## 1 Introduction  
The use of marine algae-derived supplements has gained increasing attention in sports nutrition due to their potential to support metabolic regulation, counteract oxidative stress, and modulate inflammatory pathways. Among these, _Ulva_ spp. has emerged as a promising candidate because of its rich content of bioactive compounds such as sulfated polysaccharides (ulvans), polyphenols, minerals, antioxidants, and highly bioavailable proteins [1, 2, 3]. These constituents have demonstrated various physiological effects in preclinical models, suggesting that Ulva-based supplementation may benefit physically active individuals. One of the most notable bioactive components in Ulva is ulvan, a sulfated polysaccharide that has demonstrated antihyperglycemic effects, improving insulin tolerance and enhancing antioxidant enzyme activity, which can contribute to better blood glucose control [2]. Additionally, ulvans from Ulva have exhibited gut microbiota-modulating properties, which may further support metabolic regulation and gastrointestinal health--key aspects in sports performance and recovery [3]. Beyond polysaccharides, Ulva is also rich in soluble and insoluble fibers, which have been linked to improvements in carbohydrate metabolism and lipid profiles [4]. These dietary fibers not only support gut health but also contribute to lower cholesterol levels and improved lipid metabolism, both of which are essential for sustaining energy levels in physically active individuals. Given these findings, the integration of _Ulva_-derived supplements in sports nutrition presents an opportunity to enhance metabolic efficiency and performance in athletes. Intense physical activity increases the production of reactive oxygen species (ROS), which, if not adequately neutralized, can lead to oxidative stress, cellular damage, and reduced performance [5]. Elevated oxidative stress has been associated with muscle fatigue, tissue damage, and longer recovery times [6]. Marine algae, including Ulva, contain potent antioxidants such as polyphenols, flavonoids, carotenoids, and sulfated polysaccharides, which have demonstrated strong free radical scavenging activity and the ability to enhance endogenous antioxidant defenses [7]. A recent meta-analysis on algal-based supplements found significant reductions in oxidative stress markers and improvements in antioxidant enzyme activity, further supporting their potential role in sports performance and recovery [8]. Beyond oxidative stress, prolonged high-intensity training can also lead to chronic inflammation, which may interfere with muscle regeneration and increase the risk of injuries. Markers such as myeloperoxidase (MPO) and the erythrocyte sedimentation rate (ESR) are widely used to assess inflammatory status in athletes [9]. While certain Ulva extracts have demonstrated immunomodulatory properties, their effects on inflammation markers in physically active populations remain unclear [10]. Although the effects of marine algae have been reported in animal models and populations with metabolic disorders [11] few studies have evaluated these effects in athletes, a population exposed to high metabolic demands, redox imbalance, and chronic inflammatory load. This gap in the literature represents a major limitation in applying current findings to real-world sports contexts. In addition, the potential of algae-based supplementation to support recovery, enhance metabolic efficiency, and reduce inflammation has not been clearly validated using randomized controlled trials in elite or highly trained individuals. Such knowledge is highly relevant for coaches, sports nutritionists, and athletes interested in functional strategies to support adaptation to training and prevent performance declines during intense periods [12]. This study aimed to evaluate the effects of a marine algae-based supplement derived from Ulva on glycemic control, lipid metabolism, oxidative stress, and inflammatory responses in athletes.