Optical communications downlink from a low-earth orbiting 1.5U CubeSat.

In this article, we present the first demonstration of an optical communications downlink from a low-earth orbiting free-flying CubeSat. Two 1.5U vehicles, AC7-B&C, built under NASA's Optical Communications and Sensors Demonstration (OCSD) program were launched in November 2017 and subsequently placed into a 450-km, 51.6° inc. circular orbit. Pseudorandom data streams using on-off key (OOK) modulation were transmitted from AC-7B to a 40 cm aperture telescope located at sea level in El Segundo, CA. At 200 Mbps, without forward error correction (FEC), we achieved a 115-second link that was ~78% error free, with the remaining portion exhibiting an error rate below 1E-5. At the time of the engagement, the 1064-nm laser transmitter was operating at 2 W (half capacity) with a full width half maximum (FWHM) beam divergence of ~1 mrad, which was approximately double the anticipated pointing accuracy of the vehicle.

Acoustical Method of Whole-Body Hydration Status Monitoring.

An acoustical handheld hydration monitor (HM) for assessing the water balance of the human body was developed. Dehydration is a critical public health problem. Many elderly over age of 65 are particularly vulnerable as are infants and young children. Given that dehydration is both preventable and reversible, the need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. The HM is based on an experimental fact that ultrasound velocity in muscle is a linear function of water content and can be referenced to the hydration status of the body. Studies on the validity of HM for the assessment of whole-body hydration status were conducted in the Appalachian State University, USA, on healthy young adults and on elderly subjects residing at an assisted living facility. The HM was able to track changes in total body water during periods of acute dehydration and rehydration in athletes and day-to-day and diurnal variability of hydration in elderly. Results of human studies indicate that HM has a potential to become an efficient tool for detecting abnormal changes in the body hydration status.

Impact of brain tumor location on morbidity and mortality: a retrospective functional MR imaging study.

BACKGROUND AND PURPOSE: fMRI is increasingly used in neurosurgery to preoperatively identify areas of eloquent cortex. Our study evaluated the efficacy of clinical fMRI by analyzing the relationship between the distance from the tumor border to the area of functional activation (LAD) and patient pre- and postoperative morbidity and mortality. MATERIALS AND METHODS: The study included patients with diagnosis of primary or metastatic brain tumor who underwent preoperative fMRI-based motor mapping (n=74) and/or language mapping (n=77). The impact of LAD and other variables collected from patient records was analyzed with respect to functional deficits in terms of morbidity (paresis and aphasia) and mortality. RESULTS: Significant relationships were found between motor and language LAD and the existence of either pre- or postoperative motor (P < .001) and language deficits (P=.009). Increasing age was associated with motor and language deficits (P=.02 and P=.04 respectively). Right-handedness was related to language deficits (P=.05). Survival analysis revealed that pre- and postoperative deficits, grade, tumor location, and LAD predicted mortality. Motor deficits increased linearly as the distance from the tumor to the primary sensorimotor cortex decreased. Language deficits increased exponentially as the distance from the tumor to the language areas decreased below 1 cm. Postoperative mortality analysis showed an interaction effect between motor or language LAD and mortality predictors (grade and tumor location, respectively). CONCLUSIONS: These findings indicate that tumors may affect language and motor function differently depending on tumor LAD. Overall, the data support the use of fMRI as a tool to evaluate patient prognosis and are directly applicable to neurosurgical planning.

Post-160-km race illness rates and decreases in granulocyte respiratory burst and salivary IgA output are not countered by quercetin ingestion.

This study measured the influence of the flavonoid quercetin on immune changes and incidence rates of upper respiratory tract infections in ultramarathoners competing in the 160-km Western States Endurance Run. Sixty-three runners were randomized to quercetin and placebo groups, and under double-blinded methods ingested 1000 mg/day quercetin for 3 wks before, during, and 2 wks after the race. Thirty-nine of the 63 subjects (n = 18 for quercetin, n = 21 for placebo) finished the race and provided blood and saliva samples the morning before the race and 15 - 30 min postrace. Upper respiratory tract infections were assessed during the week before and the 2-wk period after the race using an illness symptom checklist. Race times did not differ significantly between quercetin and placebo groups. Significant pre- to postrace decreases were measured for natural killer cells (43 %), granulocyte respiratory burst activity (55 %), and salivary IgA output (48 %), and increases for neutrophil (288 %) and monocyte (211 %) cell counts, with no significant group differences. Postrace illness rates did not differ between groups. In conclusion, quercetin supplementation for 3 wks before and 2 wks after the Western States Endurance Run had no effect on illness rates, perturbations in leukocyte subset counts, or decreases in granulocyte respiratory burst activity and salivary IgA.

Omni scale rating of perceived exertion at ventilatory breakpoint by direct observation of children's kinematics.

Direct kinematic observation was used to measure ratings of perceived exertion at the ventilatory breakpoint (RPE-Vpt) in 10- to 14-yr.-old girls (n=22) and boys (n=22). RPE for the overall body, legs, and chest were simultaneously estimated by a trained observer and self-rated by a subject during treadmill exercise using the Children's OMNI-Walk/Run Scale. Subjects' heart rate and oxygen consumption were measured during each minute of exercise. Vpt for the girls and boys, respectively, were 64.2 and 66.5% VO2 max. RPE-Vpt ranged from 6.0 to 6.5 Overall, 7.1 to 7.6 Legs, and 5.0 to 5.5 Chest for both the observation and self-rating procedures. Responses indicated (a) RPE-Vpt (Overall, Legs, Chest) did not differ (p>.05) between the observer and self-rating procedures and (b) Observer RPE-Vpt-Legs was greater (p<.05) than RPE-Vpt-Chest. Findings validated direct kinematic observation to code group-normalized RPE-Vpt for girls and boys performing treadmill exercise.

Carbohydrate effect: hormone and oxidative changes.

Carbohydrate administration during exercise diminishes stress hormone release, but the relationship of these hormones with oxidative stress has not been examined. Fifteen subjects functioned as their own controls and ingested carbohydrate (6 %) or placebo in a randomized design while cycling for 2.5-h ( approximately 75 % V.O (2peak)). Blood and skeletal muscle samples were collected 30 min pre-exercise, immediately post-exercise, and 12-h post-exercise and analyzed for F (2)-isoprostanes, ferric reducing ability of plasma, glucose, insulin, cortisol, epinephrine, and muscle glycogen, respectively. Statistical design was a 2 (treatment) x 3 (time) repeated measures analysis of variance. Glucose, insulin, and ferric reducing ability of plasma were significantly higher and F (2)-isoprostanes, cortisol, and epinephrine significantly lower in carbohydrate versus placebo. The decrease in muscle glycogen was not different. During cycling exercise, oxidative stress appears to be heavily influenced by carbohydrate ingestion and increased stress hormones.

Immune changes: 2 h of continuous vs. intermittent cycling.

Immune changes following 2 h of intensive cycling with or without rest intervals were measured in trained cyclists (n = 12) who functioned as their own controls during two test sessions that were separated by two weeks. Subjects cycled for 2.0 h at approximately 64 % Watts(max) continuously (C) or with 3-min rest intervals (R) interspersed every 10 min (2.6 h total time), with the order of the sessions randomized. Blood samples were collected 30-min pre-exercise, and immediately and 1-h postexercise, and assayed for blood leukocyte subset counts, plasma IL-6, IL-10, IL-1ra, IL-8, PHA-induced lymphocyte proliferation, and natural killer cell activity (NKCA). Significant time effects were measured for all immune measures, but no significant differences in the pattern of change were found between C and R exercise trials. In conclusion, immune changes induced by 2 h of intense and prolonged exercise paralleled those measured when athletes rested 3 min every 10 min of exercise.

Influence of carbohydrate ingestion on immune changes after 2 h of intensive resistance training.

Thirty strength-trained subjects were randomized to carbohydrate (CHO) or placebo (Pla) groups and lifted weights for 2 h (10 exercises, 4 sets each, 10 repetitions, with 2- to 3-min rest intervals). Subjects received 10 ml x kg(-1) x h(-1) CHO (6%) or Pla beverages during the weight training bout. Blood, saliva, and vastus lateralis muscle biopsy samples were collected before and after exercise. Blood cell counts were determined, and plasma was analyzed for IL-6, IL-10, IL-1 receptor antagonist (IL-1ra), IL-8, and cortisol. Muscle was analyzed for glycogen content and relative gene expression of 13 cytokines (IL-1alpha, IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p35, IL-12p40, IL-15, IFN-gamma, TNF-alpha) by use of real-time quantitative RT-PCR. Significant but modest increases were measured for plasma IL-6, IL-10, IL-1ra, and IL-8, but the pattern of increase did not differ between CHO and Pla groups. The rate of decrease in muscle glycogen content did not differ between CHO and Pla (P = 0.463). Muscle cytokine mRNA was detected preexercise for IL-1beta, IL-6, IL-15, IL-8, and TNF-alpha, and of these, IL-1beta, IL-6, IL-8, and TNF-alpha were significantly increased after the 2-h weight training bout. The increase in mRNA (fold difference from preexercise) did not differ between CHO and Pla groups. In summary, CHO vs. Pla ingestion did not alter modest increases measured for plasma IL-6, IL-10, IL-1ra, and IL-8, and muscle gene expression for IL-1beta, IL-6, IL-8, and TNF-alpha in strength-trained subjects lifting weights intensively for 2 h.

Carbohydrate ingestion influences skeletal muscle cytokine mRNA and plasma cytokine levels after a 3-h run.

Sixteen experienced marathoners ran on treadmills for 3 h at approximately 70% maximal oxygen consumption (Vo(2 max)) on two occasions while receiving 1 l/h carbohydrate (CHO) or placebo (Pla) beverages. Blood and vastus lateralis muscle biopsy samples were collected before and after exercise. Plasma was analyzed for IL-6, IL-10, IL-1 receptor agonist (IL-1ra), IL-8, cortisol, glucose, and insulin. Muscle was analyzed for glycogen content and relative gene expression of 13 cytokines by using real-time quantitative RT-PCR. Plasma glucose and insulin were higher, and cortisol, IL-6, IL-10, and IL-1ra, but not IL-8, were significantly lower postexercise in CHO vs. Pla. Change in muscle glycogen content did not differ between CHO and Pla (P = 0.246). Muscle cytokine mRNA content was detected preexercise for seven cytokines in this order (highest to lowest): IL-15, TNF-alpha, IL-8, IL-1beta, IL-12p35, IL-6, and IFN-gamma. After subjects ran for 3 h, gene expression above prerun levels was measured for five of these cytokines: IL-1beta, IL-6, and IL-8 (large increases), and IL-10 and TNF-alpha (small increases). The increase in mRNA (fold difference from preexercise) was attenuated in CHO (15.9-fold) compared with Pla (35.2-fold) for IL-6 (P = 0.071) and IL-8 (CHO, 7.8-fold; Pla, 23.3-fold; P = 0.063). CHO compared with Pla beverage ingestion attenuates the increase in plasma IL-6, IL-10, and IL-1ra and gene expression for IL-6 and IL-8 in athletes running 3 h at 70% Vo(2 max) despite no differences in muscle glycogen content.

Influence of skinfold sum and peak VO(2) on immune function in children.

OBJECTIVE: To measure the relationship of skinfold sum and peak VO(2) power with immune function in children. DESIGN: Cross-sectional, with all children tested twice during a 2 month period for peak VO(2), sum of two skinfolds, and immune function, with data from the two measures averaged and then correlated (alpha level, < or = 0.01). Immune measures included leukocyte and lymphocyte subset counts, delayed-typed hypersensitivity (DTH), global IgG antibody response over 4 weeks to pneumococcal vaccination (pIgG), salivary IgA concentration (sIgA), PHA-stimulated lymphocyte proliferation (PHA-SLP), natural killer cell activity (NKCA), and granulocyte and monocyte phagocytosis and oxidative burst activity. SUBJECTS: Seventy-three children (n=42 males, n=31 females) ranging in age from 7 to 13 y (mean+/-s.d. age, 9.9+/-1.7 y). The mean skinfold sum was 28.9+/-17.1 mm, and peak VO(2) 45.8+/-8.1 ml/kg/min. RESULTS: Peak VO(2), skinfold sum, and immune measures did not differ significantly by age or gender. Therefore, correlations were made on combined indices for all subjects. Peak VO(2) and the skinfold sum were not significantly correlated with NKCA, oxidative burst activity, plgG or DTH. Peak VO(2) was negatively correlated with monocyte phagocytosis (r=-0.30, P=0.012) and positively correlated with PHA-SLP (6.25 microg/ml; r=0.35, P=0.004). The skinfold sum was positively correlated with the total leukocyte count (r=0.39, P<0.001), granulocyte count (r=0.36, P=0.002), monocyte count (r=0.38, P=0.001), monocyte phagocytosis (r=0.41, P<0.001), granulocyte phagocytosis (r=0.35, P=0.003), and sIgA (r=0.32, P=0.006), and negatively correlated with PHA-SLP (6.25 microg/ml; r=-0.39, P=0.001). CONCLUSIONS: Data from this study indicate that a high skinfold sum is related to elevated leukocyte subset counts and monocyte/granulocyte phagocytosis, and low PHA-SLP in children.

Change in salivary IgA following a competitive marathon race.

The influence of carbohydrate (1 l/h of a 6 % carbohydrate beverage), gender, and age on salivary IgA (sIgA) changes and incidence of upper respiratory tract infection (URTI) was studied in 98 runners following two competitive marathon races. The pattern of change in sIgA concentration differed significantly between carbohydrate (C) (N = 48) and placebo (P) (N = 50) groups, with higher post-race values measured in P. However, when this was adjusted for saliva protein concentration and saliva secretion rate, no difference between groups was measured. For all subjects combined, sIgA concentration, saliva IgA: protein ratio (spIgA), and sIgA secretion rates fell significantly (21 %, 31 %, and 25 %, respectively) below pre-race levels by 1,5-h post-race (p < 0.001). The pattern of change in all saliva measures did not differ significantly between the 12 women and 86 men in this study, and between the 23 older (> or =50 yr) and 75 younger (< 50 yr) subjects. Ninety-three subjects returned health/sickness logs, and of these, 16 (17 %) reported developing URTI during the 15-d period following the race event. The 1.5-h post-race spIgA concentration, but not sIgA concentration or secretion rate, was lower in runners reporting URTI compared to those who did not (254 +/- 30 and 388 +/- 26 microg*g(-1), respectively, p = 0.002), and this was negatively correlated with the post-race plasma cortisol concentration (r = -0.36, p < 0.001). Of the 16 runners, six were in the C group and 10 in the P group (Chi square = 1.11, p = 0.293). In conclusion, the output of sIgA decreased in runners following a competitive marathon, and this was not influenced by carbohydrate ingestion, age, or gender.

A comparison of leg-to-leg bioelectrical impedance and skinfolds in assessing body fat in collegiate wrestlers.

A comparison of the leg-to-leg bioelectrical impedance (BIA) system and skinfold analysis in estimating % body fat in a large number of National Collegiate Athletic Association (NCAA) collegiate wrestlers was conducted. A series of 5 cross-sectional assessments, including the NCAA Division I and III Championships, were completed throughout the 1998-1999 wrestling season with samples ranging from (N = 90-274). Body density was determined from the 3 skinfold measures using the Lohman prediction equation. BIA measurements were determined using the Tanita body fat analyzer, model 305. Significant correlations between methods ranging from (r = 0.67-0.83, p < 0.001) and low standard error of estimates (SEE) for % body fat ranging from 2.1-3.5% were found throughout the 5 assessment periods. This preliminary study demonstrated that the leg-to-leg bioelectrical impedance system accurately estimated % body fat when compared to skinfolds in a diverse collegiate wrestling population.

The new National Collegiate Athletic Association wrestling weight certification program and sport-seasonal changes in body composition of college wrestlers.

Changes in body composition of college-age wrestlers (N = 21, 19.0 +/- 0.2 years of age, 8.2 +/- 0.6 years of experience) were studied throughout the season after implementation of the new National Collegiate Athletic Association (NCAA) wrestling weight certification (WWC) program. Wrestlers were divided into 2 groups, starters (n = 10) and nonstarters (n = 11), based on the number of completed matches during the 1998-1999 season. Body density was measured via hydrostatic weighing, with residual volume determined via the nitrogen washout technique. Hydration was assessed by measuring specific gravity of urine (Usg). For body mass and fat-free mass (FFM), a significant difference in the pattern of change was found (p < 0.05), highlighted by a decrease in body mass (-3.0%, -2.5 kg, -5.8 lb) and a maintenance of FFM from preseason to peak season for the starters. The pattern of change over time was significantly different for refractometry Usg (p < 0.01) but not for the test strip Usg (p = 0.54). No significant interaction effects were seen for percentage of body fat or fat mass. Significant time main effects were found for percentage of body fat, body mass, fat mass, FFM, and refractometry Usg. Taken together, the results of this investigation demonstrate that collegiate wrestlers lose body mass but maintain FFM throughout the season, which may in part be associated with the new NCAA WWC program.

Validity of leg-to-leg bioelectrical impedance measurement in males.

BACKGROUND: This study determined the validity of the leg-to-leg bioelectrical impedance analysis (BIA) system (Tanita Body Fat Analyzer, TBF 105, Tanita Corporation of America, Inc., Arlington Heights, IL) in estimating body composition in males. EXPERIMENTAL DESIGN: Fat-free mass (FFM) was estimated using BIA and underwater weighing, and compared. SETTING: Subjects were recruited from the community. PARTICIPANTS: Heterogeneous group of males (N=192) was recruited, with a mean+/-SD age of 39.0+/-16.8 yrs; body mass index, 26.0+/-4.0 kg/m2, percent body fat, 18.1+/-8.9 percent. MEASURES: Prior to BIA testing, subjects were required to adhere to standard BIA testing guidelines, and bioelectrical impedance was measured in subjects standing erect with bare feet on the analyzer's footpads, and wearing a swimsuit. Underwater weighing was conducted using standard procedures, with direct measurement of residual volume. RESULTS: A Bland-Altman plot of difference between FFM measured by underwater weighing and BIA versus average FFM by the two methods showed no systematic difference (mean difference, 0.07+/-3.5 kg). FFM was estimated at 66.3+/-8.6 kg with underwater weighing, and 66.2+/-7.7 kg with BIA (r=0.92, p<0.001; SEE 3.5 kg). CONCLUSIONS: These data indicate that the leg-to-leg bioelectrical impedance system accurately assesses FFM in a heterogenous group of males when compared to underwater weighing.

Cytokine changes after a marathon race.

The influence of carbohydrate (1 l/h of a 6% carbohydrate beverage), gender, and age on pro- and anti-inflammatory plasma cytokine and hormone changes was studied in 98 runners for 1.5 h after two competitive marathon races. The marathoner runners were randomly assigned to carbohydrate (C, n = 48) and placebo (P, n = 50) groups, with beverages administered during the races in a double-blind fashion using color codes. Plasma glucose was higher and cortisol was lower in the C than in the P group after the race (P < 0.001). For all subjects combined, plasma levels of interleukin (IL)-10, IL-1 receptor antagonist (IL-1ra), IL-6, and IL-8 rose significantly immediately after the race and remained above prerace levels 1.5 h later. The pattern of change in all cytokines did not differ significantly between the 12 women and 86 men in the study and the 23 subjects > or =50 yr of age and the 75 subjects <50 yr of age. The pattern of change in IL-10, IL-1ra, and IL-8, but not IL-6, differed significantly between the C and the P group, with higher postrace values measured for IL-10 (109% higher) and IL-1ra (212%) in the P group and for IL-8 (42%) in the C group. In conclusion, plasma levels of IL-10, IL-1ra, IL-6, and IL-8 rose strongly in runners after a competitive marathon, and this was not influenced by age or gender. Carbohydrate ingestion, however, had a major effect in attenuating increases in cortisol and two anti-inflammatory cytokines, IL-10 and IL-1ra.

Creatine supplementation and health variables: a retrospective study.

PURPOSE: Long-term safety of creatine supplementation has been questioned. This retrospective study was performed to examine markers related to health, the incidence of reported side effects and the perceived training benefits in athletes supplementing with creatine monohydrate. METHODS: Twenty-six athletes (18 M and 8 F, 24.7 +/- 9.2 y; 82.4 +/- 20.0 kg; 176.5 +/- 8.8 cm) from various sports were used as subjects. Blood was collected between 7:00 and 8:30 a.m. after a 12-h fast. Standard clinical examination was performed for CBC and 27 blood chemistries. Testosterone, cortisol, and growth hormone were analyzed using an ELISA. Subjects answered a questionnaire on dietary habits, creatine supplementation, medical history, training history, and perceived effects of supplementation. Body mass was measured using a medical scale, body composition was estimated using skinfolds, and resting heart rate and blood pressure were recorded. Subjects were grouped by supplementation length or no use: Gp1 (control) = no use (N = 7; 3 F, 4 M); Gp2 = 0.8-1.0 yr (N = 9; 2 F, 7 M); and Gp3 = 1(+) (N = 10; 3 F, 7 M). RESULTS: Creatine supplementation ranged from 0.8--4 yr. Mean loading dose for Gp2 and Gp3 was 13.7 +/- 10.0 and the maintenance dose was 9.7 +/- 5.7 g.d(-)1. Group differences were analyzed using one-way ANOVA. CONCLUSIONS: Expected gender differences were observed. Of the comparisons made among supplementation groups, only two differences for creatinine and total protein (P < 0.05) were noted. All group means fell within normal clinical ranges. There were no differences in the reported incidence of muscle injury, cramps, or other side effects. These data suggest that long-term creatine supplementation does not result in adverse health effects.

Psychological response to exercise training and/or energy restriction in obese women.

OBJECTIVE: The effect of 12 weeks of exercise training (five 45-minute walking sessions/week at 60% to 75% maximum heart rate) and/or moderate energy restriction (4.19 to 5.44 MJ or 1200 to 1300 kcal/day) on psychological general well-being (GWB) and profile of mood states (POMS) was studied in obese women (n = 91, age 45.6 +/- 1.1 years, body mass index 33.1 +/- 0.6 kg/m2). METHODS: Subjects were randomized to one of four groups: control (C); exercise (E); diet (D); and exercise and diet (ED). Psychological variables were measured in all subjects at three timepoints--prestudy, 3 weeks, and poststudy--and analyzed using a 4 x 3 repeated measures design. RESULTS: GWB but not POMS was improved in ED (but not E or D) relative to C poststudy, especially in four of six subscales: freedom from health concern or worry, life satisfaction; cheerful versus depressed mood; and relaxed versus tense feelings. CONCLUSION: These data demonstrate that the combination of moderate energy restriction and exercise training during a 12-week period improves psychological general well-being scores but not mood states in obese subjects.

Effects of exercise training on gallbladder function in an obese female population.

PURPOSE: Aerobic exercise may influence gallstone disease pathogenesis through its effect on gallbladder motility. The purpose of this investigation was to examine the effects of exercise training on gallbladder emptying in obese women. METHODS: Twenty-seven obese subjects were randomized into one of two groups: exercise (E) (five 45-min brisk walking sessions per week at 75.2 +/- 0.5% of maximum heart rate) and controls (C). Gallbladder function via cholescintigraphy, cardiorespiratory fitness, and body composition were measured in all subjects before and after a 12-wk intervention period. In each cholescintigraphy trial subjects ingested an 8-oz liquid meal 45 min after injection of 99mTc disofenin to promote gallbladder emptying. Gallbladder areas were then scanned for 60 s and then every 5 min for 60 min. RESULTS: VO2max increased significantly by 9% for E when compared with that for C (P < 0.001). Within E postprandial gallbladder ejection fraction (EF) increased significantly after training (39.5 +/- 4.9% to 54.7 +/- 6.5%, P < 0.05); however, this 15.2% increase in EF was not significantly greater than the change reported in the controls. CONCLUSIONS: Results indicate that 12 wk of moderate exercise training does improve cardiorespiratory fitness but does not significantly effect gallbladder emptying in obese women.

Effect of carbohydrate ingestion and hormonal responses on ratings of perceived exertion during prolonged cycling and running.

This randomized, double-blind, placebo-controlled study was designed to determine the influence of exercise mode, and 6% carbohydrate (C) versus placebo (P) beverage ingestion, on ratings of perceived exertion (RPE) and hormonal regulation to 2.5 h of high-intensity running and cycling (approximately 75% maximum oxygen uptake) by ten triathletes who acted as their own controls. Statistical significance was set at P < or = 0.05. The pattern of change in RPE over time was significantly different between C and P ingestion (P < 0.001) and between running and cycling modes (P = 0.001). The lowest RPE values were seen in the C-cycling sessions and the highest in the P-running sessions. The pattern of change in the respiratory exchange ratio and fat and carbohydrate oxidation rates were significantly different between the C and P conditions but not between the running and cycling modes. C relative to P ingestion (but not exercise mode) was associated with higher plasma levels of glucose and insulin and lower plasma cortisol and growth hormone levels. The pattern of change in plasma levels of catecholamines and lactate did not differ between the C and P conditions. These data indicate that a lower RPE was associated with a higher level of carbohydrate oxidation, higher plasma glucose and insulin levels, and lower plasma cortisol and growth hormone levels during cycle exercise following C supplementation as compared to P feeding. These findings support a physiological link between RPE and carbohydrate substrate availability as well as selected hormonal regulation during cycle exercise.

Influence of exercise mode and carbohydrate on the immune response to prolonged exercise.

The influence of exercise mode and 6% carbohydrate (C) versus placebo (P) beverage ingestion on lymphocyte proliferation, natural killer cell cytotoxicity (NKCA), Interleukin (IL)-1beta production, and hormonal responses to 2.5 hr of intense running and cycling (approximately 75% VO2max) was measured in 10 triathletes serving as their own controls. The C versus P condition (but not exercise mode) resulted in higher plasma glucose concentrations, lower plasma cortisol concentrations, reduced postexercise lymphocytosis and NKCA, and a lessened T-cell reduction during recovery, No condition or mode effects were observed for concanavalin A and phytohemagglutinin-induced lymphocyte proliferation. Significant mode (but not condition) effects were observed for lipopolysaccharide-induced IL-1beta production over time. However, when expressed per monocyte, the mode effect was abolished and a sustained suppression in IL-1beta/monocyte was observed in all sessions throughout recovery. These data indicate that carbohydrate ingestion significantly affects plasma glucose and cortisol concentrations, blood lymphocyte counts, and NKCA, whereas exercise mode has no effect on these parameters.