## 1 Introduction  
Athletes competing in high-level basketball must possess certain abilities and physical characteristics, such as endurance, speed, strength and explosiveness. These abilities are typically used in dynamic, demanding environments where players must move and act quickly and decisively [1, 2, 3, 4]. Therefore, a certain level of mental and physical readiness is necessary to meet the psychological and physiological requirements for the entire competitive basketball season [3, 5].  
Many fitness and basketball coaches are aiming to improve these physical abilities mainly during the pre-season period by using training protocols with increased frequency, duration and loads [6]. This approach may cause some positive effects for improving certain physical attributes, but on the other hand, it focuses more on the quantitative expression of training rather than the qualitative, something that may lead to overtraining, which will significantly increase the physical and mental fatigue and thus the probability of potential injuries [7, 8, 9].  
Considering these facts, our main goal was to investigate if some training protocols with a smaller training frequency but with an increased focus on qualitative training in relation to quantitative can cause similar or greater improvements in the physical abilities of female basketball athletes, resulting in the optimum outcome with the least possible physiological and psychological fatigue. However, it is possible that a training program with reduced training frequency will cause negative effects on the physical abilities of basketball athletes [10], but meanwhile, it can also lead to significant improvements in mental or physical fatigue [5, 11, 12]. In this case, the trainers and the coaches must reflect and process those alterations, find the appropriate balance between them and decide which plan is more suitable for every occasion.  
Pre-season period is the most important part in terms of getting basketball athletes physically ready for the competitive season, as it is the first training period of the whole season where athletes must achieve a certain level of physical, technical and tactical abilities, so they can sustain the heavy and long schedule of matches, reducing at the same time the risk of any possible injuries [3]. Also, there is a very limited amount of studies that have examined how various training aspects can affect the female basketball athletes, especially in a pre-season period [3]. Training adaptations may differ between male and female athletes, so there is a need for more studies to turn their focus on female athletes [12]. Importantly, it has not yet been researched if different training frequencies affect the physiological and biochemical markers in female basketball players during a pre-season period. The present study hopes to fill in this gap in the research area.  
More specifically, the main purpose of the present study is to apply three pre-season training protocols in professional female basketball athletes, each with a different weekly frequency of training units (TUs). Accordingly, we will examine the effect of each of the three protocols on the physical abilities and the biochemical markers of muscle damage and oxidative stress, as expressed through a physiological and biochemical evaluation. Muscle damage and oxidative stress will be evaluated using the CK and LDH enzymes, which are broadly recognized as two of the best muscle damage markers, along with the determination of GPx and PC, which are two of the most approved markers with antioxidant status. It was very important for our research to implement these specific biochemical markers, so we can better understand the effects that they may have on improving or reducing performance. Subsequently, there will be a comparison between the physiological and the biochemical alterations caused by each protocol and also an attempt to locate and demonstrate all the necessary correlations between the physiological and biochemical characteristics of the volunteers.