2.2. Experimental Procedures

Participants were instructed to perform light exercise (aerobic exercise that does not exceed 60% of maximum heart rate) and to avoid pain-relieving strategies (e.g., analgesic medications, manual massage, ice, etc.) three days before the race. In addition, participants were instructed to avoid any sources of stimulants like caffeine and alcohol for 24 h before the race. Finally, participants were not allowed to use compression clothing or socks during the race. Compliance was checked at the start and finish lines. One week before the race, the marathon runners filled out a 7-day weighed food record that has previously been utilized for the athlete population [38] with the help of an experienced dietitian-nutritionist with more than 20 years of experience working with athletes (LR003). On the day of the race, participants had their usual pre-competition meal at least 3 h before the race. The pre-competition meal was not standardized to avoid affecting individual routines prior to the race. However, it was still recorded through dietary records for later analysis. Thirty minutes before the race onset, participants arrived at the start line after their habitual warm-up and with the same shoes and clothes that they would use in the race. After these procedures, participants competed in an official marathon held in April 2016 in an area of Madrid located at an altitude of 655 m (Rock’n’Roll Madrid Marathon, Madrid, Spain). The lowest altitude of the race was 600 m and the highest altitude was 720 m. The race was completed with a mean dry temperature of 27 ± 3 °C (range from 21–30 °C; temperature readings were taken at 30 min intervals from 0–5 h after the race onset) and 27 ± 2% relative humidity. During the race, all participants wore a race bib with a timing chip to calculate the actual amount of time that it took to go from the starting line of the race to the finish line (net time). In addition, the participants drank and ate ad libitum during the race. Information about drinking and eating during the race was obtained and recorded at the end of the race through an ad-hoc questionnaire. Within three minutes of finishing the race, participants went to the end area where, after 5 min of sitting, a 7-mL venous blood sample was drawn from the median cubital vein to determine post-exercise blood values. The participants were instructed to avoid drinking and eating until blood was drawn.