Original articles   

The Journal of Sports Medicine and Physical Fitness 2000 June;40(2):145-9

Copyright © 2002 EDIZIONI MINERVA MEDICA

lingua: Inglese

Cardiorespiratory and metabolic responses during straight and bent knee cycling

Mandroukas K., Angelopoulou N., Christoulas K., Vrabas I. S.

From the Ergophysiology Laboratory Department of Physical Education and Sports Sciences Aristotelian University o f Thessaloniki, Greece

Back­ground. ­This ­study exam­ined the influ­ence of ­knee ­angle on the car­di­o­res­pir­a­to­ry ­system load­ing dur­ing sub­max­i­mal and max­i­mal sta­tion­ary ­cycle ergom­e­try.
Meth­ods. Experi­men­tal ­design and par­tic­i­pants: eight­een ­untrained wom­en (age: 21±1.88 years, ­weight: 57±5.75 kg, ­height: 165±5.03 cm, val­ues are ­mean±SD) vol­un­teered as sub­jects and under­went two-­cycle ergom­e­ter incre­men­tal (Jaeg­er ER900) ­tests: 1) ­straight ­knee (180°), 2) ­bent ­knee (140°). Meas­ures: oxy­gen ­uptake (VO2), ven­ti­la­tion (VE) and res­pir­a­to­ry ­exchange ­ratio (RER) ­were meas­ured con­tin­u­ous­ly dur­ing ­each ­test ­using an ­open cir­cuit spi­rom­e­try and ­blood lac­tate con­cen­tra­tion was deter­mined by ­means of an enzy­mat­ic meth­od.
­Results. Com­par­ing ­cycling ­with “­straight ­knee” to ­cycling ­with “bent ­knee” at 50 W, ­heart ­rate (HR), VE and VO2 ­were sig­nif­i­cant­ly high­er (10.6%, 12.5%, 17.8%). At 100 W, ­blood lac­tate was sig­nif­i­cant­ly low­er (10.8%) ­while VO2 and RER was high­er (5.5%, 7.1%). Dur­ing max­i­mal exer­cise, the ­total exer­cise ­time was sig­nif­i­cant­ly long­er (11.2%) and VE, VO2 and HR ­were sig­nif­i­cant­ly high­er dur­ing ­cycling ­with “­straight ­knee” com­pared to ­cycling ­with “­bent ­knee”. No sig­nif­i­cant dif­fer­ence in ­peak lac­tate was evi­dent ­between the two sit­ting posi­tions.
Con­clu­sions. The ­results of ­this ­study indi­cate ­that ­cycling ­with ­bent ­knee ­requires low­er oxy­gen ­uptake ­while ped­al­ing ­with ­straight ­knee is the ­only way to ­reach VO2max dur­ing ­cycle test­ing, ­since the car­di­o­res­pir­a­to­ry ­system is ful­ly ­taxed.