Measurement of pulmonary gas exchange variables and lactic anaerobic capacity during field testing in elite indoor football players.

AIM: The aims of this study were: 1) to examine the gas exchange responses of elite indoor football players to a repeated sprint ability (RSA) test; and 2) to verify whether or not the excess of carbon dioxide production (CO2excess) correlates with blood lactate accumulation during RSA field testing. METHODS: Eleven elite male indoor football players were recruited. A preliminary incremental exercise test on a treadmill was performed to elicit V'O2max. Then, participants underwent an RSA test consisting in a shuttle running through a course with various changes of direction while wearing a portable gas analyzer able to provide values of oxygen uptake, carbon dioxide production, and CO2excess. BLa concentrations during recovery were also measured. RESULTS: The main results were that: 1) during the RSA test subjects did not reached the V'O2max level achieved in the preliminary test; 2) during the RSA test BLa levels were higher compared with the preliminary test; 3) the peak BLa concentration during recovery was significantly correlated with the average CO2excess CONCLUSION: It was concluded that the RSA test did not appear to be useful to elicit V'O2max. Rather, it seemed suitable to recruit subjects' lactic anaerobic capacity. Moreover, CO2excess appeared suitable for qualitatively estimate BLa accumulation during field testing.

Transcranial Direct Current Stimulation over the Left Dorsolateral Prefrontal Cortex Improves Inhibitory Control and Endurance Performance in Healthy Individuals.

The dorsolateral prefrontal cortex (DLPFC) is a crucial brain region for inhibitory control, an executive function essential for behavioral self-regulation. Recently, inhibitory control has been shown to be important for endurance performance. Improvement in inhibitory control was found following transcranial direct current stimulation (tDCS) applied over the left DLPFC (L-DLPFC). This study examined the effect tDCS on both an inhibitory control and endurance performance in a group of healthy individuals. Twelve participants received either real tDCS (Real-tDCS) or placebo tDCS (Sham-tDCS) in randomized order. The anodal electrode was placed over the L-DLPFC while the cathodal electrode was placed above Fp2. Stimulation lasted 30min with current intensity set at 2mA. A Stroop test was administered to assess inhibitory control. Heart rate (HR), ratings of perceived exertion (RPE), and leg muscle pain (PAIN) were monitored during the cycling time to exhaustion (TTE) test, while blood lactate accumulation (∆B[La-]) was measured at exhaustion. Stroop task performance was improved after Real-tDCS as demonstrated by a lower number of errors for incongruent stimuli (p=0.012). TTE was significantly longer following Real-tDCS compared to Sham-tDCS (p=0.029, 17±8 vs 15±8min), with significantly lower HR (p=0.002) and RPE (p<0.001), while no significant difference was found for PAIN (p>0.224). ∆B[La-] was significantly higher at exhaustion in Real-tDCS (p=0.040). Our findings provide preliminary evidence that tDCS with the anodal electrode over the L-DLPFC can improve both inhibitory control and endurance cycling performance in healthy individuals.

Bilateral extracephalic transcranial direct current stimulation improves endurance performance in healthy individuals.

BACKGROUND: Transcranial direct current stimulation (tDCS) has been used to enhance endurance performance but its precise mechanisms and effects remain unknown. OBJECTIVE: To investigate the effect of bilateral tDCS on neuromuscular function and performance during a cycling time to task failure (TTF) test. METHODS: Twelve participants in randomized order received a placebo tDCS (SHAM) or real tDCS with two cathodes (CATHODAL) or two anodes (ANODAL) over bilateral motor cortices and the opposite electrode pair over the ipsilateral shoulders. Each session lasted 10 min and current was set at 2 mA. Neuromuscular assessment was performed before and after tDCS and was followed by a cycling time to task failure (TTF) test. Heart rate (HR), ratings of perceived exertion (RPE), leg muscle pain (PAIN) and blood lactate accumulation (ΔB[La-]) in response to the cycling TTF test were measured. RESULTS: Corticospinal excitability increased in the ANODAL condition (P < 0.001) while none of the other neuromuscular parameters showed any change. Neuromuscular parameters did not change in the SHAM and CATHODAL conditions. TTF was significantly longer in the ANODAL (P = 0.003) compared to CATHODAL and SHAM conditions (12.61 ± 4.65 min; 10.61 ± 4.34 min; 10.21 ± 3.47 min respectively), with significantly lower RPE and higher ΔB[La-] (P < 0.001). No differences between conditions were found for HR (P = 0.803) and PAIN during the cycling TTF test (P = 0.305). CONCLUSION: Our findings demonstrate that tDCS with the anode over both motor cortices using a bilateral extracephalic reference improves endurance performance.

Transcranial direct current stimulation improves isometric time to exhaustion of the knee extensors.

Transcranial direct current stimulation (tDCS) can increase cortical excitability of a targeted brain area, which may affect endurance exercise performance. However, optimal electrode placement for tDCS remains unclear. We tested the effect of two different tDCS electrode montages for improving exercise performance. Nine subjects underwent a control (CON), placebo (SHAM) and two different tDCS montage sessions in a randomized design. In one tDCS session, the anodal electrode was placed over the left motor cortex and the cathodal on contralateral forehead (HEAD), while for the other montage the anodal electrode was placed over the left motor cortex and cathodal electrode above the shoulder (SHOULDER). tDCS was delivered for 10min at 2.0mA, after which participants performed an isometric time to exhaustion (TTE) test of the right knee extensors. Peripheral and central neuromuscular parameters were assessed at baseline, after tDCS application and after TTE. Heart rate (HR), ratings of perceived exertion (RPE), and leg muscle exercise-induced muscle pain (PAIN) were monitored during the TTE. TTE was longer and RPE lower in the SHOULDER condition (P<0.05). Central and peripheral parameters, and HR and PAIN did not present any differences between conditions after tDCS stimulation (P>0.05). In all conditions maximal voluntary contraction (MVC) significantly decreased after the TTE (P<0.05) while motor-evoked potential area (MEP) increased after TTE (P<0.05). These findings demonstrate that SHOULDER montage is more effective than HEAD montage to improve endurance performance, likely through avoiding the negative effects of the cathode on excitability.

Assessment of circulatory adjustments during underwater apnoea in elite divers by means of a portable device.

AIM: Considering that sympathetic activation is induced by exercise, it is reasonable to assume that hemodynamic adjustments to exercise act in opposition to those elicited by the diving response. However, cardiovascular measurements have never been performed during underwater dynamic apnoea (DA), and this hypothesis remains speculative. METHODS: Data concerning heart rate (HR), stroke volume (SV) and cardiac output (CO) during static apnoea (SA) and DA were collected from 12 elite divers by means of an impedance cardiograph adapted to the underwater environment. Mean arterial pressure (MBP), systemic vascular resistance (SVR) and arterial oxygen saturation (SaO(2)) were also assessed. Five trials were performed by the divers: head-out immersion during normal breathing (test A); 3 min of SA immersed at the surface (B) and at 3 m depth (C); DA till exhaustion immersed at the surface (D) and at 3 m depth (E). RESULTS: Both B and C conditions led to bradycardia (-17%) compared to A and also induced a decrement in SV (-8%) and in CO (-25%), while MBP was maintained because of an increase in SVR. A significant MBP increment (+11%) was detected only during tests D and E, when a SaO(2) drop was also present, whereas HR, SV and CO remained unchanged. CONCLUSION: We concluded that typical diving response was present only during SA, while sympathetic activation was induced by exercise during DA, which partially obscured the effects of the diving response.

Hypothalamic growth hormone deficiency in a patient with ring chromosome 18.

We report on a boy with a ring 18 chromosome associated with hypothalamic growth hormone (GH) deficiency. A 12-month trial of GH replacement therapy (0.5 U/kg/week) resulted in a marked growth acceleration. Our findings emphasise the need of evaluating GH secretion in patients with abnormalities of the 18 chromosome.