Endothelial function, arterial stiffness and adherence to the 2010 Dietary Guidelines for Americans: a cross-sectional analysis.

Endothelial dysfunction and arterial stiffness are early predictors of CVD. Intervention studies have suggested that diet is related to vascular health, but most prior studies have tested individual foods or nutrients and relied on small samples of younger adults. The purpose of the present study was to examine the relationships between adherence to the 2010 Dietary Guidelines for Americans and vascular health in a large cross-sectional analysis. In 5887 adults in the Framingham Heart Study Offspring and Third Generation cohorts, diet quality was quantified with the 2010 Dietary Guidelines Adherence Index (DGAI-2010). Endothelial function was assessed via brachial artery ultrasound and arterial stiffness via arterial tonometry. In age-, sex- and cohort-adjusted analyses, a higher DGAI-2010 score (greater adherence) was modestly associated with a lower resting flow velocity, hyperaemic response, mean arterial pressure, carotid-femoral pulse wave velocity (PWV), and augmentation index, but not associated with resting arterial diameter or flow-mediated dilation (FMD). In multivariable models adjusting for cardiovascular risk factors, only the association of a higher DGAI-2010 score with a lower baseline flow velocity and augmentation index persisted (ß = - 0·002, P= 0·003 and ß = - 0·05 ± 0·02, P< 0·001, respectively). Age-stratified multivariate-adjusted analyses suggested that the relationship of higher DGAI-2010 scores with lower mean arterial pressure, PWV and augmentation index was more pronounced among adults younger than 50 years. Better adherence to the 2010 Dietary Guidelines for Americans, particularly in younger adults, is associated with a lower peripheral blood flow velocity and arterial wave reflection, but not FMD. The present results suggest a link between adherence to the Dietary Guidelines and favourable vascular health.

Test-retest reliability of pulse amplitude tonometry measures of vascular endothelial function: implications for clinical trial design.

Endothelial dysfunction is an important outcome for assessing vascular health in intervention studies. However, reliability of the standard non-invasive method (flow-mediated dilation) is a significant challenge for clinical applications and multicenter trials. We evaluated the repeatability of pulse amplitude tonometry (PAT) to measure change in pulse wave amplitude during reactive hyperemia (Itamar Medical Ltd, Caesarea, Israel). Twenty healthy adults completed two PAT tests (mean interval = 19.5 days) under standardized conditions. PAT-derived measures of endothelial function (reactive hyperemia index, RHI) and arterial stiffness (augmentation index, AI) showed strong repeatability (intra-class correlations = 0.74 and 0.83, respectively). To guide future research, we also analyzed sample size requirements for a range of effect sizes. A crossover design powered at 0.90 requires 28 participants to detect a 15% change in RHI. Our study is the first to show that PAT measurements are repeatable in adults over an interval greater than 1 week.

Critical environmental limits for exercising heat-acclimated lean and obese boys.

Environmental limits for uncompensable heat stress, above which an imbalance between heat gain and heat loss forces body core temperature upward (i.e., the upper limits of the prescriptive zone), are unknown for children. To determine these limits, 7 lean and 7 obese 9- to 12-year-old heat-acclimated boys performed four randomized trials each on separate days to determine the critical water vapor pressure (P (crit)) forcing an upward inflection of body core temperature at several ambient temperatures. Subjects walked continuously on a treadmill at 30% maximal aerobic capacity at a constant dry bulb temperature (T (db) = 34, 36, 38 or 42 degrees C). After a 30-min equilibration period at 9 torr, ambient water vapor pressure increased approximately 1 torr every 5-min until a distinct breakpoint in the core temperature versus time curve was evident. Compared to the lean subjects, obese subjects had significantly lower environmental limits (P < 0.03) in warm environments (P (crit), for lean vs. obese, respectively = 32.9 +/- 0.7 vs. 30.3 +/- 0.8 torr at T (db) = 34 degrees C; 29.6 +/- 0.6 vs. 27.2 +/- 0.9 torr at T (db) = 36 degrees C; 27.8 +/- 0.6 vs. 24.7 +/- 0.9 torr at T (db) = 38 degrees C; 25.5 +/- 0.7 vs. 24.5 +/- 1.5 torr at T (db) = 42 degrees C). These results suggest that separate critical environmental guidelines should be tailored to lean and obese children exercising in the heat.

Effects of dairy products on intracellular calcium and blood pressure in adults with essential hypertension.

BACKGROUND: Consumption of dairy foods has been associated with lower blood pressure in certain populations. OBJECTIVE: This study examined the effects of dairy foods on blood pressure (BP) and intracellular calcium ((Ca)(i)) and the dependence of BP changes on changes in (Ca)(i). DESIGN: Twenty-three stage 1 hypertensive adults were fed the following 3 experimental diets (5 wk each) in a randomized cross-over design study; a dairy-rich, high fruits and vegetables diet (D-FandV; 30% fat, 7% saturated fat (SFA), 3.4 servings/d dairy), a high fruits and vegetables diet (FandV; 30% fat, 7% SFA, 0.4 servings/d dairy), and an average Western diet (control; 36% fat, 15% SFA, 0.4 servings/d dairy). Systolic (SBP) and diastolic (DBP) BP, calcium regulatory hormones, and erythrocyte (Ca)(i) were determined. RESULTS: SBP and DBP were significantly reduced by approximately 2 mm Hg following both D-F&V and F&V diets vs. the control (P < 0.05). The D-F&V diet significantly lowered 1,25-dihydroxyvitaminD compared with the F&V and control diets (P < 0.01). Serum calcium, parathyroid hormone, calcitonin, and renin activity were unchanged. The D-F&V diet lowered (Ca)(i) vs. the other two diets (P < 0.01), and this change correlated with the fall in DBP (r = 0.52, P < 0.05). Subjects who responded to the D-F&V diet by significantly reducing (Ca)(i) exhibited significantly greater net decreases in DBP on the D-F&V vs. the F&V (-2.8 +/- 1.0 mm Hg) and control diets (-5.4 +/-1.0 mm Hg; diet x group interaction, P < 0.02). CONCLUSION: Consumption of dairy foods beneficially affects (Ca)(i), resulting in improved BP in a subgroup defined by (Ca)(i) response.

Progressive dehydration causes a progressive decline in basketball skill performance.

PURPOSE: To determine the effect of 1, 2, 3, and 4% dehydration (DEH) versus euhydration (EUH) on basketball performance in adult male players. METHODS: Seventeen 17- to 28-yr-old male basketball players completed 3 h of interval treadmill walking (40 degrees C and 20% relative humidity) with or without fluid replacement. Subjects completed six trials in random order: 1) EUH with a carbohydrate-electrolyte solution (CES), 2) EUH control (flavored water with 0% carbohydrate and 18 mM sodium), 3) 1% DEH, 4) 2% DEH, 5) 3% DEH, and 6) 4% DEH. After a 70-min recovery period, subjects performed a sequence of continuous basketball drills designed to simulate a fast-paced game. Measures of overall skill performance during the 80-min game included 1) total time to complete basketball-specific movement drills (sprinting, defensive slides, sprinting-defensive slides combination, and repetitive jumping drills) and 2) total number of shots (foul-line and baseline jump shots, layups, three-point, 15-ft, free throws) made per game. RESULTS: Performance during all timed and shooting drills declined progressively as % DEH increased. Total time to complete basketball-specific movement drills was slower (1%: + 7 +/- 6; 2%: + 20 +/- 5 (P < 0.05); 3%: + 26 +/- 7 (P < 0.005); 4%: + 57 +/- 9 (P < 0.0001) s), and fewer shots were made during DEH versus EUH control (1%: -5 +/- 1; 2%: -6 +/- 2 (P < 0.05); 3%: -8 +/- 2 (P < 0.005); 4%: -10 +/- 1 (P < 0.0001) shots made). There were no significant differences in performance between CES and EUH control. CONCLUSION: Basketball players experienced a progressive deterioration in performance as DEH progressed from 1 to 4%. The threshold, or % DEH at which the performance decrement reached statistical significance, was 2% for combined timed and shooting drills.

Predictive Factors of the Effectiveness of Caudal Epidural Steroid Injections in Managing Patients With Chronic Low Back Pain and Radiculopathy.

STUDY DESIGN: Retrospective clinical outcome analysis. OBJECTIVE: To evaluate and determine whether demographic, comorbid factors, or physical examination findings may predict the outcome of caudal epidural steroid injections in managing patients with chronic low back pain and radiculopathy SUMMARY OF BACKGROUND DATA:: The caudal epidural approach is commonly utilized with patients who are on anticoagulation or who have had prior lumbar surgery to treat L5 or S1 radiculopathies. METHODS: A retrospective review of 136 patients undergoing an initial caudal epidural steroid injection for radiculopathy from January 1, 2006 to August 30, 2013. The patients were assessed before their injections for their pain levels: visual analog scale, presence of lumbar paraspinal and sciatic notch sensitivity, pain with provocative maneuvers, motor weakness, and sensory loss. The patients were then reassessed following their injection for their visual analog scale pain levels, percentage improvement, and duration of pain relief. RESULTS: Stepwise regression was used to determine whether demographic, comorbid factors, or physical examination signs were predictive of percentage improvement or length of relief following an injection. Among these variables, duration of symptoms was found to be negatively significantly related with a P-value of 0.032 for percentage of improvement. For each week of the duration of symptoms, the percentage of improvement decreased by 0.07%. Regarding physical examination findings, presence of pain with lumbar extension was negatively and significantly related to length of relief duration with a P-value of 0.0124. The mean length of relief duration is 38.37 weeks for individuals without painful lumbar extension and 14.68 weeks for individuals with painful lumbar extension CONCLUSIONS:: The mean length of relief following a caudal injection is reduced by 62% in patients who exhibit pain with lumbar extension.

Two percent dehydration impairs and six percent carbohydrate drink improves boys basketball skills.

PURPOSE: To determine the effects of exercise heat-induced two percent dehydration (DEH) and euhydration (EUH) with a six percent carbohydrate-electrolyte solution (CES) compared with placebo EUH (P EUH) on basketball skills in skilled young players. METHODS: Fifteen 12- to 15-yr-old boys underwent three separate 2-h exercise heat exposures (double blind, random order): 2% DEH by limiting fluid intake during exercise in the heat and basketball skill drills, EUH (no net weight change) with a 6% CES, and EUH with a flavored water placebo (P EUH). After recovery, subjects performed an orchestrated sequence of continuous basketball drills designed to simulate a game (12-min quarters + a 10-min halftime). Performance measures and component drills inherent to basketball included various individual and combined shooting percentages (3-point, 15-foot, free-throw shots), sprint (suicides, court widths), lateral movement (zigzags, lane slides), and defensive drill (combining lateral and front-to-back movement) times. RESULTS: Compared with P EUH (53 +/- 11%), combined shooting percentage was impaired by 2% DEH (45 +/- 9%; P = 0.002) and improved by CES intake (60 +/- 8%; P = 0.003). Total sprint times showed a similar effect (83 +/- 10 vs 78 +/- 9 vs 76 +/- 9 s; DEH vs P EUH vs CES; P < 0.001 and P = 0.04, respectively). Total lateral movement times were impaired by 2% DEH (73 +/- 8 vs 68 +/- 8 s; P = 0.001). CES improved total defensive drill times compared with 2% DEH (77 +/- 10 vs 82 +/- 10; P = 0.006). CONCLUSION: Deterioration in basketball skill performance accompanies two percent dehydration in skilled 12- to 15-yr-old basketball players. Additionally, EUH with a 6% CES significantly improves shooting performance and on-court sprinting over EUH with water.

Changes in lumbar disk morphology associated with prolonged sitting assessed by magnetic resonance imaging.

OBJECTIVE: To determine what if any changes occur to the lumbar disks in the spine after prolonged sitting with and without intermittent breaks during a 4-hour period. DESIGN: A prospective observational study. SETTING: An academic outpatient clinic. METHODS: The measurement of lumbar disk changes was performed with 12 subjects after an analysis of a mid sagittal lumbar magnetic resonance image, which measured lumbar disk height and disk diameter. Scanning and analysis were done over a 2-day period: day 1 at the start of the work day and 4 hours later after continuous sitting; at the start of work day 2 and after four hours after a change in position and stretching protocol every 15 minutes. RESULTS: For this study, we first evaluated each level of the lumbar spine for any changes after prolonged sitting for 4 hours over the 2 days. Multiple comparisons bias was eliminated by a Bonferroni correction to limit the overall experiment-wise error rate to .05. The comparison was conducted by using a paired t-test when the normality condition was satisfied and by using a Wilcoxon signed rank test when normality was not satisfied. To test for normality, a Shapiro-Wilk test was used. We found that, for disk height, L4-5 was significantly decreased at the end of the sitting for day 1 but not for day 2. There were no significant height changes for the other lumbar disks. In addition, for disk diameter, there were no significant differences present for any of the disks. CONCLUSIONS: Analysis of the data shows that the greatest change in disk height is at the L4-5 level after prolonged sitting without intermittent breaks. The other levels did not show a significant change in their height. The findings also showed that the L4-5 height changes were not significant with brief positional changes every 15 minutes. Fewer changes in disk height may correlate with an improvement in low back pain and disability.

Responses of lean and obese boys to repeated summer exercise in the heat bouts.

PURPOSE: To determine the degree of natural acclimatization and artificially induced acclimation-related changes during repeated exercise in the heat bouts in seven lean and seven obese 9- to 12-yr-old boys during summer months. METHODS: Beginning at random times during the summer, subjects underwent a 70-min exercise (30% VO(2max)) in the heat exposure (38 degrees C, 50% relative humidity) on six separate days. RESULTS: On day 1, obese children were less naturally acclimatized as indicated by significantly higher baseline core temperatures (T(c)) (obese = 37.62 +/- 0.06 vs lean = 37.41 +/- 0.06; P < 0.004). By day 6 versus day 1, significant reductions in baseline T(c) were evident in both groups (obese = 37.41 +/- 0.04 vs lean = 37.18 +/- 0.04; both P < 0.05). Baseline T(c) in obese subjects by day 6 was similar to that of lean subjects on day 1. Daily reductions in exercise T(c) were evident in both groups (final exercising T(c) day 1 vs day 6: obese = 38.15 +/- 0.05 vs 37.89 +/- 0.05; lean = 38.17 +/- 0.09 vs 37.72 +/- 0.06 degrees C; both P < 0.001), occurring at a significantly slower rate in obese subjects (final exercise T(c) day 6 - day 1: obese vs lean = -0.26 +/- 0.04 vs -0.45 +/- 0.08 degrees C; P < 0.05). Significant reductions in exercising heart rate (HR) occurred in the lean but not the obese subjects by day 6 (final exercising HR day 1 vs day 6: obese = 132 +/- 3 vs 131 +/- 3, P > 0.05; lean = 138 +/- 3 vs 127 +/- 3 bpm; P < 0.001). CONCLUSIONS: During summer months, obese children are less naturally heat-acclimatized and subsequently acclimate at a slower rate.

Evaluation of Reproducibility for Paired Functional Data.

Evaluation of reproducibility is important in assessing whether a new method or instrument can reproduce the results from a traditional gold standard approach. In this paper, we propose a measure to assess measurement agreement for functional data which are frequently encountered in medical research and many other research fields. Formulae to compute the standard error of the proposed estimator and confidence intervals for the proposed measure are derived. The estimators and the coverage probabilities of the confidence intervals are empirically tested for small to moderate sample sizes via Monte Carlo simulations. A real data example in physiology study is used to illustrate the proposed statistical inference procedures.