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abstract thesis Mechanics and Energetics of Swimming.

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  • abstract thesis Mechanics and Energetics of Swimming.

    This is a summary of my thesis. I have some copies left for people who are
    interested. (the thesis is on HUMAN swimming).


    Huub M Toussaint

    In swimming some of the power output generated by the swimmer is necessarily
    expended in giving water a kinetic energy change, since the propelling
    thrust is made against masses of water that acquire a backward
    momentum. Hence the power output (Po) is apportioned between that part
    used to overcome drag (Pd) and that part which gives water a kinetic
    energy change (Pk). Hence

    Po = Pd + Pk (1)

    It will be obvious that the latter component Pk is rather difficult to
    measure. However, the apportionment of Po into Pd and Pk could be an
    important determinant of swimming performance. This idea is given
    expression in the concept of propelling efficiency ep (Toussaint et al

    ep = Pd/Po = Pd/(Pd + Pk) (2)

    The measurement of the component powers of the total mechanical power
    produced by the swimmer was made possible by the development of the
    system to measure active drag (MAD-system, Hollander et al, 1986). With
    suitable instrumentation this system allows active drag to be directly
    measured for the first time.

    Active drag related to velocity

    The drag force on the swimmer while swimming the front crawl is related
    to the swimming velocity raised to the power 2.12 1 0.2 (males) or 2.28 1
    0.35 (females). Most subjects (29) showed rather constant values of
    Fd/v2, but 12 subjects gave significantly (p < 0.01) stronger or weaker
    quadratic relationships. Differences in drag force and coefficient of drag
    between males and females (drag at 1 m/s 28.9 1 5.1 N, 20.4 1 1.9 N,
    drag coefficient: 0.64 1 0.09, 0.54 1 0.07 respectively) are especially
    apparent at the lowest swimming velocity (1 m/s), which becomes less
    at higher swimming velocities.

    Mechanical efficiency of swimming

    Mechanical efficiency can be defined as the ratio of the power output to
    the power input. The power output was assessed by use of the MAD system.
    The estimation of power input from steady state oxygen uptake
    measurements does not present major problems, provided that the
    respiratory apparatus does not increase body drag.

    A respiratory valve was developed whereby the inspiratory and expiratory
    tubing was arranged in-line and moulded over the swimmers head. Using
    the MAD system the effect on total body drag due to the addition of the
    respiratory apparatus was evaluated to be negligible. This apparatus was
    applied in the determination of mechanical efficiency in a group of male (N
    = 6) and female (N = 4) competitive swimmers. The mechanical efficiency
    ranged from 5 - 9.5%. At equal swimming speed the male competitive
    swimmers demonstrated a higher mechanical efficiency. However, this
    was due to the higher power output required by the male swimmers at a
    given speed. At the same power output the values for the mechanical
    efficiency do not differ between the male and female competitive

    Propelling efficiency of swimming

    To determine the propelling efficiency of swimming it is necessary to
    measure Pk. This can be done by comparing at the same velocity the Pi
    swimming free, where Pi reflects Pd + Pk, with the Pi obtained while
    swimming on the MAD system (Pk = 0, since the push off is made against a
    fixed point). For the four top class swimmers studied the propelling
    efficiency was found to range from 46 - 77%.

    To evaluate the significance of the propelling efficiency as a performance
    determining factor, the ep of 6 competitive swimmers was compared to
    the ep of 5 triathletes. Using regression equations the data was
    interpolated and the groups were compared at equal rates (900 Watt) of
    energy expenditure. The groups did not differ in mechanical efficiency,
    stroke frequency, and work per stroke. There was a difference in distance
    per stroke (1.28 m vs 0.99 m), and mean swimming velocity (1.11 m/s vs
    0.90 m/s). The difference in swimming speed between the two groups
    can be explained by the fact that the competitive swimmers can use a
    much higher proportion of their power output to overcome drag (44 W vs
    30 W). At the same time the competitive swimmers expend less power in
    moving water backwards (28 W vs 39 W). This difference in
    apportionnement of the power output can be characterized as the
    propelling efficiency. Mean (1SD) propelling efficiency for the competitive
    swimmers was 62 1 6% but only 44 1 4% for the triathletes.

    Since propelling efficiency was shown to be an important determinant of
    swimming performance the influence of contributing factors was
    considered. One of them, the artificial enlargement of the propelling
    surfaces of the hand, resulted at a given velocity in a decrease in energy
    expenditure (6%), power output (7.6%) and work per unit distance (7.5%). At
    the same time increases were seen in propelling efficiency (7.8%) and
    work per stroke (7%). The increase in distance per stroke and the decrease
    in stroke frequency could be explained by the increase of the propulsive

    Future directions

    It is obvious that the technique of the swimmer determines the level of
    propelling efficiency. However, the present method employed to determine
    the propelling efficiency does not relate technique to it directly. For a
    more thorough understanding of swimming it seems imperative to develop
    methods that relate the movement pattern of the swimmer to their
    propelling efficiency.


    Hollander, A.P., G. de Groot, G.J. van Ingen Schenau, H.M. Toussaint, H. de
    Best, W. Peeters, A. Meulemans, and A.W. Schreurs. Measurement of active
    drag during crawl arm stroke swimming. J. Sport Sci. 4, 21-30, 1986.

    Toussaint, H.M., F.C.T. van der Helm, J.R. Elzerman, A.P. Hollander, G. de
    Groot, and G.J. van Ingen Schenau. A power balance applied to swimming. In:
    A.P. Hollander, P.A. Huijing and G. de Groot (Eds.), Biomechanics and
    Medicine in Swimming. Champaign, IL, Human Kinetics Publishers, pp.
    165-172, 1983.

    Parts of the present thesis are published:

    Toussaint, H.M., G. de Groot, H.H.C.M. Savelberg, K. Vervoorn, A.P. Hollander,
    and G.J. van Ingen Schenau. Active drag related to velocity in male and
    female swimmers. J. Biomechanics 21, 435-438, 1988.

    Toussaint, H.M., A. Meulemans, G. de Groot, A.P. Hollander, A.W. Schreurs,
    and K. Vervoorn. Respiratory valve for oxygen uptake measurements during
    swimming. Eur. J. Appl. Physiol. 56, 363-366, 1987.

    Toussaint, H.M., A. Beelen, A. Rodenburg, A.J. Sargeant, G. de Groot, A.P.
    Hollander, and G.J. van Ingen Schenau. Propelling efficiency of front crawl
    swimming. J. Appl. Physiol. 65, ...-..., 1988.

    The following parts of the present thesis have been submitted for

    Toussaint, H.M., W. Knops, G. de Groot and A.P. Hollander. The mechanical
    efficiency of front crawl swimming. submitted to: Medicine and Science in
    Sports and Exercises.

    Toussaint, H.M. Differences in propelling efficiency between competitive
    and triathlon swimmers. submitted to: Medicine and Science in Sports and

    Toussaint, H.M., T. Janssen, and M. Kluft. Effect of propelling surfaces size
    on the mechanics and energetics of front crawl swimming. submitted to: J.
    Applied Physiology.

    Huub Toussaint
    Faculty of Human Movement Sciences
    Dept Exercise Physiology and Health
    Meibergdreef 15 (AMC)
    1105 AZ Amsterdam
    The Netherlands