increasing time spent on strength training did not lead to a proportionally larger reduction in risk. The study judged that additional risk reduction was not clear for strength training exceeding 120 minutes a week.

The group with the lowest risk of death combined strength training with aerobic exercise. Even without strength training, doing at least 150 minutes a week of moderate-intensity aerobic exercise lowered the risk of death by 26 to 43 percent. Adding 60 to 120 minutes a week of strength training reduced mortality by about 45 percent. That means the effect of combining exercises was greater than strength training alone.

The researchers cited muscle metabolic function as a background factor in strength training. Skeletal muscle is a metabolically active tissue in the body, and strengthening muscles can help store glucose and manage blood sugar, which can raise the likelihood of preventing Type 2 diabetes and heart disease. They said myokines, bioactive substances released into the bloodstream during muscle contraction, could help suppress inflammation linked to heart disease, diabetes and cancer.

It also mentioned brain health and quality of life. Recent research showed that middle-aged and older adults with greater strength were less likely to develop dementia, and stronger muscles were also advantageous in reducing the impact of falls and fractures. That suggests strength training may be linked not only to lifespan but also to maintaining daily function.

Still, the study did not prove a causal relationship. Jack McNamara (잭 맥나마라), a senior lecturer in clinical exercise physiology at the University of East London who introduced the study, pointed out that the analysis looked only at a correlation between strength training and mortality and did not prove that strength training lowers mortality.

He also assessed the exercise volume linked to longevity as attainable for the general public. McNamara said, "Doing short workouts about twice a week to train major muscle groups, and doing aerobic exercise every day, seems likely to help overall health and longevity sufficiently."

The results show that appropriate duration and combining aerobic exercise are more important than the absolute amount of strength training. In particular, with around 2 hours a week of strength training linked to long-term health indicators, time allocation is expected to emerge as a key variable in designing exercise habits.