Start Depth Modification by Adolescent Competitive Swimmers

Abstract

To expand upon previous studies showing inexperienced high school swimmers can complete significantly shallower racing starts when asked to start "shallow," 42 age group swimmers (6-14 years old) were filmed underwater during completion of competitive starts. Two starts (one normal and one "requested shallow") were executed from a 0.76 m block into 1.83 m of water. Dependent measures were maximum depth of the center of the head, head speed at maximum head depth, and distance from the starting wall at maximum head depth. Statistical analyses yielded significant main effects (p < 0.05) for start type and age. The oldest swimmers' starts were deeper and faster than the youngest swimmers' starts. When asked to start shallowly, maximum head depth decreased (0.10 m) and head speed increased (0.32 ms -1 ) regardless of age group. The ability of all age groups to modify start depth implies that spinal cord injuries during competitive swimming starts are not necessarily due to age-related deficits in basic motor skills.The safety risks associated with the execution of a competitive racing start are due to several factors. Some of these are under the swimmer's control and some are not. For example, the trajectory of the body upon leaving the starting block, the velocity at which the body is traveling, and the depth of the head during the trajectory are to a large extent determined by the swimmer or the physical body characteristics such as mass and strength. Block height and water depth, in contrast, are a function of the facility and regulatory requirements. If a swimmer comes into contact with the pool bottom, the severity of the injury that occurs is influenced by the swimmer's momentum, primarily a function of the velocity and mass of the swimmer. The swimmer's velocity is related to the forces generated by the swimmer while on the block, the swimmer's ability to reduce the resistive forces (streamline) once entering the water, and the height of the block above the water surface. The execution of a safe racing start therefore requires the swimmer to exhibit a complex blend of motor abilities, including such skills as static and dynamic balance, multiple axial movements, and ballistic locomotor skills.

Competitive Swim Start Safety

“…Despite the fact that we failed to confirm our hypothesis concerning intraindividual start depth variability, we still concluded that the youngest and most inexperienced swimmers were at the greatest risk of injury from pool bottom collisions from the perspective of the ability to control start depth. This conclusion was based on our studies of depth modification (White et al, 2011 andCornett et al, 2012a) that found, once again, younger and inexperienced swimmers could not always be relied upon to successfully modify start depth when asked to do so.…”

“…USA Swimming does have swimmers who are of high school age, but it also has swimmers who are considerably younger than this. Thus, we wanted to expand our results by performing a second study on depth modification using younger competitive swimmers (Cornett, White, Wright, Willmott, & Stager, 2012a). The competitive swimmers in the second depth modification study were grouped according to their USA Swimming age groups: 10 years and younger, 11-12 years, and 13-14 years (mean ages for the three groups were 7.9, 11.3, and 13.5 years, respectively).…”

Minimum Water Depth Rules for Competitive Swim Starts

“…The first part of the rules above, the minimum water depth, has been the subject of reasonably extensive debate within the swimming and scientific communities (Welch & Owens, 1986;Counsilman, Nomura, Endo, & Counsilman, 1988;Blanksby, Wearne, & Elliott, 1996;Gehlsen & Wingfield, 1998;Blitvich, McElroy, Blanksby, & Douglas, 1999;Blitvich, McElroy, Blanksby, Clothier, & Pearson, 2000a;and Blitvich, McElroy, & Blanksby, 2000b;Cornett, White, Wright, Willmott, & Stager, 2010, 2011a, 2011b, 2011c, 2011d, 2012aCornett, White, Wright, & Stager, 2012b, 2014Cornett, Naganobori, & Stager, 2012c;White, Cornett, Wright, Willmott, & Stager, 2011;Stager, Cornett, & Naganobori, 2013). The second aspect of the rules, the distance from the wall for which the minimum water depth must be maintained, has not received much discussion.…”

Teaching Competitive Racing Starts: Practices and Opinions of Professional Swim Coaches

“…There have been two studies that have dealt specifically with purposeful modification of racing start depth (Cornett et al, 2012;White et al, 2011). In both of these studies, swimmers were instructed to execute two racing starts: (a) a "typical" racing start and (b) a racing start in which the swimmer was asked to execute a "shallow start."…”

“…Additional work has focused on the ability of competitive swimmers of different ages and ability levels to control the depth of their starts (Blitvich et al, 2000;Cornett, White, Wright, Willmott, & Stager, 2012;White, Cornett, Wright, Willmott, & Stager, 2011). Broad conclusions from this research are that (a) maximum head depth and head speed at maximum head depth vary as a function of swimmer age, water depth, block height, and start type and (b) swimmers regardless of age and competitive experience are able to modify start depth in response to water depth and other factors.…”