## 4 Discussion  
The management of exercise-induced muscle damage (EIMD) is a primary goal for sports scientists in order to achieve rapid and effective recovery after intense training sessions and/or competitive events [44]. Oxidative stress is a key pathophysiological mechanism that leads to the clinical symptoms of EIMD [45], and the regulation of redox homeostasis following damaging protocols has been widely studied, mainly through the administration of supplements [7]. However, regardless of the relevance of EIMD mechanisms to athlete recovery, the induction of EIMD following eccentric exercise serves as a good model through which controlled oxidative stress can be induced in humans, allowing for the study of the antioxidant potential of dietary patterns, foods, and supplements [6]. In most cases, the assessment of exercise-induced oxidative stress is conducted invasively through the measurement of a limited panel of biochemical markers that often fail to capture the complexity of redox mechanisms [45]. Additionally, due to their invasive nature, they cannot be used to assess oxidative stress in the field. The analysis of volatile organic compounds (VOCs) in exhaled air represents a non-invasive technique that has rapidly developed in recent years for the prediction and diagnosis of diseases. However, its application in sports science is still quite limited, though promising. In light of the above, the primary objectives of this study were (a) to determine whether a protocol of eccentric exercise, which can induce EIMD and potentially exercise-induced oxidative stress, could affect the profile of volatile alkanes in the exhaled air of healthy volunteers, (b) to find out whether a 15-day administration of _Spirulina Nigeria_ can influence the profile of volatile alkanes in the exhaled air of healthy volunteers, and (c) to determine whether any changes in post-exercise oxidative stress with the administration of _Spirulina Nigeria_ are accompanied by changes in the profile of volatile alkanes. The VOC analysis in exhaled air has been conducted as part of a broader study aimed at examining the effect of supplemental _Spirulina Nigeria_ administration on the phenomenon of EIMD following eccentric exercise in the upper limbs. The results of that study have already been published, which indicated that the supplemental administration of _Spirulina Nigeria_ had no effect on the ergophysiological and biochemical markers of EIMD [42]. Figure 3: Effect of spirulina supplementation on TBARSs: (**a**) absolute values, (**b**) % change, and (**c**) net area under the curve. Our research team focused on the study of volatile alkanes, as they can serve as end products of lipid peroxidation. A number of studies have shown that the profile of volatile alkanes, both in terms of quantity and their relative ratios, varies in diseases where oxidative stress is either an etiological factor or coexists with the disease. Such studies have been conducted in patients with breast cancer [46], childhood obesity [47], and silicosis [34]. The team of [PERSON] et al. developed the breath methylated alkane contour (BMAC), a 3-dimensional surface plot of C4-C20 alkanes and monomethylated alkanes, through which they demonstrated predictive ability for diseases such as unstable angina pectoris [48], diabetes [49], and preeclampsia [37] in case-control studies. The aforementioned studies indicate that the profile of volatile alkanes may serve as a promising diagnostic and prognostic marker for diseases where oxidative stress coexists with the condition. However, it appears that different alkanes are associated with different pathologies, and there are no well-established biochemical mechanisms explaining the change in concentrations of these markers in various diseases. The 15-day administration of _Spirulina Nigeria_ appears to have led to a trend of decreasing levels of hexane, 2-methylhexane, 4-methyloctane, and undecane in the PL group and a trend of increasing levels in the SPI group.