In a diesel engine the fuel is heated and injected into the combustion chamber, where it is compressed by the rising piston. This causes the fuel to explode - and that’s exactly how the Diesel Strategy works.
Sometimes, the price of a stock runs up quickly and pauses for a few days, as it trends sidewards. The price bars start to compress and the stock begins to heat up. Eventually, the sell orders at the current price level are absorbed and trading volume declines. Finally, the price drops and washes out the few remaining sellers, before it reverses again like a rising piston and the price explodes upwards as volume returns.