# The Effect of Surgical Mask Use in Anaerobic Running Performance
## 2 Material and Methods
### Procedure  
To reach the study aim, participants performed two anaerobic running tests (50 m and 400 m) in an outdoor running track field with and without surgical mask, between 8:30 a.m. and 10.50 a.m., temperature of 22.1 \(\pm\) 0.5 \({}^{\circ}\)C, and 40.2 \(\pm\) 2.3% of humidity, in two different days separated by 48 h. The inclusion criteria were membership in an athletic club, a minimum of five years of training and experience, and negative PCR result one week before testing. The exclusion criteria were use of ergogenic aids, use of any other non-surgical mask, injury in the last 3 months, presence of COVID-19 symptomatology/positive in the last 4 months, presence of COVID-19 symptomatology during the week of the test, or direct contact with a positive case. Participants were then randomly divided into two groups, the first group conducted the first evaluation day of the test with mask and the second evaluation day without the mask. The other group conducted the first evaluation day without mask and the second evaluation day with the mask. In both days, participants provided a basal sample, then began a standardized warm up consisted of 5 min of running (light aerobic), joint mobility of the main joint axes, ballistic stretching, and 5 speed progressions as reported in previous research [18]. Then, they conducted a 50 m sprint test at maximum intensity and after 20 min of recovery performed a 400 m test at maximum intensity. These two tests are both considered anaerobic, excellent tests of this metabolic pathway. The 50 m is an eminently anaerobic alactic test, while 400 m is a lactic acid power test.  
Before and after tests the following parameters were evaluated [18]:  
* Body height and weight by a SECA model 714 following previous procedures [19].
* Rating of perceived exertion by the Borg Scale (6-20) [20].
* Subjective Perceived Stress (0-100) [21] as in previous psychophysiological research.  
* Blood oxygen saturation by an oximeter OXYM4000 (Quirumed, Madrid, Spain), placed in the index finger of the right arm.
* Blood glucose concentration by the analysis of 5 \(\mu\)L of capillary finger blood using a portable analyzer (One Touch Basic, LifeScan Inc., Madrid, Spain).
* Heart Rate (HR) and Heart Rate Variability (HRV) was recorded by Polar Team Pro Sensor, Polar Electro, Kempele, Finland) during the 15 min prior to warming up and during the athletic tests, following the procedures of previous research [22]. The Polar system has a sampling frequency of 1000 Hz and is able to register the RR intervals (time interval between R waves of the electrocardiogram) for the analysis of HRV and the number of beats per minute for the HR analysis. The HRV data collected was analyzed by the Kubios HRV v2.2 software program (University of Kuopio, Kuopio, Finland) with no correction factor, since the measurements obtained were clean and free of noise. The following HRV variables were analyzed [23]:
* Time-Domain. RMSSD (root mean square of successive differences between normal heartbeats, which reflects the beat-to-beat variance in HR and is the primary time-domain measure used to estimate the vagally mediated changes reflected in HRV), PNN50% (the percentage of adjacent NN intervals that differ from each other by more than 50 m, closely correlated with PNS activity) and SDNN (the standard deviation of the average normal-to-normal (NN) intervals for each of the 5 min segments) were analyzed.
* Frequency-Domain (Spectral Measures) Analysis. We analyzed the low-frequency (LF) and high-frequency (HF) power components in normalized units (n.u). The frequency ranges where, HF: 0.15-0.40 Hz and LF: 0.04-0.15 Hz.
* Nonlinear domain analysis. SD1 and SD2 were measured to reflect the fluctuations of the HRV via a Poincare chart, physiologically, on the transverse axis. SD1 reflects parasympathetic activity while SD2 reflect the long-term changes of RR intervals and is considered an inverse indicator of sympathetic activity.