Swimming in the Fast Lane

What makes water fast?

By Joe Hunsaker | 1992
Aquatics International

Speed in the water is the goal of the world-class swimmers who will journey to Athens this summer. Along with all of their efforts in preparing for the experience of a lifetime is the expectation that the Olympic pool will possess all of the qualities needed to maximize their efforts.

What makes water fast? I believe there are seven factors that must exist to maximize the performance of speed swimmers. These factors are not prioritized; however, some are more essential than others.

Chemical balance. The pool water must not be chemically aggressive to the degree that itês so irritating to the mucous membranes of the sinus, mouth and eyes (goggles can leak) that the sensation will distract an athlete and affect his or her concentration. Ideally, the water should have a free chlorine level of .5 to 1.0 ppm and a pH of 7.2 to 7.4 with an oxidation reduction potential of approximately 750 millivolts.

In some pools, these values are created with a primary or secondary treatment of the water with corna discharge ozone, bromine or ultra-violet exposure. In the final analysis, pool water must meet the quality standards of the local jurisdictional health agency.

Clarity.Pool water must be clear so that swimmers have excellent underwater vision. Turbid water can be a distraction and is therefore undesirable. Clarity is the result of efficient filtration. Particle sizes greater than 15 microns must be removed from the water through the use of screens, a filter media and by chemical oxidation caused by hypochlorous acid, hypobromous acid, ozone, ultraviolet light, etc. Water must have a turbidity level that does not exceed 0.5 nephelometer turbidity units.

Temperature.Swimmers must be comfortable in the water, which means the water temperature should be approximately 78 degrees Fahrenheit (25.5 degrees Celsius). At this temperature, the swimmerês body will not overheat at maximum aerobic effort and stress.

At temperatures much below this level, swimmers usually complain of stiffening muscles, and the body will burn more calories to offset the colder skin temperature. At water temperatures above 80 degrees Fahrenheit (26.6 degrees Celsius), swimmers usually begin to feel sluggish and tend to experience an undesirable rise in body temperature during maximum effort.

Controlling water temperature requires an understanding of the medium as a heat sink. Quiescent water will develop a thermocline with a layer of warm water above a colder mass below. With different types of supply inlet systems ® wall or floor – the warm layer will be affected differently.

A crowded indoor spectator gallery of 5,000 to 10,000 people can change the dynamics of the air temperature/water temperature relationship. When cooling systems are activated for spectators, pool water temperature and evaporation rates may be impacted. For these reasons, the system should be engineered for best-case water temperature control and then tested during swimming meets to ascertain the effectiveness of controlling water temperature.

Visibility.Good underwater visibility is the result of exceptional water clarity and the light level above the swimming pool. FINA stipulates a minimum 600 lux at the turning ends, while the NCAA requires 100-foot candles. Higher light levels will enhance the field of competition. At these light levels and with a white field and black markings on the pool interior, visibility will be satisfactory for almost all swimmers.

Water depth will affect the reflective brilliance of the pool interior. The deeper the water, the less light reaches the white reflective surface, which in turn reflects less light into the medium. The minimum light levels listed by FINA and the NCAA, in water of minimum championship depths of 2 meters and 7 feet respectively, will provide satisfactory visibility assuming the light sources are correctly located.

Direct illumination from above is recommended with fixtures located directly over the water surface. (Indirect lighting using reflective light bounced off the ceiling is not recommended.) With the overhead light source directed perpendicular to the water surface, light will penetrate the water medium most efficiently and reflect off the white pool interior.

Underwater lights will increase the light level under the water surface, and will also reflect off the white interior. This, with overhead light, will create an ideally illuminated medium through which swimmers will race. (Itês important to note that the use of underwater robot cameras using a wide-angle lens and propelled along the bottom under the racing swimmer may be affected by the permanent wall mounted lights. As this technology develops, collateral influences will have to be analyzed.)

The choice of light fixtures should be based upon several considerations. Metal halide is most often selected for overhead fixtures, while quartz lamps are preferred for underwater lights. These lamps produce a white light that is preferred for competition. Designers and owners have experimented with high-pressure sodium, but the light spectrum creates some objectionable effects in the form of reflected glare on the water surface and a diminished degree of illumination below the surface.

Subsurface turbulence.It is believed by many that subsurface turbulence can inhibit the forward motion of a swimmer. This turbulence can be caused by water currents from the poolês recirculation system. These currents seem to vary depending upon the type and location of the inlets. Currents that are the result of circulation flow can be a problem if they exist in the racecourse. Of greater interest is the theory of rebound turbulence ® created by swimmers at the surface ® which many believe reaches the bottom of the tank, rebounds to the surface and interferes with the forward progress of swimmers. If of sufficient energy and water mass, this turbulence can reduce the propulsive forces generated by the swimmer.

To date, there have been no empirical studies conducted to identify the amount and nature of the rebound turbulence that occurs when swimmers race in a pool, or what influence various pool depths have on that turbulence. The minimum depths of two meters stipulated for championship competition, especially for the Olympics and World Championships, are sufficient to minimize any subsurface turbulence that may negatively affect the swimmers at the surface above.

Surface turbulence.The effect of the water surface on forward progress has been recognized for centuries by people who have struggled to paddle a canoe or row a boat through choppy water. Swimmers have long been aware of the difficulty of swimming through rough water as compared to a smooth, flat surface. It was this understanding that led to the development of floating lane dividers and subsequently to the wave quelling designs that are used today. Floating lane lines absorb wave energy created in each lane by swimmers and contain any surface energy that is not absorbed within the lane. The primary benefit of contemporary lane lines is that they isolate the turbulence in one lane and prevent it from crossing into adjacent lanes.

To a lesser degree, surface turbulence created inside the lane by the swimmer must be dissipated. The speed of the swimmer is not impeded by the residual surface turbulence until he or she swims back through the lane. As a result, the swimmer experiences greater impedance during the first third of each length, with the exception of the first length. Conversely, the least impedance occurs in the last third of each length, when the surface has experienced the longest period of time to achieve equilibrium from the last surface agitation.

This phenomenon affects short-course races differently than long-course races. Because of the shorter time frame, the water is -rougher” for the duration of a multi-length race in a short course than it is in a long course. Itês difficult to apply a factor to the difference because other influences impact the issue, such as the number of turns and push-offs, and the possible rest or stimulation the turns provide the swimmer and the proximity of swimmers in adjacent lanes.

Psychological influence.Psychological impact is a subjective variable that influences all athletes in a positive or negative way at the start of a race. While a swimmerês mental attitude is most affected by his or her coach, plus the swimmerês preparation for the event, there are things that natatorium designers can do to influence the excitement and adrenalin level of the athletes. Architects should be educated about the experience of the competitors. This includes identifying psychological impact points, including the locker room environment, the first entry into the natatorium, the warm-up routine, the rubdown, and the sounds and smells he or she experiences as more athletes arrive.

As the time of the event draws closer, there are individual behavior patterns that each competitor will carry out. This usually includes a period of time for seclusion, meditation and concentration. Privacy may be an empty room, a corner under the stands or simply a towel over the head.

Time itself is a stimulant, so the awareness and communication of time is important. Clocks should be synchronized and located throughout the natatorium, locker rooms and support spaces.

For Olympic and world-class competition, a ready room will be provided. The location, design and appearance of this room can be a factor in motivating swimmers, as is the time spent in the room before the athletes are led out to their stations on deck before moving to the starting blocks.

These micro-stimuli affect an athlete as he or she progresses through the emotional and physical climax of the race, but there are also macro-stimuli created by the scale of the facility, the spectator noise, which becomes a part of the experience and can be a major influence. The pre- and post-race ceremonies, plus the total pageantry of a world-class championship will have an impact on the athletes ® sometimes for the better and, in some cases, for the worse.

If all of the environmental stimuli conditions come together to help produce record-breaking times, and even more important, personal-best times for those who do not win, the pool will be known as a -fast pool.” Such recognition, based upon performance, is the goal of competitive venue pool designers.