A workout does not end when you do your last rep or take the final step on the treadmill. You also need to cool down to gradually get your heart back down to its normal pace and to ease your body into a less strenuous rhythm.
The question is how long it takes you to cool down after a workout and what you need to do during this time.
I want to take a broader look than what most people do and think about your cool down as a two-part process: you have the immediate cool down while you’re still in the gym and the post-workout cool down which happens in the hours and days following your workout.
Let’s talk about the immediate cool down first. This takes a few minutes, usually no more than 10 – 15. During that time, your heart rate will gradually slow down and your breathing will ease. What you need to do during this cool down period is to continue being active but at a slow and low-intensity pace. You can walk slowly on a treadmill, cycle at a low pace on a recumbent bike, or slowly tread the elliptical.
Following a few minutes of that, you can and should do some stretching. Focus on those muscles groups that you trained during this particular workout but do not totally neglect those that you did not. Stretching will help you prevent or reduce muscle soreness and lower the risk of sports-related injuries.
The other part of the cool down period takes place up to 72 hours after your workout is completed. While you may not feel as if your body is warm or your heart rate is elevated, your body is still recovering from the endeavours of the workout you did.
Your muscles, in particular, require up to 72 hours to fully recover and grow stronger once your workout is done. During this time, it’s important to not place an additional heavy strain on them. You can continue acting normal and you’re free to do cardio workouts. I would refrain from doing additional strength workouts which target the same muscles without 48 hours, at least, have passed between one workout and the next.
So, it takes about 15 minutes to cool down after a workout and up to 72 hours for the muscles to completely recover from it. This is how long a cooldown takes.