Residual Force Enhancement in Humans: A Systematic Review

Area of Science:

• Biomechanics
• Human Physiology
• Exercise Science

Background:

• Residual force enhancement (RFE) is a phenomenon where muscle force is greater after a stretch-shortening cycle.
• Understanding RFE in vivo is crucial for optimizing training and rehabilitation strategies.

Purpose of the Study:

• To systematically review and synthesize the existing evidence on residual force enhancement in vivo human skeletal muscle.
• To assess the quality of methodologies used in RFE research.

Main Methods:

• A systematic literature search was performed across major databases (CINAHL, EBSCO, Embase, MEDLINE, Scopus) from inception to July 2017.
• Included studies assessed RFE in voluntarily contracted human skeletal muscle.
• Methodological quality was evaluated using the Downs and Black checklist.

Main Results:

• Twenty-four studies involving 424 participants were included, with an average methodological quality rated as "fair".
• RFE was consistently observed across all tested muscles, joint ranges (15°-60°), and contraction intensities (10% to >95% maximum).
• RFE magnitude was influenced by stretch amplitude and muscle length, and was independent of velocity in the isometric phase, but influenced by contraction/activation intensity.

Conclusions:

• Residual force enhancement is a reliable finding in human skeletal muscle.
• RFE can lead to increased torque production and reduced muscular activation.
• RFE demonstrates potential benefits for enhancing torque production in weakened neuromuscular systems, such as in older adults.