Key result
In small mammals, maximum heart rates followed a body size-determined pattern, and contraction rate and duration were mainly determined by myoplasmic Ca2+ handling rather than myosin-ATPase activity.
Population
Three soricine shrews (least shrew, common shrew, water shrew) and six other small mammals
Design
Preclinical
Authors
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Does not inform clinical practice; leaves open whether Ca2+ handling limits human heart rate extremes.
In small mammals, maximum heart rate scales with body size, and contraction duration is primarily driven by calcium handling rather than myosin-ATPase activity despite unique myosin compositions.
Matti Vornanen (1992) studied this question. Isoproterenol was evaluated on Maximum heart rate. In small mammals, maximum heart rates followed a body size-determined pattern, and contraction rate and duration were mainly determined by myoplasmic Ca2+ handling rather than myosin-ATPase activity.
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