Strength and cardiometabolic risk in young adults: The mediator role of aerobic fitness and waist circumference.

The aim of this study was to analyze the mediation role of cardiorespiratory fitness and waist circumference in the association between muscular strength and cardiometabolic risk. A cross-sectional study involved first-year college students (n = 370) from a Spanish public university was performed. We measured weight, height, waist circumference, blood pressure, biochemical variables, maximum handgrip strength assessment, and cardiorespiratory fitness. We calculated handgrip dynamometry/weight and a previously validated cardiometabolic risk index. Analysis of covariance models was conducted to test differences in cardiometabolic risk values across muscular strength, cardiorespiratory fitness, and waist circumference categories, controlling for confounders. Hayes' PROCESS macro was used for the multiple mediation analysis. The relationship between muscular strength and cardiometabolic risk did not remain significant (c' = 1.76 [1.4]; P > .05) in a multiple serial bootstrapped mediation model including cardiorespiratory fitness and waist circumference as mediators when controlling for age and sex. According to the indirect effect, the significant paths in the model mediating this relationship between muscular strength and cardiometabolic risk index were as follows: muscular strength → waist circumference → cardiometabolic risk index (-4.899; 95% CI: -6.690; -3.450) and muscular strength → cardiorespiratory fitness → waist circumference → cardiometabolic risk index (-0.720; 95% CI: -1.316; -0.360). Both cardiorespiratory fitness and waist circumference mediate the association between muscular strength and cardiometabolic risk in young adults. Thus, our results place cardiorespiratory fitness and waist circumference as the main targets of physical activity programmes aimed at preventing cardiometabolic diseases.

Time-course effects of aerobic interval training and detraining in patients with metabolic syndrome.

BACKGROUND AND AIMS: Exercise training can improve health of patients with metabolic syndrome (MetS). However, which MetS factors are most responsive to exercise training remains unclear. We studied the time-course of changes in MetS factors in response to training and detraining. METHODS AND RESULTS: Forty eight MetS patients (52 ± 8.8 yrs old; 33 ± 4 BMI) underwent 4 months (3 days/week) of supervised aerobic interval training (AIT) program. After 1 month of training, there were progressive increases in high density lipoprotein cholesterol (HDL-c) and reductions in waist circumference and blood pressure (12 ± 3, -3.9 ± 0.4, and -12 ± 1%, respectively after 4 months; all P < 0.05). However, fasting plasma concentration of triglycerides and glucose were not reduced by training. Insulin sensitivity (HOMA), cardiorespiratory fitness (VO2peak) and exercise maximal fat oxidation (FOMAx) also progressively improved with training (-17 ± 5; 21 ± 2 and 31 ± 8%, respectively, after 4 months; all P < 0.05). Vastus lateralis samples from seven subjects revealed that mitochondrial O2 flux was markedly increased with training (71 ± 11%) due to increased mitochondrial content. After 1 month of detraining, the training-induced improvements in waist circumference and blood pressure were maintained. HDL-c and VO2peak returned to the values found after 1-2 months of training while HOMA and FOMAx returned to pre-training values. CONCLUSIONS: The health related variables most responsive to aerobic interval training in MetS patients are waist circumference, blood pressure and the muscle and systemic adaptations to consume oxygen and fat. However, the latter reverse with detraining while blood pressure and waist circumference are persistent to one month of detraining.