system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we need to cool down from a workout? (Like after running for 2 miles it's important to walk it off as opposed to sitting down right away)

Is it something to do with the lymph system?
gpt
It's not overly important to walk after running 2 miles, your body will return to homeostasis shortly after you stop the activity one way or another.

For running specifically, your calves have veins in them that are capped by one-way valves that are only opened when the foot and calf flex in tandem.  The pressure from the muscle contraction drives blood from your legs back into circulation more quickly.

During workouts, lactate and other metabolites accumulate as a natural byproduct of muscular contraction.  There are hypotheses that exist that suggest these metabolites are functional for extended performance during difficult workouts (muscles work better with some lactate ion around them to facilitate contraction dynamics pre-failure).

There are others that suggest that their presence over time encourages gene transcription factors that drive adaptation to difficult exercise (junk around the muscles tells the muscles they aren't strong/enduring enough, which makes them adapt to become stronger/more enduring)

Unfortunately, lactate and metabolite accumulation can sometimes be quite painful, or if you exercise to the muscle's failure point, prevent you from continuing to challenge the muscle later in the workout.  In this case, walking will take advantage of your calves' second function of driving blood back into circulation.  This blood flow helps to clear metabolites, which alleviates pain and can allow you to return to intense exercise more quickly than otherwise.

There is some evidence to suggest that clearing metabolites too early can actually cause a smaller hypertrophic response to the same exercise.  So it's something to take into consideration if you don't have another intense set planned within the next few minutes; it could actually be advantageous to NOT walk afterward.  This would allow the muscle a greater exposure window to the generated metabolites.