Sense and nonsense about the Fenn effect

Area of Science:

• Muscle Physiology
• Skeletal Muscle
• Cardiac Muscle

Background:

• W.O. Fenn's 1923 paper established a key relationship between muscle energy and work.
• The implications of Fenn's work are sometimes misunderstood.
• Early muscle contraction models utilized a viscoelastic framework.

Purpose of the Study:

• To reexamine Fenn's experiments and the Fenn effect.
• To clarify the generality of Fenn's findings in light of modern research.
• To discuss factors causing deviations from Fenn's original results.

Main Methods:

• Review of Fenn's original experiments.
• Analysis of Fenn's findings within the context of 1920s viscoelastic muscle models.
• Comparison with recent skeletal and cardiac muscle data.

Main Results:

• The Fenn effect, relating energy liberation to work, is re-evaluated.
• Deviations from Fenn's results are attributed to challenges in defining energetic baselines.
• An equivalent force baseline is proposed as a unifying concept.

Conclusions:

• Clarification of the Fenn effect and its applicability across muscle types.
• Understanding the historical context and limitations of Fenn's original observations.
• The equivalent force baseline offers a way to reconcile differing results.