Study Links Muscle Strength to Teenagers' Heart Health

Larry Hand

March 31, 2014

Muscle strength may be as important as diet and exercise in losing or controlling weight and maintaining cardiometabolic health for adolescents, according to a study published online March 31 in Pediatrics.

Mark D. Peterson, PhD, from the Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, and colleagues conducted a principal components analysis to develop a cardiometabolic risk score in adolescents participating in the Cardiovascular Health Intervention Program, a population-based study of sixth graders in Michigan.

The researchers analyzed the records of 1421 adolescents (age, 10 - 13 years; 52.9% girls; 95% white). To build a metabolic risk score, or MetScore, they used linear and logistic regression analysis and then sex-stratified multiple regression analyses to assess independent associations of cardiometabolic risk factors and potential predictors of disease.

First, they assessed anthropometric and body composition measures, including height, body mass index (BMI), waist circumference, and skinfold thickness; blood pressure and fasting blood samples, to obtain lipid profiles and glucose levels; physical activity by questionnaire and student interviews; cardiovascular fitness, as determined by a 7-minute step test; and grip strength, as assessed using a hydraulic handgrip dynamometer.

The authors then assessed the 5 cardiometabolic components of percentage body fat (%BF), systolic blood pressure, triglycerides, high-density lipoprotein, and glucose to establish the MetScore. They included children with measurements in all 5 factors in their analysis (751 girls and 670 boys), with higher MetScores indicating greater risk.

BMI, Physical Activity, and Muscle Strength

Overall, they found that BMI was independently associated with higher MetScores, whereas regular physical activity and normal muscle strength were associated with lower MetScores in adjusted models. Sex, age, and cardiovascular fitness were not significantly associated with MetScores in the adjusted model. Just more than 42% of the children were overweight or obese.

"[B]oys and girls with greater strength-to-body mass ratios had lower BMIs, less body fat, smaller [waist circumferences], higher levels of [cardiorespiratory fitness], and significantly lower clinical markers of cardiometabolic risk," the researchers write. "%BF was associated with all cardiometabolic risk factors and carried the strongest loading coefficient within the continuous MetScore outcome."

"These findings are contradictory to a widely held belief that low [cardiovascular fitness] is the primary physiologic driver of cardiometabolic abnormalities across the lifespan," the researchers write.

Although most clinicians may recommend dietary modification and physical activity to patients who want to lose weight, "muscular strength capacity may be an equally important component of metabolic fitness among children and adolescents because it provides protection against insulin resistance," the researchers write.

They conclude, "[G]reater clinical attention to and support of early behavioral interventions to increase [physical activity], reduce adiposity, and increase muscular strength capacity are certainly warranted."

This research was supported by the Memorial Healthcare Foundation, Owosso, Michigan. The authors have disclosed no relevant financial relationships.

Pediatrics. Published online March 31, 2014.

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