Introduction: Fitness is an important determinant of cardiovascular health in adults. Arterial stiffness has been shown to be a useful prognostic index of cardiovascular events. However, little is known about the relationships of muscular strength with arterial stiffness.
Hypothesis: Muscular strength is inversely related to arterial stiffness index.
Methods: We utilized baseline data collected from the UK Biobank project, an ongoing UK national cohort study of 502,656 adults. Of 169,835 adults that undertook arterial stiffness tests, 136,854 (aged 40-70yrs; 52.4% females) with all essential variables were included for cross-sectional analyses. Maximal hand grip strength was measured once in each hand via a Jamar J00105 hydraulic hand dynamometer (Lafayette Instrument, USA). Values from both hands were averaged, and then divided by body weight to normalize grip strength for body size. Arterial stiffness was assessed using the pulse waveform measured by photo-plethysmography of the index finger (PulseTrace PCA2, Carefusion, USA). Arterial stiffness index (m/s) was calculated by dividing participants’ height (m) by the difference in time (s) between the first systolic peak and early diastolic peak in the waveforms. Quantile regression was performed to examine cross-sectional associations of grip strength with 5 different percentiles of arterial stiffness index: 10th, 30th, 50th, 70th and 90th. The analyses were adjusted for age, gender, percent body fat, ethnicity, smoking status, employment, household income, deprivation index, self-rated health status, medication use, alcohol consumption, parental history of cardiovascular events, assessment centers, self-reported sedentary time and moderate-to-vigorous physical activity time. Analyses were also stratified by gender, age groups and weight status.
Results: One unit increase in grip strength was significantly associated with reductions in arterial stiffness index by 0.68m/s (confidence interval [CI]: 0.54, 0.83), 1.25m/s (CI: 1.08, 1.42), 1.31m/s (CI: 1.13, 1.49), 1.23m/s (CI: 1.00, 1.45) and 1.32m/s (CI: 0.93, 1.71) at the 10th, 30th, 50th, 70th and 90th percentile of arterial stiffness index, respectively. However, stratified analyses revealed stronger negative associations at higher percentiles of the arterial stiffness index in females versus males, younger (<65yrs) versus older individuals and normal versus overweight/obese individuals.
Conclusions: Hand grip strength was inversely associated with arterial stiffness index; the relationships were, in general, stronger at the upper tail of the arterial stiffness index distribution. Additional research is needed to understand biological mechanisms through which various genetic and lifestyle factors improve muscular strength, as well as causal relationships between muscular strength and arterial stiffness.