This study examined the validity and reliability of a sequential "Run-Bike-Run" test (RBR) in age-group triathletes. Eight Olympic distance (OD) specialists (age 30.0 ± 2.0 years, mass 75.6 ± 1.6 kg, ...run VO2max 63.8 ± 1.9 ml· kg(-1)· min(-1), cycle VO2peak 56.7 ± 5.1 ml· kg(-1)· min(-1)) performed four trials over 10 days. Trial 1 (TRVO2max) was an incremental treadmill running test. Trials 2 and 3 (RBR1 and RBR2) involved: 1) a 7-min run at 15 km· h(-1) (R1) plus a 1-min transition to 2) cycling to fatigue (2 W· kg(-1) body mass then 30 W each 3 min); 3) 10-min cycling at 3 W· kg(-1) (Bsubmax); another 1-min transition and 4) a second 7-min run at 15 km· h(-1) (R2). Trial 4 (TT) was a 30-min cycle - 20-min run time trial. No significant differences in absolute oxygen uptake (VO2), heart rate (HR), or blood lactate concentration (BLA) were evidenced between RBR1 and RBR2. For all measured physiological variables, the limits of agreement were similar, and the mean differences were physiologically unimportant, between trials. Low levels of test-retest error (i.e. ICC <0.8, CV<10%) were observed for most (logged) measurements. However BLA post R1 (ICC 0.87, CV 25.1%), BLA post Bsubmax (ICC 0.99, CV 16.31) and BLA post R2 (ICC 0.51, CV 22.9%) were least reliable. These error ranges may help coaches detect real changes in training status over time. Moreover, RBR test variables can be used to predict discipline specific and overall TT performance. Cycle VO2peak, cycle peak power output, and the change between R1 and R2 (deltaR1R2) in BLA were most highly related to overall TT distance (r = 0.89, p < 0. 01; r = 0.94, p < 0.02; r = 0.86, p < 0.05, respectively). The percentage of TR VO2max at 15 km· h(-1), and deltaR1R2 HR, were also related to run TT distance (r = -0.83 and 0.86, both p < 0.05).
Celotno besedilo
Dostopno za:
DOBA, FSPLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Interferon (IFN)-γ release assays (IGRAs) are used to diagnose latent tuberculosis (TB) infection (LTBI). To improve the accuracy of these tests, different approaches, such as alternative cytokine ...detection and using different antigens, are considered. Following this purpose, this study aims to evaluate the addition of EspC, EspF and Rv2348-B to those present in the QuantiFERON-TB Gold In-Tube (QFN-G-IT). We included 115 subjects: 74 active TB patients, 17 LTBI individuals and 24 healthy controls. Whole blood samples were collected in QFN-G-IT and in-house tubes containing different combinations of EspC, EspF and Rv2348-B, together with ESAT-6, CFP-10, and TB7.7. After overnight incubation at 37 ºC, plasma was harvested and IFN-γ quantified. IFN-γ levels in the QFN-G-IT and in-house tubes correlated very good (Spearman Rho(r) > 0.86). In-house antigen combinations distinguished healthy individuals from those with active TB and LTBI (specificities and sensitivities higher than 87.5% and 96.3%, respectively AUC > 0.938). Adding EspC, EspF and Rv2348-B, increased the sensitivity of the test, being the addition of EspC and Rv2348-B the combination that yielded a higher sensitivity with no specificity loss. Addition of these antigens could improve diagnosis in patients with impaired or immature immune response who are at high risk of developing TB.
Tacrolimus is an immunosuppressive drug that has proved effective in the treatment of psoriasis when administered systemically. Topically, it seems only useful in thin psoriasis plaques located on ...the face, genitalia, and intertriginous areas. We present an open-label clinical trial to test the efficacy of 0.1% tacrolimus ointment in patients with psoriasis on the face, intertriginous areas, both, and in corporal plaques. Efficacy was assessed with the evaluation of erythema, desquamation, infiltration, reduction of the PASI, and reduction of itching. A total of 15 patients were enrolled in the study. In all the localizations evaluated, each of the signs (erythema, desquamation, and infiltration) showed a statistically significant improvement when compared to the baseline (p < .001). Itching also improved rapidly. PASI was also reduced from a mean of 12 at baseline to 2.2 at the end of the study. Of the 15 patients, only 2 experienced an adverse effect (13%), which was described as a warm sensation in facial lesions which was transient and self-limited. In conclusion, tacrolimus ointment may be an alternative to classical options for the treatment of psoriasis, not only for intertriginous, genital, and facial areas, but also for corporal plaques without occlusion, with good tolerance.
Objectives: To examine changes in exercise characteristics, maximal voluntary contraction, and explosive strength during prolonged tennis playing. Methods: Maximal isometric voluntary contraction ...(MVC), leg stiffness (hopping), and peak power in squat (SJ) and countermovement (CMJ) jumps were measured before, every 30 minutes during, and 30 minutes after a three hour tennis match in 12 well trained players. Heart rate (HR), the effective playing time (EPT), rating of perceived exertion (RPE), and muscle soreness of knee extensors were also measured. Results: Decreases in MVC (−9%; p<0.05) and leg stiffness (−9%; p = 0.17) were observed after the match and were significantly correlated (r = 0.66; p = 0.05). Peak power in SJ and CMJ tests was maintained during the match but was lower (p<0.001) 30 minutes after. Average HR and EPT were 144 (8) beats/min and 21 (4)% respectively. A strong correlation was found between EPT and HR (r = 0.93; p<0.05). RPE and muscle soreness increased linearly during the exercise and were significantly correlated (r = 0.99; p<0.001). Conclusions: Progressive reductions in maximal voluntary strength and leg stiffness highly correlated with increases in perceived exertion and muscle soreness were observed throughout a three hour tennis match, whereas explosive strength was maintained and decreased only after the match. These alterations may result in less efficient on-court movement and stroke production. They are, however, lower than those reported during continuous exercise of the same duration. The intermittent pattern of tennis and the numerous stretch-shortening cycle movements partly explain these results.
Cell failure mechanisms in PEM water electrolyzers Millet, P.; Ranjbari, A.; de Guglielmo, F. ...
International journal of hydrogen energy,
November 2012, 2012-11-00, Letnik:
37, Številka:
22
Journal Article
Recenzirano
PEM water electrolysis offers an efficient and flexible way to produce “green-hydrogen” from renewable (intermittent) energy sources. Most research papers published in the open literature on the ...subject are addressing performances issues and to date, very few information is available concerning the mechanisms of performance degradation and the associated consequences. Results reported in this communication have been used to analyze the failure mechanisms of PEM water electrolysis cells which can ultimately lead to the destruction of the electrolyzer. A two-step process involving firstly the local perforation of the solid polymer electrolyte followed secondly by the catalytic recombination of hydrogen and oxygen stored in the electrolysis compartments has been evidenced. The conditions leading to the onset of such mechanism are discussed and some preventive measures are proposed to avoid accidents.
► Hydrogen production by PEM water electrolysis. ► Investigation of cell failure mechanisms and discussion on safety issues. ► Conditions for membrane perforation at elevated current densities. ► Hydrogen–oxygen combustion and irreversible electrolysis stack degradation.
The purpose of this study was to test the hypothesis that athletes having a slower oxygen uptake ( VO(2)) kinetics would benefit more, in terms of time spent near VO(2max), from an increase in the ...intensity of an intermittent running training (IT). After determination of VO(2max), vVO(2max) (i.e. the minimal velocity associated with VO(2max) in an incremental test) and the time to exhaustion sustained at vVO(2max) ( T(lim)), seven well-trained triathletes performed in random order two IT sessions. The two IT comprised 30-s work intervals at either 100% (IT(100%)) or 105% (IT(105%)) of vVO(2max) with 30-s recovery intervals at 50% of vVO(2max) between each repeat. The parameters of the VO(2) kinetics (td(1), tau(1), A(1), td(2), tau(2), A(2), i.e. time delay, time constant and amplitude of the primary phase and slow component, respectively) during the T(lim) test were modelled with two exponential functions. The highest VO(2) reached was significantly lower ( P<0.01) in IT(100%) run at 19.8 (0.9) km(.)h(-1) 66.2 (4.6) ml(.)min(-1.)kg(-1) than in IT(105%) run at 20.8 (1.0) km(.)h(-1) 71.1 (4.9) ml(.)min(-1.)kg(-1) or in the incremental test 71.2 (4.2) ml(.)min(-1.)kg(-1). The time sustained above 90% of VO(2max) in IT(105%) 338 (149) s was significantly higher ( P<0.05) than in IT(100%) 168 (131) s. The average T(lim) was 244 (39) s, tau(1) was 15.8 (5.9) s and td(2) was 96 (13) s. tau(1) was correlated with the difference in time spent above 90% of VO(2max) ( r=0.91; P<0.01) between IT(105%) and IT(100%). In conclusion, athletes with a slower VO(2) kinetics in a vVO(2max) constant-velocity test benefited more from the 5% rise of IT work intensity, exercising for longer above 90% of VO(2max) when the IT intensity was increased from 100 to 105% of vVO(2max).
Abstract Objective The aim of this study was to determine whether V ˙ O 2 kinetics and specifically, the time constant of transitions from rest to heavy ( τp H) and severe ( τp S) exercise ...intensities, are related to middle distance swimming performance. Design Fourteen highly trained male swimmers (mean ± SD: 20.5 ± 3.0 yr; 75.4 ± 12.4 kg; 1.80 ± 0.07 m) performed an discontinuous incremental test, as well as square wave transitions for heavy and severe swimming intensities, to determine V ˙ O 2 kinetics parameters using two exponential functions. Methods All the tests involved front-crawl swimming with breath-by-breath analysis using the Aquatrainer swimming snorkel. Endurance performance was recorded as the time taken to complete a 400 m freestyle swim within an official competition (T400), one month from the date of the other tests. Results T400 (Mean ± SD) (251.4 ± 12.4 s) was significantly correlated with τp H (15.8 ± 4.8 s; r = 0.62; p = 0.02) and τp S (15.8 ± 4.7 s; r = 0.61; p = 0.02). The best single predictor of 400 m freestyle time, out of the variables that were assessed, was the velocity at V ˙ O 2 max v V ˙ O 2 max , which accounted for 80% of the variation in performance between swimmers. However, τp H and V ˙ O 2 max were also found to influence the prediction of T400 when they were included in a regression model that involved respiratory parameters only. Conclusions Faster kinetics during the primary phase of the V ˙ O 2 response is associated with better performance during middle-distance swimming. However, v V ˙ O 2 max appears to be a better predictor of T400.
Vleck, VE, Bentley, DJ, Millet, GP, and Cochrane, T. Triathlon event distance specializationtraining and injury effects. J Strength Cond Res 24(1)30-36, 2010-We conducted a preliminary, ...questionnaire-based, retrospective analysis of training and injury in British National Squad Olympic distance (OD) and Ironman distance (IR) triathletes. The main outcome measures were training duration and training frequency and injury frequency and severity. The number of overuse injuries sustained over a 5-year period did not differ between OD and IR. However, the proportions of OD and IR athletes who were affected by injury to particular anatomical sites differed (p < 0.05). Also, fewer OD athletes (16.7 vs. 36.8%, p < 0.05) reported that their injury recurred. Although OD sustained fewer running injuries than IR (1.6 ± 0.5 vs. 1.9 ± 0.3, p < 0.05), more subsequently stopped running (41.7 vs. 15.8%) and for longer (33.5 ± 43.0 vs. 16.7 ± 16.6 days, p < 0.01). In OD, the number of overuse injuries sustained inversely correlated with percentage training time, and number of sessions, doing bike hill repetitions (r = −0.44 and −0.39, respectively, both p < 0.05). The IR overuse injury number correlated with the amount of intensive sessions done (r = 0.67, p < 0.01 and r = 0.56, p < 0.05 for duration of “speed run” and “speed bike” sessions). Coaches should note that training differences between triathletes who specialize in OD or IR competition may lead to their exhibiting differential risk for injury to specific anatomical sites. It is also important to note that cycle and run training may have a “cumulative stress” influence on injury risk. Therefore, the tendency of some triathletes to modify rather than stop training when injured-usually by increasing load in another discipline from that in which the injury first occurred-may increase both their risk of injury recurrence and time to full rehabilitation.
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