Tennis tournaments often involve playing several consecutive matches interspersed with short periods of recovery. 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. 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 (1.5éday 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 `resté 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. 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. 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. ClinicalTrials.gov: NCT01353872.

Various continental sporting events have exposed team sports referees to different environmental conditions. Several studies have focused on strategies to prevent athlete performance impairment induced by heat or warm (or both) conditions, but few authors have investigated the effect of heat on referees' performance. In a thermoneutral environment, referees' physical activity induced mild 2.0% dehydration, which was responsible for reductions in physical, psychomotor, and cognitive performances. Therefore, the hydration status of referees should be taken into account to reduce referees' errors and misjudgments in the heat.

The aim of this study was to compare respiratory measures taken simultaneously using the Cosmed K4b² and Cortex Metamax II portable metabolic systems. 10 trained male cyclists performed a graded exercise cycle test to exhaustion (40w.3 min^− 1) under standardized conditions. The measured respiratory variables were significantly correlated between both devices: r=0.97 and 0.98 (n=10, p<0.01) for oxygen uptake ( V˙O₂) and ventilation (V_E), respectively. Further Bland and Altman plots revealed a good level of agreement for measures of V˙O₂ expressed in mL.min^− 1 [− 670 to 486] (mean bias of − 91.7, i. e., − 3.1%) or in mL.min^− 1.kg^− 1 [− 7.3 to 9.0] (mean bias of 0.85, i. e., 2.3%) and V_E [− 23.1 to 18.2] (L.min^− 1, mean bias of − 2.4, i. e. − 4.1%). However, poor agreement was found for measures of carbon dioxide (VCO₂, mL.min^− 1) [− 280 to 1 394] (mean bias of 671 i.e., 20.3%). VCO₂ at maximal exercise intensity was also significantly (p<0.01) greater in the Cortex compared to the Cosmed system. The higher measured CO₂ concentrations led to significantly (p<0.01) higher calculated respiratory exchange ratio (RER) values with the Cortex device. In conclusion, there was satisfactory agreement between the Cosmed K4b² and Cortex Metamax II systems for most respiratory measures; however there was a poor level of agreement between VCO₂ and calculated RER measurements between the 2 systems.

Chronic kidney disease (CKD) poses a significant threat, with increased rates of cardiovascular and all-cause mortality. Anemia, common in CKD, is associated with accumulation of uremic toxins in the bloodstream. We previously demonstrated that the uremic toxin indoxyl sulfate (IS) impacts the regulation of erythropoiesis in cellular and preclinical CKD models. Here, the role of non-coding RNAs in this toxic effect was evaluated. The effect of IS on microRNA expression was measured in human erythropoietic cell line UT7/EPO, using nanostring. We found a significant increase of miR-223 in cells treated with IS. This finding was further validated in human primary CD34⁺ cells, a more physiological model for human erythropoiesis. Finally, serum levels of miR-223 correlated with representative uremic toxins, including IS, in patients with various stages of CKD, and also with endothelial dysfunction markers, indicating a link with vascular damage. These correlations varied according to erythropoietin treatment and dialysis. These findings suggest that miR-223 may play a role in the development of anemia in CKD. Further investigation into the involvement of miR-223 in erythropoiesis is needed for a better understanding of the mechanisms underlying anemia in CKD and the potential role of uremic toxins. Ultimately, this may open up new therapeutic possibilities for the management of anemia in CKD.