## 1 Introduction  
Padel could be defined as a new doubles racket sport since the first record of this sport practice date back to the mid-20 th century. Despite this, padel has enjoyed a growing popularity during the last decades. According to the International Padel Federation (IPF), over 25 million people play padel in over 90 countries worldwide [1]. Similarly, padel has attracted considerable scientific interest in the last few years. To our best knowledge, since 2011, when the first article was published [2], more than 150 padel studies have been performed by different sports scientists who have focused on topics related to padel performance. A recent scoping review [3] showed that the most interesting research topics in padel are \"match analysis\", \"training\", \"epidemiology of injuries\", \"biomechanical analysis\", and \"physiology and physical performance\". In fact, several studies have been conducted under a physiological perspective to (a) describe and compare anthropometric and physical fitness attributes of padel players according to their competitive level, and also to establish a functional anthropometric and physical profile [4]; (b) examine the fitness characteristics and to identify the influence of gender and practice experience between young amateur padel players [5; 6]; (c) monitor heart rate variability (HRV) responses during a padel match and characterize them using linear and non-linear metrics; and (d) evaluate the responses of several myokines in trained players and to determine whether these responses were sex-dependent [7].  
Although the physiological demands of padel are already well-known (match play oxygen consumption below 50% of VO2 max and mean HR between 80 and 85% of maximum have been previously reported) [2], there is a lack of information on the metabolic effects of a padel match play. Only few studies have reported the impact of padel on energy regulation or metabolic systems. [PERSON] et al. [8] evaluated the urinary excretion of seven essential trace minerals after a padel match. Although creatinine, arsenic, and selenium concentrations did not change, nickel, zinc, and copper urinary levels showed significant increases, whereas a decrease in lithium concentrations was also reported. As the authors stated, these exercise-induced responses failed to explain to what extent padel has an impact on the energy balance system. In another study, researchers assessed different biochemical and hematological markers after a padel match in professional players. Sex-related differences in blood red cells count, hemoglobin, glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvate transaminase (GPT), lactate dehydrogenase (LDH), albumin, urea, and uric acid were found in resting conditions. These differences remained after padel match where significant increases in urea blood levels were also observed in female players [9]. Similar results were obtained by [PERSON] et al. [10], who determined the impact of a simulated padel match competition on hematological and urinary parameters. Moreover, no red blood cells were found in urine after padel match but a significant increase in micro-albuminuria was observed independently of sex.  
Although these previous studies indicate that both inter-individual differences and exercise intensity variability are two of the main factors that could explain the lack of clear responses of these biomarkers, there is no doubt about the need for new studies to clarify these biochemical responses and where they are coherent to the physiological cost of padel competition. Thus, the main aim of this study was to analyze the effects of padel match play on circulating parameters including substrates, metabolites, energy balance enzymes, and muscle damage biomarkers. In addition, possible sex-related differences were evaluated.