Related Experiment Video
Updated: Oct 9, 2026

Measurement of Mitochondrial Respiration in Human and Mouse Skeletal Muscle Fibers by High-Resolution Respirometry
Published on: October 4, 2024
Reserve capacity for ATP consumption during isometric contraction in human skeletal muscle fibers
Y S Han1, D N Proctor, P C Geiger
1Department of Anesthesiology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
Abstract:
Maximum velocity of the actomyosin ATPase reaction (V(max) ATPase) and ATP consumption rate during maximum isometric activation (ATP(iso)) were determined in human vastus lateralis (VL) muscle fibers expressing different myosin heavy chain (MHC) isoforms. We hypothesized that the reserve capacity for ATP consumption [1 -- (ratio of ATP(iso) to V(max) ATPase)] varies across VL muscle fibers expressing different MHC isoforms. Biopsies were obtained from 12 subjects (10 men and 2 women; age 21--66 yr). A quantitative histochemical procedure was used to measure V(max) ATPase. In permeabilized fibers, ATP(iso) was measured using an NADH-linked fluorometric procedure. The reserve capacity for ATP consumption was lower for fibers coexpressing MHC(2X) and MHC(2A) compared with fibers singularly expressing MHC(2A) and MHC(slow) (39 vs. 52 and 56%, respectively). Tension cost (ratio of ATP(iso) to generated force) also varied with fiber type, being highest in fibers coexpressing MHC(2X) and MHC(2A). We conclude that fiber-type differences in the reserve capacity for ATP consumption and tension cost reflect functional differences such as susceptibility to fatigue.
Related Concept Videos
Energy Supply for Muscle Contraction
Actin and Myosin in Muscle Contraction
Cross-bridge Cycle
Muscle Recovery and Fatigue
Classification of Skeletal Muscle Fibers
Slow-Twitch Muscle Fibers
Slow oxidative, muscle fibers appear red due to large numbers of capillaries and high levels of...
Types of Skeletal Muscle Fibers
Fast-twitch fibers
Fast-twitch fibers, or Type II fibers, are designed for quick, powerful bursts of speed and strength. They reach peak tension within approximately 0.01 seconds following stimulation. Characterized by a large diameter and densely packed myofibrils, these fibers contain...

