Why is so and so not as sore, fatigued, or worn down as me?

“Why is so and so not as sore, fatigued, or worn down as me?”

It’s a common question in sport.

Every athlete pays a unique currency to cover the cost of the game. That cost isn’t standardized—it is, to some degree, mediated by their internal constraints. Some athletes simply don’t have the “funds” available, and when costs exceed their capacity, debt accumulates—manifesting as soreness, fatigue, or pain.

These constraints—whether at the joint level (reduced degrees of freedom) or at the neuromuscular level (limited impulse generation)—reduce the variability with which an athlete can engage with their environment. And when variability is low, the game can be more expensive.

I define variability as the ability to alter solutions in response to a changing environment. It’s not randomness—it’s adaptability. Impulse variability, for instance, refers to the task-specific iterations of force across varying timescales, tailored to the moment.

The amalgamation of ecology-specific variability—spanning, but not limited to, joints and impulse generation—can potentiate more effective action capabilities. This enhanced optionality builds robustness and increases the margin for error. In financial terms, it’s like having a savings account ready for the unpredictable “expenses” the game will inevitably require.

Athletes with more constraints, however, are more exposed. With fewer affordances available to them, they may have less ability to distribute and reallocate stress-strain patterns throughout the musculoskeletal ecosystem. Their system lacks the internal diversification to spread load efficiently. This drives up the cost of play.

It’s not unlike the stock market: being overly reliant on a single solution or strategy is like investing all your money in one company. If that company fails, you absorb the full loss. But a diversified portfolio—like an index fund—spreads the risk. It protects against volatility. Similarly, variability is a form of movement diversification, protecting the athlete from the downside of their constraints.

The solution?

Make consistent deposits toward the most influentially constrained system. These small, targeted investments—whether mechanical, neural, or biological—have a compounding effect and ensure you’re not underfunding. Over time, they can expand variability, reduce cost, and build robustness.

-Jarred