Key result
A shortening ramp performed during a partially fused tetanus caused an increase in myofibrillar free calcium concentration and a simultaneous decrease in active force in frog muscle fibres.
Active shortening of striated muscle causes sustained release of calcium from thin filaments, reducing contractile strength.
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Findings from frog fibres should not change clinical practice; they leave open mechanisms of calcium-force coupling during shortening.
Edman et al. (2017) studied this question. Shortening ramp during a partially fused tetanus vs. Stretch ramp during activity was evaluated on Myofibrillar free calcium concentration and active force. A shortening ramp performed during a partially fused tetanus caused an increase in myofibrillar free calcium concentration and a simultaneous decrease in active force in frog muscle fibres.
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