(I assume you are talking about the watch, but not which colleague)
The watch is the Forerunner235
Nice! Monitoring exercise both during and after can be quite useful both for refining technique (i've learned how to go up and down hills without much variation in heartrate) and tracking progress.
I have never time myself or whatever before. Wearing that watch makes a difference. It is mercyless with its beep and time/km on the last km every single km!! BTW, I have learnt quite a lot during my 1st training run with it yesterday (24.5km, 1st half uphill to the nearest ski resort, 2nd half same way back home, total elevation gain 320m, no warm-up), e.g. I have realized that any ascending elevation loses you a lot of time, and that elevation is asymetrical in the sense that climbing up loses you way more time that seconds gained when it goes down.
The way up involves an effort to overcome gravity which is linear in altitude. But the way down involves an effort to overcome air resistance which is the square of velocity. If you have the capacity for a little extra effort, it's better to expend it on the uphill than the downhill.
If you redo this run several times and test different allocations of effort, you can plot a curve of total time as a function of % of time required to get to the top. It will probably be a concave bathtub curve showing that it's possible to push too hard to the top and possible to save too much from the second half.
Then there's a lot you can learn from heartrate in terms of both short-term (managing a run) and long-term (monitoring improvements). For long-distance events, I use heartrate alerts to tell me if I'm pushing too hard or slacking.