Determination of hydrodynamic drag forces and drag coefficients on human leg/foot model during knee exercise

Objective. The purpose of this laboratory experiment was to measure hydrody namic drag forces in barefoot/hydro-boot conditions and accordingly, to det ermine the coefficients of drag on human leg/foot model during simulated kn ee extension-flexion exercise. Design. The prosthesis of the human lower leg was set in a water tank and c onnected into an isokinetic force dynamometer to measure resistive forces d uring knee motion. Background. Quantifying resistance for aquatic exercises has been a challen ge in hydrotherapy. The use of models of foot/leg provides a practical meth od to calculate coefficients of drag and to estimate resistance for rehabil itation purposes in musculoskeletal and amputee patients. Methods. The dynamometer produced constant angular velocities of 250 degree s/s, 270 degrees/s and 300 degrees/s to the prosthesis. The baseline for me asurements was performed in barefoot condition. A hydro-boot was used to st udy effects of increased frontal area (30%) of the leg on drag forces and c oefficients. Results. The maximal drag force values were 61 N (300 degrees/s) in barefoo t and 770 N (270 degrees/s) in hydro-boot condition. Related drag coefficie nt values during the range of motion were from 0.3 to 0.1 and from 1 to 0.8 , respectively. Conclusions. Drag force and related drag coefficient were highest during th e early part of extension (150-140 degrees flexion) as the model was opposi ng the lift forces with the influence of water resistance, The effect of ve locity was remarkable on drag forces but minimal on drag coefficient values .