We gathered at the pool at 7pm, started a smooth 20 mins run to behind the Comedor Universitario: where many state grad students have their meals. Once there, outside, we stretched a little bit and did a soft jog to prepare for 200 meter sprints (x20). I was first assigned to go with a very quick group at a high pace. The intention was to finish each stretch in 36 seconds. I got to do aprox 4/5 of those sprints with the group and could feel the speed of the wind, even if getting tired. I also noticed that I allowed my body/torso to lean much more forward.
However, I was absolutely exhausted. I was in the brink of fainting or getting a leg strain. Fortunately none of the two happened. Instead, a new runner (Fede) arrived later and we did the remaining together at a slower pace, in stretches of 40 seconds. And to be honest, I couldn't keep up much with that and ended doing several stretches at 42-44 seconds. Dante advised wisely to not start so so quick on each stretch. My inner thought is that I'm one of the oldest of this group as far as I can tell. This implies that my heart rate can only reach to certain point, a little lower than younger runners.
(Notes on Fede. He's a friend of Pablo PP, and told me that he normally trained easily and trying not to get broken. That's why he doesn't play soccer in a championship where stakes are high and a lot of legs hit and get hit. And he also told me that last year, 2017, he ran his 1st Marathon with a total time of 3 hours, 17 minutes. But, he stopped running for some weeks/months since he felt very bad afterwise.)
After training sprints we went back to the everyday starting point, and streched a bit. It was a great day.