Key result
During unloaded shortening starting at the end of latency relaxation, the number of actin-attached myosin motors per half-thick filament is as low as 1-4.
Population
Tetanized single skeletal muscle fibres from Rana esculenta (frog) at 4°C and sarcomere length 2.15 μm
Design
Preclinical
Authors
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Challenges conventional cross-bridge occupancy estimates; extends skeletal muscle data but leaves open cardiac applicability.
The study demonstrates that during unloaded shortening in skeletal muscle, the number of attached myosin motors is extremely low (1-4 per half-filament), explaining the low rate of ATP utilization.
Fusi et al. (2016) studied this question. Unloaded shortening (V0) vs. Maximum isometric force was evaluated on Number of actin-attached motors per half-thick filament (n). During unloaded shortening starting at the end of latency relaxation, the number of actin-attached myosin motors per half-thick filament is as low as 1-4.
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