Re: Re:
JayKosta said:
Alex Simmons/RST said:
...
That's not the limiter to TT power output. Ability to generate/regenerate a supply of ATP is the limiter. There's no free lunch.
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I agree! The 'pedaling technique' issue is about how to maximize the net power that can be generated (possibly along with aerodynamic concerns) with the amount of ATP that is available.
A 'big question' is whether the conventional pedaling style makes best use of the muscles and ATP. Perhaps someone can do a thoughtful examination of the 'muscle usage' details in the paper and see an opportunity to STOP using muscles when they don't produce a worthwhile amount of power for their ATP consumption, and to START using muscles (and joint angles) that would be more effective in power production. It would be a big advance if the 'simulated work loops' modeling can be used proactively to suggest / recommend ways in which the muscles can be used to produce better results.
Jay
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4894017/
" Abstract
The extremities of the human body contain several bi-articular muscles. The actions produced by muscles at the joints they cross are greatly influenced by joint moment arms and muscle length. These factors are dynamic and subject to change as joint angles are altered. Therefore, to more completely understand the actions of such muscles, the angles of both joints must be manipulated. This report reviews investigations, which have explored the actions of two bi-articular muscles of the lower extremities (gastrocnemius and rectus femoris) as the joints they cross are moved into various combinations of angles. The findings have both clinical and physical performance ramifications.
Introduction
Bi-articular muscles are commonly found in the upper and lower extremities of the human body. These muscles generally cross two joints and influence movement at both. The rectus femoris (RF) spans the hip and knee, and the gastrocnemius (GA) crosses the knee and ankle.
The actions of these muscles at their primary joints have been known for well over 100 years. The RF is an extensor of the leg, and the GA is a powerful plantarflexor. The descriptions of these particular actions have been relatively unchanged for many years and appear in most anatomy textbooks. However, these muscle action descriptions do not consider the influence the second joint may have on the muscle’s action at the primary joint, or vice versa. For example, considering the GA action at the ankle, how does the plantarflexion (PF) torque it generates change as the angles of the knee and ankle change? At what combination does muscular insufficiency arise? Advances in technology have made it possible to answer questions of this type, resulting in more detailed descriptions of the bi-articular muscles of the extremities. In our previous papers, we discussed in some detail issues such as muscle tissue, joint moments and moment arms and their effects on bi-articular muscle actions.
GA
The GA is one of 14 muscles that act upon the knee, and nine of these, including the GA are bi-articular. However, the GA is only one of these nine that acts on both the knee and ankle, and the others cross the knee and hip. At the knee, the GAs’ actions oppose those of the quadriceps femoris, acting synergistically with the other primary knee flexors (biceps femoris, semitendinosus, semimembranosus, gracilis, popliteus, and sartorius). But it also belongs to another group of muscles that cross the ankle. It opposes the action of the dorsiflexors (e.g., tibialis anterior, extensor digitorum longus and hallucis longus) and it is a powerful plantar flexor working with other posterior leg muscles (e.g., soleus, tibialis posterior, flexor digitorum and hallucis longus).
PF forces can be quite high. It is estimated that young males can generate PF torque ranging between 1,000 to 1,780 N.
The GA consists of two heads arising from the posterior aspects of the femoral condyles. These merge into a common belly that rides on the proximal half of the sural aspect of the leg. It shares an insertion with the soleus on the calcaneus via the achilles tendon. The GA and soleus are collectively referred to as the triceps surae and the innervation is supplied by the tibial nerve entering the proximal segments of the muscles. These two muscles provide approximately 80% of force of PF, which is a principal component to a large portion of the gait cycle and essential to nearly all forms of human locomotion. "
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Instead of using the lower leg as a means of transferring generated power from the knee to the pedal*, the combination of the powerful muscles of the lower and upper leg can replace the dead spot sector with the same torque as that applied between 2-4 o'c. The simple technique of indoor tug o'war is all that's required for this combination of the leg's most powerful muscles. Simulated work loop modeling of the indoor tug o'war technique and its force vectors should give interesting results. When you can get a higher torque return from the same force applied by a natural pedaler, it could be said you are getting a free lunch.
*Jim's findings and conclusion drawn from his latest study on natural pedalling, " Thus, during maximal cycling, humans maximize muscle power at the hip and knee, but the ankle acts to transfer (instead of maximize) power. Given that only the timing of muscle stimulation onset and offset were altered, these results suggest that human motor control strategies may optimize muscle activation to maximize power ".
* "We maximized the power that every muscle produced throughout the pedal cycle and came up with patterns that look almost identical to what cyclists do. That means there is nothing else the muscles can do to produce power in some other technique. Any other technique will be less powerful, not more. The differences we saw at the ankle occur during the middle of the recovery portion of the cycle where an active ankle extension would be counter productive. That is, even though soleus could produce more power during that portion of the cycle, doing so would produce negative power on the crank."
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All natural pedallers completely ignore this most powerful and most fatigue resistant muscle in the leg,
" The action of the calf muscles, including the soleus, is plantar flexion of the foot (that is, they increase the angle between the foot and the leg). They are powerful muscles and are vital in walking, running, and keeping balance. The soleus specifically plays an important role in maintaining standing posture; if not for its constant pull, the body would fall forward.
Also, in upright posture, the soleus is responsible for pumping venous blood back into the heart from the periphery, and is often called the skeletal-muscle pump, peripheral heart or the sural (tricipital) pump.
Soleus muscles have a higher proportion of slow muscle fibers than many other muscles. In some animals, such as the guinea pig and cat, soleus consists of 100% slow muscle fibers. Human soleus fiber composition is quite variable, containing between 60 and 100% slow fibers.
The soleus is the most effective muscle for plantar flexion in a bent knee position *. This is because the gastrocnemius originates on the femur, so bending the leg limits its effective tension. During regular movement (i.e., walking) the soleus is the primary muscle utilized for plantar flexion due to the slow twitch fibers resisting fatigue."
*
Which makes it ideal for maximal torque through 12 and 1 o'c.
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By using the interaction of muscles (from hip to ball of foot) and variation of angles at hip, knee and ankle joints, plantar flexion force can be increased and applied in a forward direction at 12 o'c, retaining its force and full tangential effect as it turns downward towards 2 o'c. It's the inclusion of the hip muscles (GM) in the PF force generation that makes PF force adaptable for use in the pedalling technique because apart from increasing the force, it gives the pedaller complete control over its direction.
https://www.youtube.com/watch?v=7hh2DcgpnkU
Pedalling using plantar flexion technique. (180 deg. of torque from each leg, PF force 11-2 o'c, natural force 2-5 o'c). Peak torque is being applied between 1 and 2 o'c
http://www.thebikecomesfirst.com/jacques-anquetil-the-man-the-mystery-the-legend-video/
See 7.30 to 9.15
The feet continue to point down because they have to remain set for their powerful plantar flexor mode which can take effect from 11 o'c, the angle of point down depends on the forward/rearward position on saddle.
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