Fractal fluctuations in muscular activity contribute to judgments of length but not heaviness via dynamic touch.

The applied muscular effort to wield, hold, or balance an object shapes the medium by which action-relevant perceptual judgments (e.g., heaviness, length, width, and shape) are derived.

Muscular effort differentially mediates perception of heaviness and length via dynamic touch.

Our ability to perceive properties of handheld objects (e.g., heaviness, orientation, length, width, and shape) by wielding via dynamic touch is crucial for tooling and other forms of object manipulation-activities that are the basis of much human experience.

Location of a grasped object's effector influences perception of the length of that object via dynamic touch.

Perception of properties of a grasped object via dynamic touch (wielding) contributes to dexterity in tool use (e.g., using a hammer, screwdriver) and sports (e.