Greater Muscular Strength Tied to Lower Cardiometabolic Risk in Youths
Teenagers with greater muscular strength have a lower overall risk of developing cardiometabolic problems such as diabetes and heart disease, according to a study published online today in the journal Pediatrics.
The study authors sought to determine the association between muscular strength and cardiometabolic-disease risk in children. They analyzed health data from 1,421 6th graders in total—670 boys and 751 girls—including percent body fat, fasting glucose, blood pressure, plasma triglycerides levels, and HDL cholesterol. Using those five data points, the authors created an aggregate cardiometabolic-risk score for each child.
The children participated in a seven-minute step test, which was used to evaluate their cardiorespiratory fitness levels, and a grip strength test, which previous research has shown to be correlated with total muscle strength in children and adolescents. The authors also asked each child about his or her physical-activity levels via questionnaire during the health screening.
Both boys and girls in the "high strength" groups had significantly lower body mass indexes, waist circumferences, percent body fat, fat-free mass and absolute fat mass, along with significantly lower levels of cardiometabolic risk. Percent body fat was associated with all cardiometabolic risk factors and carried the strongest weight of all factors.
BMI, physical activity and strength capacity were the most influential predictors of overall cardiometabolic risk. The latter finding runs contrary to a previously held belief that cardiorespiratory fitness is most closely tied to cardiometabolic diseases over the course of a person's life.
Based on their findings, the authors concluded that resistance exercise, also known as strength training, should be a fundamental component of health-related activity in youths.
"Unfortunately, and despite the fact that [resistance exercise] has gained some recent attention for its potency in enhancing cardiovascular and metabolic health in adolescents, blanket clinical recommendations still generally entail dietary modification and aerobic [physical activity] for the 'treatment' of obesity," they wrote. "However, muscular strength capacity may be an equally important component of metabolic fitness among children and adolescents because it provides protection against insulin resistance."
The authors warned that they couldn't disentangle the cause-effect relationship between muscular strength and cardiometabolic risk factors. It's unclear whether lower strength capacities "cause" such diseases or whether the diseases are a cause of lower muscular function.
Regardless, the findings "bolster the importance of early strength acquisition and healthy body composition in childhood," they concluded.
The World Health Organization certainly agrees. In its 2010 "Global Recommendations on Physical Activity for Health," the WHO suggested youths between the ages of 5 and 17 should participate in at least three days of resistance exercise per week. The 2014 international consensus position statement on youth resistance training also echoes the importance of resistance exercise for youths.
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