Sweat, and specifically Sodium, is one of the three “levers” for endurance athletes when it comes to hydration and nutrition (fueling) and subsequently your performance. The other two key elements or levers are Carbohydrates and Fluids.
The most important part about sodium/sweat is that everyone has a unique sweat loss rate, and a unique sodium content ratio in their sweat. So while a more generalized approach can be defined for consuming carbohydrates, the same is not true for electrolyte loss. This is why having a sweat test is critical for athletes wanting to perform, understand and take advantage of their data to understand their personal needs and requirements.