Extensor Paradox
ex·ten·sor
/ikˈstensər/
noun
a muscle whose contraction extends or straightens a limb or other part of the body.
par·a·dox
/ˈperəˌdäks/
noun
a seemingly absurd or self-contradictory statement or proposition that when investigated or explained may prove to be well founded or true.
Definition
The extensor paradox describes the finding that the leg extensor muscles—muscles that straighten the hip, knee, and ankle, most notably the quadriceps—are largely inactive during late stance in running, despite the common belief that they generate forward propulsion through push-off.
Explanation
Electromyography (EMG) studies show that extensor activity diminishes as the body passes over the support foot and approaches toe-off. This contradicts the traditional assumption that active leg extension is responsible for propelling the runner forward.
The paradox resolves when running is understood as movement organized under gravity: forward motion results from body alignment and the position of the center of mass relative to the support point, not from muscular pushing. Extensors act earlier in stance to manage load and alignment, not to drive propulsion.
Why It Matters
The extensor paradox reframes running mechanics away from push-off and toward technique, timing, and interaction with external forces—particularly gravity and ground reaction forces.
Significance of the Extensor Paradox
The extensor paradox is significant for several reasons:
- Supports Gravity-Based Running Paradigm: It provides evidence against the traditional push-off model of running and supports the concept of gravity as the primary motive force.
- Highlights Efficiency of Pose Method: The findings align with the Pose Method of running, which emphasizes a controlled fall facilitated by a forward shift of body’s COG and a pulling action of the foot from the ground. This technique minimizes reliance on forceful muscular contractions and maximizes the utilization of gravity’s pull.
- Explains “Electrical Silence” of Extensors: The paradox explains the lack of significant electrical activity in the leg extensor muscles during push-off, which would be puzzling under the traditional running model.
- Underscores Importance of Technique: The extensor paradox emphasizes the importance of proper running technique for optimizing efficiency and minimizing muscular effort.
Dr. Romanov postulates that the extensor paradox, far from being a true paradox, is a natural consequence of the body’s adaptation to running within a gravitational field. By accepting and understanding this concept, runners can refine their technique to leverage gravity’s might, minimizing unnecessary muscular effort and enhancing their overall running efficiency.
Read full article Theory & Practice: The Extensor Paradox In Running.