Gaizka Mejuto

Cerebral hemodynamics during graded Valsalva maneuvers

The Valsalva maneuver (VM) produces large and abrupt changes in mean arterial pressure (MAP) that challenge cerebral blood flow and oxygenation. We examined the effect of VM intensity on middle cerebral artery blood velocity (MCAv) and cortical oxygenation responses during (phases I–III) and following (phase IV) a VM. Healthy participants (n = 20 mean ± SD: 27 ± 7 years) completed 30 and 90% of their maximal VM mouth pressure for 10 s (order randomized) whilst standing. Beat-to-beat MCAv, cerebral oxygenation (NIRS) and MAP across the different phases of the VM are reported as the difference from standing baseline. There were significant interaction (phase * intensity) effects for MCAv, total oxygenation index (TOI) and MAP (all P < 0.01). MCAv decreased during phases II and III (P < 0.01), with the greatest decrease during phase III (−5 ± 8 and −19 ± 15 cm·s−1 for 30 and 90% VM, respectively). This pattern was also evident in TOI (phase III: −1 ± 1 and −5 ± 4%, both P < 0.05). Phase IV increased MCAv (22 ± 15 and 34 ± 23 cm·s−1), MAP (15 ± 14 and 24 ± 17 mm Hg) and TOI (5 ± 6 and 7 ± 5%) relative to baseline (all P < 0.05). Cerebral autoregulation, indexed, as the %MCAv/%MAP ratio, showed a phase effect only (P < 0.001), with the least regulation during phase IV (2.4 ± 3.0 and 3.2 ± 2.9). These data illustrate that an intense VM profoundly affects cerebral hemodynamics, with a reactive hyperemia occurring during phase IV following modest ischemia during phases II and III.

JUMP LANDING CHARACTERISTICS IN ELITE SOCCER PLAYERS WITH CEREBRAL PALSY

The aim of the present study was to analyse the parameters that characterize the vertical ground reaction force during the landing phase of a jump, and to determine the relationship among these parameters in elite soccer players with cerebral palsy (CP). Thirteen male members of the Spanish national soccer team for people with CP (mean age: 27.1 ± 4.7 years) volunteered for the study. Each participant performed three counter movement jumps. The characteristics of the first peak of the vertical ground reaction force during the landing phase of a jump, which corresponds to the forefoot contact with the ground, were similar to the results obtained in previous studies. However, a higher magnitude of rearfoot contact with the ground (F2) was observed in participants with CP than in participants without CP. Furthermore, a significant correlation between F2 magnitude and the elapsed time until its production (T2) was not observed (r = -0.474 for p = 0.102). This result implies that a landing technique based on a delay in the production of F2 might not be effective to reduce its magnitude, contrary to what has been observed in participants without CP. The absence of a significant correlation between these two parameters in the present study, and the high magnitude of F2, suggest that elite soccer players with CP should use footwear with proper cushioning characteristics.

Physiological and kinanthropometrical parameters of an elite climber. Single case study

BackgroundExtremealtitudeclimbingeffectshavebeendescribedinseveralstudies.�Usuallythesestudiesarecarriedoutonex- peditionsbutnotlongitudinally.�Theaimofthisstudyistodescribephysiologicalandkinanthropometricalchang- esoverthetimeinatop-levelclimber. �:� Thisisasingle-subjectstudyonanindividualcareerpart�(fromages�27�to�41).�Somephysiologicalandkinanthro- pometricalparameterswereanalysedin�3�differentseasonpartsatsealevel;�before�(PRE),�after�(POST)�andoff� climbingexpeditions�(OFF).�Allexpeditionswere�>7000�m. � Results:� Nochangeswerefoundinphysiologicalparametersduringtheperiodofstudyregardingtoseasonpart.� Kinanthropometryincontrast,� presentedsignificantchanges� (P<0.01)� intwoskinfolds� (PRE/OFFvs.� POST),� whereas�∑�ofSFshoweddifferencesbetween�(PREvs.�OFF).�Resultsalsoindicatesomesignificantcorrelations� (P<0.05)�betweenbothkinanthropometricalandphysiologicalvariablesandtheparticipantagingprocess. � Conclusions:� Thehighfitnessleveloftheparticipantcombinedwithhisgiftforacclimatizationandabroadclimbingcareer,� maintainphysiologicalandkinanthropometricalstabilityduringtheanalysedperiodevenafterrepeatedexposure� toextremealtitudes.�However,�agingprocessappearstobeinvolvedinmaximalexercisecardiovascularcapacity� decline.�Surprisingly,�kinanthropometricalvariablessuchasweight,�BMIandfatpercentageshowedlowervalues� throughthetimeattributableprobablytoahighphysicalactivity.

The effect of ice slurry ingestion on body temperature and cycling performance in competitive athletes

The effects of pre cooling on endurance performance are widely known. In contrast, the approach of cooling during endurance exercise in combination with pre-exercise cooling has been poorly understood. The purpose of the present study was to determine whether the effects of precooling and cooling during exercise enhance exercise performance compared to the ingestion of a thermo-neutral beverage (20 °C) or precooling alone in cycling performance. This was an experimental study using a randomised crossover design in which 7 cyclists underwent three trials comprising of 45 min steady state cycling (SS) at 70% VO2 max and a subsequent 10 km time trial (TT) in hot conditions (32 °C, 50% relative humidity). Rectal temperature (Tre), heat storage (HS), heart rate (HR), blood lactate concentration (BLA) and thermal sensation (TS) were measured. The intervention consisted of: (1) ingestion of thermo-neutral beverage before and during SS cycling (TN), (2) ingestion of ice slurry beverage and application of iced towels (precooling) prior to exercise, and then ingestion of thermo-neutral beverage during SS (PRE) and (3) precooling strategy as above plus ice slurry ingestion during SS cycling (PRE + MID). The intake of thermo-neutral or ice slurry beverage (14 g/kg) occurred over 30 min before and every 15 min during SS cycling. There was no significant difference in TT performance between all the conditions (P =0.72). However, PRE and PRE + MID caused a significant decrease in Tre (P < 0.05) from TN during exercise. Accordingly, both precooling and a combination of precooling and mid-cooling during exercise in hot conditions may be a practical and effective way of reducing core temperature. Future studies should investigate longer distance events and timing of ice slurry ingestion.

Validity and reliability of a global positioning system to assess 20 m sprint performance in soccer players

The aims of the present study were (1) to analyze the association between the time score obtained by a global positioning system device at a frequency of 10 Hz and by timing gates and (2) to assess intrarater reliability and agreement of these two methods in a 20 m straight sprint test. Twelve amateur soccer players (age: 21.08 ± 1.57 years) gave their voluntary consent to take part in this study. Each player performed five repetitions of a 20 m sprint test in each of the two test sessions. The start of the sprint for the global positioning system device was determined by a continuous increase in speed from below (0–0.1 km/h). No significant relationship (r = 0.118, p > 0.05) between 20 m straight sprint times measured by the timing gates and the global positioning system was found. The test–retest intra-class correlation coefficient obtained from the measurement of sprint times with the global positioning system device was small (r = 0.118, p > 0.05). The continuous increase in speed from below (0–0.1 km/h) seems not to be a precise way to evaluate the sprint time by a global positioning system device in a 20 m straight sprint test.

Hematological Changes in an Elite Climber Over 18 Years

AIMS To evaluate the influence of repeated exposure to high altitude over a period of 18 years in an elite climber, red blood cell related parameters were analyzed. Red blood cell levels, hemoglobin concentration, and hematocrit were taken before and after expedition. RESULTS The analysis, revealed an average increase of 15% in red blood cell related parameters, and showed a negative correlation (p<0.01) between age and post-expedition results. Furthermore, the first part of the study period was statistically different compared to the second (p<0.01). CONCLUSION Exposure to extreme altitudes does lead to an increase in red blood cell parameters in the subject of the present study, as it can be seen from the results. Interestingly, this hematological response to extreme hypobaric hypoxia stimuli was attenuated over time. This however is a case report on an elite climber, and further research is needed in order to determine if such responses can be observed in other populations.