CON Trial Research Articles

Energy replacement using glucose does not increase postprandial lipemia after moderate intensity exercise.

BackgroundAerobic exercise can decrease postprandial triglyceride (TG) concentrations but the relationship between exercise-induced energy deficits and postprandial lipemia is still unclear. The aim of the present study was to examine the effect of a single bout of aerobic exercise, with and without energy replacement, on postprandial lipemia and on peripheral blood mononuclear cell (PBMC) mRNA expression of very low density lipoprotein (VLDL) and low density lipoprotein (LDL) receptors and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR).MethodsNine healthy male humans completed three two-day trials in a random order. On day 1, volunteers rested (CON), completed 60 minutes of treadmill walking at 50% of VO2peak (EX) or completed the same bout of walking but with the energy replaced afterwards with a glucose solution (EXG). On day 2, volunteers rested and consumed a high fat test meal in the morning.ResultsTotal and incremental TG AUC were significantly lower on the EXG (P < 0.05) and EX (P < 0.05) trials than the CON trial with no difference between the two exercise trials. No significant difference was observed in VLDL or LDL receptor mRNA expression among the trials (P > 0.05).ConclusionsIn conclusion, energy replacement by glucose did not affect the decrease in postprandial TG concentrations observed after moderate intensity exercise and exercise does not affect changes in PBMC HMGCR, VLDL and LDL receptor mRNA expression.

Lower-leg compression, running mechanics, and economy in trained distance runners.

The efficacy of and mechanisms behind the widespread use of lower-leg compression as an ergogenic aid to improve running performance are unknown. The purpose of this study was to examine whether wearing graduated lower-leg compression sleeves during exercise evokes changes in running economy (RE), perhaps due to altered gait mechanics. Sixteen highly trained male distance runners completed 2 separate RE tests during a single laboratory session, including a randomized-treatment trial of graduated calf-compression sleeves (CS; 15-20 mm Hg) and a control trial (CON) without compression sleeves. RE was determined by measuring oxygen consumption at 3 constant submaximal speeds of 233, 268, and 300 m/min on a treadmill. Running mechanics were measured during the last 30 s of each 4-min stage of the RE test via wireless triaxial 10-g accelerometer devices attached to the top of each shoe. Ground-contact time, swing time, step frequency, and step length were determined from accelerometric output corresponding to foot-strike and toe-off events. Gait variability was calculated as the standard deviation of a given gait variable for an individual during the last 30 s of each stage. There were no differences in VO2 or kinematic variables between CON and CS trials at any of the speeds. Wearing lower-leg compression does not alter the energetics of running at submaximal speeds through changes in running mechanics or other means. However, it appears that the individual response to wearing lower-leg compression varies greatly and warrants further examination.

Effects of Ramadan fasting on substrate oxidation, physiological and perceptual responses during submaximal intensity running in active men

This study examines the effects of Ramadan fasting on various psycho-physiological measures during submaximal exercise, under real-world ecologically valid conditions. Eleven Muslim men performed a 30-min continuous running on a treadmill at intensity 65 % VO2max in the Ramadan fasted (RAM) and non-fasted (or Control, CON) state, on two separate occasions in a crossover and counter-balanced order. The amount of calories and fluid volume intake of participants’ last pre-exercise main meal, i.e., ~3–4 h prior to CON and ~10–12 h prior to RAM trial, were standardized. To simulate real world scenario, their 24 h pre-trial sleep hours and pattern were typical of the Ramadan and non-Ramadan period. There was no significant difference in total training load for the week prior to the RAM and CON exercise trials. Results showed no differences between RAM and CON trial for both carbohydrate and fat oxidation rate (both p > 0.05; effects size (d) = small and trivial, respectively). Blood glucose in RAM trial was lower at pre-exercise and higher at post-exercise than CON trial (both p 0.05; d = trivial). Heart rate throughout run (p = 0.03) and ratings of perceived exertion (p = 0.03, d = small) were higher in RAM. In conclusion, Ramadan fasting has no major impact on substrate utilization and is not an effective ‘fat-burning’ enhancing activity to lose fat mass. Running in the Ramadan fasted state led to a greater psycho-physiological stress compared to the same run in the non-fasted state.

Arterial compliance and stiffness following low-intensity resistance exercise

Although acute high-intensity resistance exercise to exhaustion decreases arterial compliance and increases arterial stiffness, the effect of low-intensity resistance exercise (LRE) to exhaustion on arterial compliance and stiffness remains unknown. The present study investigated the acute effects of LRE on arterial compliance and stiffness. Ten healthy individuals (age 26 ± 5 years) performed LRE (40% of 1 repetition maximum) and control (CON: seated rest in the exercise room) trials on separate days in a randomized controlled crossover fashion. The LRE comprised three sets of bench presses to exhaustion with an inter-set rest period of 2 min. In the CON trial, LRE was not performed. Carotid arterial compliance, the β-stiffness index (via simultaneous B-mode ultrasound and applanation tonometry), carotid and brachial blood pressure and heart rate were measured before and at 30 and 60 min after both trials. Carotid arterial compliance and the β-stiffness index significantly increased and decreased, respectively (both P < 0.05), at 30 and 60 min after the LRE trials, but neither significantly differed after the CON trials. Carotid and brachial blood pressure and heart rate did not change at 30 and 60 min after both trials from baseline. These results suggest that LRE acutely increases arterial compliance and decreases arterial stiffness.

The effects of lower-body compression garments on recovery between exercise bouts in highly-trained cyclists

The use of compression garments as a recovery strategy has become popular amongst athletes. The aim of the current study was to investigate the effect of lower-body compression garments on recovery between two cycling bouts. Ten highly-trained cyclists (mean ± SD; age = 31 ± 6 years; height = 181 ± 6 cm; mass = 75.9 ± 5.9 kg; VO2peak = 66.6 ± 3.8 mL.kg.-1min.-1) performed two 30-minute cycling bouts (15-minutes at a fixed power output, 15-minute time-trial) on a cycle ergometer, separated by a 60-minute passive recovery period where either lower-body compression garments (LBCG) or loose-fitting shorts (CON) were worn. Subject’s performed both trials in a randomized, crossover design separated by three days. Blood lactate, leg girths and perceived soreness was measured throughout the recovery period. Results indicated a small but significant improvement (P < 0.05) in recovery as evidenced by the maintenance of power output in the second exercise bout in the LBCG trial when compared to the CON trial (-0.20% and -2.15%, respectively. Effect Size (ES); 0.22). LBCG were also associated with significant reductions in limb girths and blood lactate concentration when compared to CON. While not statistically significant, there was a moderate effect on perceived soreness in the LBCG trial (ES; -0.62). We would suggest that lower-body compression garments enhance recovery between cycling bouts and improve subsequent performance.

Acute effect of brisk walking with graduated compression stockings on vascular endothelial function and oxidative stress

The purpose of this study was to investigate the acute effect of brisk walking with and without graduated compression stockings (GCSs) on vascular endothelial function and oxidative stress. Ten young healthy subjects walked briskly for 30min with (GCS trial) and without (CON trial) GCSs in a randomized crossover trial. Brachial artery flow-mediated dilation (FMD) was measured as the per cent rise in the peak diameter from the baseline value at prior occlusion at each FMD measurement using B-mode ultrasonography before and 30min after walking in the two trials. Derivatives of reactive oxygen metabolites (d-ROM), as an index of products of reactive oxygen species, and biological anti-oxidant potential (BAP), as an index of anti-oxidant potential, were also measured using a free radical elective evaluator before and 30min after walking in both trials. FMD significantly decreased after brisk walking in both trials (P<0·05). However, FMD after brisk walking in the GCS trial was significantly higher than that in the CON trial (P<0·05). The d-ROM did not change before and after both trials, whereas the BAP significantly increased after walking in the GCS trial (P<0·05). These findings demonstrate that brisk walking while wearing GCSs suppresses the decrease in FMD and increases BAP.

Ingestion of sodium plus water improves cardiovascular function and performance during dehydrating cycling in the heat

We studied if salt and water ingestion alleviates the physiological strain caused by dehydrating exercise in the heat. Ten trained male cyclists (VO2max : 60 ± 7 mL/kg/min) completed three randomized trials in a hot-dry environment (33 °C, 30% rh, 2.5 m/s airflow). Ninety minutes before the exercise, participants ingested 10 mL of water/kg body mass either alone (CON trial) or with salt to result in concentrations of 82 or 164 mM Na(+) (ModNa(+) or HighNa(+) trial, respectively). Then, participants cycled at 63% of VO2 m ⁢ a x for 120 min immediately followed by a time-trial. After 120 min of exercise, the reduction in plasma volume was lessened with ModNa(+) and HighNa(+) trials (-11.9 ± 2.1 and -9.8 ± 4.2%) in comparison with CON (-16.4 ± 3.2%; P < 0.05). However, heat accumulation or dissipation (forearm skin blood flow and sweat rate) were not improved by salt ingestion. In contrast, both salt trials maintained cardiac output (∼ 1.3 ± 1.4 L/min; P < 0.05) and stroke volume (∼ 10 ± 11 mL/beat; P < 0.05) above CON after 120 min of exercise. Furthermore, the salt trials equally improved time-trial performance by 7.4% above CON (∼ 289 ± 42 vs 269 ± 50 W, respectively; P < 0.05). Our data suggest that pre-exercise ingestion of salt plus water maintains higher plasma volume during dehydrating exercise in the heat without thermoregulatory effects. However, it maintains cardiovascular function and improves cycling performance.

Acute changes in glycemic homeostasis in response to brief high-intensity intermittent exercise in obese adults

This study investigated the acute changes in glycemic homeostasis in response to brief, high-intensity, intermittent exercise in obese adults. Ten obese adults (age: 25.3±5.1 years; body mass index: 32.0±4.0) volunteered to participate in the study. The time-course changes in blood glucose in response to a 75-g oral glucose tolerance test were examined following: high-intensity intermittent exercise (HIE) of four 30-second all-out cycling efforts interspersed with 4-minute active recovery periods; 24 hours of recovery post-HIE (REC); and no treatment (control, CON). Blood glucose in each trial was measured before, and 30, 60, 90, and 120 minutes after glucose intake (GI). Blood glucose (mmol/L) at 30 minutes post-GI in the HIE (6.9±0.4) trial was significantly lower (p<0.05) than the corresponding values of the CON (9.0±0.4) and REC (8.8±0.4) trials. Blood glucose concentration at 120 minutes post-GI in the REC (5.7±0.3) trial was also significantly lower (p<0.05) than the corresponding value of the CON (6.9±0.4) trial. When blood glucose values were plotted against corresponding time points, the area under the curve (mmol/L/minute) of the CON (890±43) trial was significantly greater (p<0.05) than that of the HIE (834±40) and REC (846±32) trials. The HIE and REC conditions were not significantly different (p>0.05). This study demonstrated the improvement in glycemic homeostasis in obese adults immediately after brief, high-intensity, intermittent exercise. These effects were maintained for at least 24 hours postexercise. The findings may be useful in the development of time-efficient lifestyle intervention strategies for improving obesity-related risk factors for diabetes.

Acute tryptophan depletion does not improve endurance cycling capacity in a warm environment

Newsholme's theory of central fatigue suggests that acute tryptophan depletion should improve endurance exercise capacity in a warm environment by reducing serotonergic activity in the brain. Eight males cycled to volitional exhaustion at 55 % VO(2) peak in 30.1 ± 0.5 °C and 30 ± 7 % relative humidity on two separate occasions, after consuming either an amino acid load to deplete their circulating tryptophan concentration (TD), or a control amino acid load (CON). Blood samples were taken before ingesting the amino acids, before the start of exercise, every 15 min during exercise and at the point of exhaustion. Heart rate (HR), core (Tc) and skin (Tsk) temperatures and ratings of perceived exertion (RPE) and thermal comfort (TC) were also monitored every 10 min during exercise. Plasma tryptophan (P = 0.003) and free tryptophan (P < 0.001) concentrations, and the free tryptophan to branched-chain amino acid ratio (P = 0.004) were all lower on the TD trial than on the CON trial. There was no difference in endurance exercise capacity (TD 99.2 ± 24.4 min as compared to CON 108.4 ± 21.6 min; P = 0.088). There was a tendency for HR (P = 0.053) and Tc (P = 0.069) to be higher on the TD trials. There were no differences for any of the other parameters. Endurance cycling capacity in a warm environment is not improved by acute tryptophan depletion, suggesting tryptophan availability is not a significant factor in the development of fatigue in such situations.

Effects of exercise before or after meal ingestion on fat balance and postprandial metabolism in overweight men

It is unclear how timing of exercise relative to meal ingestion influences substrate balance and metabolic responses. The present study aimed to compare the effects of exercise performed before or after breakfast on fat balance and postprandial metabolism. A total of ten sedentary overweight men (aged 28.1 (SEM 10.7) years, BMI 29.0 (SEM 2.8) kg/m2) underwent three trials in random order involving: (1) performing no exercise (CON), or walking for 60 min at 50% maximal O2 uptake either (2) before (Ex-Meal) or (3) after (Meal-Ex) consuming a standardised breakfast meal. In each trial an ad libitum lunch was provided 3.5 h after breakfast. Substrate utilisation was assessed by indirect calorimetry and blood was taken at regular intervals over an 8.5 h observation period. At the end of the observation period, fat balances in the Ex-Meal (-1043 (SEM 270) kJ) and Meal-Ex (-697 (SEM 201) kJ) trials were both significantly lower than CON (204 (SEM 165) kJ) and fat balance in the Ex-Meal trial was significantly lower than in the Meal-Ex trial (all P , 0.0001). Compared with the CON trial, the 8.5 h postprandial TAG response was only significantly lowered in the Ex-Meal trial (-17%, P = 0.025) and not in the Meal-Ex trial (-11%, P < 0.20). Both the Ex-Meal and Meal-Ex trials showed significantly lowered insulin responses relative to the CON trial (by 19 and 24%, respectively, P < 0.01 for both). There were no differences in lunch energy intake between trials. The present findings suggest that there may be an advantage for body fat regulation and lipid metabolism in exercising before compared with after breakfast. However, further study is needed to determine whether the present findings extend over the long term under free-living conditions.

Exercise Stress Testing in Asymptomatic People with Type 2 Diabetes Referred to Exercise Programs: a Retrospective Data Linkage Study

s / Can J Diabetes 36 (2012) S2eS22 S15 7.1 1.1%, aged 31.8 15.8 years) either rested for 45 minutes, ran on a treadmill for 45 minutes (60% VO2peak), or performed 45 minutes of weight lifting (3 sets of 8 repetitions of seven different exercises at the participants’ 8-repetition maximum) while wearing a Medtronic CGM System Gold monitor. Blood samples were collected at regular intervals for determination of plasma glucose. Data are presented as mean SD. Sensor values generally underestimated plasma glucose both during both exercise modalities and at rest. Mean underestimation was greatest during the CON trial with -14.1 13.2% difference from plasma values (p<0.001). A mean difference of -8.6 17.1% was calculated for RES (p<0.001). No differences were found between the sensor and the plasma glucose levels during AER (mean difference -1.91 30.6%, p1⁄40.445). These data indicate that sensor accuracy is not impaired during either type of exercise. Improved blood flow-mediated equilibration between plasma and interstitial fluid may partially explain improved sensor accuracy during exercise, especially during aerobic exercise.

Resistance Exercise in Already-active Type 1 Diabetic Individuals: The READI Trial

s / Can J Diabetes 36 (2012) S2eS22 S15 7.1 1.1%, aged 31.8 15.8 years) either rested for 45 minutes, ran on a treadmill for 45 minutes (60% VO2peak), or performed 45 minutes of weight lifting (3 sets of 8 repetitions of seven different exercises at the participants’ 8-repetition maximum) while wearing a Medtronic CGM System Gold monitor. Blood samples were collected at regular intervals for determination of plasma glucose. Data are presented as mean SD. Sensor values generally underestimated plasma glucose both during both exercise modalities and at rest. Mean underestimation was greatest during the CON trial with -14.1 13.2% difference from plasma values (p<0.001). A mean difference of -8.6 17.1% was calculated for RES (p<0.001). No differences were found between the sensor and the plasma glucose levels during AER (mean difference -1.91 30.6%, p1⁄40.445). These data indicate that sensor accuracy is not impaired during either type of exercise. Improved blood flow-mediated equilibration between plasma and interstitial fluid may partially explain improved sensor accuracy during exercise, especially during aerobic exercise.

Dehydration decreases saliva antimicrobial proteins important for mucosal immunity

The aim of the study was to investigate the effect of exercise-induced dehydration and subsequent overnight fluid restriction on saliva antimicrobial proteins important for host defence (secretory IgA (SIgA), α-amylase, and lysozyme). On two randomized occasions, 13 participants exercised in the heat, either without fluid intake to evoke progressive body mass losses (BML) of 1%, 2%, and 3% with subsequent overnight fluid restriction until 0800 h in the following morning (DEH) or with fluids to offset losses (CON). Participants in the DEH trial rehydrated from 0800 h until 1100 h on day 2. BML, plasma osmolality (Posm), and urine specific gravity (USG) were assessed as hydration indices. Unstimulated saliva samples were assessed for flow rate (SFR), SIgA, α-amylase, and lysozyme concentrations. Posm and USG increased during dehydration and remained elevated after overnight fluid restriction (BML = 3.5% ± 0.3%, Posm = 297 ± 6 mosmol·kg⁻¹, and USG = 1.026 ± 0.002; P < 0.001). Dehydration decreased SFR (67% at 3% BML, 70% at 0800 h; P < 0.01) and increased SIgA concentration, with no effect on SIgA secretion rate. SFR and SIgA responses remained unchanged in the CON trial. Dehydration did not affect α-amylase or lysozyme concentration but decreased secretion rates of α-amylase (44% at 3% BML, 78% at 0800 h; P < 0.01) and lysozyme (46% at 3% BML, 61% at 0800 h; P < 0.01), which were lower than in CON at these time points (P < 0.05). Rehydration returned all saliva variables to baseline. In conclusion, modest dehydration (~3% BML) decreased SFR, α-amylase, and lysozyme secretion rates. Whether the observed magnitude of decrease in saliva AMPs during dehydration compromises host defence remains to be shown.

Moderate Exercise Effects on Orthostatic Intolerance While Wearing Protective Clothing

Wearing protective clothing can have deleterious effects on operational capacities and can cause non-compensable thermal stress. We studied the effects of moderate exercise on orthostatic tolerance while wearing protective clothing in eight healthy subjects tolerant to orthostatism. Subjects performed a 60-min moderate exercise on a treadmill followed by a 45-min head-up tilt test. Subjects performed the moderate exercise either in a comfortable condition (control, CON) or wearing protective clothing (PRO) in a random order. Compared with the CON trial, exercise in the PRO trial induced higher body dehydration, heart rate, and rectal temperature and a decrease in plasma volume. Orthostatic tolerance was significantly reduced in the PRO trial (23.7 +/- 0.2 min) compared with the CON trial (40.7 +/- 1.0 min). Transition from supine to head-up position caused a significant decrease in blood pressure in the PRO compared with the CON. RR interval was smaller in the PRO trial compared with CON in both the supine and head-up positions. Spontaneous baroreflex sensitivity was decreased in the PRO, either supine or standing, compared to CON (4.6 +/- 0.5 ms x mmHg(-1) and 14.5 +/- 4.2 ms x mmHg(-1) in supine, and 3.3 +/- 0.6 ms x mmHg(-1) and 7.0 +/- 0.6 ms x mmHg(-1) in standing, for PRO and CON, respectively). These results suggest that the large decrease in the tolerance to orthostatism after exercise while wearing protective clothing was due to the impossibility of maintaining an adapted blood pressure induced by a conflict between the needs of peripherical vasoconstriction linked to the standing posture, the needs of vasodilatation linked to thermoregulation, and a drop in the sensibility of the spontaneous baroreflex.

Impact of Intensive High-Fat Ingestion in the Early Stage of Recovery from Exercise Training on Substrate Metabolism during Exercise in Humans

Not only increasing body carbohydrate (CHO) stores before exercise but also suppressing CHO oxidation during exercise is important for improving endurance performance. We tested the hypothesis that intensive high-fat ingestion in the early stage of recovery from exercise training (ET) for 2 d would suppress CHO oxidation during exercise by increasing whole body lipolysis and/or fat oxidation. In a randomized crossover design, on days 1 and 2, six male subjects performed cycle ET at 50% peak oxygen consumption (VO(2 peak)) for 60-90 min, and consumed a control diet (CON: 1,224 kcal, 55% carbohydrate, 30% fat) or the same diet supplemented with high fat (HF: 1,974 kcal, 34% carbohydrate, 56% fat) 1 h after ET, with the diet other than post-ET similar in both trials. On day 3, subjects performed cycle exercise at 65% VO(2 peak) until exhaustion. Exercise time to exhaustion was longer in the HF trial than in the CON trial (CON: 48.9 ± 6.7 vs. HF: 55.8 ± 7.7 min, p<0.05). In the HF trial, total fat oxidation until exhaustion was higher, accompanied by higher post-exercise plasma glycerol concentration, than in the CON trial (CON: 213 ± 54 vs. HF: 286 ± 63 kcal, p<0.05), whereas total carbohydrate oxidation until exhaustion was not different between trials. These results suggest that intensive high-fat ingestion in the early stage of recovery from ET for a few days until the day before exercise was an effective means of eliciting a CHO-sparing effect during exercise by enhancing fat metabolism.

Exercise-induced stress inhibits both the induction and elicitation phases of in vivo T-cell-mediated immune responses in humans

Little is known about the influence of exercise on induction and elicitation phases of in vivo immunity in humans. We used experimental contact-hypersensitivity, a clinically relevant in vivo measure of T cell-mediated immunity, to investigate the effects of exercise on induction and elicitation phases of immune responses to a novel antigen. The effects of 2h-moderate-intensity-exercise upon the induction (Study One) and elicitation of in vivo immune memory (Study Two) to diphenylcyclopropenone (DPCP) were examined. Study One: matched, healthy males were randomly-assigned to exercise (N=16) or control (N=16) and received a primary DPCP exposure (sensitization), 20min after either 2h running at 60% V˙ O2peak (EX) or 2h seated rest (CON). Four weeks later, participants received a low, dose-series DPCP challenge (elicitation) on their upper inner arm, which was read at 24 and 48h as clinical score, oedema (skinfold thickness) and redness (erythema). Study Two: pilot; 13 healthy males were sensitized to DPCP. Elicitation challenges were repeated every 4weeks until responses reached a reproducible plateau. Then, N=9 from the pilot study completed both EX and CON trials in a randomized order. Elicitation challenges were applied and evaluated as in Study One. Results demonstrate that exercise-induced stress significantly impairs both the induction (oedema −53% at 48h; P<0.001) and elicitation (oedema −19% at 48h; P<0.05) phases of the in vivo T-cell-mediated immune response. These findings demonstrate that prolonged moderate-intensity exercise impairs the induction and elicitation phases of in vivo T-cell-mediated immunity. Moreover, the induction component of new immune responses appears more sensitive to systemic-stress-induced modulation than the elicitation component.

Novel Precooling Strategy Enhances Time Trial Cycling in the Heat

To develop and investigate the efficacy of a new precooling strategy combining external and internal techniques on the performance of a cycling time trial (TT) in a hot and humid environment. Eleven well-trained male cyclists undertook three trials of a laboratory-based cycling TT simulating the course characteristics of the Beijing Olympic Games event in a controlled hot and humid environment (32°C-35°C at 50%-60% relative humidity). The trials, separated by 3-7 d, were undertaken in a randomized crossover design and consisted of the following: 1) CON-no treatment apart from the ad libitum consumption of cold water (4°C), 2) STD COOL-whole-body immersion in cold (10°C) water for 10 min followed by wearing a cooling jacket, or 3) NEW COOL-combination of consumption of 14 g of ice slurry ("slushie") per kilogram body mass made from a commercial sports drink while applying iced towels. There was an observable effect on rectal temperature (T(rec)) before the commencement of the TT after both precooling techniques (STD COOL < NEW COOL < CON, P < 0.05), but pacing of the TT resulted in similar T(rec), HR, and RPE throughout the cycling protocol in all trials. NEW COOL was associated with a 3.0% increase in power (approximately 8 W) and a 1.3% improvement in performance time (approximately 1:06 min) compared with the CON trial, with the true likely effects ranging from a trivial to a large benefit. The effect of the STD COOL trial compared with the CON trial was "unclear." This new precooling strategy represents a practical and effective technique that could be used by athletes in preparation for endurance events undertaken in hot and humid conditions.

Brief, high intensity exercise alters serum ghrelin and growth hormone concentrations but not IGF-I, IGF-II or IGF-I bioactivity

Exercise stimulates growth hormone (GH) release, but there are conflicting reports regarding the acute effects of exercise on circulating ghrelin and insulin-like growth factor (IGF) concentrations. This investigation examined (1) the effect of a single sprint on circulating GH, ghrelin and IGF concentrations as well as a marker of IGF-I bioactivity, and (2) whether the number of muscle actions performed during a sprint influences these responses. Seven healthy men completed 3 trials in a random order. In two exercise trials they performed a single 30-s sprint on a cycle ergometer against a resistance equivalent to either 7% (FAST) or 9% (SLOW) of their body mass. In the other they rested in the laboratory (CON). Blood samples were taken pre-, immediately post-, 10 and 30 min post-exercise, and at equivalent times in the CON trial. Total ghrelin concentrations declined after the sprint and were significantly lower after 30 min of recovery than they were pre-exercise (pre-exercise vs. 30 min; FAST, 0.62 (0.19) vs. 0.49 (0.16) μg/L, P < 0.001; SLOW, 0.59 (0.15) vs. 0.47 (0.13) μg/L, P < 0.001). GH concentrations increased in both exercise trials and were greater in the FAST than the SLOW trial. Serum concentrations of total IGF-I, free IGF-I, total IGF-II, and IGF-I bioactivity did not change after sprinting. In conclusion, sprint exercise suppresses total ghrelin concentrations and stimulates GH release but does not alter IGF concentrations or bioactivity.

The endothelial microparticle response to a high fat meal is not attenuated by prior exercise

Triglyceride-rich postprandial lipoproteins are known to activate endothelial cells in vitro, contributing to atherosclerosis. Endothelial microparticles (EMP) are membranous vesicles released into the circulation from vascular endothelial cells that permit cell activation to be monitored in vivo. The objective of the study was to examine changes in EMP following a high fat meal, consumed with and without prior exercise. Eight recreationally active young men underwent two oral fat tolerance tests following either 100 min exercise at 70% VO(2)peak (EX trial) or no exercise (CON trial) on the previous evening. Postprandial triglycerides were reduced (1.97 +/- 0.31 vs. 1.17 +/- 0.13 mmol L(-1), p < 0.05) and HDL-cholesterol (HDL-C) increased (1.20 +/- 0.07 vs. 1.30 +/- 0.08 mmol L(-1), p < 0.05) in the EX compared to CON trial. EMP (CD31+/42b-) increased postprandially (p < 0.05). However, counts were not different between trials (postprandial CON and EX trial counts x 10(3 )microL(-1), 3.10 +/- 0.14 vs. 3.26 +/- 0.37). There were no changes in sICAM-1 or sVCAM-1 postprandially and no differences between trials. Interleukin-6 (IL-6) and leukocytes increased postprandially (p < 0.05). IL-6 values were not different between trials. Leukocytes were higher at 0 h in the EX trial with CON and EX trial values similar at 6 h. EMP, but not sICAM-1 or sVCAM-1, increase in response to a high fat meal. However, EMP are not attenuated by acute exercise, despite a considerable reduction in postprandial lipemia and an increase in HDL-C.

No effect of short-term arginine supplementation on nitric oxide production, metabolism and performance in intermittent exercise in athletes

Arginine supplementation has been shown to alleviate endothelial dysfunction and improve exercise performance through increasing nitric oxide production in patients with cardiopulmonary diseases. In addition, arginine supplementation could decrease accumulations of lactate and ammonia, metabolites involved in development of muscular fatigue. The aim of this study was to investigate the effect of short-term arginine supplementation on performance in intermittent anaerobic exercise and the underlying mechanism in well-trained male athletes. Ten elite male college judo athletes participated with a randomized crossover, placebo-controlled design. The subjects consumed 6 g/day arginine (ARG trial) or placebo (CON trial) for 3 days then performed an intermittent anaerobic exercise test on a cycle ergometer. Blood samples were collected before supplementation, before and during exercise and 0, 3, 6, 10, 30 and 60 min after exercise. ARG trial had significantly higher arginine concentrations than CON trial at the same time point before, during and after exercise. In both trials, nitrate and nitrite concentration was significantly higher during and 6 min after exercise comparing to the basal concentration. The increase in nitrate and nitrite concentration during exercise in both trials was parallel to the increase in plasma citrulline concentrations. There was no significant difference between the 2 trials in plasma nitrate and nitrite, lactate and ammonia concentrations and peak and average power in the exercise. The results of this study suggested that short-term arginine supplementation had no effect on nitric oxide production, lactate and ammonia metabolism and performance in intermittent anaerobic exercise in well-trained male athletes.