SWIMMING TECHNIQUE

BY ROD HAVRILUK , Ph.D.

MAXIMIZING SWIMMING VELOCITY (Part 2): STROKE CYCLE PHASES

As explained in Part 1 of this series (SW May 2021), stroke rate and stroke length typically vary inversely. When a swimmer increases stroke rate, he/she usually decreases stroke length. When a swimmer increases stroke length, he/she usually decreases stroke rate.

The previous article also explained the relationship of stroke time (the time for an arm to complete a stroke cycle) to both stroke rate and stroke length. This article identifies the component phases of stroke time and potential changes to improve performance.

STROKE TIME

The inverse relationship between stroke length and stroke rate is primarily because both variables are directly related to the time for each stroke cycle (stroke time), as shown in Fig. 1. A decrease in stroke time increases stroke rate, while an increase in stroke time increases stroke length. This makes it a challenge to optimize stroke time for the fastest swimming velocity.

STROKE TIME PHASES

Strategies to optimize stroke time become apparent from analysis of the component phases. Each stroke cycle includes two propulsive phases (pull and push) and two non-propulsive phases (entry and recovery), also shown in Fig. 1. The four phases of the freestyle stroke cycle were previously defined (Chollet, Chalies & Chatard, 2000): • Entry: from when the hand enters the water until the beginning of backward hand motion

• Pull: from the beginning of backward hand motion until the hand passes beneath the vertical plane of the shoulder

• Push: from when the hand passes beneath the vertical plane of the shoulder until the hand’s release from the water

• Recovery: from the hand’s release from the water until it enters the water

Although the stroke cycle phases were originally developed for freestyle, they also apply to butterfly and backstroke. Similarly, the breaststroke cycle has four phases with two propulsive (outward and inward sculling motions) and two non-propulsive (recovery and glide) components.

STROKE TIME DECREASE WITH SWIMMING VELOCITY INCREASE

Numerous studies show similar changes in the duration of each stroke phase with an increase in swimming velocity. For example, elite male swimmers increased swimming velocity on a series of swims from distance to sprint pace in all four strokes. The results are shown in Fig. 2 for butterfly (Chollet, Seifert, Boulesteix, Carter, 2006), backstroke (Chollet, Seifert, Carter, 2008), breaststroke (Leblanc, Seifert, Baudry & Chollet, 2005) and freestyle (Seifert,

FIG. 1 > Swimming velocity is the product of stroke length and stroke rate, which are both related to stroke time. The four phases of stroke time are entry, pull, push and recovery.

Chollet & Bardy, 2004).

To swim faster, swimmers naturally move their arms faster. Consequently, there is a decrease in the time duration for each of the four phases for all strokes from distance to sprint pace. The phase time decreases from the slowest to the fastest velocity, as shown in Fig. 3. For breaststroke, the outward and inward sculling motions are shown as the pull and push phases, and the glide phase is shown as the entry phase.

With an increase in swimming velocity, there is a substantial decrease in the non-propulsive phase times—specifically, the entry phase for all four strokes and the recovery phase for backstroke and freestyle. In contrast, there is a very small decrease in the propulsive phase times.

STROKE TIME PHASES AT SPRINT PACE

The phase time duration for all four stroke phases for all four strokes at sprint pace (the fastest velocity from Fig. 2) is shown in Fig. 4. While the swimmers substantially decreased the duration of the entry and recovery phases at the fastest velocity, there is still a considerable amount of non-propulsive time—at least 2-tenths of a second of entry time and at least 3-tenths of a second of recovery time.

Further decreases in non-propulsive time would decrease stroke time and increase stroke rate and swimming velocity without compromising stroke length produced by propulsive phases. For example, as the entry phase in butterfly, backstroke and b reaststroke is the non-propulsive time from when the hand enters the water until propulsion begins, this phase could be further decreased by directly submerging the hand to a position where propulsion could immediately begin. v

FIG. 2 > The graphs show the decrease in the duration of all four stroke phases with an increase in swimming velocity for all four strokes.

FIG. 3 > The decrease in the time duration from distance to sprint pace for all four stroke cycle phases for all four strokes. FIG. 4 > The time duration at sprint pace for all four stroke cycle phases for all four strokes.

SUMMARY

Swimmers typically decrease non-propulsive time to decrease stroke time, increase stroke rate and swim faster. Research shows that a further decrease in the non-propulsive time is possible and should produce further performance improvement. Future articles in this series will present strategies for optimizing the duration of the stroke cycle phases.

Dr. Rod Havriluk is a sport scientist and consultant who specializes in swimming technique instruction and analysis. His newest ebooks in the “Approaching Perfect Swimming” series are “Optimal Stroke Technique” and “Swimming Without Pain,” and are available at swimmingtechnology. com. Contact Rod through info@swimmingtechnology.com. All scientific documentation relating to this article, including scientific principles, studies and research papers, can be provided upon demand.