Figure 5.

Illustration of the contributions of glucose and lactate to cardiac metabolism in healthy men studied at rest and during supine leg cycle ergometry at 40% VO₂max (see Figure 1) (29). Results are to be compared with those in the same subjects resting and exercising at 40% of VO₂max (see Figure 4). Results are also to be compared with those on one subject, the author, but in Figure 2 the role of fatty acids in supplying energy for cardiac metabolism is depicted. Results show that the contribution of lactate to cardiac energy need depends on arterial lactate concentration and is significantly greater than that of glucose . Results in Figure 2 also show crossover from fatty acid to lactate dependence in heart during exercise. Data from (28).