Plasma adiponectin response to sculling exercise at individual anaerobic threshold in college level male rowers

The purpose of the investigation was to study plasma adiponectin response to a single exercise session in male rowers. Eight college level, single scull rowers (VO2max: 5.01+/-0.43 l.min-1; age: 21.5+/-4.5 yrs; height: 184.9+/-5.0 cm; body mass: 78.5+/-8.4 kg; body fat: 11.8+/-1.2%) participated in this study. Venous blood samples were obtained before, immediately after, and following the first 30 min of recovery of constant load on-water rowing over a distance of 6.5 km (approximately 30 min) at the individual anaerobic threshold (75.2+/-2.9% of VO2max). Adiponectin was unchanged (p>0.05) immediately after the exercise. However, adiponectin was significantly increased above the resting value after the first 30 min of recovery (+14.7%; p<0.05). Similarly, leptin was unchanged immediately after exercise and was significantly decreased after the first 30 min of recovery (-18.2%; p<0.05). Plasma insulin was significantly reduced immediately after exercise and remained significantly lower during the first 30 min of recovery period. Glucose increased with exercise and returned to the pre-exercise level after the first 30 min of recovery. Basal adiponectin was significantly related to VO2max (r=-0.62; p=0.034). However, there was no relationship between basal adiponectin and other measured variables. Similarly, basal leptin demonstrated no relationship with other measured variables. In conclusion, the results of the present study suggest that plasma adiponectin is sensitive in the first 30 min of recovery to the effects of relatively short-term exercise at individual anaerobic threshold when all major muscle parts are involved.     

Effect of hydration state on testosterone and cortisol responses to training-intensity exercise in collegiate runners

Exercise intensity powerfully influences testosterone, cortisol, and testosterone : cortisol ratio (T:C) responses to endurance exercise. Hydration state may also modulate these hormones, and therefore may alter the anabolic/catabolic balance in response to endurance exercise and training. This study examined the effect of running intensity on testosterone, cortisol, and T : C when exercise was initiated in a hypohydrated state. Nine male collegiate runners (age = 20 +/- 0 y, height = 178 +/- 2 cm, mass = 67.0 +/- 1.8 kg, body fat % = 9.8 +/- 0.7 %, V.O2max = 65.7 +/- 1.1 ml.kg (-1).min (-1)) completed four 10-min treadmill runs differing in pre-exercise hydration status (euhydrated, or hypohydrated by 5 % of body mass) and exercise intensity (70 % or 85 % V.O2max). Body mass, urine osmolality, and urine-specific gravity documented fluid balance; blood samples drawn pre-, immediately post-, and 20 min post-exercise were analyzed for testosterone, cortisol, and T : C. Except for heart rate measured during the 70 % V.O2max trials, heart rate, V.O2, and plasma lactate were similar between euhydrated and hypohydrated conditions for a given intensity, suggesting hypohydration did not measurably increase the physiological stress of the exercise bouts. Furthermore, hydration state had no measurable effect on testosterone concentrations before, during, or after exercise at either intensity. Regardless of exercise intensity, cortisol concentrations were greater during hypohydration than euhydration pre-exercise and 20 min post-exercise. Additionally, T : C was significantly lower 20 min post-exercise at 70 % V.O2max when subjects were initially hypohydrated (T : C = 0.055) versus euhydrated (T : C = 0.072). These findings suggest that depending on exercise intensity, T : C may be altered by hydration state, therefore influencing the balance between anabolism and catabolism in response to running exercise performed at typical training intensities.     

Aerobic exercise adaptations in trained adolescent runners following a season of cross-country training

Adaptations in aerobic exercise responses as well as the relationship between aerobic exercise responses and running performance were examined in a group of previously trained adolescent runners (n = 9; 15.9 +/- 1.0 years) over the course of a competitive cross-country season. Running economy (RE), submaximal blood lactate concentration [BLa] and VO2max were assessed before and immediately after the season. Five-km race time improved (P < 0.05) from 18.68 +/- 1.10 min at the beginning of the season to 18.16 +/- 1.11 min at the end of the season. Significant increases were observed in peak VO2 (61.6 +/- 3.5 to 65.3 +/- 2.9 mL x kg(-1) x min(-1)) and graded exercise test time (11.32 +/- 1.56 to 12.22 +/- 0.79 min). There was a tendency for RE (P = 0.051) to worsen slightly and for [BLa] (P = 0. 057) to decline as a result of training. At the beginning of the season submaximal [BLa] at 14 km x hr(-1) (r = 0.86) and graded exercise test time (r = -0.87) were significantly related to 5-km time. At the end of the season, RE (r = 0.78) and [BLa] (r = 0.77) at 14 km x hr(-1) and graded exercise test time (r = -0.69) were significantly related to race time. In this well-trained group of runners, further training during the cross-country season increased peak VO2 and improved race time. Submaximal [BLa] and graded exercise test time appear to be the most robust predictors of performance, while RE became a significant predictor of race time at the end of the season.     

Plasma beta-endorphin immunoreactivity during graded cycle ergometry

The present study was undertaken to define the response of plasma beta-endorphin immunoreactivity (ir-BE) to exercise of increasing intensity. Nineteen healthy males performed continuous exercise for 32 min on a cycle ergometer, comprised of 8-min bouts at %VO2max approximating 25, 50, and 75% of maximal exercise. Venous blood samples were collected before exercise (T = -20 and 0 min), during exercise (T = 8, 16, 24, and 32 min), and in recovery (T = +15, +30 min). Ir-BE in plasma was measured by radioimmunoassay using Immuno Nuclear assay kits. Plasma ir-BE level (pg X ml-1) was not altered from pre-exercise (18.3 +/- 1.3) after 8 min of exercise at 25 and 50% VO2max intensity; however, ir-BE rose significantly after 8 min of 75% VO2max work intensity (27.1 +/- 2.4) and was further elevated at maximal exercise (74.1 +/- 8.6). Ir-BE level remained elevated 15 min (60.9 +/- 8.1) and 30 min (35.2 +/- 5.2) post-exercise. The response pattern was further characterized by a significant (P less than 0.05) inter-individual variation, both at rest and during exercise; also, regression analysis indicated the ir-Be levels attained at maximal exercise were inversely related to the relative VO2max (ml X kg-1 X min-1) of the subject (predicted ir-BE = 248.2 - 3.39 VO2max; r = -0.397, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of pre-exercise cooling on high intensity running performance in the heat

The purpose of this study was to determine the effect of pre-exercise cooling on high intensity, moderate duration running performance and thermoregulatory responses in a hot environment (38 degrees C, 40 %RH). On separate days, 11 male subjects completed two treadmill runs to exhaustion at 100% of maximal aerobic power with (CL) and without (CT) pre-exercise cooling. Cooling consisted of 20 min of standing rest in a 22 degrees C environment with fan cooling (4.0 m x sec -1) and water spraying (50 ml x min -1) applied to both anterior and posterior body surfaces. Core temperature (T(c)) was determined with an esophageal T(es) probe, and skin temperatures (T(sk)) were measured using surface thermistors positioned at four sites. Finger prick blood samples were taken before and after exercise for the determination of blood lactate. Heart rates and ratings of thermal sensations and comfort were also recorded. Time to exhaustion was significantly shorter in the CL condition (368.9 +/- 56.2) compared to the CT condition (398.8 +/- 55.5 sec). Peak T(es) (37.51 +/- 0.57 vs. 38.56 +/- 0.30 degrees C for CL and CT, respectively), T(sk) (34.18 +/- 1.22 vs. 36.15 +/- 0.70 degrees C for CL and CT, respectively), rates of heat gain (0.20 +/- 0.05 vs. 0.28 +/- 0.05 degrees C x min -1 for CL and CT, respectively), and net heat storage (238.4 +/- 109.6 vs. 531.9 +/- 78.3 kJ for CL and CT, respectively) were all lower in the CL compared to CT throughout the treadmill runs. There were no differences in lactate accumulation between the two conditions. Based on these data, it can be concluded that pre-exercise cooling influences thermoregulatory responses during high intensity, moderate duration exercise; however, performance is impaired compared to a control trial in which no cooling procedures were employed.     

The effect of exercise intensity on serum lipoprotein responses

The purpose of this study was to determine the effect of exercise intensity on lipoprotein responses. Eleven normolipidemic male volunteers (X +/- SD = 23.1 +/- 2.4) participated in the study. The subjects were assessed for VO2max and ventilatory threshold (VT), matched for VO2max and then randomly assigned to one of two groups: Group A, which exercised for 12 minutes at an intensity 15% below VT (n = 5), and Group B, which exercised for 12 minutes at an intensity 15% above VT (n = 6). The lipoprotein measures HDL-C, LDL-C, total cholesterol (TC), and triglycerides (TG) were assessed from blood samples taken pre-exercise and immediately post-exercise as well as one, 24, and 48 hours post-exercise. A 2 X 5 split plot ANCOVA (controlling for pre-exercise values), revealed no significant differences between groups for HDL-C, TC or LDL-C. However, when means were collapsed across groups, TC levels measured immediately post-exercise were significantly higher than those taken 24 and 48 hours post-exercise (168.0, 159.1, and 159.9 mg.dl-1, respectively; p less than 0.05). A significant interaction was found for the TG measurements. For Group A, TG levels were elevated immediately post-exercise, but decreased significantly at the 1 and 24 hours post-exercise sampling, before returning to baseline levels at the 48 hour post-exercise measurement (93.2 +/- 3.1, 69.5 +/- 4.2, 66.8 +/- 6.7 and 99.5 +/- 2.1 mg.dl-1, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased fat availability enhances the capacity of trained individuals to perform prolonged exercise

METHODS: After a familiarization period, six well-trained males participated in a diet and exercise regimen lasting 9 d and comprising three cycling tests to exhaustion. A work rate was selected during the familiarization period that would result in fatigue after approximately 90-100 min at an ambient temperature of 10 degrees C (i.e., approximately 75% of VO2max). The first exercise test was a depletion trial and was preceded by a period during which the subjects' normal diet was consumed. A prescribed 70% carbohydrate (CHO) diet was then consumed for 3.5 d. After this diet, a second exercise test was performed; one of two isoenergetic experimental meals was consumed 4 h before this test (70% CHO meal, CHO trial; or 90% fat meal, fat trial). The second exercise test was followed by a further 3.5-d period on the high CHO diet. Four hours before the third test, subjects consumed the other meal. Heparin was administered intravenously 30 min (1000 U), 15 min (500 U), and 0 min (500 U) before exercise on the fat trial. Subjects were assigned to the two meals in randomized order. RESULTS: Time to exhaustion increased from 118.2 (12.4) min on the CHO trial to 127.9 (12.1) min on the fat trial (P = 0.001). Although no difference in VO2, RER, HR or RPE was found between trials, there was an earlier reduction in RER and an earlier rise in RPE on the fat trial. No difference in total CHO oxidation was found between trials (383 +/- 70 g on the CHO trial and 362 +/- 59 g on the fat trial). CONCLUSIONS: These results suggest that increasing fat availability immediately before exercise by acute fat feeding and heparin infusion can improve endurance exercise in a cool environment in well-trained individuals. This study was not intended to have immediate application to the sports performance field but rather to contribute to our understanding of the factors that may limit endurance performance. Heparin injection to elevate plasma fatty acid concentration would not represent sound medical practice.     

The effect of exercise performed before and 24 hours after blood withdrawal on serum erythropoietin and growth hormone concentrations in humans

In the present experiment we have studied the effect of exercise performed before and 24 h after withdrawal of 450 ml of blood on the serum erythropoietin and growth hormone (GH) levels, in humans. Twelve male subjects (x +/- SD) aged 23.2 +/- 2.6 y, with a body mass of 74.8 +/- 7.2 kg, height 178.0 +/- 7.6 cm, BMI 23.6 +/- 2.1 kg x m(-2), VO2 max 2937 +/- 324 ml x min(-1), participated in this study. The subjects performed twice an incremental exercise test until exhaustion, separated by a period of about 7 - 10 days. The second test was performed 24 h after withdrawal of 450 ml of blood (honorary blood donation). In the control study we found no effect of the incremental exercise on the serum erythropoietin concentration, which amounted to 14.24 +/- 7.66 mU x ml(-1) at rest and 14.97 +/- 6.07 mU x ml(-1) at the end of the incremental test. Serum GH level in the control study rose considerably from 0.158 +/- 0.024 nmol x l(-1) at rest to 1.523 +/- 0.336 nmol x l(-1) at the end of exercise and returned to initial value 2 h after the exercise. During the experiment performed 24 h after withdrawal of 450 ml of blood the serum erythropoietin concentration at rest was significantly elevated (p < 0.01) in relation to the control measurement (amounting to 24.85 +/- 13.60 mU x ml(-1)) and at the end of the incremental exercise a tendency towards further elevation (p = 0.09) in erythropoietin concentration up to 28.32 +/- 14.51 mU x m(-1) was observed. Serum GH level during the experiment after blood withdrawal was similar to that in control test and exercise caused a rise in the GH level to 1.056 +/- 0.52 nmol x l(-1), significantly less than in control test, but this increment fell to control value 2 h after exercise. The elevated level of erythropoietin 24 h after blood withdrawal was accompanied by a significant increase (p < 0.015) in blood hydrogen ion concentration [H +] b at rest from 48.2 +/- 2.8 nmol x l(-1) in the control study to 52.9 +/- 4.5 nmol x l(-1) after blood donation. No effect of blood withdrawal on pre-exercise level of plasma lactate concentration, end-tidal O2 and end-tidal CO2 was found. We concluded that withdrawal of 450 ml of blood, within 24 hours significantly increased serum erythropoietin concentration and caused non-lactic acidosis. A single bout of maximal incremental exercise, performed before and 24 hours after blood withdrawal, had no effect on serum erythropoietin concentration in humans but the exercise-induced increase in serum GH concentration performed after blood withdrawal tended to be lower than in the control study.     

Effects of strength training on running economy

The objective of this study was to compare the effect of different strength training protocols added to endurance training on running economy (RE). Sixteen well-trained runners (27.4 +/- 4.4 years; 62.7 +/- 4.3 kg; 166.1 +/- 5.0 cm), were randomized into two groups: explosive strength training (EST) (n = 9) and heavy weight strength training (HWT) (n = 7) group. They performed the following tests before and after 4 weeks of training: 1) incremental treadmill test to exhaustion to determine of peak oxygen uptake and the velocity corresponding to 3.5 mM of blood lactate concentration; 2) submaximal constant-intensity test to determine RE; 3) maximal countermovement jump test and; 4) one repetition maximal strength test in leg press. After the training period, there was an improvement in RE only in the HWT group (HWT = 47.3 +/- 6.8 vs. 44.3 +/- 4.9 ml . kg (-1) . min (-1); EST = 46.4 +/- 4.1 vs. 45.5 +/- 4.1 ml . kg (-1) . min (-1)). In conclusion, a short period of traditional strength training can improve RE in well-trained runners, but this improvement can be dependent on the strength training characteristics. When comparing to explosive training performed in the same equipment, heavy weight training seems to be more efficient for the improvement of RE.     

Exercise thermoregulation in men after 1 and 24-hours of 6 degrees head-down tilt

BACKGROUND: Exercise thermoregulation is dependent on heat loss by increased skin blood flow (convective and conductive heat loss) and through enhanced sweating (evaporative heat loss). Reduction of plasma volume (PV), increased plasma osmolality, physical deconditioning, and duration of exposure to simulated and actual microgravity reduces the ability to thermoregulate during exercise. HYPOTHESIS: We hypothesized that 24 h of head down tilt (HDT24) would alter thermoregulatory responses to a submaximal exercise test and result in a higher exercise rectal temperature (Tre) when compared with exercise Tre after 1 h of head down tilt (HDT1). METHODS: Seven men (31+/-SD 6 yr, peak oxygen uptake (VpO2peak) of 44+/-6 ml x kg(-1) x min(-1)) were studied during 70 min of supine cycling at 58+/-SE 1.5% VO2peak at 22.0 degrees C Tdb and 47% rh. RESULTS: Relative to pre-tilt sitting chair rest data, HDT1 resulted in a 6.1+/-0.9% increase and HDT24 in a 4.3+/-2.3% decrease in PV (delta = 10.4% between experiments, p<0.05) while plasma osmolality remained unchanged (NS). Pre-exercise Tre was elevated after HDT24 (36.71 degrees C +/-0.06 HDT1 vs. 36.93 degrees C+/-0.11 HDT24, p<0.05). The 70 min of exercise did not alter this relationship (p<0.05) with respective end exercise increases in Tre to 38.01 degrees C and 38.26 degrees C (degrees = 1.30 degrees C (HDT1) and 1.33 degrees C (HDT24)). While there were no pre-exercise differences in mean skin temperature (Tsk), a significant (p<0.05) time x treatment interaction occurred during exercise: after min 30 in HDT24 the Tsk leveled off at 31.1 degrees C, while it continued to increase reaching 31.5 degrees C at min 70 in HDT1. A similar response (NS) occurred in skin blood velocity. Neither local sweating rates nor changes in body weight during exercise of -1.63+/-0.24 kg (HDT1) or - 1.33+/-0.09 kg (HDT24) were different (NS) between experiments. CONCLUSION: While HDT24 resulted in elevated pre-exercise Tre, reduced PV, attenuation of Tsk and skin blood velocity during exercise, the absolute increase in exercise Tre was not altered. But if sweat rate and cutaneous vascular responses were similar at different core temperatures (unchanged thermoregulation), the Tre offset could have been caused by the HDT-induced hypovolemia.     

Effect of pre-exercise carbohydrate feedings on endurance cycling performance

Six men were studied to compare the effects of pre-exercise carbohydrate feedings on endurance performance and muscle glycogen utilization during prolonged exercise. Trials consisted of a cycling ride to exhaustion at 75% maximal oxygen uptake preceded by the ingestion of either 75 g of glucose in 350 ml of water (GLU), 75 g of fructose in 350 ml of water (FRU), or 350 ml of an artificially sweetened and flavored placebo (CON). No differences were observed between trials for oxygen uptake, respiratory exchange ratio, heart rate, or exercise time to exhaustion (CON = 92.7 +/- 5.2 min, FRU = 90.6 +/- 12.4, and GLU = 92.8 +/- 11.3, mean +/- SE). Blood glucose was elevated as a result of the GLU feeding, but fell rapidly with the onset of exercise, reaching a low of 4.02 +/- 0.34 mmol X l-1 at 15 min of exercise. Serum insulin also increased following the GLU feeding but had returned to pre-drink levels by 30 min of exercise. No differences in blood glucose and insulin were observed between FRU and CON. Muscle glycogen utilization during the first 30 min of exercise (CON = 46.3 +/- 8.2 mmol X kg-1 wet weight, FRU = 56.3 +/- 3.0 mmol X kg-1 wet weight, GLU = 50.0 +/- 4.9 mmol X kg-1 wet weight) and total glycogen use (CON = 93.4 +/- 11.1, FRU = 118.8 +/- 10.9, and GLU = 99.5 +/- 4.3) were similar in the three trials.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of exercise mode on muscle glycogen restorage during repeated days of exercise

The purpose of this study was to examine differences in muscle glycogen storage during three successive days of running or cycling. In a crossover design, seven male subjects performed two 3-d trials of either running (trial R) or cycling (trial C) for 60 min at 75% VO2max. Biopsy samples were obtained before and after each day's exercise from the gastrocnemius (trial R) or vastus lateralis (trial C) muscle. Diets in the 2 d preceding and during each trial contained 5 g carbohydrate.kg-1.d-1 and 14,475 +/- 402 kJ.d-1. Mean pre-exercise glycogen content (mmol.kg-1 wet wt.) was significantly reduced in both trials on day 3 (103.4 +/- 6.0) when compared to day 1 and day 2 (119.9 +/- 6.8 and 116.4 +/- 5.7, respectively). Day 1 glycogen reduction was significantly greater in trial C (P less than 0.03), and glycogen restorage was greater (P less than 0.02) only in trial C between the 1st and 2nd d. On day 3, spectrophotometric analysis of PAS strains showed that pre-exercise glycogen content in either muscle group was significantly (P less than 0.01) less in Type I as compared to Type II fibers. This difference in fiber glycogen storage did not appear to be attributable to muscle damage as negligible leukocyte infiltration and low blood CK levels were obtained. No difference between modes were observed for CK values throughout the trials. These data suggest that the depressed glycogen storage before the 3rd d of exercise was due to the moderate carbohydrate intake.     

Sampling time is crucial for measurement of aerobic exercise-induced oxidative stress

PURPOSE: To thoroughly investigate the time-course changes of several commonly used markers of oxidative stress by performing serial measurements during a 24-h period after an acute bout of strenuous cardiovascular exercise. METHODS: Eleven untrained men performed two trials. In the experimental trial, the subjects exercised for 45 min at 70-75% VO2max and then at 90% VO2max to exhaustion on a treadmill; in the control trial, the subjects remained at rest. Blood samples were drawn before and after exercise (immediately after exercise and at 0.5, 1, 2, 3, 4, 5, 6, 8, 10, and 24 h). Reduced glutathione (GSH), oxidized glutathione (GSSG), GSH/GSSG, thiobarbituric acid-reactive substances (TBARS), protein carbonyls, catalase activity, and total antioxidant capacity (TAC) were determined. RESULTS: The time to lowest concentration after exercise was 1.7 +/- 0.7 h (mean +/- SD) for GSH/GSSG, and the time to highest concentration after exercise was 1.2 +/- 0.6 h for TBARS, 4.4 +/- 0.5 h for protein carbonyls, 0.5 +/- 0.4h for catalase, and 2.2 +/- 0.9 h for TAC. The greatest change after exercise was -74 +/- 9% for GSH/GSSG, 129 +/- 29% for TBARS, 135 +/- 53% for protein carbonyls, 51 +/- 16% for catalase, and 24 +/- 10% for TAC. CONCLUSION: There is no best time point applying to all markers for collecting blood samples after aerobic exercise. The optimum postexercise time points for blood collection in untrained individuals are immediately after exercise for catalase, 1 h for TBARS, 2 h for TAC, GSH, and GSSG, and 4 h after exercise for protein carbonyls.     

Influence of high and low glycemic index meals on endurance running capacity

PURPOSE: The purpose of this study was to examine the effect of high and low glycemic index (GI) carbohydrate (CHO) pre-exercise meals on endurance running capacity. METHODS: Eight active subjects (five male and three female) ran on a treadmill at approximately 70% VO2max to exhaustion on two occasions separated by 7 d. Three hours before the run after an overnight fast, each subject was given in a single-blind, random order, isoenergetic meal of 850+/-21 kcal (mean+/-SEM; 67% carbohydrate, 30% protein, and 3% fat) containing either high (HGI) or low (LGI) GI carbohydrate foods providing 2.0 g CHO.kg(-1) body weight. RESULTS: Ingestion of the HGI meal resulted in a 580% and 330% greater incremental area under the 3-h blood glucose and serum insulin response curves, respectively. Performance times were not different between the HGI and LGI trials (113+/-4 min and 111+/-5 min, respectively). During the first 80 min of exercise in the LGI trial, CHO oxidation was 12% lower and fat oxidation was 118% higher than in the HGI trial. Although serum insulin concentrations did not differ between trials, blood glucose at 20 min into exercise in the HGI trial was lower than that during the LGI trial at the same time (3.6+/-0.3 mmol.L(-1) vs 4.3+/-0.3 mmol.L(-1); P < 0.05). During exercise, plasma glycerol and serum free fatty acid concentrations were lower in the HGI trial than in the LGI trial. CONCLUSIONS: This results demonstrate that although there is a relative shift in substrate utilization from CHO to fat when a low GI meal is ingested before exercise compared with that for a high GI meal, there is no difference in endurance running capacity.     

The influence of pre-exercise glucose ingestion on endurance running capacity.

Drinking a concentrated glucose solution less than 1 h before the start of prolonged submaximal exercise has been reported to reduce endurance capacity during cycling. The purpose of this study was to re-examine the influence of pre-exercise ingestion of a concentrated glucose solution on endurance running capacity. Nine recreational runners (five men and four women) ran to exhaustion on a level treadmill, at speeds equivalent to 70% VO2max, on two occasions separated by at least 1 week. The runners ingested either a solution containing 75 g of glucose in 300 ml of water (G trial), or 300 ml of sweetened water (P trial) 30 min before each trial. As a consequence, the blood glucose concentrations were 55% higher at the beginning of the G trial compared with those recorded for the P trial (G trial, mean(s.e.) blood glucose = 6.3(0.7) mmol l-1 versus P trial, mean(s.e.) blood glucose = 4.1(0.3) mmol l-1; P < 0.01). Nevertheless, there were no differences in the running times to exhaustion between the two trials (G trial, mean(s.e.) 133.79(11.0) min versus P trial, mean(s.e.) 121.16(8.1) min). The results of this study show that ingesting a 25% glucose solution 30 min before exercise does not reduce the endurance capacity of recreational runners when the exercise intensity is equivalent to 70% VO2max.     

Effect of exercise and fluid consumption on salivary flow and pH

Recent claims have been made regarding the putative erosive effects of regularly ingesting low-pH beverages on the integrity of tooth enamel. The purpose of this study was to determine whether fluid consumption during exercise affects the body's defenses against enamel erosion: saliva flow and salivary pH. Males and females (n=50) exercised in the heat (26.7 degrees C, 40 % RH) for 75 min on four occasions. Within each session, subjects consumed ad-lib either water, a sports drink (Gatorade), diluted orange juice, or a homemade sports drink, with the latter three fluids all having low pH values (3.0 to 4.0). Prior to and following exercise, subjects performed a standard stimulated saliva collection procedure. Immediately following collection, saliva flow rate and pH were determined for each sample. Repeated-measures ANOVA were used to evaluate the data. Compared to pre-exercise salivary flow rates (2.6+/- 0.8 ml/min), the post-exercise rate was not different when consuming the sports drink (2.6+/- 0.9 ml/min), but decreased when water or the homemade sports drink was ingested (2.4+/- 0.9 ml/min; p<0.05). A time-by-drink interaction (p<0.05) revealed slight differences in saliva pH after exercise, depending on the beverage consumed; post-exercise saliva pH was highest for water (7.2+/- 0.2) and lowest for the homemade sports drink (7.1+/- 0.2), with the sports drink and diluted orange juice values falling in between. The results suggest that minimal changes occur in saliva pH and the rate of stimulated saliva flow with beverage consumption during exercise. Subsequent research is needed to determine whether maintenance of saliva production by drinking beverages during exercise influences the body's defenses against dental erosion via saliva production.     

Effects of repeated bouts of soccer-specific intermittent exercise on salivary IgA

Failure to recover fully between sessions has been suggested to cause immunodepression. Therefore, the cumulative effects of soccer-specific intermittent exercise undertaken on different days 48 h apart on salivary IgA, cortisol and total protein concentration were investigated. Nine male subjects completed two trials of soccer-specific intermittent exercise 48 h apart on a motorised treadmill. Timed unstimulated saliva samples were collected immediately before and after exercise, and 24 and 48 h post-exercise. Salivary IgA concentration (EX (1): 215 +/- 160 to 335 +/- 246 and EX (2): 144 +/- 93 to 271 +/- 185 mg . l (-1), p = 0.007), osmolality (p = 0.001) and total protein (p = 0.001) increased immediately following exercise in both trials and decreased 24 h afterwards, whereas saliva flow rate decreased significantly (p = 0.015) before returning to pre-exercise values 24 h postexercise. The IgA secretion rate, IgA to osmolality ratio, IgA to total protein, solute secretion rate, total protein secretion rate, and cortisol did not differ between the time-points. The results suggest that performing two bouts of moderate intensity soccer-specific intermittent exercise 48 h apart does not suppress resting salivary IgA concentration significantly although a small progressive reduction in salivary IgA was observed. These findings may not extend to successive competitive soccer games when vulnerable players might experience clinically relevant reductions in s-IgA.     

Effect of branched-chain amino acids (BCAA), glucose, and glucose plus BCAA on endurance performance in rats

PURPOSE: The purpose of this study was to assess the effects of pre-exercise administration of branched-chain amino acids (BCAA), glucose, and glucose plus BCAA on time to exhaustion during treadmill exercise in rats. METHODS: Wistar rats were injected intraperitoneally with 1 mL of saline (0.9% NaCl), BCAA (30 mg), glucose (100 mg), or glucose plus BCAA 5 min before either 45 min of submaximal exercise (N = 32) or running to exhaustion (N = 24). After the submaximal exercise test, blood was collected for the measurement of ammonia, BCAA, free tryptophan (free TRP), glucose, free fatty acid, and lactic acid, and muscle samples were taken from the m. soleus for determination of glycogen content. RESULTS: Mean run time to exhaustion was significantly longer after BCAA administration (158+/-26 min) compared with that after saline (118+/-35 min)(P<0.05) but not compared with that after glucose administration (179+/-21 min). When glucose is administered before exercise, the supplementary administration of BCAA had no additional effect on performance (171+/-12 min). The data on blood ammonia, ratio of free TRP/BCAA, and muscle glycogen did not provide a clue for explaining the higher endurance performance after BCAA supplementation. CONCLUSION: The results support the hypothesis that the effect of BCAA administration on performance could be related to carbohydrate availability during exercise.     

Value of a radionuclide limb blood flow technique in the assessment of percutaneous balloon and dynamic angioplasty.

In a prospective study, a radionuclide technique was used to evaluate the limb blood flow (LBF) changes in 30 patients undergoing dynamic (n = 15) or balloon (n = 15) angioplasty for arterial occlusions or stenoses, respectively. The results were compared with Doppler Ankle Brachial Index (DABI) and treadmill exercise tests. Whilst LBF values (ml of blood flow per 100 ml of limb volume per min) were significantly lower in limbs with arterial occlusion than stenosis (4.5 +/- 0.46 and 6.4 +/- 0.74, respectively; P less than 0.05). DABI provided no discrimination. Immediately after balloon angioplasty, there was a fall in DABI, from 0.60 +/- 0.05 to 0.47 +/- 0.04 (P less than 0.05), which rose 24 h later to 0.73 +/- 0.02 (P less than 0.01). Following dynamic angioplasty, DABI improved from 0.60 +/- 0.05 to 0.66 +/- 0.02 (P less than 0.05). At 3 weeks, the LBF improved from 4.6 +/- 0.66 to 11.1 +/- 0.53 (P less than 0.001) following dynamic angioplasty and from 6.2 +/- 0.68 to 8.53 +/- 0.81 (P less than 0.001) following balloon angioplasty. "Normal" LBF (greater than 10 ml/100 ml per min) was achieved in 80% of patients who underwent successful dynamic angioplasty but in only 36% of the balloon group (P less than 0.05, chi 2-test). Reproducibility of repeated LBF measurements in control limbs was superior to that of DABI. This was indicated by a lower coefficient of variation, 13.8% compared with 25.2%, and a higher correlation coefficient, r = 0.79 compared with 0.27. Treadmill exercise tests were invalid or impossible in 30% of all occasions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of carbohydrate on portal vein blood flow during exercise

Effects of carbohydrate ingestion and exercise on portal vein blood flow were studied. Flow was measured by pulsed-electronic Doppler. Eight male subjects performed four tests after a standardised breakfast and 5 h fast. Beverages were CHO (10 % glucose, 30 mmol . l (-1) NaCl) and W (water, 30 mmol . l (-1) NaCl). Exercise experiments comprised a resting measurement, 10 min warm-up and 60 min 70 % VO(2)max cycling. Every 10 min subjects stopped cycling briefly (approximately 30 s) for measurements. Beverage was consumed after warm-up (500 ml) and at 20 and 40 min (250 ml). Similar tests were done at rest. Blood samples were taken concurrently with flow measurements for hormonal concentrations. Exercise decreased blood flow (repeated measures ANOVA, p < 0.0001) and carbohydrate ingestion increased flow (p = 0.015). At rest, flow was greater with CHO than with W at 20 (177 +/- 31; 101 +/- 25 %, resp.) (mean +/- SE), 30 (209 +/- 37; 120 +/- 20 %), 40 (188 +/- 32; 108 +/- 12 %), and 60 min (195 +/- 19; 112 +/- 12 %) (1-way ANOVA, Fisher's PLSD, p < 0.05). Flow was similar during exercise with CHO and W, with a tendency for CHO to maintain flow better, at 10 (124 +/- 27; 77 +/- 21 %), 20 (81 +/- 10; 60 +/- 13 %), 30 (106 +/- 26; 56 +/- 10 %), 40 (109 +/- 28; 54 +/- 8 %), 50 (85 +/- 17; 54 +/- 13 %), and 60 min (61 +/- 15; 47 +/- 7 %). A positive correlation between glucagon and flow and an inverse correlation between noradrenaline and flow were observed. Exercise reduces, and carbohydrate increases, portal vein flow. Changes in plasma concentrations suggest that noradrenaline and glucagon, respectively, may play a role in modulating flow.