how long does the effect of exercising last?
<answer> 5 - 10 minutes at the beginning of an exercise session. <context> 1 Perform warm-up exercises for 5 - 10 minutes at the beginning of an exercise session. 2  Older people need a longer period to warm up their muscles. 3  Stretching exercises, gentle calisthenics, and walking are ideal. 4  To cool down, you should walk slowly until the heart rate is 10 - 15 beats above your resting heart rate.