Laura K. Stewart

Effects of different doses of physical activity on C-reactive protein among women.

UNLABELLED Elevated C-reactive protein (CRP) is associated with an increased risk of cardiovascular disease. Physical activity has been inversely associated with CRP. However, the clinical trials examining the effect of exercise training have produced conflicting results. PURPOSE The purpose of this study was to examine the influence an exercise training program on CRP in postmenopausal women. METHODS Sedentary, overweight, or obese postmenopausal women with elevated systolic blood pressure (120-160 mm Hg; n = 464) were randomized into one of four groups: a nonexercise control or one of three aerobic exercise groups; exercise energy expenditure of 4, 8, or 12 kcal·kg(-1)·wk(-1) (KKW) for 6 months at a training intensity of 50% of peak VO2. RESULTS Complete data for 421 participants were available, and mean (SD) baseline CRP was 5.7 (5.5) mg·L(-1), with no significant differences across groups. Although VO2 increased in a dose-response manner, there were no significant changes in CRP in any of the exercise intervention groups compared with the control group. Change in fitness was not associated with change in CRP, whereas change in weight was significantly associated with change in CRP. CONCLUSIONS Despite increasing fitness, 6 months of aerobic exercise training did not improve CRP. However, improvements in CRP were associated with reductions in weight.

Curvilinear dose-response relationship of carbohydrate (0-120 g·h(-1)) and performance.

BACKGROUND There is a lack of consensus regarding the optimal range of carbohydrate (CHO) ingestion rates recommended for endurance athletes. PURPOSE This study investigated the relationship between CHO dose and cycling time trial performance to identify an optimal range of CHO ingestion rates for endurance performance. METHODS Fifty-one cyclists and triathletes (28 ± 7 yr, mean ± SD) across four research sites completed four trials. Each trial consisted of a 2-h constant load ride at 95% of the workload that elicited a 4-mmol·L(-1) blood lactate concentration immediately followed by a computer-simulated 20-km time trial, which subjects were asked to complete as quickly as possible. Twelve CHO electrolyte (18 mmol·L(-1) Na, 3 mmol·L(-1) K, and 11 mmol·L(-1) Cl) beverages (three at each site) were tested in a double-blind manner, providing subjects 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 g CHO (1:1:1 glucose-fructose-maltodextrin) per hour during the 2-h constant load ride at a fluid intake rate of 1 L·h(-1). All subjects also consumed a noncaloric placebo on one counterbalanced test occasion. Data were natural log transformed, subjected to a mixed-model analysis, and are reported as adjusted treatment means. RESULTS We estimate incremental performance improvements of 1.0%, 2.0%, 3.0%, 4.0%, and 4.7% at 9, 19, 31, 48, and 78 g·h, respectively, with diminishing performance enhancement seen at CHO levels >78 g·h(-1). CONCLUSIONS CHO beverage ingestion and endurance (∼160 min) performance appear to be related in a curvilinear dose-response manner, with the best performance occurring with a CHO (1:1:1 glucose-fructose-maltodextrin) ingestion rate of 78 g·h(-1).

Vitamin D status, body composition, and fitness measures in college-aged students.

Abstract Forney, LA, Earnest, CP, Henagan, TM, Johnson, LE, Castleberry, TJ, and Stewart, LK. Vitamin D status, body composition, and fitness measures in college-aged students. J Strength Cond Res 28(3): 814–824, 2014—Low vitamin D, commonly assessed as serum 25-hydroxyvitamin D (25OHD), is associated with the development of many age-related chronic diseases. A positive relationship exists between elevated 25OHD and muscle synthesis, strength, power, and decreased body fat in elderly individuals. However, these findings have not been consistently reported in younger healthy populations. The purpose of this study was to investigate the relationship between 25OHD and measures of body size, composition, metabolism, and physical fitness in a young physically active population. Thirty-nine subjects (20 men, 19 women; aged 23 ± 0.7 years) reported 6 times for testing. Blood was collected to determine 25OHD. Primary outcomes included the following: body mass index (BMI) and percent body fat (dual x-ray absorptiometry); resting metabolic rate; maximal oxygen uptake (V[Combining Dot Above]O2max); power output (Wingate); and muscular strength (8 repetition maximum for bench press, upright row, and leg extension and flexion exercises). Our analysis included all participants, and subgroup analyses for individuals with suboptimal 25OHD concentration below 35 ng·mL-1 (“low”; n = 20, 25.97 ± 1.97 ng·mL−1) or equal to and above 35 ng·mL−1 (“high”; n = 19, 44.15 ± 2.17 ng·mL−1). Twenty subjects in this study had serum levels of 25OHD below 35 ng·mL−1. There was a significant positive relationship between V[Combining Dot Above]O2max and serum 25OHD and a negative relationship between BMI and serum 25OHD. These data suggest that vitamin D deficiency is prevalent even in a young physically active population in the southern United States and that there was a positive relationship between a measure of cardiovascular fitness and serum 25OHD, and a negative relationship between serum 25OHD and BMI.

The Melanocortin 3 Receptor: A Novel Mediator of Exercise-Induced Inflammation Reduction in Postmenopausal Women?

The purpose of this study was to determine whether resistance exercise training-induced reductions in inflammation are mediated via melanocortin 3 receptor expression in obese (BMI 32.7 ± 3.7) women (65.6 ± 2.8 yrs) randomized to either a control (N = 11) or resistance training group (N = 12). The resistance trained group performed resistance training 3 days/week for 12 weeks. Resting blood samples were collected before and after the training intervention in both resistance trained and control groups. Resistance training upregulated melanocortin 3 receptor mRNA by 16-fold (P = .035) and decreased monocyte count, without changing leukocyte number, body composition, or body weight. Resistance trained individuals exhibited increased sensitivity to inflammatory stimuli, whereas control individuals exhibited no change. While there was no change in whole blood tumor necrosis factor alpha mRNA between the groups, whole blood interleukin 10 mRNA was higher in the resistance trained group following the intervention period. In summary, it appears that resistance training may modulate melanocortin 3 receptor expression, providing a possible mechanism for the anti-inflammatory effects of exercise training.

Energy Restriction with Different Protein Quantities and Source: Implications for Innate Immunity

Objective: Physical age, energy restriction (ER), and weight loss have been reported to suppress indices of innate immunity, which may increase the risk of illness. To evaluate these interactions, we recruited older, postmenopausal women (50 to 80 years) to fill one of the following 9‐week ER (1250 kcal/d) groups: beef [n = 14; reported intakes 46% carbohydrate (CHO):24% protein (PRO):30% fat], chicken (n = 15; 51% CHO:25% PRO:24% fat), or CHO (n = 14; 59% CHO:17% PRO:24% fat), or a non‐intervention control (n = 11).

Dietary Quercetin Attenuates Adipose Tissue Expansion and Inflammation and Alters Adipocyte Morphology in a Tissue-Specific Manner

Chronic inflammation in adipose tissue may contribute to depot-specific adipose tissue expansion, leading to obesity and insulin resistance. Dietary supplementation with quercetin or botanical extracts containing quercetin attenuates high fat diet (HFD)-induced obesity and insulin resistance and decreases inflammation. Here, we determined the effects of quercetin and red onion extract (ROE) containing quercetin on subcutaneous (inguinal, IWAT) vs. visceral (epididymal, EWAT) white adipose tissue morphology and inflammation in mice fed low fat, high fat, high fat plus 50 μg/day quercetin or high fat plus ROE containing 50 μg/day quercetin equivalents for 9 weeks. Quercetin and ROE similarly ameliorated HFD-induced increases in adipocyte size and decreases in adipocyte number in IWAT and EWAT. Furthermore, quercetin and ROE induced alterations in adipocyte morphology in IWAT. Quercetin and ROE similarly decreased HFD-induced IWAT inflammation. However, quercetin and red onion differentially affected HFD-induced EWAT inflammation, with quercetin decreasing and REO increasing inflammatory marker gene expression. Quercetin and REO also differentially regulated circulating adipokine levels. These results show that quercetin or botanical extracts containing quercetin induce white adipose tissue remodeling which may occur through inflammatory-related mechanisms.