Biomedical subjects

David C Nieman

Publications and source records attributed to David C Nieman.

29 records · Page 2Linked to original sources

PubMed2003

Influence of vitamin C supplementation on oxidative and salivary IgA changes following an ultramarathon.

This randomized study measured the influence of vitamin C ( N=15) compared to placebo ( N=13) supplementation on oxidative and salivary immunoglobulin A (sIgA) changes in runners competing in an ultramarathon race. Seven days prior to the race, subjects ingested in randomized, double-blind fashion three 500-mg tablets of vitamin C or placebo each day. On race day, blood and saliva samples were collected 1 h pre-race, after 32 km of running, and then again immediately post-race. During the race, runners received 1 l/h carbohydrate beverages (60 g/l) with vitamin C (150 mg/l) or without in a double-blinded fashion. The runners also ingested two to three carbohydrate gel packs per hour (25 g each). Subjects in both groups ran a mean of 69 km (range 48-80 km) in 9.8 h (range 5-12 h) and maintained an intensity of approximately 75% maximal heart rate (HR(max)) throughout the ultramarathon race. Plasma ascorbic acid was higher in the vitamin C compared to placebo group pre-race, and increased significantly in the vitamin C group during the race [post-race, 3.21 (0.29) and 1.28 (0.12) microg/100 microl, respectively, P<0.001]. No significant group or interaction effects were measured for lipid hydroperoxide and F(2)-isoprostane, but both oxidative measures rose significantly during the ultramarathon race. Saliva volume, sIgA concentration, sIgA secretion and sIgA:saliva protein ratio all decreased significantly (P<0.001) during the race, but the pattern of change in all saliva measures did not differ significantly between groups. No significant correlations were found between post-race plasma vitamin C, oxidative, and saliva measures, except for a positive correlation between post-race serum cortisol and serum vitamin C (r=0.50, P=0.006). These data indicate that vitamin C supplementation in carbohydrate-fed runners does not serve as a countermeasure to oxidative and sIgA changes during or following a competitive ultramarathon race.

Administration, Oral↗

PubMed2003

A new handheld device for measuring resting metabolic rate and oxygen consumption.

OBJECTIVE: The purpose of this study was to test a new handheld device, the BodyGem (HealtheTech Inc., Golden, CO), that measures resting metabolic rate (RMR). SUBJECTS/DESIGN: Sixty-three adults (43 women, 20 men) (mean+/-SD, age 41.3+/-11.2 years and body mass index, 26.5+/-6.6 kg/m(2)) were tested during two separate sessions within a 2-week period, and, in each session, two BodyGem and two Douglas bag RMR measurements were made in a random and counterbalanced order. MAIN OUTCOME MEASURES: Resting oxygen consumption and energy expenditure. STATISTICAL ANALYSES PERFORMED: A 2 (methods) x 4 (time points) repeated measures ANOVA, Pearson product-moment coefficients, Bland-Altman plots. RESULTS: Within session reliability for measurement of O(2), consumption was high on both days for the BodyGem (r=0.97). During the 4 single tests, BodyGem and Douglas bag O(2) consumption values were significantly correlated (r=0.81-0.87), with SEEs ranging from 22 to 28 mL. min(-1). Mean O(2) consumption and RMR values for all 4 tests were 241+/-46 and 240+/-45 mL x min(-1) (r=0.91, SEE 18.7 mL x min(-1)) and 1,657+/-324 and 1,650+/-307 kcals x day(-1) (r=0.91, SEE 134 kcals x day(-1)) for the BodyGem and Douglas bag methods, respectively. APPLICATIONS/CONCLUSIONS: These data indicate that the BodyGem is an accurate and reliable device for measuring oxygen consumption and calculating RMR during repeated tests within a day, single tests on separate days, or when measurements are averaged.

Adult↗

PubMed2003

Influence of carbohydrate ingestion on oxidative stress and plasma antioxidant potential following a 3 h run.

Concentrations of reactive oxygen species (ROS) increase during exercise secondary to increased oxygen uptake, xanthine oxidase activity, and immune system activation. Carbohydrate compared to placebo beverage ingestion is associated with an attenuated cortisol and catecholamine response. Catecholamines can undergo autooxidation to form ROS. We hypothesized that during intense exercise, ingestion of carbohydrate compared to placebo would diminish oxidative stress. Sixteen experienced marathoners ran on treadmills for 3 h at approximately 70% VO2(max) on two occasions while receiving carbohydrate or placebo beverages (11/h, double-blinded) in a randomized, counterbalanced order. Blood samples were collected before and immediately after exercise, snap frozen in liquid nitrogen, and stored at -80 degrees C until analysis. Plasma samples were analyzed for F2-isoprostanes (FIP) and lipid hydroperoxides (ROOH) as measures for lipid peroxidation, ferric reducing ability of plasma (FRAP) as a measure of plasma antioxidant potential and for cortisol. The pattern of change in cortisol was significantly different between carbohydrate and placebo conditions (P = 0.024), with post-exercise levels higher in the placebo condition. Under both carbohydrate and placebo conditions, significant increases in FIP, ROOH, and FRAP were measured, but the pattern of increase was not different (FIP, interaction effect, P = 0.472; ROOH, P = 0.572; FRAP, P = 0.668). Despite an attenuation in the cortisol response, carbohydrate compared to placebo ingestion does not counter the increase in oxidative stress or modulate plasma antioxidant potential in athletes running 3 h at 70% VO2(max).

Adult↗

PubMed2003

Current perspective on exercise immunology.

By far, the most important finding that has emerged from exercise immunology studies is that positive immune changes take place during each bout of moderate physical activity. Over time, this translates to fewer days of sickness with the common cold and other upper respiratory tract infections. This is consistent with public health guidelines urging individuals to engage in near-daily physical activity of 30 minutes or more. Risk of upper respiratory tract infections can increase when athletes push beyond normal limits. The infection risk is amplified when other factors related to immune function are present, including exposure to novel pathogens during travel, lack of sleep, severe mental stress, malnutrition, or weight loss. Many components of the immune system exhibit adverse change after prolonged, heavy exertion lasting longer than 90 minutes. These immune changes occur in several compartments of the immune system and body (eg, the skin, upper respiratory tract mucosal tissue, lung, blood, and muscle). During this "open window" of impaired immunity (between 3 and 72 hours, depending on the immune measure), viruses and bacteria may gain a foothold, increasing the risk of subclinical and clinical infection. In general, if symptoms are from the neck up, moderate exercise is probably acceptable (and some researchers would argue even beneficial) when an athlete is sick, whereas bed rest and a gradual progression to normal training are recommended when the illness is systemic.

Attitude of Health Personnel↗

PubMed2003

Ratings of perceived exertion throughout an ultramarathon during carbohydrate ingestion.

Ratings of perceived exertion (RPE) and their relation to selected physiological mediators during endurance exercise have been limited to laboratory settings. The present study characterized the pattern of change in perceptual responses and examined the relation between RPE and selected physiological variables during a long competitive sporting event, i.e., an ultramarathon race (68 km). A single-group design was employed in which all of the 28 subjects provided their perceptual ratings 11.9 +/- 0.2) and heart rate (HR) (138 +/- 3) periodically (every 5 km) throughout the ultramarathon, and selected physiological responses were measured before, once during (32 km), and immediately after the race. Runners drank approximately 1,000 ml of carbohydrate beverage each hour (60 gm carbohydrate hr.(-1)) and ate 2 or 3 carbohydrate gel packs per hour (25 gm each(-1)). RPE increased significantly throughout the course of the ultramarathon. No significant correlations were found between RPE and HR at any time throughout the ultramarathon. RPE averaged 10.4 +/- 0.4 at the beginning of the race (6.4 km) and 15.4 +/- 0.4 at the conclusion of the race. Subjects maintained 76.9 +/- 1.1% of maximal heart rate; however, there was a tendency for heart rate to drop significantly after 32 km. Significant time main effects were found for serum glucose, insulin, and cortisol throughout the race. However, no significant correlations were found between RPE and any of these physiological mediators. These data indicate that during an ultramarathon race there is a progressive increase in RPE without an accompanying increase in HR or decrease in blood glucose. Therefore, during competitive self-paced exercise the perceptual responses may be mediated through other neurological and physiological mechanisms.

Adult↗

PubMed2002

Reducing diet and/or exercise training decreases the lipid and lipoprotein risk factors of moderately obese women.

OBJECTIVE: This study was designed to measure the influence of diet, exercise or both on serum lipids and lipoproteins in obese women. METHODS: Obese subjects were randomly divided into one of four groups: diet alone (1,200-1,300 kcal/day, NCEP, Step I), exercise alone (five 45 minute sessions per week at 78.4+/-0.5% maximum heart rate), exercise and diet, and controls. Maximal aerobic power, body composition, diet, serum lipids and lipoproteins were measured in all subjects at baseline and after a 12-week intervention period. Subjects included 91 moderately obese (45.6+/-1.1 y, body mass index 33.1+/-0.6 kg/m2) and 30 nonobese (43.2+/-2.3 y, body mass index 21.4+/-0.34 kg/m2) women who were recruited from the surrounding community. Independent t tests were used to compare obese and nonobese subjects at baseline. The 12-week intervention data from the obese groups were analyzed using a 4 x 2 repeated measures ANOVA design. RESULTS: Cross-sectional comparisons at baseline showed obese subjects had significantly higher total cholesterol, triacylglycerol. total cholesterol/HDL-C and LDL-C values and lower HDL-C values. Prospective results showed that subjects in diet and exercise and diet lost 7.8+/-0.7 and 8.1+/-0.6 kg body mass, with no significant change for exercise relative to control. Serum cholesterol and triacylglycerol improved in both diet and in exercise and diet after 12 weeks of intervention, and was most strongly related to weight loss. CONCLUSION: Weight loss is the most effective means of reducing lipid and lipoprotein risk factors in obese women.

Adult↗

PubMed2002

Children's OMNI Scale of Perceived Exertion: walking/running evaluation.

PURPOSE: The Children's OMNI-walk/run Scale of Perceived Exertion (category range, 0-10) was evaluated using male and female children (6-13 yr of age) during a treadmill graded exercise test. METHODS: A cross-sectional, perceptual estimation paradigm using a walking/running test protocol was administered. Oxygen uptake (VO(2), mL x min(-1)), %VO(2max), ventilation (VE, L x min(-1)), respiratory rate (RR, breaths x min(-1)), respiratory exchange ratio (RER), heart rate (HR, beats x min(-1)), V(E)/VO(2) ratio, and ratings of perceived exertion (RPE) measurements were made every minute throughout the test. RESULTS: Significant correlations were found between OMNI-walk/run Scale RPE responses and VO(2), %VO(2max), HR, V(E)/VO(2) ratio, and RR throughout the maximal treadmill exercise test. The strongest correlations were found between RPE and %VO(2max) (r = 0.41-0.60, P < 0.001) and HR (r = 0.26-0.52, P < 0.01). CONCLUSION: The psychophysiological responses provide validity evidence for use of the Children's OMNI-walk/run Scale over a wide range of exercise intensities during both walking and running.

Adolescent↗

PubMed2002

Effect of carbohydrate ingestion on ratings of perceived exertion during a marathon.

PURPOSE: The purpose of this study was to investigate the effects of carbohydrate substrate availability on ratings of perceived exertion (RPE) and hormonal regulation during a competitive marathon. METHODS: A randomized, double-blind study design was used in which subjects ran the marathon, and every 3.2 km, RPE and heart rate were measured. The marathoners were randomly assigned to receive carbohydrate (C) (N = 48) or placebo (P) (N = 50) beverages at a rate of 1 L x h(-1) during the race. RESULTS: Heart rate (%(HRMAX) ) was lower in P (82.0% +/- 0.6) than C (84.2% +/- 0.6) (P < 0.01), especially during the final 10 km: (78.7% +/- 1.0) and (84.5% +/- 0.7), respectively (P < 0.001). RPE was not significantly different between P and C throughout the marathon (P = 0.08) or during the final 10 km: (16.8 +/- 0.3) and (16.1 +/- 0.3), respectively (P = 0.06). Postrace plasma glucose (P < 0.001), insulin (P < 0.001), and lactate (P < 0.05) levels were significantly lower in P than C, and postrace cortisol (P < 0.05) significantly higher in P compared with C. CONCLUSIONS: Marathoners ingesting carbohydrate compared with placebo beverages were able to run at a higher intensity while reporting a nonsignificant difference in RPEs during a competitive race.

Adult↗

PubMed2002

Influence of vitamin C supplementation on oxidative and immune changes after an ultramarathon.

The purpose of this randomized study was to measure the influence of vitamin C (n = 15 runners) compared with placebo (n = 13 runners) supplementation on oxidative and immune changes in runners competing in an ultramarathon race. During the 7-day period before the race and on race day, subjects ingested in randomized, double-blind fashion 1,500 mg/day vitamin C or placebo. On race day, blood samples were collected 1 h before race, after 32 km of running, and then again immediately after race. Subjects in both groups maintained an intensity of approximately 75% maximal heart rate throughout the ultramarathon race and ran a mean of 69 km (range: 48-80 km) in 9.8 h (range: 5-12 h). Plasma ascorbic acid was markedly higher in the vitamin C compared with placebo group prerace and rose more strongly in the vitamin C group during the race (postrace: 3.21 +/- 0.29 and 1.28 +/- 0.12 microg/100 microl, respectively, P < 0.001). No significant group or interaction effects were measured for lipid hydroperoxide, F2-isoprostane, immune cell counts, plasma interleukin (IL)-6, IL-10, IL-1-receptor antagonist, or IL-8 concentrations, or mitogen-stimulated lymphocyte proliferation and IL-2 and IFN-gamma production. These data indicate that vitamin C supplementation in carbohydrate-fed runners does not serve as a countermeasure to oxidative and immune changes during or after a competitive ultramarathon race.

Administration, Oral↗

PubMedDate not supplied

Validation of Cosmed's FitMate in measuring oxygen consumption and estimating resting metabolic rate.

The purpose of this study was to assess the validity and reliability of the FitMate metabolic system (Cosmed, Rome, Italy) in measuring oxygen consumption and estimating resting metabolic rate (RMR). The FitMate is a new, small (20 x 24 cm) metabolic analyzer designed for measurement of oxygen consumption and energy expenditure during rest and exercise. Subjects included 60 healthy adults (N = 30 males, N = 30 females) ranging in age from 19 to 65 years (mean +/- SD age, 36.9 +/- 13.4 years) and body mass index (BMI) from 19.2 to 44.8 kg/m2 (27.7 +/- 6.2 kg/m2). Subjects were given two 10 min RMR tests in one test session during which RMR was measured simultaneously with the Douglas bag and FitMate systems. No significant differences were found between Douglas bag and FitMate systems for oxygen consumption (242 +/- 49 and 240 +/- 49 ml/min, respectively, P = 0.066, r = 0.97, mean +/- SD absolute difference 2.83 +/- 11.68 ml/min) or RMR (1,662 +/- 340 and 1,668 +/- 344 kcal/day, P = 0.579, r = 0.97, mean +/- SD absolute difference 5.81 +/- 80.70 kcal/day). These data indicate that the FitMate is a reliable and valid system for measuring oxygen consumption and RMR in adults.

Adult↗

PubMedDate not supplied

Influence of carbohydrate on immune function following 2 h cycling.

The influence of carbohydrate compared with placebo ingestion on changes in immune cell counts and functions following 2 h intensive cycling was studied in 12 trained cyclists who functioned as their own controls. The subjects performed two tests 2 weeks apart where they cycled for 2 h at approximately 64% Watts(max) while receiving 4 mL x kg(-1) x 15 min(-1) carbohydrate (6%) (Cho) or placebo (Pla) beverages. Blood samples were collected 30 min preexercise, and immediately and 1 h postexercise. The samples were assayed for plasma cortisol and epinephrine, blood leukocyte subset counts, PHA-induced lymphocyte proliferation, and natural killer cell activity (NKCA). Compared with Pla ingestion, Cho attenuated exercise-induced changes in plasma cortisol, blood neutrophil, and monocyte counts, but not in total blood lymphocyte, T cell, and NK cell counts, PHA-induced lymphocyte proliferation, and NKCA. Thus despite a strong attenuating influence of carbohydrate ingestion on exercise-induced changes in plasma cortisol and blood neutrophil and monocyte counts, other immune measures related to lymphocyte subset counts, and function were unaffected.

Adult↗