Added mass in human swimmers: age and gender differences

INTRODUCTION: In unstationary swimming (changing velocity), some of the water around the swimmer is set in motion. This can be thought of as an added mass (AM) of water. Previously only one other study (Klauck, 1999) has investigated added mass on swimmers during passive gliding, and reported added mass values in a range of 30-70kg. The purpose of this study was to find added mass on human swimmers and the effects of age and genders on added mass. METHODS: 31 subjects between the ages of 12 to 36 years were included. They where recruited into three groups; boys (aged 13.7±1.1years), women (21.8±3.4years) and men (25.2±4.9years) with body mass of 52.6±10,6kg, 63.9±5.3kg and 78.2±6.3kg, respectively. 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 period of oscillations it was possible to find the added mass of the swimmer, given the known masses of the bar and swimmer. RESULTS: Added mass for the three groups were 14.5±3.1kg, 15.1±1.2kg and 21.1±2.5kg for boys, women and men, respectively. This corresponds to relative added mass (AM%) of, respectively 27.8±2.9%, 23.6±1.5% and 27±2.2% of the subjects¿ body mass. This study reported significant difference in AM (p