If anybody ever suggests you try interval training, stop them, turn around, and run away. On paper, “Intervals” sound simple: you sprint for 40 seconds, walk for 180 seconds and repeat five times. What they don’t tell you is that your heart is likely to explode right about the third repetition. It is pure hell!

I had my first experience of Intervals today. I woke up bright and early, put on my running clothes and ambled to the park.

In addition to the intense physical pain Intervals induce, the experience also induces the most intense feelings of embarrassment and humiliation — I lost count of the number of dog-walkers that looked at me with a mixed expression of pity, confusion and just a hint of fear.

Twenty minutes later, I crawled back home oozing sweat and, quite possibly, internal organs. Thank goodness today is high carb day — bring on the potatoes!