Association of muscular strength with incidence of metabolic syndrome in men.

PURPOSE: To examine the association between muscular strength and incidence of metabolic syndrome. METHODS: Participants were 3233 men (20-80 yr) initially free of metabolic syndrome who had two or more clinical examinations between 1980 and 2003, including baseline muscular strength and cardiorespiratory fitness assessment. Metabolic syndrome was defined according to NCEP-ATP III criteria. Muscular strength was quantified by combining body weight-adjusted one-repetition maximal measures for leg and bench presses. Cardiorespiratory fitness was assessed by maximal treadmill test. RESULTS: A total of 480 men developed metabolic syndrome during a mean follow-up period of 6.7 +/- 5.2 yr. In a Cox regression analysis adjusted for age, the hazard ratios (95% confidence intervals) of metabolic syndrome associated with the incremental categories of muscular strength were 1.00 (referent), 0.88 (0.69-1.12), 0.77 (0.60-0.98), and 0.54 (0.42-0.71), respectively (linear trend P < 0.0001). The inverse trend persisted after adjustment for smoking, alcohol intake, number of baseline metabolic syndrome risk factors, family history of diabetes, hypertension, and premature coronary disease (P = 0.004), but was attenuated (P = 0.06) when further adjusted for cardiorespiratory fitness. Compared with the lowest strength category, the highest strength category was associated with 44 and 39% lower risk (P < 0.05 each) of incident metabolic syndrome among normal weight body mass index (BMI < 25) and overweight or obese (BMI > or = 25) men, respectively. An inverse association of incident rates was also seen within stratum of age (20-39 yr, P < 0.001; 40-49 yr, P < 0.01; and 50+ yr, P < 0.05). CONCLUSIONS: Muscular strength was inversely associated with metabolic syndrome incidence, independent of age and body size. Potential benefits of greater muscular strength presumably through resistance exercise training should be considered in primary prevention of metabolic syndrome.

Assessing cardiorespiratory fitness without performing exercise testing.

BACKGROUND: Low cardiorespiratory fitness (CRF) is associated with increased risk of chronic diseases and mortality; however, CRF assessment is usually not performed in many healthcare settings. The purpose of this study is to extend previous work on a non-exercise test model to predict CRF from health indicators that are easily obtained. METHODS: Participants were men and women aged 20 to 70 years whose CRF level was quantified with a maximal or submaximal exercise test as part of the National Aeronautics and Space Administration/Johnson Space Center (NASA, n = 1863), Aerobics Center Longitudinal Study (ACLS, n = 46,190), or Allied Dunbar National Fitness Survey (ADNFS, n = 1706). Other variables included gender, age, body mass index, resting heart rate, and self-reported physical activity levels. RESULTS: All variables used in the multiple linear regression models were independently related to the CRF in each of the study cohorts. The multiple correlation coefficients obtained within NASA, ACLS, and ADNFS participants, respectively, were 0.81, 0.77, and 0.76. The standard error of estimate (SEE) was 1.45, 1.50, and 1.97 metabolic equivalents (METs) (1 MET = 3.5 ml O(2) uptake.kilograms of body mass(-1).minutes(-1)), respectively, for the NASA, ACLS, and ADNFS regression models. All regression models demonstrated a high level of cross-validity (0.72 < R < 0.80). The highest cross-validation coefficients were seen when the NASA regression model was applied to the ACLS and ADNFS cohorts (R = 0.76 and R = 0.75, respectively). CONCLUSIONS: This study suggests that CRF may be accurately estimated in adults from a non-exercise test model including gender, age, body mass index, resting heart rate, and self-reported physical activity.

Cardiorespiratory fitness is inversely associated with the incidence of metabolic syndrome: a prospective study of men and women.

BACKGROUND: Few studies have reported the relationship between cardiorespiratory fitness and metabolic syndrome incidence, particularly in women. METHODS AND RESULTS: We prospectively studied 9007 men (mean+/-SD age, 44+/-9 years; body mass index, 25+/-3 kg/m2) and 1491 women (age, 44+/-9 years; body mass index, 22+/-2 kg/m2) who were free of metabolic syndrome and for whom measures of waist girth, resting blood pressure, fasting lipids, and glucose were taken during baseline and follow-up examinations. Baseline cardiorespiratory fitness was quantified as duration of a maximal treadmill test. Metabolic syndrome was defined with NCEP ATP-III criteria. During a mean follow-up of 5.7 years, 1346 men and 56 women developed metabolic syndrome. Age-adjusted incidence rates were significantly lower (linear trend, P<0.001) across incremental thirds of fitness in men and women. After further adjustment for potential confounders, multivariable hazard ratios for incident metabolic syndrome among men in the low, middle, and upper thirds of fitness, were 1.0 (referent), 0.74 (95% CI, 0.65 to 0.84), and 0.47 (95% CI, 0.40 to 0.54) (linear trend P<0.001); in women, they were 1.0 (referent), 0.80 (95% CI, 0.44 to 1.46), and 0.37 (95% CI, 0.18 to 0.80) (linear trend P=0.01), respectively. Similar patterns of significant inverse associations between fitness and metabolic syndrome incidence were seen when men were stratified on categories of body mass index, age, and number of baseline metabolic risk factors, but patterns were variable in women. CONCLUSIONS: Low cardiorespiratory fitness is a strong and independent predictor of incident metabolic syndrome in women and men. Clinicians should consider the potential benefits of greater cardiorespiratory fitness in the primary prevention of metabolic syndrome, particularly among patients who have already begun to cluster metabolic syndrome components.

Associations of muscle strength and fitness with metabolic syndrome in men.

PURPOSE: To examine the associations for muscular strength and cardiorespiratory fitness with the prevalence of metabolic syndrome among men. METHODS: Participants were 8570 men (20-75 yr) for whom an age-specific muscular strength score was computed by combining the body weight adjusted one-repetition maximum measures for the leg press and the bench press. Cardiorespiratory fitness was quantified by age-specific maximal treadmill exercise test time. RESULTS: Separate age and smoking adjusted logistic regression models revealed a graded inverse association for metabolic syndrome prevalence with muscular strength (beta = -0.37, P < 0.0001) and cardiorespiratory fitness (beta = -1.2, P < 0.0001). The association between strength and metabolic syndrome was attenuated (beta = -0.08, P < 0.01) when further adjusted for cardiorespiratory fitness. The association between cardiorespiratory fitness and metabolic syndrome was unchanged (beta = -1.2, P < 0.0001) after adjusting for strength. Muscular strength added to the protective effect of fitness among men with low (P trend = 0.0002) and moderate (P trend < 0.0001) fitness levels. Among normal weight (BMI < 25), overweight (BMI 25-30), and obese (BMI >or= 30) men, respectively, being strong and fit was associated with lower odds (73%, 69%, and 62% respectively, P < 0.0001) of having prevalent metabolic syndrome. CONCLUSIONS: Muscular strength and cardiorespiratory fitness have independent and joint inverse associations with metabolic syndrome prevalence.

Effects of oral ATP supplementation on anaerobic power and muscular strength.

PURPOSE: We examined 14 d of oral adenosine 5'-triphosphate (ATP) supplementation on indices of anaerobic capacity and muscular strength. METHODS: Twenty-seven healthy males successfully completed the trial, after randomly receiving in a double-blind manner an oral dose of low dose (150 mg) or high dose (225 mg) ATP, or matched placebo. To improve absorption characteristics, the ATP was enterically coated. Total blood ATP (whole blood and plasma ATP) concentrations, two Wingate anaerobic power tests (30 s), and muscular strength (1RM and three sets of repetitions to fatigue at 70% of 1RM) were measured under three conditions: (i) baseline; (ii) acutely (7d later, no prior supplementation and 75 min after ATP ingestion); and (iii) after 14 d of daily ingestion (post). RESULTS: Statistical analyses showed no significant between or within group treatment effects for whole blood ATP or plasma ATP concentrations for any treatment condition. We also did not observe any treatment effects for any Wingate testing parameter including peak PO, total work, average PO for 30 s, or post-Wingate lactate accumulation. Overall, we observed no significant between group treatment effects for any muscular strength parameter. We did observe several within group differences for the group ingesting the high ATP dosage including 1RM (6.6%; P < 0.04) and repetitions to fatigue during set 1 of posttesting (18.5%; P < 0.007) and total lifting volume at post (22%; P < 0.003). CONCLUSIONS: We conclude that enterically coated oral ATP supplementation may provide small ergogenic effects on muscular strength under some treatment conditions.

Eight weeks of moderate-intensity exercise training increases heart rate variability in sedentary postmenopausal women.

BACKGROUND: Regular exercise is associated with increased heart rate variability (HRV). However, results from studies examining the effect of exercise training on HRV in postmenopausal women are inconclusive. In addition, the effect of hormone replacement therapy (HRT) on HRV remains a subject of speculation. METHODS: We examined 88 sedentary postmenopausal women in a randomized controlled trial who were assigned to exercise (n = 49) or control (n = 39) groups. The exercising women performed 8 weeks of aerobic exercise training at a heart rate equivalent to 50% of VO2max, consisting on average of 44 minutes per session, 3 to 4 times per week. Resting HRV was measured in each participant at baseline and after 8 weeks of intervention. Ten minutes of resting R-R intervals were analyzed by time (standard deviation of mean R-R intervals, root of mean square successive differences) and frequency domain methods: low-frequency (LF) was defined as 0.04 to 0.15 Hz, high-frequency (HF) as 0.15 to 0.40 Hz, and total spectral power as 0.00 to 0.40 Hz. The LF and HF components in normalized units were also calculated. RESULTS: At baseline, there were no significant differences in HRV between control and exercise groups. Additionally, there were no differences in any HRV variables when women were grouped by HRT use (no HRT, estrogen-only HRT, and progestin-containing HRT). After 8 weeks, women randomly assigned to the exercise group increased all absolute time and frequency domain indexes (all P <.001) and reduced resting heart rate (P =.002) compared with women in the control group. The LF and HF components expressed as normalized units remained unchanged after exercise intervention. Additionally, HRT use did not modify the exercise-induced changes in HRV. CONCLUSIONS: We conclude that moderate aerobic exercise increases HRV in sedentary postmenopausal women. This benefit is not influenced by the use of HRT.

Effects of a commercial herbal-based formula on exercise performance in cyclists.

INTRODUCTION/PURPOSE: We examined the effects of a commercially marketed herbal-based formula purported to increase endurance on oxygen consumption (VO2) in 17 competitive category III/IV amateur cyclists [mean (SEM) age: 31.1 (1.8) yr; height: 178.5 (1.8) cm; weight: 77.1 (1.6) kg]. METHODS: Each cyclist participated in two (pre/post) cycling tests progressing 25 W.4 min(-1) starting at 100 W administered in a randomized, placebo-controlled, double-blind fashion. The second trial was performed 14 d after the ingestion of a manufacturer recommended loading phase (4 d x 6 caps.d(-1)) and a maintenance phase (11 d x 3 caps.d(-1)). Three treatment capsules contained 1000 mg of Cordyceps sinensis (CS-4) and 300 mg Rhodiola rosea root extract as the primary ingredients; 800 mg of other ingredients included calcium pyruvate, sodium phosphate, potassium phosphate, ribose, and adenosine and 200 mcg of chromium. RESULTS: Using a 2 x 2 ANOVA, we observed no significant treatment effect for any between or within group variables including peak VO2 [treatment 4.14 (0.2) L.min(-1); placebo 4.10 (0.2) L.min(-1)], time to exhaustion [treatment 38.47 (1.7) min; placebo 36.95 (1.8) min], peak power output (PO) [treatment 300.00 (12.1) W; placebo 290.63 (12.9) W], or peak heart rate. We also observed no differences for any subpeak exercise variable including the PO eliciting 2 mmol.L(-1) blood lactate (BLa) [treatment 201.00 (18.1) W; placebo 167.50 (19.2) W] and 4 mmol.L(-1) BLa [treatment 235.88 (15.8) W; placebo 244.78 (14.9) W], ventilatory threshold, respiratory compensation point, or Vo2 L.min(-1) gross efficiency at each stage. CONCLUSION: A 2-wk ingestion schema of a commercial herbal-based formula is insufficient to elicit positive changes in cycling performance.

Dose Response to Exercise in Women aged 45-75 yr (DREW): design and rationale.

INTRODUCTION AND PURPOSE: Physical inactivity in postmenopausal women contributes to a rise in atherogenic risk factors associated with the metabolic syndrome. Although regular physical activity positively contributes to health, inactivity progressively increases with age. The Dose Response to Exercise in Women aged 45-75 yr (DREW) study is designed to investigate the effect of different amounts of exercise training on cardiorespiratory fitness and risk factors for cardiovascular disease (CVD) in postmenopausal women at moderately increased risk of CVD. METHODS: DREW will recruit 450 sedentary, healthy, postmenopausal women with a body mass index of 25-40 kg.m-2, resting systolic blood pressure (BP) of 120-159 mm Hg, and a resting diastolic BP of < or = 99 mm Hg. Laboratory and self-report measures completed at baseline and 6 months include maximal oxygen consumption (.VO2max), resting BP, anthropometry, dietary habits, physical activity history, medication use, menstrual history, personal and family medical history, and fasting HDL cholesterol, LDL cholesterol, triglycerides, and glucose. Eligible participants are randomly assigned to a nonexercise group or one of three exercise groups. Participants exercise 3 to 4x wk-1 at a heart rate equivalent to 50% of .VO2max expending 4, 8, or 12 kcal.kg-1.wk-1, depending on group assignment. This study will allow quantification of possible dose-response relations (50%, 100%, and 150% of the consensus physical activity recommendation) between exercise training and study outcomes. CONCLUSION: DREW can make important contributions to our understanding of the effects of physical activity in postmenopausal women and help refine public health and clinical recommendations for this group.