Dynamic electrocardiography, the electromechanical S wave: the problem of the contradictory converse

Two basic hypotheses concerning an electromechanical S wave of the electrocardiogram during exercise have been expanded to five to include the effect of recovery which should produce converse changes. Four hypotheses have been supported and the fifth contradicted. An attempt has been made to analyse the ensuing dilemma and a conclusion is reached that either the electromechanical hypothesis is in error or a new hypothesis, which predicts an increase in the cardiac end-diastolic volume after exhaustive exercise, must be proposed. This new hypothesis is commonly accepted by physical educationalists but appears to be rarely discussed in physiological texts.