NEW: Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases: a systematic review and meta-analysis of cohort studies

Haruki Momma, Ryoko Kawakami, Takanori Honda, Susumu S Sawada

https://bjsm.bmj.com/content/early/2022/01/19/bjsports-2021-105061


PURPOSE:

To quantify the associations between muscle-strengthening activities and the risk of non-communicable diseases (NCD) and mortality in adults independent of aerobic activities.


PROCEDURE:

Systematic review and meta-analysis of prospective cohort studies that examined the association between muscle-strengthening activities and health outcomes in adults aged ≥18 years without severe health conditions. MEDLINE and Embase were searched from inception to June 2021 and the reference lists of all related articles were reviewed.


LIMITATIONS OF THE SYSTEMATIC REVIEW:

1. The meta-analysis included only a small number of studies.


2. The included studies evaluated muscle-strengthening activities using a self-reported

     questionnaire or the interview method.


3. Because most of the included studies were conducted in the USA, the generalizability of the

     findings is limited.


4. Observational studies were included in the meta-analysis and were thus potentially

     influenced by residual, unknown, and unmeasured confounding factors.


5. Only two databases were searched, and therefore some relevant studies may have been

     missed.


6. The findings should be interpreted with caution because the number of included studies was

     small and we could not directly examine the frequency of muscle-strengthening activities.

     Large-scale studies are needed to examine the health benefits of high-volume muscle-

     strengthening activities. Moreover, attention should also be paid to evidence that most programs 

     providing benefits for musculoskeletal health in elderly people are performed ≥2 days/week. The 

     longitudinal influence of muscle-strengthening activities on mortality and NCDs should be further 

     investigated with a focus on the elderly population in future studies.


MORE DETAILS:

Joint analysis between muscle-strengthening and aerobic activities showed that a greater benefit for all-cause, cardio-vascular disease (CVD), and total cancer mortality was obtained when these two types of activities were combined. Therefore, beyond aerobic activities, muscle-strengthening activities may provide additional benefits for preventing mortality.


The abovementioned previous meta-analysis reported that performing resistance training 1–2 times/week was associated with a lower all-cause mortality but increasing the volume to >2 times/week was not. This result supports a potential non-linear association between muscle-strengthening activities and all-cause mortality.


J-shaped associations with the maximum risk reduction (10–20%) at approximately 30–60 min/week of muscle-strengthening activities were observed for all-cause mortality, CVD, and total cancer.

The study is the first to systematically evaluate the longitudinal association between muscle-strengthening activities and the risk of diabetes. The findings showed that muscle-strengthening activities were associated with a 17% lower incidence of diabetes, with the risk of diabetes sharply decreasing until up to 60 min/week of muscle-strengthening activities followed by a gradual decrease. Because muscle-strengthening activities increase or preserve skeletal muscle mass, which has been identified as the major tissue in glucose metabolism, a clear dose–response association can be established.


The findings showed that the maximum risk reduction for all-cause mortality, CVD, and total cancer was obtained at approximately 30–60 min/week of muscle-strengthening activities, and the risk reduction was low for up to approximately 130–140 min/week. Therefore, the current recommendation of at least 2 days/week could be reasonable, although a higher volume may require caution.


Several physical activity guidelines recommend that adults perform muscle-strengthening activities at least twice a week, however, the influence of a higher volume of muscle-strengthening activities on health benefits is unclear.


RESULTS:

o Muscle-strengthening activities were associated with a 10–17% lower risk of all-cause mortality,

    cardiovascular disease (CVD), total cancer, diabetes, and lung cancer.


o No association was found between muscle-strengthening activities and the risk of some site-

    specific cancers (colon, kidney, bladder, and pancreatic cancers).


o J-shaped associations with the maximum risk reduction (approximately 10–20%) at approximately 

    30–60 min/week of muscle-strengthening activities were found for all-cause mortality, CVD, and 

    total cancer.


o L-shaped association showing a greater risk reduction at up to 60 min/week of muscle-

    strengthening activities was observed for diabetes.


o Combined muscle-strengthening and aerobic activities (versus none) were associated with a lower 

    risk of all-cause, CVD and total cancer mortality.


CONCLUSIONS:

1. Muscle-strengthening activities were inversely associated with the risk of all-cause mortality and 

     major non-communicable diseases including CVD, total cancer, diabetes, and lung cancer.


2. The influence of a higher volume of muscle-strengthening activities on all-cause mortality, CVD, 

     and total cancer is unclear when considering the observed J-shaped associations.


3. In addition, the combination of muscle-strengthening and aerobic activities may provide a greater 

     benefit for reducing all-cause, CVD, and total cancer mortality.


4. 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.