Isometric Strength Training in Endurance Runners: A Theoretical Framework for Adaptations and Performance Outcomes

ABSTRACT Isometric strength training (IST) has been shown to be beneficial for endurance runners. It seems to improve running performance by enhancing running economy and tendon stiffness. A proposed advantage of IST is that it facilitates these adaptions while inducing less fatigue than dynamic strength training (DST). Current evidence points to the use of 3-second contractions, with 10–20 contractions being performed per session. This recommendation is based on limited research evidence because only 3 studies have reported findings on the use of IST in endurance runners. The purpose of this brief review was to examine the theoretical framework for expected adaptations to IST, identify methods for programming IST, and suggest areas for future research. These future research areas should include IST using multiple joint angles, IST in combination with DST methods, IST at long muscle lengths, IST using different types of isometric contraction, and IST using different contraction durations.