Keep the faith! If you’re disciplined about it, the pace at that intensity will increase. If you’re not, then it will continue to be slow and higher paces will be less efficient.
In the long term, it is really worth putting in this time to increase your aerobic capacity.
Spoiler: Delayed gratification is key.
That is, the total volume of the athletes’ hearts, scaled not with the intensity of training, but with the average weekly volume! This makes good physiological sense, since we know that for the majority of people, stroke volume reaches its maximum limit at relatively low intensities of training (~40-60% VO2 max).3However, as the Berbalk data suggests, it takes a whole lot of beats to make these significant changes!