While everyone chortles at your comical writhing, your body's effort to deal with the pain has you sweating buckets. A racing pulse raises your body temperature, causing the eccerine sweat glands all over your body to secrete in a bid to cool you down. Avoid the agony of a mangled midsection by wearing groin protection when next taking the sporting field. You might also consider wearing a crucifix in future.
Your heart's job is simple: supply your body with enough blood to fuel your hysteria. With your brain, pain receptors and nervous system shifting into overdrive, your ticker has to double its beating. The veins leading to your heart siphon vast amounts of claret around your body. Insure your heart (if not your plums) against the strain, by getting on your bike. Researchers at Yale University have found that cycling three times a week for two years can increase the size and efficiency of your heart by 40%.
The news of your crushed grapes is transmitted via your spinal column, to your somatosensory cortex – the part of your brain that registers physical sensation. The body releases endorphins, but in this instance, that's like treating a gun shot wound with a hug. This leaves your brain bereft of oxygen, resulting in a pounding head to match your throbbing swingers. Fend off the pain with an ice-pack ASAP.