Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: englishgent on 13/05/2005 19:04:00

Title: mulitjoint muscle fibres
Post by: englishgent on 13/05/2005 19:04:00
The rectus femoris is the only quadricep muscle that crosses two joints. It is responsible for flexion on the hip and extension of the knee. How is it possible for me to flex my hip using the rectus femoris without extending my knee as all muscle fibres stretch the entire length of the muscle and contract across its whole length or not at all?
          I understand that the hip flexor muscles are also working during flexion of the hip but the rectus femoris is also working so how is this possible.
          I have been puzzeled by this for a while now and have also had difficluty getting a definitive explaination for 'Lomards parodox'. Can anyone shed any light on this for me ?
Title: Re: mulitjoint muscle fibres
Post by: rosy on 13/05/2005 21:24:58
Pure speculation here, but it's not something daft like when you're using this muscle to flex your hip your calf muscle has tocontract to balance the strain and keep your knee bent?
*stands back from computer and tries a few experimental leg movements*
Hmm, hard to find out if your calf muscle's tensed or not when you're waving it about on the other side of a flexing hip.
Title: Re: mulitjoint muscle fibres
Post by: englishgent on 14/05/2005 07:38:31
No nice idea but no muscle contraction is needed to keep the knee in a flexed position because gravity does that for us. I always stand up and do the movements too lol ha ha ha. When i was in one of my exams i could see people twitching in their seats wanting to get up lol.