Refining Selection for Elite Troops by Predicting Military Training Outcome.

INTRODUCTION: Paratrooper training courses are very demanding, leading to a high number of drop-outs, despite existing selection criteria. This study investigated physiological, neuropsychological, and subjective data of completers and drop-outs during paratrooper training to identify potential predictive indices. METHODS: Tested were 24 paratrooper soldiers before (t0), after 8 wk (t1), and at the end of a 12-wk training camp (t2). There were 11 soldiers who completed the course and 13 dropped out. The Training OPtimalisation test (TOPtest) uses two maximum exercise events to assess changes in measured parameters. The TOPtest was administered at t0, t1, and t2; physiological [i.e., adrenocorticotrophic hormone (ACTH), cortisol, heart rate (HR)], neuropsychological (Stroop, Flanker, Go NoGo, Task Switch), and subjective data [Profile of Mood States (POMS)] were collected. Physiological and subjective raw data was gathered pre- and post-test from each of the two maximum exercise tests. The pre/post-test change of each parameter's raw values was calculated as the parameter's reactivity (or delta score). RESULTS: At t0, drop-outs showed a significantly smaller HR reactivity (117.9 ± 14.0 vs.107.7 ± 10.6). Delta scores of tension and fatigue values differed significantly between completers and drop-outs at t0. Completers' physiological reactivity during the TOPtest at t2 (HR: 105.91 ± 13.68 vs. 95.55 ± 10.28) was significantly reduced and became comparable to the drop-outs' reactivity at t0. Delta scores of fatigue and tension values showed a similar pattern. DISCUSSION: Reactivity of HR, tension, and fatigue parameter values were found to have predictive value in identifying completers vs. drop-outs of an elite paratrooper training course.Vrijkotte S, Meeusen R, Roelands B, Kubesch S, Mairesse O, de Schutter G, Pattyn N. Refining selection for elite troops by predicting military training outcome. Aerosp Med Hum Perform. 2017; 88(9):850-857.

Time trial performance in normal and high ambient temperature: is there a role for 5-HT?

The original central fatigue hypothesis suggested that fatigue during prolonged exercise might be due to higher 5-HT activity. Therefore, we examined the effects of acute administration of a selective 5-HT reuptake inhibitor (SSRI) on performance and thermoregulation. Eleven healthy trained male cyclists completed four experimental trials (two in 18 degrees C, two in 30 degrees C) in a double-blind randomised crossover design. Subjects ingested either a placebo (PLA: lactose 2 x 10 mg) or citalopram (CITAL 2 x 10 mg) on the evening before and the morning of the trial. Subjects cycled for 60 min at 55% W(max), immediately followed by a time trial (TT) to measure performance. The significance level was set at P < 0.05. Acute SSRI did not significantly change performance on the TT (18 degrees C P = 0.518; 30 degrees C P = 0.112). During recovery at 30 degrees C, core temperature was significantly lower in the CITAL trial (P < 0.012). At 30 degrees C heart rate was significantly lower after exercise in CITAL (P = 0.013). CITAL significantly increased cortisol concentrations at rest (P = 0.016), after the TT (P = 0.006) and after 15-min recovery (P = 0.041) at 30 degrees C. 5-HT reuptake inhibition did not cause significant reductions in performance. Core temperature was significantly lower only after the time trial in heat after CITAL administration. The present work failed to prove whether or not 5-HT has an exclusive role in the onset of centrally mediated fatigue during prolonged exercise in both normal and high ambient temperature.

Performance and thermoregulatory effects of chronic bupropion administration in the heat.

UNLABELLED: The combination of acute dopamine/noradrenaline reuptake inhibition (bupropion; BUP) and heat stress (30 degrees C) significantly improves performance (9%). Furthermore the maintenance of a higher power output resulted in the attainment of significantly higher heart rates and rectal temperatures--above 40 degrees C--in the BUP trial compared to the placebo trial. Since BUP is an aid to cease smoking that is taken for longer periods, question remains if similar performance and thermoregulatory effects are found following administration of BUP over several days (10 days). The purpose of the present study was to examine the effects of chronic BUP on exercise performance, thermoregulation and hormonal variables in the heat. Eight trained male cyclists participated in the study. Subjects completed two trials consisting of 60 min fixed intensity exercise (55% W (max)) followed by a time trial (TT) in a double-blind randomized crossover design. Exercise was performed in 30 degrees C. Subjects took either placebo (PLAC) or BUP (Zyban) for 3 days (150 mg), followed by 300 mg for 7 days. Chronic BUP did not influence TT performance (BUP 40'42'' +/- 4'18''; PLAC 41'36'' +/- 5'12''), but significantly increased core temperature (P = 0.030). BUP significantly increased circulating growth hormone levels (PLAC: 9.8 +/- 5.8 ng L(-1); BUP: 13 +/- 6.8 ng L(-1); P < 0.008). DISCUSSION/CONCLUSION: Chronic BUP did not influence TT performance in 30 degrees C and subjects did not reach core temperature values as high as observed during the acute BUP study. It seems that chronic administration results in an adaptation of central neurotransmitter homeostasis, resulting in a different response to the drug.

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.

Unravelling intracellular immune dysfunctions in chronic fatigue syndrome: interactions between protein kinase R activity, RNase L cleavage and elastase activity, and their clinical relevance.

This study examined possible interactions between immunological abnormalities and symptoms in CFS. Sixteen CFS patients filled in a battery of questionnaires, evaluating daily functioning, and underwent venous blood sampling, in order to analyse immunological abnormalities. Ribonuclease (RNase) L cleavage was associated with RNase L activity (rs=0.570; p=0.021), protein kinase R (PKR) (rs=0.716; p=0.002) and elastase activity (rs=0.500; p=0.049). RNase L activity was related to elastase (rs=0.547; p=0.028) and PKR activity (rs=0.625; p=0.010). RNase L activity (rs=0.535; p=0.033), elastase activity (rs=0.585; p=0.017) and RNase L cleavage (rs=0.521; p=0.038) correlated with daily functioning. This study suggests that in CFS patients an increase in elastase activity and subsequent RNase L cleavage is accompanied by increased activity of both the PKR and RNase L enzymes. RNase L and elastase activity are related to daily functioning, thus evidence supporting the clinical importance of these immune dysfunctions in CFS patients was provided.

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.

Chronic fatigue syndrome: exercise performance related to immune dysfunction.

PURPOSE: To date, the exact cause of abnormal exercise response in chronic fatigue syndrome (CFS) remains to be revealed, but evidence addressing intracellular immune deregulation in CFS is growing. Therefore, the aim of this cross-sectional study was to examine the interactions between several intracellular immune variables and exercise performance in CFS patients. METHODS: After venous blood sampling, subjects (16 CFS patients) performed a maximal exercise stress test on a bicycle ergometer with continuous monitoring of cardiorespiratory variables. The following immune variables were assessed: the ratio of 37 kDa Ribonuclease (RNase) L to the 83 kDa native RNase L (using a radiolabeled ligand/receptor assay), RNase L enzymatic activity (enzymatic assay), protein kinase R activity assay (comparison Western blot), elastase activity (enzymatic-colorimetric assay), the percent of monocytes, and nitric oxide determination (for monocytes and lymphocytes; flow cytometry, live cell assay). RESULTS: Forward stepwise multiple regression analysis revealed 1) that elastase activity was the only factor related to the reduction in oxygen uptake at a respiratory exchange ratio (RER) of 1.0 (regression model: R = 0.53, F (1,14) = 15.5, P < 0.002; elastase activity P < 0.002); 2) that the protein kinase R activity was the principle factor related to the reduction in workload at RER = 1.0; and 3) that elastase activity was the principle factor related to the reduction in percent of target heart rate achieved. CONCLUSION: These data provide evidence for an association between intracellular immune deregulation and exercise performance in patients with CFS. To establish a causal relationship, further study of these interactions using a prospective longitudinal design is required.

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.