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Purpose: It is well-documented that severe cold stress impairs exercise performance. Repeated immersion in cold water induces an insulative type of cold acclimation, wherein enhanced vasoconstriction leads to greater body heat retention, which may attenuate cold-induced exercise impairments. The purpose of this study, therefore, was to investigate changes in exercise performance during a 7-day insulative type of cold acclimation., Methods: Twelve healthy participants consisting of eight males and four females (mean ± SD age: 25.6 ± 5.2 years, height: 174.0 ± 8.9 cm, weight: 75.6 ± 13.1 kg) performed a 20 min self-paced cycling test in 23 °C, 40% humidity without prior cold exposure. Twenty-four hours later they began a 7-day cold acclimation protocol (daily 90 min immersion in 10 °C water). On days one, four, and seven of cold acclimation, participants completed the same cycling test. Measurements of work completed, core and skin temperatures, heart rate, skin blood flow, perceived exertion, and thermal sensation were measured during each cycling test., Results: Successful insulative cold acclimation was observed. Work produced during the baseline cycling test (220 ± 70 kJ) was greater (p < 0.001) than all three tests that were performed following immersions (195 ± 58, 197 ± 60, and 194 ± 62 kJ) despite similar ratings of perceived exertion during each test, suggesting that cold exposure impaired cycling performance. This impairment, however, was not attenuated over the cold acclimation period., Conclusions: Results suggest that insulative cold acclimation does not attenuate impairments in exercise performance that were observed following acute cold water immersion.

Aim: To examine the isolated and combined effects of severe hypoxia and a mild thermal challenge on performance, physiological measures, cognition, and serum brain-derived neurotrophic factor (BDNF)., Methods: Nine trained male athletes (age: 23 ± 3 years; W max: 333 ± 45 W) completed four experimental trials (CON: 15 °C/0 m, ALT: 15 °C/3800 m, TEMP: 25 °C/0 m, ALT + TEMP: 25 °C/3800 m) in a double blind, randomized, cross-over design. Subjects cycled for 30 min in a self-paced test starting at 75% W max, their goal was to 'perform as much work as possible in 30 min.' Power output, heart rate, blood lactate, pulse oximetry, core and skin temperature, thermal sensation, ratings of perceived exertion, reaction time (RT), and BDNF were assessed., Results: The amount of work produced in 30 min was reduced by temperature (F(1,8) = 7.1; p = 0.029; 360 ± 19 kJ in 15 °C; 344 ± 18 kJ in 25 °C) and altitude (F(1,8) = 94.2; p < 0.001; 427 ± 24 kJ at sea level; 277 ± 15 kJ at altitude), yet there was no interaction effect. Altitude increased mean RT (F(1,8) = 8.0; p = 0.022; 281.9 ± 9.4 ms at sea level; 289.3 ± 10.0 ms at altitude) and RT variability (F(1,8) = 8.5; p = 0.020; 44 ± 3 ms at sea level: 50 ± 4 ms at altitude). Exercise increased BDNF (F(1,8) = 15.2; p = 0.005; PRE: 21.8 ± 1.3 ng/mL; POST: 26.5 ± 2.1 ng/mL)., Conclusion: Exercise capacity was significantly reduced due to an increase in altitude (3800 m; -34.3%) or a 10 °C increase in ambient temperature (-3.2%). The combination of both stressors showed to be additive (-38.0 %). Altitude induced an increase in RT and RT variability presenting a deterioration in cognitive functioning during acute hypoxia. Exercise significantly increased BDNF, but no effect of altitude on the BDNF concentration was observed.

Caffeine, an adenosine receptor antagonist, has shown to improve performance in normal ambient temperature, presumably via an effect on dopaminergic neurotransmission through the antagonism of adenosine receptors. However, there is very limited evidence from studies that administered caffeine and examined its effects on exercise in the heat. Therefore, we wanted to study the effects of caffeine on performance and thermoregulation in high ambient temperature. Eight healthy trained male cyclists completed two experimental trials (in 30°C) in a double-blind-randomized crossover design. Subjects ingested either placebo (6 mg/kg) or caffeine (6 mg/kg) 1 h prior to exercise. Subjects cycled for 60 min at 55% W (max), immediately followed by a time trial to measure performance. The significance level was set at p < 0.05. Caffeine did not change performance (p = 0.462). Rectal temperature was significantly elevated after caffeine administration (p < 0.036). Caffeine significantly increased B-endorphin plasma concentrations at the end of the time trial (p = 0.032). The present study showed no ergogenic effect of caffeine when administered 1 h before exercise in 30°C. This confirms results from a previous study that examined the effects of caffeine administration on a short (15 min) time trial in 40°C. However, caffeine increased core temperature during exercise. Presumably, the rate of increase in core temperature may have counteracted the ergogenic effects of caffeine. However, other factors such as interindividual differences in response to caffeine and changes in neurotransmitter concentrations might also be responsible for the lack of performance improvement of caffeine in high ambient temperature.

The purpose of the study was to examine the acute effect of a strength training session on brain-derived neurotrophic factor and insulin-like growth factor 1. Furthermore, the influence of a 10-week strength training program on brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1) resting levels and memory performance was studied. Fifteen untrained subjects followed a strength training program for 10 weeks. Eight control subjects remained physically inactive. To study the influence of an acute strength training session, blood samples were taken before and after the sixth and 30th sessions. Training effects were evaluated by taking blood samples at rest before and following the training program. Short- and mid-term memories were assessed using the digit span and a recall of images test. BDNF, IGF-1 and its binding protein (IGFBP-3) were measured in serum samples. Data were analyzed (p < 0.05) using a mixed design ANOVA model, Duncan's multiple range post hoc tests, and Pearson's correlation. A single strength training session did not influence BDNF and IGF-1 concentrations. No effect of the strength training period on BDNF, IGF-1, and IGFBP-3 was found. No correlation was found between peripheral BDNF and IGF-1. Short-term memory improved in both the experimental and control groups, but no difference between groups was present. Mid-term memory did not improve following the 10 weeks of training. A period of strength training in sedentary subjects does not significantly change the growth factors or memory function compared to a control group. Also, BDNF and IGF-1 are not acutely influenced by a training session. Further research should focus on the beneficial role of physical exercise in neurodegenerative diseases.

Elevated plasma free fatty acid (FFA), inflammatory marker, and altered adipokine concentrations have been observed in obese type 2 diabetes patients. It remains unclear whether these altered plasma concentrations are related to the diabetic state or presence of obesity. In this cross-sectional observational study, we compare basal plasma FFA, inflammatory marker, and adipokine concentrations between obese and non-obese type 2 diabetes patients and healthy, non-obese controls. A total of 20 healthy, normoglycemic males (BMI <30 kg/m(2)), 20 non-obese (BMI <30 kg/m(2)) and 20 obese (BMI >35 kg/m(2)) type 2 diabetes patients were selected to participate in this study. Groups were matched for age and habitual physical activity level. Body composition, glycemic control, and exercise performance capacity were assessed. Basal blood samples were collected to determine plasma leptin, adiponectin, resistin, tumor necrosis factor alpha (TNFalpha), interleukin-6 (IL-6), high-sensitivity C-reactive protein (hsCRP) and FFA concentrations. Plasma FFA, inflammatory marker (hsCRP, IL-6, TNFalpha), adipokine (adiponectin, resistin, leptin), and triglyceride concentrations did not differ between non-obese diabetes patients and healthy, normoglycemic controls. Plasma FFA, IL-6, hsCRP, leptin, and triglyceride levels were significantly higher in the obese diabetes patients when compared with the healthy normoglycemic controls (P < 0.05). Furthermore, plasma hsCRP and leptin levels were significantly higher in the obese versus non-obese diabetes patients (P < 0.05). Significant correlations between plasma parameters and glycemic control were observed, but disappeared after adjusting for trunk adipose tissue mass. Elevated plasma leptin, hsCRP, IL-6, and FFA concentrations are associated with obesity and not necessarily with the type 2 diabetic state.

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.

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.

In cardiac rehabilitation, different endurance exercises such as walking and cycling are often performed. The training intensity for these modes is determined from a single treadmill or bicycle test by ventilatory threshold (VT). In this study, differences of VT between walking and cycling and agreement of VT between training modes were assessed in cardiac patients. A total of 46 cardiac rehabilitation patients (mean age 59.5+/-8.4 years, 45 males) (31 untrained and 15 trained) completed a maximal exercise test on bicycle and treadmill, with breath-by-breath analysis of oxygen uptake (VO2), carbon dioxide production and expiratory volume. VT was determined by V-slope method. Correlations of VT and VO2peak were calculated between exercise modes. Bland-Altman plots were made for determining VT agreement between modes. VT was significantly different between walking and cycling in trained patients (P<0.05), but not in untrained patients (P>0.05). When untrained and trained patients were compared, VT correlation was lower (r=0.50) in the former group, as compared to the latter group (r=0.78). Also, Bland-Altman plots showed smaller limits of agreement for VT in trained (2 SD -1.6 to 7.8 ml/min/kg), as compared to untrained patients (2 SD -7.0 to 9.6 ml/min/kg). In trained patients, VT correlates well between training methods, but is highly exercise mode specific. In untrained patients, VT is not exercise mode specific, but the VT has a low correlation between training modes. This study shows that VT should be assessed by the appropriate exercise model for determining exercise intensity in cardiac rehabilitation.

The objectives of this study were to (1) continuously assess oxygen uptake and heart rate; (2) quantify the extent to which maximal whole-body cardiorespiratory capacity is utilized during climbing on four routes with the same difficulty but different steepness and/or displacement. Fifteen expert climbers underwent a maximal graded exercise test (MT), on a treadmill, in order to assess their maximal physiological capacity. After MT, four sport routes, equal in difficulty rating but different in steepness and/or displacement, were climbed. Oxygen uptake and heart rate were continuously measured. Respiratory exchange ratio (RER) was calculated. Blood lactate concentration and rating of perceived exertion (RPE) were taken before and directly after climbing. Data were expressed as peak values (HRpeak, VO2peak and RERpeak) and as averages over the entire climb (HRavg, VO2avg and RERavg). During climbing, higher HRpeak and HRavg were found in routes with a vertical upward displacement in comparison to traversing routes with a horizontal displacement. The average absolute and relative oxygen uptake was significantly lower in the traversing route in comparison with the three other routes. The traverse is done at a lower percent of the running maximum. Comparing four routes with the same difficulty but different steepness and/or displacement shows that (1) routes with an upward displacement causes the highest peak and average heart rate; (2) routes with a vertical displacement on overhanging wall is physiologically the most demanding; (3) the traverse is physiologically the less demanding.