Effects of sports drinks on the maintenance of physical performance during 3 tennis matches: A randomized controlled study

Background: Tennis tournaments often involve playing several consecutive matches interspersed with short periods of recovery. Objective: The objective of this study was firstly to assess the impact of several successive tennis matches on the physical performance of competitive players and secondly to evaluate the potential of sports drinks to minimize the fatigue induced by repeated matches. Methods: This was a crossover, randomized controlled study. Eight male regionally-ranked tennis players participated in this study. Players underwent a series of physical tests to assess their strength, speed, power and endurance following the completion of three tennis matches each of two hours duration played over three consecutive half-days (1.5 day period for each condition). In the first condition the players consumed a sports drink before, during and after each match; in the second, they drank an identical volume of placebo water. The results obtained were compared with the third 'rest' condition in which the subjects did not play any tennis. Main outcomes measured were maximal isometric strength and fatigability of knee and elbow extensors, 20-m sprint speed, jumping height, specific repeated sprint ability test and hand grip strength. Results: The physical test results for the lower limbs showed no significant differences between the three conditions. Conversely, on the upper limbs the EMG data showed greater fatigue of the triceps brachii in the placebo condition compared to the rest condition, while the ingestion of sports drinks attenuated this fatigue. Conclusions: This study has demonstrated for the first time that, when tennis players are adequately hydrated and ingest balanced meals between matches, then no large drop in physical performance is observed even during consecutive competitive matches

Interaction of alpha particles at the cellular level - Implications for the radiation weighting factor

Since low dose effects of alpha particles are produced by cellular hits in a relatively small fraction of exposed cells, the present study focuses on alpha particle interactions in bronchial epithelial cells following exposure to inhaled radon progeny. A computer code was developed for the calculation of microdosimetric spectra, dose and hit probabilities for alpha particles emitted from uniform and non-uniform source distributions in cylindrical and Y-shaped bronchial airway geometries. Activity accumulations at the dividing spur of bronchial airway bifurcations produce hot spots of cellular hits, indicating that a small fraction of cells located at such sites may receive substantially higher doses. While presently available data on in vitro transformation frequencies suggest that the relative biological effectiveness for alpha particles ranges from about 3 to 10, the effect of inhomogeneous activity distributions of radon progeny may slightly increase the radiation weighting factor relative to a uniform distribution. Thus a radiation weighting factor of about 10 may be more realistic than the current value of 20, at least for lung cancer risk following inhalation of short-lived radon progeny. © Oxford University Press 2004; all rights reserved

Monte Carlo code for microdosimetry of inhaled α emitters

A Monte Carlo code has been developed to calculate the local energy deposited by α emitters deposited on the inner surface in the lung airway. Developed to deal further with airway bifurcations, this code has been as a first step validated in a cylindrical airway configuration by comparison with well-established analytical codes in the case of contamination of bronchiolar airways with actinides. The code has then been applied to the study of uniform and non-uniform contamination of cylindrical bronchial airways by radon progeny in indoor and mine exposure conditions. In addition to the microdosimetric spectra, the average microdosimetric parameters (z̄F, n̄, z̄) have been evaluated. The work currently in progress consists in adapting this developed Monte Carlo code to the configuration of an airway bifurcation with realistic particles deposition

Using LiF:Mg,Cu,P TLDs to estimate the absorbed dose to water in liquid water around an 192^{192}Ir brachytherapy source

International audiencePurpose:The absorbed dose to water is the fundamental reference quantity for brachytherapy treatment planning systems and thermoluminescence dosimeters (TLDs) have been recognized as the most validated detectors for measurement of such a dosimetric descriptor. The detector response in a wide energy spectrum as that of an$^{192}$Ir brachytherapy source as well as the specific measurement medium which surrounds the TLD need to be accounted for when estimating the absorbed dose. This paper develops a methodology based on highly sensitive LiF:Mg,Cu,P TLDs to directly estimate the absorbed dose to water in liquid water around a high dose rate $^{192}$Ir brachytherapy source.Methods:Different experimental designs in liquid water and air were constructed to study the response of LiF:Mg,Cu,P TLDs when irradiated in several standard photon beams of the LNE‐LNHB (French national metrology laboratory for ionizing radiation). Measurement strategies and Monte Carlo techniques were developed to calibrate the LiF:Mg,Cu,P detectors in the energy interval characteristic of that found when TLDs are immersed in water around an$^{192}$Ir source. Finally, an experimental system was designed to irradiate TLDs at different angles between 1 and 11 cm away from an $^{192}$Ir source in liquid water. Monte Carlo simulations were performed to correct measured results to provide estimates of the absorbed dose to water in water around the $^{192}$Ir source.Results:The dose response dependence of LiF:Mg,Cu,P TLDs with the linear energy transfer of secondary electrons followed the same variations as those of published results. The calibration strategy which used TLDs in air exposed to a standard N‐250 ISO x‐ray beam and TLDs in water irradiated with a standard $^{137}$Cs beam provided an estimated mean uncertainty of 2.8% ($k$ = 1) in the TLD calibration coefficient for irradiations by the $^{192}$Ir source in water. The 3D TLD measurements performed in liquid water were obtained with a maximum uncertainty of 11% ($k$ = 1) found at 1 cm from the source. Radial dose values in water were compared against published results of the American Association of Physicists in Medicine and the European Society for Radiotherapy and Oncology and no significant differences (maximum value of 3.1%) were found within uncertainties except for one position at 9 cm (5.8%). At this location the background contribution relative to the TLD signal is relatively small and an unexpected experimental fluctuation in the background estimate may have caused such a large discrepancy.Conclusions:This paper shows that reliable measurements with TLDs in complex energy spectra require a study of the detector dose response with the radiation quality and specific calibration methodologies which model accurately the experimental conditions where the detectors will be used. The authors have developed and studied a method with highly sensitive TLDs and contributed to its validation by comparison with results from the literature. This methodology can be used to provide direct estimates of the absorbed dose rate in water for irradiations with HDR192Ir brachytherapy sources