Luk Buyse

The effects of acute dopamine reuptake inhibition on performance.

INTRODUCTION Acute bupropion (dopamine/noradrenaline reuptake inhibitor) administration significantly improved time trial performance and increased core temperature in the heat (30 degrees C). PURPOSE The present study was performed to examine the effect of a dopaminergic reuptake inhibitor on exercise capacity and thermoregulation during prolonged exercise in temperate and warm conditions. METHODS Eight healthy well-trained male cyclists participated in this study. Subjects ingested either placebo (PLA; 20 mg) or methylphenidate (MPH; Ritalin; 20 mg) 1 h before the start of exercise in temperate (18 degrees C) or warm (30 degrees C) conditions and cycled for 60 min at 55% Wmax, immediately followed by a time trial (TT; PLA18 and MPH18; PLA30 and MPH30) to measure exercise performance. RESULTS MPH did not influence TT performance at 18 degrees C (P = 0.397). TT was completed 16% faster in MPH30 (38.1 +/- 6.4 min) than in PLA30 (45.4 +/- 7.3 min; P = 0.049). In the heat Tcore was significantly higher at rest (P = 0.009), and throughout the TT in MPH30 (P < 0.018), reaching values above 40 degrees C. Throughout MPH30, heart rates were significantly higher (P < 0.05). CONCLUSIONS These results show that MPH has a clear ergogenic effect that was not apparent in 18 degrees C. The combination of a dopamine reuptake inhibitor and exercise in the heat clearly improved performance and caused hyperthermia without any change in the perception of effort or thermal stress compared with the PLA trial. This response may potentially increase the risk of developing heat illness during exercise in individuals taking drugs of this nature.

Acute norepinephrine reuptake inhibition decreases performance in normal and high ambient temperature

Combined inhibition of dopamine (DA)/norepinephrine (NE) reuptake improves exercise performance and increases core temperature in the heat. A recent study demonstrated that this effect may primarily be related to increased DA activity. NE reuptake inhibition (NERI), however, has received little attention in humans, certainly in the heat, where central fatigue appears to be a main factor influencing performance. Therefore the present study examines the effect of NERI (reboxetine) on exercise capacity, thermoregulation, and hormonal response in normal and high temperature. Nine healthy well-trained male cyclists participated in this study. Subjects ingested either placebo (Pla; 2 x 8 mg) or reboxetine (Rebox; 2 x 8 mg). Subjects exercised in temperate (18 degrees C) or warm (30 degrees C) conditions and cycled for 60 min at 55% W(max) immediately followed by a time trial (TT; Pla18/Rebox18; Pla30/Rebox30) to measure exercise performance. Acute NERI decreased power output and consequently exercise performance in temperate (P = 0.018) and warm (P = 0.007) conditions. Resting heart rate was significantly elevated by NERI (18 degrees C: P = 0.02; 30 degrees C: P = 0.018). In Rebox18, heart rate was significantly higher than in the Pla18, while in the heat no effect of the drug treatment was reported during exercise. In Rebox30, all hormone concentrations increased during exercise, except for growth hormone (GH), which was significantly lower during exercise. In Rebox18, prolactin (PRL) concentrations were significantly elevated; GH was significantly higher at rest, but significantly lower during exercise. In conclusion, manipulation of the NE system decreases performance and modifies hormone concentrations, thereby indicating a central NE effect of the drug. These findings confirm results from previous studies that predominantly increased DA activity is important in improving performance.

No effect of a noradrenergic reuptake inhibitor on performance in trained cyclists

INTRODUCTION According to the central fatigue hypothesis, serotonin (5-HT) is related to fatigue, whereas the noradrenergic system is primarily concerned with arousal and motivation, and therefore hypothesized to enhance performance. The purpose of the present study was to examine the effects of a selective noradrenergic reuptake inhibitor (reboxetine 2 x 4 mg REB-NARI) on exercise performance. METHODS Seven healthy well-trained male cyclists (age: 23 +/- 1.7 yr, height: 182 +/- 5.8 cm, weight: 73.5 +/- 8.5 kg, VO2max: 73.5 +/- 6.4 mL x kg(-1) x min(-1), Watt(max): 376 +/- 11.7 W) participated to the study. Subjects completed two endurance tests (time trials) starting at 65% Wmax in a double-blind randomized cross-over design. Blood samples were collected for adrenocorticotropin, prolactin, cortisol, growth hormone (GH), beta-endorphins, and catecholamines and were taken at 30-min time intervals until the end of exercise. Performance was analyzed with a paired t-test, whereas data for hormonal and metabolic differences during the trials were analyzed using an ANOVA repeated measures design and an LSD-planned comparisons test. Significance level was set at P < 0.05. RESULTS Performance was not influenced by the NARI (REB: 97 min +/- 3 min, placebo (PLAC): 92 min +/- 1 min). All hormones increased during exercise except for GH in the REB trial, which was significantly lower than PLAC. The other hormones were significantly higher in the REB trial versus the PLAC trial at the end of exercise and during recovery. CONCLUSION In conclusion, the results demonstrate that the drug had a central effect. In particular, the higher resting GH concentrations indicated a marked and selective noradrenergic effect of REB. However, performance was not influenced by a selective NARI in well-trained endurance athletes.

Diagnosing overtraining in athletes using the two-bout exercise protocol

Objective In this work, whether a two-bout exercise protocol can be used to make an objective, immediately available distinction between non-functional over reaching (NFO) and overtraining syndrome (OTS) was studied. Design Underperforming athletes who were diagnosed with the suspicion of NFO or OTS were included in the study. Recovery of the athletes was monitored by a sports physician to retrospectively distinguish NFO from OTS. Setting Sports medicine laboratory Participants The protocol was started and completed by 10 underperforming athletes. NFO was retrospectively diagnosed in five athletes, and OTS was diagnosed in five athletes. Interventions A two-bout maximal exercise protocol was used to measure physical performance and stressinduced hormonal reactions. Main outcome measurements Exercise duration, heart rate and blood lactate concentration were measured at the end of both exercise tests. Venous concentrations cortisol, adrenocorticotrophic hormone (ACTH), prolactin and growth hormone were measured both before and after both exercise tests. Results Maximal blood lactate concentration was lower in OTS compared with NFO, while resting concentrations of cortisol, ACTH and prolactin concentrations were higher. However, sensitivity of these measures was low. The ACTH and prolactin reactions to the second exercise bout were much higher in NFO athletes compared with OTS and showed the highest sensitivity for making the distinction. Conclusions NFO might be distinguished from OTS based on ACTH and prolactin reactions to a two-bout exercise protocol. This protocol could be a useful tool for diagnosing NFO and OTS; however, more data should be collected before this test can be used as the gold standard.

Hormonal responses during prolonged exercise are influenced by a selective DA/NA reuptake inhibitor

Objective: A decrease in dopamine activity is thought to lead to a reduction in motivation and arousal and therefore to the “central” component of fatigue. The purpose of the present study was to investigate the effects of a dopamine (DA) noradrenaline (NA) reuptake inhibitor, bupropion (Zyban™), on exercise performance and on the hormonal response to exercise. Methods: Eight healthy well trained male cyclists (Wattmax 397±15 W) participated in the study. Subjects completed one maximal exercise test (to determine maximal power output Wattmax), and two endurance performance tests (time trials) in a double blind randomised cross-over design. Subjects took either placebo capsules (lactose) or 2×300 mg bupropion (BUP). Blood samples were collected for adrenocorticotropin (ACTH), prolactin, cortisol, growth hormone, beta-endorphins, and catecholamines. Results: Performance was not influenced by BUP (placebo: 89±1 min; BUP 2×300 mg: 89±0.7 min). All hormones increased during exercise in all trials. Cortisol plasma concentrations were significantly higher in the BUP trial at rest, at min 60, and at the end of exercise, while beta-endorphins were higher in the BUP trial at the end of exercise and during recovery, and ACTH at the end of exercise. Conclusion: From the present results, we can conclude that bupropion had a more marked central noradrenergic effect (compared to dopaminergic) on the hormonal response to exercise, but no effect on the outcome of performance.

Effects of different types of acute and chronic (training) exercise on glycaemic control in type 1 diabetes mellitus: a meta-analysis

OBJECTIVE Exercise has been accepted and generally recommended for the management of type 1 diabetes mellitus (T1D) and for improving the overall quality of life in affected individuals. This meta-analysis was conducted to determine the overall effects of exercise (acute bouts of exercise and chronic exercise [or training]) on acute and chronic glycaemic control in patients with T1D, the effects of different types of exercise on glycaemic control and which conditions are required to obtain these positive effects. METHODS PubMed, ISI Web of Knowledge and SPORTDiscus™ were consulted to identify studies on T1D and exercise. Cohens d statistics were used for calculating mean effect sizes (ES) as follows: small d = 0.3, medium d = 0.5 and large d = 0.8. Ninety-five percent confidence intervals (95% CIs) were used to establish the significance of our findings. RESULTS From a total of 937 studies, 33 that met the inclusion criteria were selected. Nine studies were used to calculate the ES of a single bout of aerobic exercise; 13 studies to calculate the ES of aerobic training; 2 studies to calculate the ES of strength training; 4 studies to calculate the ES of combined (aerobic and strength) training and 6 studies to calculate the ES of high-intensity exercise (HIE) and training. ES for exercise on acute glycaemic control were large, while they were small for chronic glycaemic control. Aerobic exercise, resistance exercise, mixed exercise (aerobic combined with resistance training) and HIE acutely decreased blood glucose levels. To prevent late-onset hypoglycaemic episodes, the use of single bouts of sprints into an aerobic exercise can be recommended. This meta-analysis also showed that a regular exercise training programme has a significant effect on acute and chronic glycaemic control, although not all exercise forms showed significant results. Specifically, aerobic training is a favourable tool for decreasing chronic glycaemic control, while resistance training, mixed and HIE did not significantly improve chronic glycaemic control. Although, this meta-analysis showed there was a tendency for improvement in glycaemic control due to resistance training or resistance training combined with endurance training, there were not enough studies and/or subjects to confirm this statistically. CONCLUSIONS Based on this meta-analysis, we can conclude that the addition of brief bouts of high-intensity, sprint-type exercise to aerobic exercise can minimize the risk of sustaining a hypoglycaemic episode. We can also conclude that only regular aerobic training will improve the glycated haemoglobin level of a patient with T1D.

Effects of Different Types of Acute and Chronic (Training) Exercise on Glycaemic Control in Type 1 Diabetes Mellitus

ObjectiveExercise has been accepted and generally recommended for the management of type 1 diabetes mellitus (T1D) and for improving the overall quality of life in affected individuals. This meta-analysis was conducted to determine the overall effects of exercise (acute bouts of exercise and chronic exercise [or training]) on acute and chronic glycaemic control in patients with T1D, the effects of different types of exercise on glycaemic control and which conditions are required to obtain these positive effects.MethodsPubMed, ISI Web of Knowledge and SPORTDiscus™ were consulted to identify studies on T1D and exercise. Cohen’s d statistics were used for calculating mean effect sizes (ES) as follows: small d = 0.3, medium d = 0.5 and large d = 0.8. Ninety-five percent confidence intervals (95% CIs) were used to establish the significance of our findings.ResultsFrom a total of 937 studies, 33 that met the inclusion criteria were selected. Nine studies were used to calculate the ES of a single bout of aerobic exercise; 13 studies to calculate the ES of aerobic training; 2 studies to calculate the ES of strength training; 4 studies to calculate the ES of combined (aerobic and strength) training and 6 studies to calculate the ES of high-intensity exercise (HIE) and training. ES for exercise on acute glycaemic control were large, while they were small for chronic glycaemic control. Aerobic exercise, resistance exercise, mixed exercise (aerobic combined with resistance training) and HIE acutely decreased blood glucose levels. To prevent late-onset hypoglycaemic episodes, the use of single bouts of sprints into an aerobic exercise can be recommended. This meta-analysis also showed that a regular exercise training programme has a significant effect on acute and chronic glycaemic control, although not all exercise forms showed significant results. Specifically, aerobic training is a favourable tool for decreasing chronic glycaemic control, while resistance training, mixed and HIE did not significantly improve chronic glycaemic control. Although, this meta-analysis showed there was a tendency for improvement in glycaemic control due to resistance training or resistance training combined with endurance training, there were not enough studies and/or subjects to confirm this statistically.ConclusionsBased on this meta-analysis, we can conclude that the addition of brief bouts of high-intensity, sprint-type exercise to aerobic exercise can minimize the risk of sustaining a hypoglycaemic episode. We can also conclude that only regular aerobic training will improve the glycated haemoglobin level of a patient with T1D.

Type 1 diabetes-associated cognitive decline: A meta-analysis and update of the current literature

Type 1 diabetes (T1D) can have a significant impact on brain structure and function, which is referred to as T1D‐associated cognitive decline (T1DACD). Diabetes duration, early onset disease, and diabetes‐associated complications are all proposed as factors contributing to T1DACD. However, there have been no comparisons in T1DACD between children and adults with T1D. To obtain a better insight into the occurrence and effects of T1DACD in T1D, the aim of the present meta‐analysis was to investigate differences between children and adults and to analyse factors contributing T1DACD.

Type 1 diabetes-associated cognitive decline: A meta-analysis and update of the current literature 1型糖尿病相关的认知能力下降：一项对最新文献的meta分析

Type 1 diabetes (T1D) can have a significant impact on brain structure and function, which is referred to as T1D‐associated cognitive decline (T1DACD). Diabetes duration, early onset disease, and diabetes‐associated complications are all proposed as factors contributing to T1DACD. However, there have been no comparisons in T1DACD between children and adults with T1D. To obtain a better insight into the occurrence and effects of T1DACD in T1D, the aim of the present meta‐analysis was to investigate differences between children and adults and to analyse factors contributing T1DACD.

No Effect of a Selective Serotonergic/Noradrenergic Reuptake Inhibitor on Endurance Performance

The purpose of the present study was to examine the effects of a selective serotonin/noradrenaline (5-HT/NA) reuptake inhibitor (SNRI) on exercise performance. Seven well-trained male cyclists completed 2 time trials in a doubleblind randomized crossover design ingesting either placebo (PLAC) or 2 × 37.5 mg of Venlafaxine (VEN). Blood samples were collected for adrenocorticotropin hormone (ACTH), prolactin (PRL), cortisol, growth hormone (GH), beta-endorphins, and catecholamines and were taken at rest, at 30-min time intervals, at the end of exercise, and during recovery. Performance was not influenced by the SNRI (VEN: 92 min ± 3 min, PLAC: 92 min ± 1 min). Lactate concentrations, heart rate, and fatigue scores were not different between trials. All hormones increased during exercise in both trials. In the VEN trial, ACTH, beta endorphins, and NA concentrations were higher. The results from the present study demonstrate that a SNRI is not able to affect endurance performance in well-trained cyclists. However, it seems as though the hormonal response to the combination of the pharmacological manipulation and exercise is regulated more by the noradrenergic drive.