Oberth effect

The Oberth effect is an astrodynamic effect where the same amount of work or effort at the right point can achieve signifcantly greater effect than applied at other points.

The Oberth effect is a mathematically predictable and measureable example of you can get much more value out of effort when you're moving at high speed than when you're moving slowly.

Wikipedia: the Oberth Effect

Using the same amount of fuel at high speeds adds more energy (speed) than at low speeds.

From a work standpoint, formal training, especially on-site, can boost productivity because of the preparartions that occur prior to training.  Companies tend to want to get the most out of the time and expense of multi-day training, so they tend to prepare for it.  Preparations in thinking about their business processes, their weaknesses in collaboration, design and production workflows, etc. mobilize the team that attends the training as well as the greater organization.  The benefit of the investment in training is as much as what happens before the event as during the event.