The swimmer is faced with the task of performing his movements in such a way that the forward speed is as uniform as possible. It depends not only on the nature and magnitude of the thrust applied by the swimmer, but also on the timing of the phases. It is necessary that the pause between the end of the effective part of the stroke with one hand and the beginning of this part of the other be minimized.

Naturally, the more time the swimmer spends on the auxiliary phases, the longer the pause between the effective parts of the strokes. The fact is that while the swimmer is performing the effective part of the stroke with one hand, the other hand makes auxiliary movements. Since the hand does not have time to start the effective part of the stroke in turn and complete the auxiliary movements, pauses are formed.

For example, when a swimmer moves forward with a front crawl, the cycle is 1.8 seconds. In this cycle, we distribute the time as follows:

Influx – 0.5 s.
Supporting part – 0.2 s.
The main part is 0.4 s.
The exit of the hand above the water is 0.1 s.
Hand movement on the surface – 0.6 s.
The effective part of the stroke when swimming on the front crawl will include the support (0.2 s) and the main part (0.4 s). While with one hand the swimmer performs the effective part of the stroke, which is 0.6 s, with the other hand he does not have time to complete the entire auxiliary part, equal to 1.2 s. The time remaining is 0.6 seconds. Since there are two pauses per cycle of movements, their duration is 0.3 s.

In the event that a swimmer, when swimming in front crawl, arbitrarily increases any auxiliary phase, this will lead not only to a drop in speed, but also to its large fluctuation.