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A new model triathlon suit (NMS) was developed to help the swimming performance of athletes. The NMS is made of highly compressed and highly water-repellent fabric, which is used in competitive swimwear. The aim of this study was to evaluate the NMS by measuring the passive drag and body position during underwater streamline position. The NMS and the old model suit (OMS) were worn by 11 highly competitive varsity swimmers (eight males and three females). The passive drag and body position were measured when both suits were worn in the circulating water channel. The coefficient of passive drag was calculated by the equation. On average, for the whole measurements, there was a reduction in passive drag when wearing the NMS suit of 1.1±5.3% compared with the OMS, whereas there was no statistically significant. The coefficient of the passive drag was not significant difference between both suits. Wearing the NMS showed higher body position compared to the OMS at any velocity, although not significantly. These results suggest that wearing the NMS might help improve swimming performance.

In order to understand the physical origin of passive resistance in swimming the resistance breakdown for a swimmer is investigated. A combination of empirical methods and theoretical analysis is used to predict passive resistance in the speed range 0 – 2ms-1 and is shown to provide similar results to those from experimental testing. Typical magnitudes of wave, viscous pressure and skin friction resistance contribute 59%, 33% and 8% of total passive resistance respectively at free swim speed. A comparison is made between the widely used Velocity Perturbation Method and a Naval Architecture based approach in predicting active drag. For the swimmer investigated the two approaches predict active drag of 131.4N and 133.9N for a swimming speed of 1.53ms-1. However, the results predicted from the Velocity Perturbation Method have a much higher uncertainty and the Naval Architecture based approach is suggested as a more robust method of predicting active drag.

A cross-sectional comparison between the buoyancy, passive and net active drag force characteristics of full-length, Fastskin™ swimsuits with that of standard swimsuits was completed with nine Open National level swimmers (5 males and 4 females). Subjects were weighed in a hydrostatic tank and then towed via a mechanical winch on the surface and 0.4 m deep at 1.6, 2.2 and 2.8 m/s. The subjects performed a prone streamlined glide and maximum effort flutter kick at each towing velocity and depth. Hydrostatic weight differences between swimsuit types were not significant (p> 0.05. Fastskin™ passive drag values were significantly less than normal swimsuits during surface towing at 1.6 and 2.8 m/s; and at 0.4 m deep towing at 1.6, 2.2 and 2.8 m/s. Net active drag force values also were lower for the Fastskin™ suits when compared with those of normal swimsuits and a significant difference existed for surface towing at all three velocities of 1.6, 2.2 and 2.8 m/s. The full-length, Fastskin™ swimsuits created less total hydrodynamic resistance than normal swimsuits while providing no additional buoyancy benefits.

By comparing the time of the same distance swum with and without an added resistance, under the assumption of an equal power output in both cases, the drag of 73 top swimmers was estimated. The active drag Fr(a.d.) at maximal swimming velocities varied considerably across strokes and individuals. In the females Fr(a.d.) ranged from 69.78 to 31.16 N in the front-crawl, from 83.04 to 37.78 N in dolphin, from 93.56 to 45.19 N in breaststroke, and from 65.51 to 37.79 N in back-stroke. In the males Fr(a.d.) ranged from 167.11 to 42.23 N in front-crawl, from 156.09 to 46.95 N in dolphin, from 176.87 to 55.61 N in breaststroke, and from 146.28 to 46.36 N in back-stroke. Also, the ratio of Fr(a.d.) to the passive drag Fr(a.d.) as determined for the analogical velocity in a tugging condition (in standard body position-front gliding) shows considerable individual variations. In the female swimmers variations in Fr(a.d.)/Fr(p.d.) ranged from 145.17 to 59.94% in front-crawl, from 192.39 to 85.57% in dolphin, from 298.03 to 124.50% in breaststroke, and from 162.87 to 85.61% in back-stroke. In the male swimmers variations in Fr(a.d.)/Fr(p.d.) ranged from 162.24 to 62.39% in front-crawl, from 191.70 to 70.38% in dolphin, from 295.57 to 102.83% in breaststroke, and from 198.82 to 74.48% in back-stroke. The main reason for such variations is found in the individual features of swimming technique and can be quantitatively estimated with the hydrodynamic force coefficient, which thus provides an adequate index of technique.

In a quadruple approach we have suggested the ergonomics links between fundamental hydrodynamics, applied dynamics of swimming, electromyographical aspects and specific training. Fundamental and applied hydrodynamics were investigated in a Dutch Marine Ship model test station allowing for the measurement of passive drag in different positions and of active (swimming) drag. It was found that drag in a prone position under the water surface was greater than at the water surface, but active drag while swimming reached twice the drag values of any passive drag condition. This indicates that body form has no influence on drag and propulsion. Since it is merely the technical execution of the swimming movement that will influence performance, telemetric EMG of the involved musculature has allowed a complete kinesiological picture of the front crawl movements to be made. This knowledge is basic for the study of specific and alternative training systems, such as specific dry land training.

Propulsive arm forces of 32 male and 9 female swimmers were measured during front crawl swimming using arms only, in a velocity range between 1.0 m s-1 and 1.8 m s-1. At constant velocity, the measured mean propulsive force Fp equals the mean active drag force (Fd). It was found that Fd is related to the swimming velocity v raised to the power 2.12 +/- 0.20 (males) or 2.28 +/- 0.35 (females). Although many subjects showed rather constant values of Fd/v2, 12 subjects gave significantly (p less than 0.01) stronger or weaker quadratic relationships. Differences in drag force and coefficient of drag between males and females (drag: 28.9 +/- 5.1 N, 20.4 +/- 1.9 N, drag coefficient: 0.64 +/- 0.09, 0.54 +/- 0.07 respectively) are especially apparent at the lowest swimming velocity (1 m s-1), which become less at higher swimming velocities. Possible explanations for the deviation of the power of the velocity from the ideal quadratic dependency are discussed.