What is the second hardest sport in the world?

Today at the gym the dread locked Handball player told us that Handball is "the second hardest sport in the world after boxing." I did a little digging and found no proof supporting his claim, but I did find a website comparing Racquetball to Handball that reports "A University of Utah study showed Handball to be superior to Racquetball in all four of the the fitness indicators that were measured."

Handball vs. Racquetball
1. Calories burned per hour (751 VS. 644)
2. Average Heart Rate (164 VS. 137)
3. Average Oxygen Uptake (30.1 VS. 25.8)
4. Average Ventilation Rate(85.9 VS. 70.9)

I have no idea what Average Oxygen Uptake and Average Ventilation Rate are but I trust people from Utah. Please shoot me a note if you have any idea what those fitness indicators measure.

I would like to try Handball next week even thought it might result in a few twisted fingers. It appears to be sport at its purest. You just hit a small rubber ball against a wall with your hand. It doesn't get any more simple. Also, seems like a great city sport because you can pick up games at most parks in the city. It might be good to try because the site claims you develop "coordination and power in your non dominant hand because you hit the ball with both hands" Most sports are pretty unilateral and only require the use of your dominant hand. I'm all for any sport that helps me develop some left hand / eye coordination.

Source: HandballCity.com