Daniel M. Croymans

Effects of resistance training on central blood pressure in obese young men

Central blood pressure is a predictor of the risk of cardiovascular disease (CVD), and the effects of resistance training (RT) on central blood pressure are largely unknown. This study explored the effects of high-intensity RT on central blood pressure, indices of arterial stiffness and wave reflection and inflammatory/atherogenic markers in overweight or obese, sedentary young men. Thirty-six participants were randomized to RT (12 weeks of training, 3/wk, n=28) or control groups (C, 12 weeks of no training, n=8) and assessed for changes in central and brachial blood pressures, augmentation index (AIx), carotid–femoral pulse wave velocity (cfPWV), carotid intima-media thickness (cIMT), body composition, lipids and inflammatory/atherogenic markers. High-intensity RT resulted in decreased central and brachial systolic/diastolic blood pressures (all P⩽0.03), despite not altering AIx (P=0.34) or cfPWV (P=0.43). The vascular endothelial growth factor increased (P=0.03) after RT, without any change in cIMT, C-reactive protein, oxidized LDL (oxLDL) or other inflammatory markers (all P⩾0.1). Changes in the central systolic blood pressure (cSBP) were positively correlated with changes in oxLDL (r=0.42, P=0.03) and soluble E-selectin (r=0.41, P=0.04). In overweight/obese young men, high-intensity RT decreases cSBP, independently of weight loss and changes in arterial stiffness. The cardioprotective effects of RT may be related to effects on central blood pressure.

Resistance training increases SHBG in overweight/obese, young men

OBJECTIVE Evidence suggests that SHBG affects glycemic control, predicts both T2D and metabolic syndrome, and is low in obese subjects. We sought to determine if resistance exercise training (RT) can increase sex hormone-binding globulin (SHBG) and ameliorate levels of related steroid hormones in overweight/obese, sedentary young men. MATERIALS/METHODS 36 participants (BMI 31.4 kg/m(2), age 22 years) were randomized into an RT (12 weeks of training, 3/week) or control group (C, 12 weeks no training), and assessed for changes in SHBG, cortisol, testosterone, free testosterone (FT) and free androgen index (FAI). In addition, body composition and oral glucose tolerance testing was performed. RESULTS 12 weeks of RT increased SHBG (P=0.01) and decreased FAI (P<0.05) and cortisol (P<0.05) compared to C. FT decreased in RT (P=0.01). Total testosterone did not change in either group. These changes were noted without weight loss, and in concert with increases in lean body mass (P=0.0002 vs C) and decreases in glucose area under the curve (AUC) (P=0.004), insulin AUC (P=0.03), and total (P=0.002) and trunk (P=0.003) fat mass in RT. CONCLUSION In overweight/obese young men, RT increases SHBG and lowers FAI in obese young adult men.

Resistance training improves indices of muscle insulin sensitivity and β-cell function in overweight/obese, sedentary young men.

We examined the effects of RT on oral glucose tolerance test (OGTT)-derived indices of muscle insulin sensitivity, hepatic insulin resistance, β-cell function, and skeletal muscle proteins related to glucose transport in overweight/obese, sedentary young men. Twenty-eight participants [median body mass index (BMI) 30.9 kg/m(2); age 22 yr] completed 12 wk of RT (3 sessions/wk) and were assessed for changes in OGTT-derived indices, resting metabolic rate, body composition, serum adipokines, and skeletal muscle protein content [hexokinase 2 (HK2), glucose transporter type 4 (GLUT4), RAC-β serine/threonine-protein kinase (AKT2), glycogen synthase kinase 3β, and insulin receptor substrate 1]. Individualized responses to RT were also evaluated. RT significantly improved insulin and glucose area under the curve (both P < 0.03). With the use of OGTT indices of insulin action, we noted improved muscle insulin sensitivity index (mISI; P = 0.03) and oral disposition index (P = 0.03). BMI, lean body mass (LBM), and relative strength also increased (all P < 0.03), as did skeletal muscle protein content of HK2, GLUT4, and AKT2 (26-33%; all P < 0.02). Hepatic insulin resistance index, adiponectin, leptin, and total amylin did not change. Further analysis demonstrated the presence of highly individualized responsiveness to RT for glucose tolerance and other outcomes. RT improved oral indices of muscle insulin sensitivity and β-cell function but not hepatic insulin resistance in overweight/obese young men. In addition to the increase in LBM, the improvements in insulin action may be due, in part, to increases in key insulin signaling proteins.

Untrained young men have dysfunctional HDL compared with strength-trained men irrespective of body weight status

We examined the impact of strength fitness and body weight on the redox properties of high-density lipoprotein (HDL) and associations with indices of vascular and metabolic health. Ninety young men were categorized into three groups: 1) overweight untrained (OU; n = 30; BMI 30.7 ± 2.1 kg/m(2)); 2) overweight trained [OT; n = 30; BMI 29.0 ± 1.9; ≥4 d/wk resistance training (RT)]; and 3) lean trained (LT; n = 30; BMI 23.7 ± 1.4; ≥4 d/wk RT). Using a novel assay on the basis of the HDL-mediated rate of oxidation of dihydrorhodamine (DOR), we determined the functional (redox) properties of HDL and examined correlations between DOR and indices of vascular and metabolic health in the cohort. DOR was significantly lower in both trained groups compared with the untrained group (LT, 1.04 ± 0.49; OT, 1.39 ± 0.57; OU, 1.80 ± 0.74; LT vs. OU P < 0.00001; OT vs. OU P = 0.02), however, DOR in the OT group was not significantly different from that of the LT group. DOR was negatively associated with HDL-cholesterol (R = -0.64), relative strength (R = -0.42), sex hormone-binding globulin (R = -0.42), and testosterone (R = -0.35) (all P ≤ 0.001); whereas DOR was positively associated with triglycerides (R = 0.39, P = 0.002), oxidized low-density lipoprotein (R = 0.32), body mass index (R = 0.43), total mass (R = 0.35), total fat mass (R = 0.42), waist circumference (R = 0.45), and trunk fat mass (R = 0.42) (all P ≤ 0.001). Chronic RT is associated with improved HDL redox activity. This may contribute to the beneficial effects of RT on reducing cardiovascular disease risk, irrespective of body weight status.

Strength Fitness and Body Weight Status on Markers of Cardiometabolic Health

INTRODUCTION Recent evidence suggests that resistance training (RT) may reduce metabolic and cardiovascular disease risk. We investigated whether overweight/class I obese individuals by BMI classification with high strength fitness exhibit cardiovascular/metabolic phenotypes similar to those overweight/obese and untrained or those normal-weight with high strength fitness. METHODS A total of 90 young males were categorized into three groups: overweight untrained (OU, n = 30, BMI > 27 kg·m⁻²), overweight trained (OT, n = 30, BMI > 27 kg·m⁻², RT ≥ 4 d·wk⁻¹), and normal-weight trained (NT, n = 30, BMI < 25 kg·m⁻², RT ≥ 4 d·wk⁻¹). Participants were assessed for strength, body composition, central/peripheral blood pressures, arterial stiffness, and markers of cardiovascular and metabolic health. RESULTS Body weight was similar in OT and OU and greater than NT (P < 0.00001), and fat mass was different in all groups (P < 0.001). Compared to OU, NT and OT groups exhibited higher relative strength (NT = 46.7%, OT = 44.4%, P < 0.00001), subendocardial viability ratio (NT = 21.0%, P < 0.001; OT = 17.0%, P < 0.01), and lower brachial/central blood pressures (NT P < 0.001; OT P ≤ 0.05); augmentation index and pulse-wave velocity were lower only in OT (P < 0.05). Total cholesterol, low-density lipoprotein (NT P < 0.01, OT P < 0.05), triglycerides (NT = -50.4%, OT = -41.8%, P < 0.001), oxidized LDL (NT = -39.8%, OT = -31.8%, P < 0.001), and CRP (NT = -63.7%, OT = -67.4%, P < 0.01) levels were lower and high-density lipoprotein (NT = 26.9%, OT = 21.4%, P < 0.001) levels were higher in NT and OT compared to OU. NT and OT also exhibited lower amylin (NT = -55.8%, OT = -40.8%) and leptin (NT = -84.6%, OT = -59.4%) and higher adiponectin (NT = 87.5%, P < 0.001; OT = 78.1%, P < 0.01) and sex hormone-binding globulin (NT = 124.4%, OT = 92.3%, P < 0.001). Despite greater total and trunk fat in OT compared with NT, other than glucose and insulin, which were lower in NT than in both OT and OU (OT P < 0.01, OU P < 0.001), OT did not exhibit any impaired biomarker/phenotype compared to NT. CONCLUSIONS These findings provide evidence that overweight/class I obese individuals with high strength fitness exhibit metabolic/cardiovascular risk profiles similar to normal-weight, fit individuals rather than overweight/class I obese unfit individuals. Strength training may be important to metabolic and cardiovascular health.

Carotid intima-media thickness, dietary intake, and cardiovascular phenotypes in adolescents: relation to metabolic syndrome.

Little is known about the interrelationships between metabolic syndrome (MS), uric acid, and early carotid atherosclerosis with diet in adolescents. We investigated associations among diet, carotid intima-media thickness (cIMT), MS, uric acid, and other cardiovascular risk factors in adolescents. Two hundred forty-nine adolescents from 3 high schools in Central California-a predominately Hispanic (n = 119, 16.1 +/- 0.9 years old, 94% Hispanic), a mixed-ethnicity (n = 94, 15.7 +/- 1.2 years old), and a Seventh-day Adventist (SDA) (n = 33, 17.0 +/- 1.3 years old) high school-were assessed for cIMT, blood lipids, uric acid, blood glucose, systolic and diastolic blood pressure, body mass index (BMI), and dietary intake. Compared with SDA adolescents, the predominately Hispanic and mixed-ethnicity high school adolescents exhibited higher low-density lipoprotein and BMI percentile, whereas adolescents from the SDA and mixed-ethnicity high schools exhibited lower uric acid and fasting glucose levels than those from the Hispanic high school. After adjusting for age and sex, cIMT was only correlated with systolic blood pressure percentile (r = 0.16, P < .01). Controlling for age, levels of uric acid were correlated with BMI percentile (males: r = 0.59, P < .001; females: r = 0.24, P < .01), low-density lipoprotein (males: r = 0.40, P < .001; females: r = 0.20, P < .01), and total cholesterol in males (r = 0.38, P < .001). Despite no significant differences in the high school frequency of MS risk factors, 59% of adolescents had one or more MS risk factors. A relationship was noted between the number of MS risk factors and uric acid (P < .002). Most of the adolescents presented MS risk factors independent of ethnicity or a purportedly healthier lifestyle (SDA). Uric acid association with MS and its risk factors suggests its potentially heightened importance for the assessment of adolescent cardiovascular health.

Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet

To the Editor: How do Shai et al. (July 17 issue)1 explain why the subjects in their study regained weight between month 6 and month 24, despite a reported reduction of 300 to 600 calories per day? Contributing possibilities may include the notion that a food-frequency questionnaire cannot precisely determine energy or macronutrient intake but, rather, ascertains general dietary patterns. Certain populations may underreport intake2,3 and have a decreased metabolic rate. The authors did not measure body composition, which is critical for documenting weight-loss components. In addition, the titles of the diets that are described in the article are misleading. Labeling the “low-carbohydrate” diet as such is questionable, since 40 to 42% of calories were from carbohydrates from month 6 to month 24, and data regarding ketosis support this view. Participants in the low-fat and Mediterranean-diet groups consumed between 30% and 33% of calories from fat and did not increase fiber consumption, highlighting the importance of diet quality. Furthermore, the authors should have provided baseline values and P values for within-group changes from baseline (see Table 2 of the article). Contrary to the authors’ assertion, it is not surprising that the effects on many biomarkers were minimal, since the dietary changes were minimal. The absence of biologically significant weight loss (2 to 4% after 2 years) highlights the fact that energy restriction and weight loss in themselves may minimally affect metabolic outcomes and that lifestyle changes must incorporate physical activity to optimize the reduction in the risk of chronic disease.4,5 Christian K. Roberts, Ph.D. R. James Barnard, Ph.D. Daniel M. Croymans, B.S.