Downward dog is a popular pose in yoga that stretches the hamstrings and calves. In this position, your head is lower than your heart, so it also improves the blood flow through your body and relieves tension in the neck and back.
To start this exercise, set yourself up into a downward dog. From all fours, push your bottom up towards the air, straighten out the legs and push your hands into the ground so your back is flat. Don't worry if you have a bend in the knee, find what is comfortable for you. Spend 10-15 seconds here, pedalling out the feet to feel a nice stretch in the calf muscles.
From here, move into a high plank position with a slightly rounded back and take your right arm towards your left toe. Tap your left toe or shin, before returning to the starting position and repeating on the other side. Move through this sequence with control and repeat 4-6x on each side.