The influence of resistance training on patients with metabolic syndrome--significance of changes in muscle fiber size and muscle fiber distribution

People who are afflicted with "metabolic syndrome" exhibit multiple coronary disease risk factors such as insulin resistance, hypertension, hyperlipidemia, or obesity. Twenty-six volunteers (13 women and 13 men) with such disease risk factors (56 ± 5 years) participated in a 14-week resistance training program. Given the fact that resistance training may improve cardiometabolic parameters, the fasting total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, insulin, glucose value, homeostatic model assessment (HOMA) index, and blood pressure and body mass index (BMI) were measured before and after the training intervention. In addition, muscle biopsies from the vastus lateralis muscle of 11 of the men and 5 of the women were analyzed to determine whether changes in the muscle morphology influence the cardiometabolic parameters. Resistance training resulted in a significant increase in fasting HDL for the entire group (from 44.35 ± 9.43 to 48.57 ± 10.96 mg·dl(-1), p = 0.016). No other blood parameter changed significantly. No change was observed in the HOMA index, blood pressure, or BMI. The muscle fiber type distribution did not change, but a significant hypertrophy of muscle fibers was evident (an increase of the ellipse minor axis of 67.3 ± 16.6 to 72.1 ± 12.3 μm, p = 0.004). Moderate intensity resistance training, as was performed in our study, induces hypertrophic impulses but does not seem to have a clear positive influence on cardiometabolic risk factors. However, 2 sessions of moderate intensity resistance training per week can enhance the fasting HDL cholesterol in middle-aged subjects.