Keppenham, B. C., & Yanai, T. (1995). Limb motions and body roll in skilled and unskilled front crawl swimmers. Medicine and Science in Sports and Exercise, 27(5), Supplement abstract 1299.

The coordination of limb movements and body roll in skilled (S) and unskilled swimmers (U) was investigated. Specifically, the timing of the hand entry with respect to body roll, and the timing of the strong beat kick with respect to body roll were analyzed.

Shoulder (S 80 degrees; U 70 degrees) and hip (S 50 degrees; U 40 degrees) rolls were similar for both groups as was the duration of the recovery phase of the stroke. The coordination of the strong beat kick with body roll was also similar between the groups.

The coordinations of the initial arm movement, body roll, and strong beat kick were different between the groups.

1. Skilled swimmers rolled the shoulders and hips together during the strong beat kick. Unskilled swimmers rolled the hips first and then the shoulders.
2. Skilled swimmers executed the strong beat kick after entry 2% into the stroke time while unskilled swimmers waited until 13% of the stroke duration had passed.
3. Skilled swimmers entered the recovery arm when the body roll was greater than 40 degrees (9% of stroke time after attainment of the maximum shoulder roll) while for unskilled swimmers the entry occurred when the body roll was less than 0 degrees (20% of stroke time after attainment of the maximum shoulder roll).
4. The body roll was not a continuous fluid motion. The roll remained on the side while the strong beat kick was executed. This suggests that for a considerable part of the arm pull under water, the body is on its side.

It was concluded that the strong beat kick was highly associated with body and hip roll and that unskilled swimmers delay the timing of arm movements with respect to shoulder and hip roll.

Implications. The following are suggested as teaching ingredients for crawl stroke timing.

1. Roll the hips and shoulders as a unit and to a considerable degree (as much as 90 degrees).
2. The initiation of the arm pull should occur as the hand entry is made and timed with the shoulder (body) roll in the stroke.
3. The body roll and arm pull should be timed together.
4. Emphasize being rotated in the first and middle portion of the underwater pull.

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