The Heel-Strike Fallacy and Cadence Beliefs in Distance Running: A Narrative Review.

Running-technique recommendations often convert group-level observations and acute biomechanical responses into universal prescriptions. This narrative review examines three beliefs: rearfoot striking is inherently harmful, 180 steps/min is universally optimal, and increasing cadence while maintaining a given running speed consistently reduces loading and overuse injury risk. Current evidence does not support these generalizations. First, rearfoot striking is not consistently associated with greater impact-related metrics or overuse injury risk, and external impact measures do not directly represent tissue-specific loading. Second, cadence varies substantially with running speed, morphology, footwear, and surface, while energetically optimal cadence varies between individuals rather than being fixed at 180 steps/min. Third, although increasing cadence can acutely modify selected mechanical variables, these responses are heterogeneous, have not been shown to consistently reduce injury risk, and may partly reflect concurrent changes in stance-flight organization. Duty factor (DF), the proportion of the stride spent in contact with the ground, provides a complementary temporal descriptor that can help interpret these cadence-related responses. Under level, submaximal running conditions, DF is associated with selected external and modeled internal loads, but current evidence is predominantly mechanistic. Clinical application should therefore begin by determining whether change is warranted, identifying the tissue-specific or functional objective, and selecting whether and how to modify foot-strike pattern or cadence according to condition-specific evidence and the runner's response. DF may additionally be monitored to characterize accompanying changes in stance-flight organization. Acute biomechanical changes should not be assumed to improve symptoms or performance, or to reduce injury risk. Future studies should test sustained clinical effects, individual response patterns, and transfer to real-world conditions.