Intra-Individual Head Depth Variability During the Competitive Swim Start

The research on the competitive swim start primarily consists of group mean and maximum depths with little attention given to individual variability. The purpose of this study was to quantify intra-individual racing start depth variability and use it to assess minimum water depth standards. Twenty-two competitive swimmers executed five racing starts into a water depth of 3.66 m. Intra-individual variability was quantified by taking the standard deviation of the maximum depth of the center of the head for the five racing starts executed by each swimmer. The mean value was 0.09 m with a standard deviation of 0.06 m. Analysis of means and standard deviations showed that about one-third of swimmers would be expected to have a head depth deeper than the current minimum water depth requirement (i.e., 1.22 m) for at least 10% of starts. Based on this research conducted in deep water, our recommendation is that swimmers demonstrate both consistency and control of racing start depth before being permitted to execute starts in shallow water. Most competitive swimming races begin with the swimmers diving into the water from a starting platform elevated above the water surface. The potential for injury exists during the execution of this complex motor task if an athlete contacts the pool bottom due to a dive that is too deep and/or a pool that is too shallow. When a swimmer comes into contact with the pool bottom during the start, the risk and severity of injury is influenced by many factors such as (a) the swimmer’s momentum; (b) the swimmer’s age and physical traits; (c) the orientation of the head, neck, and torso; and (d) the location of impact and interface (Viano & Parenteau, 2008). Depending on the factors above, injuries may be as minor as bumps, scrapes, or bruises and as severe as cervical vertebrae fractures or dislocations. In an effort to prevent all such injuries from occurring during the execution of racing starts, governing bodies in the sport mandate the minimum water depth at the starting end of competitive swim pools. In the United States, for example, USA Swimming (USAS), the National Federation of State High School Associations (NFHS), and the National Collegiate Athletic Association (NCAA) require a minimum water depth of 1.22 m (4 ft) in order for swimmers to execute competitive racing starts from a starting block (USA Swimming, 2012; National Federation of