SWIMMING TECHNIQUE CONCEPTS BY ROD HAVRILUK
FREESTYLE TECHNIQUE FOR SPRINT AND DISTANCE (Part 2)
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any sources suggest that swimmers use a different freestyle technique for sprint and distance events. For example, a “straight-arm” underwater motion is often promoted for sprinting and a “bent arm” is frequently suggested for distance events. As explained in Part 1 (SW Jan), science—both physics and research— shows us that a swimmer can optimize performance in events of all distances by using the same arm motion with a different arm coordination. Part 1 also explained the most effective arm coordination for distance events. This article—Part 2 and the final part in this series—explains the arm coordination for sprint events. OPPOSITION COORDINATION FOR SPRINT OR DISTANCE The Index of Coordination (IdC) quantifies the relative position of the arms in a stroke cycle (Chollet, Chalies & Chatard, 2000). When one hand begins to pull at the same time that the opposite hand completes the push, the arms are in opposition, and the IdC is zero (Fig. 1, left panel). Swimmers can use opposition coordination for a range of swimming velocities by varying the average propulsive force. For example, opposition coordination hand force curves for sprint (solid lines) and distance (dotted lines) are shown in Fig. 2. For both the sprint and distance curves, the duration of the propulsion and nonpropulsion phases are both 0.6 seconds for a stroke time of 1.2 seconds and consistent with the model in the left panel of Fig. 1 and the data presented in Part 1 (SW Jan). The sprint and distance curves are different in the average force generated on each underwater arm motion. For a distance swim— with a peak force of 40 pounds and an average force of 20 pounds per stroke cycle—the velocity is calculated as 1.5 meters/second (substituting values that are typical for fast swimmers: body crosssectional area of 1,000 cm2 and an active drag coefficient of 0.8). For a sprint, fast swimmers often achieve a peak hand force of 65 pounds for an average force of 30 pounds per stroke cycle and a swimming velocity of 1.8 meters per second. TYPICAL ARM COORDINATION FOR SPRINT While a swimmer can use opposition coordination for a range of swimming velocities, his/her strength will limit propulsion and, therefore, velocity. Studies conducted over the past 20 years consistently show that swimming velocity increases with the IdC, as shown in Fig. 3. The data points represent measurements of elite, male swimmers from two studies: in red (Seifert, Chollet, Rouard, 2007) and in blue (Seifert, Chollet, Bardy, 2004). The dotted lines show predicted velocities for higher IdC values. The data also show that swimmers generally increase their IdC over zero as they increase their swimming velocity to sprint pace. 36
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SUPERPOSITION ARM COORDINATION FOR SPRINT An IdC greater than zero is also called superposition. As explained last month in Part 1, swimmers usually have a propulsion phase of about 0.6 seconds, regardless of swimming velocity. For the arms to cycle in opposition, the non-propulsion phase must also be 0.6 seconds for a stroke cycle time of 1.2 seconds, as shown in the left panel of Fig. 1. To increase the IdC to a positive value, a swimmer must decrease the duration of the non-propulsion phase by eliminating wasted time in the entry phase and moving the arm faster on the recovery phase. As shown in the right panel of Fig. 1, the model completes the propulsion phase in 0.6 seconds and the non-propulsion phase in 0.4 seconds for a stroke cycle time of only 1.0 seconds. Since one arm begins pulling 0.1 seconds before the opposite arm finishes pushing, there is a total overlap of 0.2 seconds on every stroke cycle for a positive IdC of 20%. Force curves for opposition (solid lines) and superposition (dotted lines) arm coordinations are shown in Fig. 4. For each underwater arm motion, the curves have identical force values over 0.6 seconds of propulsion time. For opposition coordination, the force for one arm begins when the force for the other arm finishes for a stroke cycle time of 1.2 seconds. The average force is 30 pounds per stroke cycle, and the swimming velocity is 1.8 meters per second. For superposition coordination, the force for one arm begins 1-tenth of a second before the force for the other arm finishes for a stroke cycle time of 1.0 seconds. The average force is 38 pounds per stroke cycle, and the swimming velocity is 2.1 meters per second. The benefit in sprinting with superposition as opposed to opposition coordination is a 100-meter time of 46 seconds instead of 52 seconds.
Dr. Rod Havriluk is a sport scientist and consultant who specializes in swimming technique instruction and analysis. His newest ebooks are “Approaching Perfect Swimming: Optimal Stroke Technique” and “Swimming Without Pain: A Comprehensive Guide to Preventing and Rehabilitating Shoulder Injuries,” 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. TOTAL ACCESS MEMBERS CLICK HERE TO LEARN MORE ABOUT THE REFERENCES FOR THIS ARTICLE. NOT A TOTAL ACCESS MEMBER? YOU’RE JUST A CLICK AWAY: SWIMMINGWORLD.COM/VAULT
