Related Experiment Video
Updated: Jul 16, 2026

08:42
Myo-mechanical Analysis of Isolated Skeletal Muscle
Published on: February 22, 2011
Myosin head movements are synchronous with the elementary force-generating process in muscle
M Irving1, V Lombardi, G Piazzesi
1Department of Biophysics, Cell and Molecular Biology, King's College London, UK.
Nature
|May 14, 1992
Summary
Myosin motor proteins in muscle generate force through a structural working stroke. New measurements show myosin heads move approximately 10 nm, matching the timing of this force-generating process.
Area of Science:
- Biochemistry
- Molecular Biology
- Muscle Physiology
Background:
- Motor proteins like myosin, dynein, and kinesin convert ATP hydrolysis energy into mechanical force or motion.
- The precise molecular mechanisms underlying motor protein function remain incompletely understood.
- Myosin motors interacting with actin filaments are crucial for muscle contraction, but their detailed working stroke mechanism is debated.
Purpose of the Study:
- To elucidate the molecular mechanism of the myosin motor's force-generating process.
- To provide definitive structural evidence for the myosin 'working stroke'.
- To temporally resolve the elementary force-generating events in muscle contraction.
Main Methods:
- Utilizing advanced measurement techniques to analyze muscle fiber dynamics.
- Employing X-ray diffraction to observe structural changes in myosin heads during muscle shortening.
- Correlating structural movements with the temporal course of force generation.
Main Results:
- Rapid shortening of active muscle fibers leads to an initial force decrease followed by a partial recovery within milliseconds.
- X-ray diffraction revealed a significant decrease in the 14.5 nm reflection intensity during shortening, indicative of structural changes.
- The study demonstrates that myosin heads move approximately 10 nm, with a time course synchronized with the elementary force-generating process.
Conclusions:
- The observed 10 nm movement of myosin heads directly correlates with the elementary force-generating process in muscle contraction.
- These findings provide strong support for a structural 'working stroke' model of myosin motor function.
- Improved measurement techniques have enabled the temporal resolution of key events in muscle motor protein mechanics.
Related Concept Videos
Muscle Contraction
Muscle Contraction
In skeletal muscles, acetylcholine is released by nerve terminals at the motor endplate—the point of synaptic communication between motor neurons and muscle fibers. The binding of acetylcholine to its receptors on the sarcolemma allows entry of sodium ions into the cell and triggers an action potential in the muscle cell. Thus, electrical signals from the brain are transmitted to the muscle. Subsequently, the enzyme acetylcholinesterase breaks down acetylcholine to prevent excessive muscle...
Excitation-Contraction Coupling in Skeletal Muscles
Excitation-contraction coupling is a series of events that occur between generating an action potential and initiating a muscle contraction. It occurs at the triad, a structure found in skeletal muscle fibers that comprise a T-tubule and terminal cisternae of the sarcoplasmic reticulum on each side. These triads are visible in longitudinally sectioned muscle fibers. They are typically located at the A-I junction — the junction between the A and I bands of the sarcomere.
When an action potential...
When an action potential...
Motor Unit Stimulation
When the neuron of a motor unit fires an action potential, it triggers a series of events, leading to a twitch contraction in the muscle fibers. The process of excitation-contraction coupling is crucial in relaying the action potential to the muscle fibers.
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
Isotonic and Isometric Muscle Contractions
Two primary types of muscle contractions are isotonic and isometric, each serving unique functions and involving distinct mechanisms. Both isotonic and isometric contractions are integral to the body's complex system of movement and stability. Isotonic exercises contribute significantly to functional strength and movement, while isometric contractions are crucial for maintaining posture and joint stability.
Isotonic contractions
Isotonic contractions occur when a muscle changes length while the...
Isotonic contractions
Isotonic contractions occur when a muscle changes length while the...
Exercise and Muscle Performance
Exercise induces a range of adaptations in muscle tissue, depending on the type and duration of activity. Such physical training can be broadly categorized into two types: endurance exercises and resistance exercises.
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...
Endurance exercises
Endurance exercises involve running, swimming, or cycling, which require repetitive movements with low force output. When a person engages in endurance exercise, a few noticeable changes occur in their skeletal muscles. For instance, the number of capillaries...

