You are working out at the local gym. The man next to you, who appears to be around 60 years old, is sitting on the floor stretching. As he gets up from the floor he appears a little pale and sweaty, then suddenly becomes unconscious. Before you have time to ask if he is OK, he wakes up and tells you that he is OK and that you should not worry, that this kind of thing happens to him occasionally. What do you think is most likely to have happened