What happens when adapting PC’s from the road to aero (tri) position? The ROM changes somewhat, but are different muscle groups involved?
What happens when adapting PC’s from the road to aero (tri) position? The ROM changes somewhat, but are different muscle groups involved?
The ROM doesn’t change somewhat, it changes a lot. The way of looking at what happens is to do this. Stand against a wall and put a 14 inch step (the approximate distance you have to raise your foot when pedaling) next to one of your feet. Then raise the foot and it isn’t to hard. Then bend over some and raise the foot, it gets harder. Then bend over more, it gets harder. Then bend to a 90 degree angle (the approximate tri position) and it becomes very difficult. The more you bend over the closer you are getting to end of the range of motion of the hip joint and the muscles contract less efficiently at this point so it becomes much harder. So, it is the same group of muscles but they are less efficient.
At least that is what I think is going on.
It seems to me that there are two components to the upstroke:
- Flexion at the hips done primarily by the ileopsoas and possibly also the rectus femoris
- Flexion at the knee done primarily by the hamstrings and possibly also the gastrocnemius
If the ability of the ileopsoas to flex the hips is impaired by the positioning as you described, will the hamstrings contribute more to the upstroke?
It seems to me that there are two components to the upstroke:
- Flexion at the hips done primarily by the ileopsoas and possibly also the rectus femoris
- Flexion at the knee done primarily by the hamstrings and possibly also the gastrocnemius
If the ability of the ileopsoas to flex the hips is impaired by the positioning as you described, will the hamstrings contribute more to the upstroke?
What the hip and knee do are pretty much unrelated. If the hip has to flex x amount, it cannot be aided in this effort by the hamstrings so the amount the muscles have to contract is the same. However, the force the muscles have to exert during these contractions is related because of gravity. If one is sitting back, most of the upward movement of the foot comes from upward movement of the thigh (the hamstrings are moving the feet backwards). If one is forward, the upward movement of the foot is transferred more and more to the hamstrings and the thigh moves more back and forth. So, the the amount of contraction the various muscles have to do are pretty much independent but the relative amount of work that the various muscles have to do does depend upon the position on the bicycle and is related. Hope this makes sense.
To really feel this difference (or to emphasize the hamstring workout) put the bike on the trainer and come out of the saddle, lean against the handlebars (bringing yourself as far forward as possible) and pedal one legged. Feel the difference in the hamstrings compared to pedaling one legged sitting on the saddle.