Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
©Journal of Sports Science and Medicine (2024) 23, 17 - 24   DOI:

Research article
Estimating Active Drag Based on Full and Semi-Tethered Swimming Tests
Matteo Cortesi1, Giorgio Gatta1, Rémi Carmigniani2, Paola Zamparo3, 
Author Information
1 Department for Life Quality Studies, University of Bologna, Italy
2 LHSV, Ecole des Ponts, EDF R&D, Chatou, France
3 Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Italy

Paola Zamparo
✉ Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Italy
Publish Date
Received: 13-06-2023
Accepted: 28-11-2023
Published (online): 01-03-2024

During full tethered swimming no hydrodynamic resistance is generated (since v = 0) and all the swimmer’s propulsive force (FP) is utilized to exert force on the tether (FT = FP). During semi-tethered swimming FP can be made useful to one of two ends: exerting force on the tether (FST) or overcoming drag in the water (active drag: Da). At constant stroke rate, the mean propulsive force (FP) is constant and the quantity FP - FST (the “residual thrust”) corresponds to Da. In this study we explored the possibility to estimate Da based on this method (“residual thrust method”) and we compared these values with passive drag values (Dp) and with values of active drag estimated by means of the “planimetric method”. Based on data obtained from resisted swimming (full and semi-tethered tests at 100% and 35, 50, 60, 75, 85% of the individual FT), active drag was calculated as: DaST = kaST .vST2 = FP - FST (“residual thrust method”). Passive drag (Dp) was calculated based on data obtained from passive towing tests and active drag (“planimetric method”) was estimated as: DaPL = Dp.1.5. Speed-specific drag (k = D/v2) in passive conditions (kp) was )25 kg.m-1 and in active conditions (ka) )38 kg.m-1 (with either method); thus, DaST > Dp and DaST > DaPL. In human swimming active drag is, thus, about 1.5 times larger than passive drag. These experiments can be conducted in an ecological setting (in the swimming pool) by using basic instrumentation and a simple set of calculations.

Key words: Hydrodynamic resistance, resisted swimming, front crawl, biomechanics, water locomotion

           Key Points
  • The active drag of a swimmer is about 1.5 times larger than the passive drag
  • The planimetric method and the residual thrust method yield similar active drag values
  • The active drag can be estimated by means of resisted swimming tests
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