Every coach and athlete looks for ways to improve. The search for a competitive advantage spans the range of technologies – from naked eye observation (basic) to synchronized video and force analysis (advanced) – that aim to help both coach and athlete. Gaining the most benefit from advanced technology involves employing a variety of analysis procedures. For example, technology that measures hand force clearly identifies stroke-to-stroke variations in how the hand presses on the water to generate force (Figure 1). When synchronized with video, force variations within each stroke indicate the exact arm position that limits performance. While these analysis procedures require time and effort, the potential for improvement is substantial - often more than .1 second per stroke - for even the fastest swimmers.

Figure 1. The force curves for the left hand of a male high school swimmer show variations from stroke to stroke.

Analysis of Stroke-to-Stroke Consistency

To swim as fast as possible, a swimmer must maximize the benefit of each stroke. Figure 1 shows smaller force values on the second and fourth strokes, indicating that the swimmer is taking far less advantage of his strength on every other stroke. Movement of the head or body that decreases the effectiveness of the arm motion often causes stroke-to-stroke differences. For example, excess head rotation on breathing can distort the body position and change the arm motion. If the hand force curves are not consistent from stroke to stroke (as typically seen in younger and less experienced swimmers), minimizing extraneous head and body motion is the primary initial corrective action.

Analysis of Bilateral Symmetry

Once a swimmer has stroke-to-stroke consistency, a hand force analysis can show if there are differences between arms. Force curves for a world champion distance freestyler (in the left image of Figure 2) show stroke-to-stroke consistency (especially with his left arm), but a dramatic difference between his left and right arm. After testing, the swimmer explained that he had suffered a broken right arm and had his cast removed the previous day. A posttest confirmed that rehab was complete as he was able to generate identical force values for both arms.

Figure 2. Hand force curves for a world champion distance freestyler (left) and a two-time Olympic breaststroker (right). The difference between arms in the left graph is due to an injury while the bilateral asymmetry in the graph on the right is due to a technique limitation.

Hand force analysis is sensitive enough to identify bilateral differences caused by technique as well as injury. A small amount of torso rotation (virtually unnoticeable from the pool deck) can cause a different motion for each arm, resulting in bilateral asymmetry in force for the Olympic breaststroker in Figure 2 (right). Just as with stroke-to-stroke inconsistencies, dealing with the head and body position must precede adjusting arm motions - no matter what level the swimmer.

Analysis of Peak Force – Magnitude, Location, Slope, and Duration

After a swimmer neutralizes head and body issues, it is appropriate to analyze his/her peak force (the highest force value within a stroke cycle as indicated by the vertical grey line on the force curves in Figures 2 and 3). This “magnitude of the peak force” is the most straightforward way to identify a technique strength or weakness. Generally, females must generate 30 lbs of force (as shown by the breaststroker in Figure 2 and the backstroker in Figure 3) and males must generate 50 lbs of force to compete with the fastest sprinters. While lower force values often reflect a lack of strength, an ineffective technique limits a swimmer’s ability to use his/her strength.

Figure 3. Hand force curves for a female world champion in backstroke.

In addition to the magnitude, the location of the peak force (within a stroke) indicates a great deal about a swimmer’s technique. Technically proficient swimmers move their arm into an increasingly stronger position at an increasingly faster speed, so that the peak force is located at a point well after the arm passes the shoulder (about halfway into the push phase). For example, the elite backstroker in Figure 3 achieves her peak force at .82 sec into the stroke. Less proficient swimmers often reach peak force at the end of the pull phase (as the arm passes the shoulder), such as the high school swimmer in Figure 4 who reaches peak at only .34 sec into the stroke.

Figure 4. Hand force curves for a male high school backstroker.

Swimmers that are more proficient also increase force with a smooth and steep slope to a peak, as exemplified by the breaststroker in Figure 2. With an effective breaststroke technique, the force will double in value from the outward scull to the inward scull (or from the pull phase to the push phase in butterfly, backstroke, or freestyle). In addition to the impressive slope, she maintains a force near the peak for a duration of about .2 sec. In comparison, the peak duration of the backstroker in Figure 3 is less than .1 sec.

Regardless of the location, slope, or duration of the peak, increasing the magnitude of the peak (sometimes just by pushing harder) will increase the average hand force, and therefore, increase swimming velocity (Havriluk, 2003). Efforts to increase magnitude may also increase duration. Improving the location and slope of the peak, however, requires considerable instruction and the feedback provided by regular testing.

Analysis of Force Losses – Sudden Changes in Hand Path, Pitch, or Speed

A fast swimmer often displays impressive peak force qualities, but has a noticeable decrease in force just prior to the peak. For example, the Olympic sprint medalist in Figure 5 has a force loss of over 10 lbs (indicated by the vertical grey line), typical of the transition from pull phase to push phase (as the arm passes the shoulders). This loss of force results from a sudden change in the hand path, pitch, or speed. Elite swimmers rarely have sudden changes in hand pitch, so the hand path or speed is usually responsible for the force loss.

Figure 5. Male Olympic freestyle medalist with force loss during pull to push transition.

As different muscle groups are involved in pulling and pushing, the transition from the pull phase to the push phase is not seamless. A resulting decrease in hand speed shows up on the force curve as a decrease in hand force. Making an effort to increase hand speed from pull to push can help overcome this limitation, which is characteristic of some of the world’s fastest sprinters.

Analysis of Wasted Motion – Nonproductive Vertical and Lateral Hand Motion

Wasted motion is another typical technique element that limits even the fastest swimmers. Any failure to move the arm into an increasingly stronger position is wasted motion. Wasted motion causes a constant (and often negligible) force over a time of .1 to .5 sec, as seen in the beginning of each stroke of the Olympian in Figure 6. Her arms enter in front of and at the same level as her shoulders (left image). However, she then moves her arms laterally with no elbow flexion. Consequently, her arms remain in such a weak position that she is only able to generate about 5 lbs of force for the first .2 sec of the pull.

Figure 6. Olympian with .2 sec of wasted motion at the beginning of the butterfly pull. The vertical grey lines on the force curves are synchronized with the video image.

Once a quantitative analysis confirms wasted motion, it is easier for a swimmer to understand the coach’s instruction for change. Flexing the elbows immediately after arm entry helps to minimize wasted motion at the beginning of the fly pull. Eliminating only .1 sec of wasted motion on every stroke adds up to a substantial time drop.

Analysis of Arm Synchronization – Overlap Force Curves for Continuous Propulsion

Wasted motion (or lack of motion) in the unilateral strokes (freestyle and backstroke) can adversely affect arm synchronization, causing gaps in propulsion. The national caliber male swimmer in Figure 7 hesitates his left arm for about .3 sec after entry, resulting in the noncontinuous propulsion style known as “catch-up stroke.” Although he is capable of generating a peak force of over 40 lbs, he only has 3 lbs of total force for a gap of over .1 sec on every stroke cycle.

Figure 7. Hand force curves for a national caliber male distance swimmer with “catch-up” freestyle. The left hand force is in black and total force from both hands is in outline.

In contrast, the female Olympic medalist (Figure 8) only generates a maximum peak force of 25 lbs with either hand, but because she has such an effective arm overlap (one arm begins generating substantial force at the beginning of the pull before the other arm completes the push), her minimum total force is rarely less than 14 lbs. Her more continuous source of propulsion results in a more constant body velocity and a more efficient use of energy. Swimmers using catch-up stroke can significantly improve performance by beginning the pull immediately after arm entry.

Figure 8. Freestyle hand force curves for a female Olympic medalist with an effective overlap of hand force. The left hand force is in black and total force from both hands is in outline.

An Optimal Model for Technique Based on Advanced Technology Analysis Procedures

All of the technique limitations described (and the suggested changes that mitigate these limitations) have been derived from over 20 years of research including thousands of analysis trials with swimmers at every level. This exhaustive study clearly shows that while faster swimmers have more positive technique elements than slower swimmers, even the fastest swimmers have technique limitations. Because swimming technique is so complex, a biomechanical (nonhuman) model (Figure 9, left) is necessary to demonstrate optimal technique.

Figure 9. Synchronized video and force data for a biomechanical model of optimal butterfly technique (left) and a human who has numerous effective technique elements (right).

The model in Figure 9 shows stroke-to-stroke consistency; bilateral symmetry; a smooth, steady increase in force to a peak; no force losses; and no wasted motion. The human swimmer (right) shows considerable similarity with both the video and force curves of the model, although she has a substantial force loss in the middle of each stroke. As a swimmer’s technique progresses, advanced technology analysis procedures clearly pinpoint remaining limitations.

Summary

Swimmers with advanced skills can benefit greatly from information derived from the use of advanced technology. A comprehensive battery of analysis procedures provides quantitative data to augment a coach’s qualitative analysis. Advanced technology does not eliminate the work that coaches and swimmers must do to improve technique. On the contrary, such thorough analysis adds to the coach’s workload while making more effective use of his/her coaching skills. At the same time, the additional feedback adds to the swimmer’s mental load by requiring constant focus to master the technique changes. The extra effort is warranted, however, as advanced technology can be used to address technique limitations that would otherwise go unnoticed.

Author Notes

Dr. Rod Havriluk is a sport scientist and former coach. He conducts clinics worldwide and consults with teams, swimming associations, and national training centers about technology applications for improving performance. He can be reached at the Swimming Technology Research website - swimmingtechnology.com.

References

Havriluk, R. (2003). Performance level differences in swimming drag coefficient. Paper presented at the VIIth IOC Olympic World Congress on Sport Sciences, Athens, Greece.