Influence of the MCT1-T1470A polymorphism (rs1049434) on repeated sprint ability and blood lactate accumulation in elite football players: a pilot study.

PURPOSE: The aim of this study is to investigate the influence of the MCT1 T1470A polymorphism (rs1049434) on repeated sprint ability (RSA) and lactate accumulation after RSA testing. METHODS: Twenty-six elite Italian male football players (age: 17.7 ± 0.78 years; height: 179.2 ± 7.40 cm; weight: 72.1 ± 5.38 kg) performed RSA testing (6 × 30-m sprints with an active recovery between sprints), and lactate measurements were obtained at 1, 3, 5, 7, and 10 min post-exercise. Genotyping for the MCT1 T1470A polymorphism was performed using PCR. RESULTS: Genotype distributions were in Hardy-Weinberg equilibrium, being 42% wildtype (A/A), 46% heterozygotes (T/A), and 12% mutated homozygotes (T/T). Significant differences between genotypic groups were found in the two final sprint times of the RSA test. Under a dominant model, carriers of the major A-allele (Glu-490) in the dominant model showed a significantly lower sprint time compared to footballers with the T/T (Asp/Asp) genotype (5th Sprint time: A/A + T/A = 4.60 s vs TT = 4.97 s, 95% CI 0.07-0.67, p = 0.022; 6th Sprint: A/A + T/A = 4.56 s vs T/T = 4.87 s, 95% CI 0.05-0.57, p = 0.033). CONCLUSIONS: The T1470A (Glu490Asp) polymorphism of MCT1 was associated with RSA. Our findings suggest that the presence of the major A-allele (Glu-490) is favourable for RSA in football players.

Electrical Impedance to Easily Discover Undeclared Freeze-thaw Cycles in Slaughtered Bovine Meat.

A portable electrical impedance spectroscopy device was developed to monitor the bioimpedance resistive component of bovine meat by injecting a sinusoidal current of 1 mA at 65 kHz. Both right and left longissimus dorsi muscles were trimmed from 4 slaughtered cows. The left muscle portions were frozen to -18 °C for 7 days while the right ones were meantime maintained at 5 °C. Mean value of impedance per length (Ω/cm) of frozen and thawed left samples was 31% lower than that of right non-frozen one (P = 0.0001). It was concluded that the device is reliable for monitoring the maturation of beef meat in situ with the possibility of revealing undeclared freeze-thaw cycles.

Cardiovascular responses during free-diving in the sea.

Cardiac output has never been assessed during free-diving diving in the sea. Knowledge of human diving response in this setting is therefore scarce. 3 immersions were performed by 7 divers: at depths of 10 m, 20 m and 30 m. Each test consisted of 3 apnea phases: descent, static and ascent. An impedance cardiograph provided data on stroke volume, heart rate and cardiac output. Mean blood pressure, arterial O2 saturation and blood lactate values were also collected. Starting from a resting value of 4.5±1.6 L∙min(-1), cardiac output at 10 m showed an increase up to 7.1±2.2 L∙min(-1) (p<0.01) during the descent, while conditions during the static and ascent phases remained unchanged. At 20 m cardiac output values were 7.3±2.4 L∙min(-1) and 6.7(±1).2 L∙min(-1) during ascent and descent, respectively (p<0.01), and 4.3±0.9 L∙min(-1) during static phase. At 30 m cardiac output values were 6.5±1.8 L∙min(-1) and 7.5±2 L∙min(-1) during descent and ascent, respectively (p<0.01), and 4.7±2.1 L∙min(-1) during static phase. Arterial O2 saturation decreased with increasing dive depth, reaching 91.1±3.4% (p<0.001 vs. rest) upon emergence from a depth of 30 m. Blood lactate values increased to 4.1±1.2 mmol∙L(-1) at the end of the 30 m dive (p<0.001 vs. rest). Results seem to suggest that simultaneous activation of exercise and diving response could lead to an absence of cardiac output reduction aimed at an oxygen-conserving effect.

Muscle ischemic preconditioning does not improve performance during self-paced exercise.

Muscle ischemic preconditioning (IP) has been found to improve exercise performance in laboratory tests. This investigation aims at verifying whether performance is improved by IP during self-paced exercise (SPE) in the field. 11 well-trained male runners performed 3 randomly assigned 5 000 m self-paced running tests on an outdoor track. One was the reference (RT) test, while the others were performed following muscle IP (IPT) and a control sham test (ST). Average speeds were measured during each test. Mean values in oxygen uptake (VO2), aerobic energy cost (AEC) during race and post-race blood lactate (BLa) were gathered. Data showed that none of the studied variables were affected by IPT or ST with respect to the RT test. Average speeds were 4.63±0.31, 4.62±0.31 and 4.60±0.25 m·s(-1) for the RT, the ST and the IPT tests, respectively. Moreover, there was no difference among tests in speed reached during each lap. VO2 was 3.5±0.69, 3.74±0.85 and 3.62±1.19 l·min(-1). AEC was 1.04±0.15, 1.08±0.1 and 1.09±0.15 kcal·kg(-1)·km(-1). Finally, post-race BLa levels reached 12.85±3.54, 11.88±4.74 and 12.82±3.6 mmol·l(-1). These findings indicate that performance during SPE is not ameliorated by ischemic preconditioning, thereby indicating that IP is not suitable as an ergogenic aid.

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.

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.

Poor reliability of heart rate monitoring to assess oxygen uptake during field training.

The aim of this study was to quantify the error associated with the assessment of oxygen uptake (VO2) by heart rate (HR) monitoring in 15 athletes freely performing their training session. A laboratory-derived equation was used on the running track to calculate VO2 (VO2est) from HR. Oxygen uptake was also assessed by means of a portable gas analyzer (VO2real). Bland and Altman statistics were carried out in order to evaluate agreement between VO2real and VO2est. The excess in carbon dioxide production (CO2excess) was measured to test the hypothesis that the subject with the highest CO2excess had the highest VO2est - VO2real difference. VO 2real was on average 0.14 l x min (-1) below VO2est. The limits of agreement of this difference were between + 0.77 and - 0.48 l x min (-1). Thus, on average VO2real was overestimated by VO2est. Spearman non-parametric statistics found a significant correlation between CO2excess and VO2est - VO2real difference (R = 0.55, p = 0.031). This study demonstrates that the use of HR monitoring to assess VO2 during field training overestimates VO2real, especially when a substantial increase in CO2excess occurs. Therefore, this method should be used with care when an excessive amount of CO2 is produced as occurs in activities that involve the lactic acid anaerobic source of energy production.

The different apoptotic potential of the p53 codon 72 alleles increases with age and modulates in vivo ischaemia-induced cell death.

A common arginine to proline polymorphism is harboured at codon 72 of the human p53 gene. In this investigation, we found that fibroblasts and lymphocytes isolated from arginine allele homozygote centenarians and sexagenarians (Arg+) undergo an oxidative-stress-induced apoptosis at a higher extent than cells obtained from proline allele carriers (Pro+). At variance, the difference in apoptosis susceptibility between Arg+ and Pro+ is not significant when cells from 30-year-old people are studied. Further, we found that Arg+ and Pro+ cells from centenarians differ in the constitutive levels of p53 protein and p53/MDM2 complex, as well as in the levels of oxidative stress-induced p53/Bcl-xL complex and mitochondria-localised p53. Consistently, all these differences are less evident in cells from 30-year-old people. Finally, we investigated the in vivo functional relevance of the p53 codon 72 genotype in a group of old patients (66-99 years of age) affected by acute myocardial ischaemia, a clinical condition in which in vivo cell death occurs. We found that Arg+ patients show increased levels of Troponin I and CK-MB, two serum markers that correlate with the extent of the ischaemic damage in comparison to Pro+ patients. In conclusion, these data suggest that p53 codon 72 polymorphism contributes to a genetically determined variability in apoptotic susceptibility among old people, which has a potentially relevant role in the context of an age-related pathologic condition, such as myocardial ischaemia.

Does reduction of blood prolactin levels reveal the activation of central dopaminergic pathways conveying reward in top athletes?

Prolactin blood levels are modulated directly by CNS via the known tubero-infundibular dopaminergic neurons which exert an inhibitory action on lactotrope cells in the hypophysis. Prolactin is devoid of peripheral negative feedback and via lesser known central pathways (e.g., mesolimbic and mesocortical) might be further tuned by means of appropriate stimuli (e.g., addictive drugs, gambling, exercise and so forth). Therefore, a prolactin test can be utilised to obtain an objective index to assess the compliance to exercise in men. This index may be used to identify the most suitable athlete for a given sport and mainly to survey exercise as rewarding behaviour in trained people. Prolactin was assessed in male top world windsurfers (WS) and in a control group of non-windsurfer trained subjects (CS) during an exercise simulating marine windsurfing. The result was that prolactin levels decreased significantly in WS with respect to CS when compared with pre-test levels (WS: -22.7%; P<0.05).

External mechanical work versus oxidative energy consumption ratio during a basketball field test.

BACKGROUND: A field test consisting of 5 continuous runs at the maximum speed possible, playing the ball, starting from the centre line to the basket with a final shot, was studied in order to obtain an index of mechanical work efficiency in basketball players (micro-index=Jmec/Joxy) and evaluate the correlation between micro-index and velocity, acceleration, mechanical power and lactacid anaerobic capacity, respectively. METHODS: Eight male basketball players were studied; Jmec was the external mechanical work output obtained by means of a video image analysis software which gave the potential and the kinetic translational energies of athletes running and jumping and their velocity, acceleration and mechanical power. By means of a telemetric device (Kosmed K4), for measuring O2 consumption ( VO2), we obtained oxidative work (Joxy). By using this device we also assessed the excess of CO2, which was considered an index of lactacid anaerobic capacity. RESULTS: Non-parametric Spearman statistics revealed a significant correlation between mu index and mean velocity (p<0.01, r=0.90), acceleration (p<0.05, r=0.78), mechanical power (p<0.05 r=0.76) and CO2 excess (p<0.01, r=0.95). Consequently athletes who had the best index of mechanical efficiency also had the best biomechanical quality and the greatest lactacid anaerobic capacity. CONCLUSIONS: This study strongly supports the hypothesis that in basketball anaerobic capacity is important in achieving high values of speed, acceleration, mechanical power and endurance velocity.

Increased paroxysmal activity of partial seizures in man by apomorphine.

In order to study the role of dopamine (DA) in the regulation of seizure mechanisms in man, a non-emetic dose of apomorphine, a direct stimulant of DA receptors, was administered to eight patients effected by different types of epilepsy. The EEG changes induced by apomorphine administration in comparison to those elicited by promazine or placebo were evaluated in a double blind cross-over study. Similarly to promazine treatment, apomorphine worsened the EEG recordings of some patients. The apomorphine-induced increase in paroxysmal activity was observed in patients affected by partial epilepsy and was not related to the sleep-inducing properties of the drug. This effect is interpreted as being the result of a stimulation of DA autoreceptors, mediating a decrease of dopaminergic activity in the central nervous system. The use of apomorphine as an EEG activating agent is suggested.