Winning a five-set match at a Grand Slam is one of the most physically brutal challenges in professional sport. Over three, four, or sometimes five hours of relentless competition, a player can cover more than ten kilometers of court, execute over a thousand strokes, and experience heart rate levels comparable to those of an endurance athlete at maximum effort. In this context, the difference between winning and losing the fifth set is rarely about who is more talented — it is almost always about who has more left in the tank. And that, more than any other factor, is determined by the efficiency of their technique. Biomechanics is the science that explains exactly why.