Abstract
Added mass is the mass of water a swimmer has to accelerate in addition to his body during changes in velocity. It is an important concept in determining the total energy expenditure of human swimmers during unsteady motion. Previous research on added mass gave only anecdotal results, Klauck (1999) found added mass for male swimmers to be 30-70kg. The aim of our study was to find the added mass for human swimmers. Ten male adult subjects between the ages of 20 to 29 years with a body mass of 78.2±6.3kg were included. The subjects were connected to a 2.8m long bar with handles, attached with springs (stiffness k=318N/m) and a force cell. By oscillating this system vertically and registering the time period of oscillations it is possible to find the added mass of the swimmer, given the known masses of the bar and swimmer. A mean added mass of 21.2±2.5kg was found. This represents 27.0±2.2% of the subjects¿ body mass. The added mass values found in the present research seem to be somewhat lower than previously reported, and within a smaller range. One possible explanation for this discrepancy might be due to different measuring methods. An added mass of 27% of the body weight might significantly influence the resistance of a gliding swimmer. The added mass effect contributes to approximately 9 and 3% of the total resistance force, during accelerated motion (a=0.5m¿s-2) at v=1.5 and 3.0m¿s-1 respectively. Furthermore, during swimming strokes, intracyclic velocity fluctuations, especially in breaststroke, is quite large, and added mass most certainly will influence the active resistance and possibly also be a momentum conserving mechanism. These factors must be subject for further studies in the future.
