The association between blood pressure and grip strength in adolescents: does body mass index matter?

Increased body mass index (BMI) has been related to both low grip strength and high blood pressure (BP) in adolescents. Previous reports of high BP associated with decreased grip strength could be due to the inherent increase in BP in youths with high BMI. This cross-sectional study aimed to examine the association between grip strength and BP in adolescents independent of BMI. A total of 88 865 Chinese adolescents aged 13-17 years were included in this study. Sex-, age- and height-specific references were applied to calculate the BP z-score and define elevated BP. Grip strength was evaluated as handgrip (kg)/weight (kg) and converted into a sex- and age-specific z-score for analysis. Using fractional polynomial regression, we found that increased BMI was associated with enhanced BP and decreased grip strength; however, after stratification by or adjustment for BMI, strong grip strength was related to an increased BP. Logistic regression models revealed that a one s.d. increase in boys' grip strength z-score was associated with an 18% (95% confidence interval: 12, 25) to 37% (19, 59) higher risk of elevated BP when adjusted for BMI. These associations remained significant after further adjustment for cardiorespiratory fitness. A similar pattern was also observed in girls. These results indicated that strong grip strength was associated with increased adolescent BP after adjustment for BMI. Our findings raise questions about using muscle-strengthening training as an approach to improve the BP profile in adolescents.