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Related Experiment Video

Updated: Jul 14, 2026

Isolating Myofibrils from Skeletal Muscle Biopsies and Determining Contractile Function with a Nano-Newton Resolution Force Transducer

Isolating Myofibrils from Skeletal Muscle Biopsies and Determining Contractile Function with a Nano-Newton Resolution Force Transducer

Published on: May 7, 2020

Passive force enhancement in single myofibrils.

V Joumaa¹, D E Rassier, T R Leonard

¹Human Performance Laboratory, University of Calgary, Calgary, Canada.

Pflugers Archiv : European Journal of Physiology

|June 7, 2007

Summary

Passive force enhancement occurs in single myofibrils, similar to whole muscle preparations. This phenomenon, potentially driven by titin

Area of Science:

Muscle physiology
Biophysics
Skeletal muscle research

Background:

Passive force enhancement (PFE) is a known phenomenon in muscle and fiber preparations.
The underlying mechanisms of PFE, particularly at the myofibrillar level, remain incompletely understood.
Titin is recognized as a primary contributor to passive muscle force.

Purpose of the Study:

To investigate the occurrence of passive force enhancement in single myofibrils.
To determine if PFE can be observed at the scale of individual myofibrils.
To explore the potential role of titin in myofibrillar PFE.

Main Methods:

Isolation of single myofibrils (n=6) from rabbit psoas muscle.
Fixation of myofibrils at a sarcomere length of 2.4 microm.

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Dissecting Mechanoenzymatic Properties of Processive Myosins with Ultrafast Force-Clamp Spectroscopy

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Last Updated: Jul 14, 2026

Isolating Myofibrils from Skeletal Muscle Biopsies and Determining Contractile Function with a Nano-Newton Resolution Force Transducer

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Published on: May 7, 2020

Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers

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Published on: May 4, 2022

Dissecting Mechanoenzymatic Properties of Processive Myosins with Ultrafast Force-Clamp Spectroscopy

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Published on: July 1, 2021

Passive and active stretching protocols to a sarcomere length of 3.4 microm, followed by deactivation.

Main Results:

Passive force after deactivation was significantly higher following active stretching compared to passive stretching.
Passive force enhancement was confirmed in single myofibrils.
Observed PFE in myofibrils ranged from 86% to 145% of steady-state passive force.

Conclusions:

Passive force enhancement is a characteristic of single myofibrils, mirroring observations in larger muscle preparations.
Titin is proposed as the key protein responsible for PFE in myofibrils.
Increased titin stiffness, potentially due to elevated calcium concentrations during activation, may underlie myofibrillar PFE.