Platform Tennis Heart Rate

Some pictures showing our platform tennis group are shown on www.centralny-organizations.blogspot.com .
Wednesdays we do play tennis outdoors. On several occasions, I have taken my heart rate monitor and stored the information on my Polar S410 watch. What is nice about this system is that I can download the graph of my activity later on.
We played Canadian Doubles since we had only three people. Each person rotates to the server position where he plays the other two. Two-thirds of the time you are playing with someone else, one third playing alone. This is shown on the graph as there are periodic peaks when I am playing alone.
Above is my first heart rate graph from last night's platform tennis
