August 13, 2018
Adolescents with a strong hand grip are less likely to develop cardiometabolic problems, such as diabetes and heart disease, over time compared with their peers who have weaker grips, a prospective study shows.
"Even after taking into account other factors like cardiorespiratory fitness, physical activity and lean body mass, we continue to see an independent association between grip strength and both cardiometabolic health maintenance and health improvements," coauthor Paul M. Gordon, PhD, professor and chair of health, human performance and recreation in Baylor's Robbins College of Health and Human Sciences, Waco, Texas, said in a university press release.
Mounting evidence demonstrates an inverse relationship between muscle strength, as measured by handgrip, and multiple cardiometabolic risk factors, including obesity, dyslipidemia, hypertension, type 2 diabetes mellitus, and cardiovascular disease in adults.
Now, Mark D. Peterson, PhD, MS, from the Department of Physical Medicine & Rehabilitation, University of Michigan in Ann Arbor, and colleagues investigated the extent to which weak grip strength predicts subsequent changes in adolescent health status. They report their findings in an article published online today in The Journal of Pediatrics.
Using data from the Cardiovascular Health Intervention Program, a longitudinal study of cardiovascular risk profiles in Southern Maine, the authors analyzed data from adolescents (mean age, 9.2 years), comparing changes in percentage body fat, fasting glucose, blood pressure, plasma triglycerides levels, and high-density lipoprotein cholesterol at baseline (n = 474) and at 2 years (n = 368), relative to the participants' baseline grip strength.
Grip strength was measured by using a hydraulic handgrip dynamometer and was normalized as strength per body mass. Participants completed a questionnaire about their physical activity levels and underwent a 7-minute step test to assess cardiorespiratory fitness a the beginning of fourth grade and again at the end of fifth grade. In addition, physical activity levels were objectively measured via an accelerometer that participants wore on their wrists continuously for 7 days at baseline and follow-up.
At baseline, 27.9% of the boys and 20.1% of the girls were classified as having low strength levels, based on previously established cutpoints for normalized grip-strength (NGS) weakness (≤0.45 for boys and ≤0.36 for girls).
The prevalence of health decline among boys and girls with low baseline grip strength was 60.2% and 51%, respectively, compared with 15.3% and 21.9% of boys and girls with strong baseline grip strength.
After adjustment for fat-free mass index, cardiorespiratory fitness, and objectively measured levels of physical activity, adolescents who were strong at baseline were significantly more likely to demonstrate health maintenance (odds ratio [OR], 3.54; 95% confidence interval [CI], 1.80 - 6.97) and health improvement (OR, 1.30; 95% CI, 1.05 - 1.60) at follow-up.
According to the authors, the findings offer valuable insight into the protective effect of muscular fitness as early as adolescence. "[W]e have demonstrated for the first time that greater NGS was associated with longitudinal health maintenance and health improvements even in adolescents," they write "Conversely, NGS weakness may be used as a prognostic indicator of onset of cardiometabolic risk and to identify adolescents who would benefit most from lifestyle interventions to improve muscular fitness and reduce risk."
Or particular importance, the authors explain, is the apparent independent role of relative muscular strength on cardiometabolic health in this population, as indicated by the significant association between strength and cardiometabolic health status after adjustment for fitness, activity, and fat-free mass.
"Given that grip strength is a simple, risk-stratifying indicator for all-cause death, cardiovascular death, and cardiovascular disease in adults, future research is warranted to better understand how weakness during childhood tracks into and throughout adulthood," the authors state. In particular, research into the age- and sex-specific strength trajectories as predictors of comorbidities across the lifespan is warranted, they note.
The findings are not surprising and, in fact, indicate a "troubling trend" from a health perspective, according to Mark Tremblay, PhD, MSc, professor of pediatric medicine at the University of Ottawa and director of the Healthy Active Living and Obesity Research Group, Children's Hospital of Eastern Ontario Research Institute, Canada. He noted that the amount of time today's adolescents spend "gently gripping" their smart phones is taking away from the time they should and could be spending developing the muscle strength needed to protect them from negative health risks identified in the study.
Although handgrip strength should not be used in isolation to assess strength and fitness in children and adolescents, it should be included as a component of a multidimensional health evaluation, Tremblay said in an interview with Medscape Medical News. The results, he explained, "can open the door to important conversations between clinicians and children and parents about the dangers of a sedentary lifestyle and the importance of physical activity."
The study authors and Tremblay have disclosed no relevant financial relationships.