# The Effect of Surgical Mask Use in Anaerobic Running Performance
## 4 Discussion  
The present study aimed to analyze the effect of surgical mask use on the anaerobic running performance of athletes. The initial hypothesis was confirmed, since there was a decrease of anaerobic running performance while wearing a surgical mask. Results suggested that wearing a surgical mask negatively affected anaerobic running performance, since there was a time increase of 12.51% on 50 m and 19.09% on 400 m test. This loss of performance has been attributed by authors to a metabolic shift and a decrease in muscle efficiency, a consequence of impaired autonomic stability, lower cardiac fitness and muscle blood supply [8]. However, other authors attributed the loss of performance to the discomfort associated with mask-wearing, higher ratings of dyspnea and lower blood oxygen saturation, showing a 14% reduction in exercise time and 29% decrease in VO2 max after maximal treadmill effort with surgical mask [24]. Our data support both studies, and are consistent with the lower blood oxygen saturation and greater values of RPE found in the present study after both tests. Interestingly, blood glucose levels were higher in participants when wearing surgical masks after the 400 m test, but not after the 50 m. In short anaerobic efforts, like the 50 m test, the organism obtains energy from phosphocreatine, which is used as the principal energy substrate, followed by the use of glucose when not highly active [25], explaining the lack of differences of glucose values in this test between the use and no use of mask. However, in the 400 m test, the mobilization of glucose is higher than in the 50 m test, the large metabolic demands, and the increased fermentation of glucose to respond to the high energy demand [26] explains the higher glucose value in this 400 m test than in the 50 m test. The higher blood lactate value after the test when athletes used a mask may be due to a higher activation of the anaerobic lactic metabolism. As the oxygen supply to the cell is lower due to the re-inhalation of CO2 due to the use of the mask, the activation of aerobic metabolism is less, allowing a greater stimulus to produce energy by the lactic anaerobic metabolic pathways [27]. Which stimulates the mobilization of organic glucose to reach the active muscle cell and be consumed as an energy source. Contrary to our results, previous authors found no differences with and without mask on blood lactate values in a continuous cycling exercise [28] or steady state exercise [15]. The intensity of the activity performed in these studies was lower than in the actual study, close to the anaerobic threshold (\(\approx\)4.2 mmol), thus, the contribution of anaerobic metabolism for this activity is lower and lactate concentration is more resistant to modification. Rating of perceived exertion showed values close to maximum after the 400 m [29], being higher with the use of surgical mask. Authors suggested that the increased breathing resistance, heat, tightness, and overall discomfort while wearing masks, are items that increase subjective perception of effort, which is even greater when wearing an FP2/KN95 mask [27]. Furthermore, increases of more than 60% in RPE have been reported in resis