*2.6. Day 1 Passive Drool Instructions*

At the end of day 1, participants were given 9 Salivette® Cortisol vials (Sarstedt AG & Co., Nümbrecht, Germany) without the synthetic swab, and instructed to take baseline salivary samples for three days at 8:00 a.m., 11:00 a.m., and 2:00 p.m. Participants were given clear written and verbal instructions on the PD method.

#### *2.7. Procedure: Day 2*

Day 2 consisted of two different test conditions, separated by a recovery period of 20 min. The first test condition was the startle condition, and it took place at 8:00 a.m. The second condition was the fatigue condition, and it took place at 8:30 a.m. The order of the test conditions was fixed to eliminate the effects of physiological and psychological fatigue in the startle condition. Since the climbing route of the startle condition was more difficult and required a high cognitive, physical, and tactical demand, this condition was performed first. Before climbing, participants had their resting blood pressure taken, and they completed the FSST and CSAI-2R. They provided saliva samples via passive drool, and their 3 min average pre-climb heart rate (Pre-HR3min) was recorded.

The startle condition consisted of a loud stimulus and the added stress of having to lead climb a route that gradually increased in difficulty. There were two possible routes in this condition: either a route that progressed in difficulty from 6b to 6c+ or from 6b to 7b. When the participants were preparing to make a key jump to a more difficult section, an air horn was used to startle them (Goodmark®, Llantarnam, UK). Three of the final participants had an alternate audio stimulus due to lack of gas in the air horn. With these final participants, the investigator hit a pan with a wooden spatula and screamed.

During the climb, the climb duration, success/fail, HR at the start of the climb (HRstart), HR average (HRavg), and peak HR (HRpeak) were recorded. Immediately after the climb, blood pressure was measured, and participants completed the FSST and CSAI-2R. The climbs were filmed with a Samsung N363 digital camcorder (Samsung Group, Hwaseong, South Korea). Fifteen minutes after the startle, post-climb salivary samples were taken. The time for HR to return to pre-climb levels (Post-HRrecovery) was also recorded.

In the fatigue condition, participants had to top rope climb a predetermined route as fast as they could and as many times as they could, until muscular failure. There were three routes that varied in difficulty (6b, 6c+, 7b), and the specific route assigned to each participant was based on their self-reported skill level. Time splits of each climb, the number of falls until fatigue, and HRstart, HRavg, and HRpeak were all recorded. Each climb was filmed. Immediately post-climb, participants had their blood pressure measured, and they completed the FSST and CSAI-2R. Fifteen minutes post-climb, they completed a final salivary sample. Their post-HRrecovery time was also recorded.
