By Jane Cappaert, M.S., USS Biomechanics Director
Australian Kieren Perkins ' remarkable distance swims have several characteristics that seem to be important to fast distance swimming. One of them is that he is still able to maintain very similar body position from the beginning to the end of the race. Although his stroke rate increases, his body position is similar. Figure 1 (not shown here) exhibits a front view comparison of the first 100m and the last 100m of his 1500m race. The line between the right and left elbows is very similar and his body roll improves (especially the hips) as the race progresses. During the first 100m his hips roll flatter (28 degrees) than the last 100m where his hips roll almost equal to his shoulders (42 deg). Body roll allows swimmers to utilize the trunk muscles in the generation of stroke propulsion. Additionally, it may also have streamlining benefits.
In the first 100m of the 1500m race, there is a large imbalance between the right (Figure 2A) and left (Figure 2B) pulling patterns. The left arm is able to create significantly higher propulsive forces due to a more streamlined entry into the water and a stronger insweep phase. During the last 100m, there is evidence of fatigue in the pulling patterns. The side views of both arms show a flattening out of the pattern, and the left arm shifts emphasis to the finish phase (Figure 2C and Figure 2D). There is, however, a maintenance and even a slight improvement of propelling efficiency. Possibly toward the end of the race, neuromuscular, learned patterns are the dominant factors in his technique. This may suggest that swimmers must use correct technique at all times during workouts, even when they're tired, to train the motor pathways properly.
The imbalance in pulling patterns had a an affect on Perkins' forward swimming velocity. His velocity increased dramatically during the time in which the left arm was in the insweep phase. The increase in velocity during the right arm insweep phase did not match the change due to the left arm. Another factor in the decrease in velocity is the two beat, energy conservative kick that is used by distance freestylers. This less propulsive kick does not maintain swimming velocity as well as a six beat, sprinter kick.
Perkins' technique is highlighted by his ability to: