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"Pumped-up propulsion" during front crawl swimming.
Huub M Toussaint1, Coen Van den Berg, Wiero J Beek
1Institute for Fundamental and Clinical Human Movement Science, Faculty of Human Movement Science, Vrije Universiteit, Amsterdam, The Netherlands. h_m_toussaint@fbw.vu.nl
Medicine and Science in Sports and Exercise
|February 6, 2002
Summary
Human front crawl swimming propulsion is not solely from hand forces. Unsteady, rotational arm movements create axial flow, potentially enhancing propulsion by increasing hand pressure differences.
Area of Science:
- Biomechanics
- Fluid Dynamics
- Human Locomotion
Background:
- Current understanding attributes front crawl propulsion to hand-generated lift and drag forces.
- The quasi-steady assumption simplifies calculations but may not reflect real swimming dynamics.
- Emerging theories suggest unsteady and rotational mechanisms play a significant role.
Purpose of the Study:
- To investigate the role of unsteady and rotational movements in human front crawl swimming propulsion.
- To test theoretical predictions of proximodistal pressure gradients and axial flow induced by arm rotation.
Main Methods:
- Flow visualization using tufts to observe arm and hand flow directions during front crawl phases (glide, insweep, outsweep).
- Pressure measurements at various points along the arm and hand during the stroke.
Main Results:
- Observed highly unsteady flow during insweep and parts of the outsweep.
- Confirmed largely rotational arm movements.
- Detected a distinct axial flow component along the arm during insweep and outsweep.
- Evidence from tuft patterns and pressure recordings supports a predicted pressure gradient along the arm during outsweep.
Conclusions:
- Validated the existence of predicted rotational and unsteady effects in front crawl swimming.
- Hypothesize that observed axial flow enhances propulsion by increasing hand pressure differences.
- Further research is needed to precisely quantify the contribution of axial flow to propulsion.