How should I ride the bike, to ride it well ? Cadence, power generated and the riding technique.

                Usually when I get on my bike, I tend to just ride, without wondering of the technique like gear ratio or position etc.. Perhaps the body adjusts itself and its optimum can be relied on natural law. But the local optimum found by the body by trial and error is not necessarily a global optimum. The task of finding such points belong to doctors and physicists. Their academic achievements translate into sporting achievements of their clients .

                Initially, it is worth mentioning that from the standpoint of physics, work is force (F) multiplied by the displacement (S), while the power is work (W) divided by time, ie the product of force and velocity (V).

P = W / t = F * S / t = F * V

                Pedaling cadence must be optimal if it is too low or too high, the muscles will function with large losses, which means severe fatigue and low speed! As can be seen for longer crank arms, pedaling frequency should be lower than for shorterones (the product of angular velocity  and radius should remain constant).

                In the past, Hill dealt with experiments on muscle contraction. In practice, Hill's muscle model does not reflect the 100% real muscle, nor contractions are not perfectly isotonic. From this experience, however, comes a crucial and practical application. Muscles are most effective when working  at a load equal to about 30% of maximum force generated.  

Linear velocity  of muscle contractions is the product of the angular velocity (omega) and the length of an crank arm (radius, r), thus :

 P = F * omega * r = M * omega

                The cross product of crank arm position and force delivered to the pedal is torque (M). Simplifying we can just multiply force acting effectively ( 90* to the current crank position) by length of crank arm which is radius (r).  The notation is often used in mechanical engineering. Depending on the position of leg, defined by an angle, effective force has a different value and it’s delivered by different muscle groups.

                On the first picture one can see 3 reference curves. The red curve represents the power generated in the short term. And here you can see, the maximum force falls to the low frequency of pedaling. However, this type of movement is far from optimal. As mentioned above, we try to find not the highest generated force, but power instead, and not the short term, but long term power, associated with optimal movement pattern.

                 Practical conclusion? Do not choose low cadence, this causes inefficient muscle operation, rapid fatigue, and damage to cartilage and ligamentous elements, increased sensitivity to the incorrect angle of spinning legs while pedaling. The problem of maintaining high cadence is not in the muscle itself, but in the mind, that must be properly trained to generate correct movement pattern. As seen in other curves - white and yellow, professional cyclists generate the greatest long-term power, with high pedaling cadence.  

By generated long-term power, I  mean power generated during  aerobic work, for time greatest than  21 minutes. As can be seen, for very slow rotation, the values of power are low. It is associated with physiological feature of the blood vessels to collapse under pressure from the outside. Ischemic muscle, quickly ceases to generate power efficiently, accumulate in the lactate, decreasing the pH (acidosis). Increasing the frequency of rotation improves circulation by usage of muscle pump and muscle can longer perform high power generation. Unfortunately there may be an additional load on the cardio – vascular system due to peripheral resistance decrease, as more blood flows through the muscles and we can feel shortness of breath. We probably will note higher pulse rate to maintain perfusion pressure.

                On the second graph I drew a curve of power generated against  the amount of crank revolutions per minute (rpm - revolutions per minute). The maximum force generated for a long time falls for a much lower term - about 50 to 100 per minute, then rapidly decreases. Scientists say the optimum is to ride a 100-120 RPM, and some riders prefer the even moments to 150RPM. Power, is the product of force and speed, this means that the maximum power falls to a higher cadence than the maximum strength.

Last graph takes into account the power dependence on speed. We know that for each of the gears, for a given cadence, it translates into speed of the bicycle ride. One should choose the gear, to maintain steady and comfortable cadence, independent of bike speed. If road gets steep, the wind starts to blow, we get tired, gear ratio should be reduced so as to always operate at maximum limit our effectiveness, and steady pedaling rate. 

 The summary of this piece of my work, you may quote from the blog http://michaelsleen.blogspot.com:

"If your legs hurt more than your Lungs, Increase cadence. If your Lungs hurt more than your legs, use lower cadence. “

Altitude training.

Mountain camp in Zakopane, Poland

                One can hear a growing number of news about beneficial effects of altitude training. Athletes sometimes even do a break in one or series of competitions to spend several weeks in the mountains. In today's world with so tight sport competition, this must be meaningful. 

Natural question, why is that so ? 

                The whole story begins, as always, with basic sciences. This time with physics. Quite intuitively, we can assume that at high altitude there is less oxygen. But the percentage through, is quite the same as in the lowlands (about 21%). The difference lies in the pressure of the gas mixture. The lower the pressure of gas mixture, the lower partial pressure of each gas in this mixture there is, including oxygen. A lower pressure results in a smaller gradient, which drives the oxygen exchange in the lungs. This means that oxygen moves more slowly into the blood. The whole problem gets complicated, because of the shape of the curve representing saturation of hemoglobin as a function of O2 partial pressure in the air. One should remember, that very little oxygen is dissolved in plasma, and must have its own specific carrier, which is hemoglobin (Hb). 

                Higher concentration of carrier (Hb) increases the oxygen capacity of blood, the amount of oxygen that is located in a unit volume of blood. Oxygen supply of tissues in resultant volume is cardiac output, blood oxygen capacity and frequency of breaths, not complicating matters by going further in the regulation of hormonal, nervous, etc. But you can say that the respiratory rate should be synchronized with the cardiac output, enough to ensure optimal oxygenation blood flowing through the lungs. 

Let us write: Oxygen supply is equal to pulse rate times [Hb] times k, where k is a factor. 

                Below 3500 m it can be considered that the decrease of pressure is linear and equal to 1hPa per every 10m up. The total effort on the heights, is associated with additional losses like effort of breathing and maintaining a high pulse, because the power needed to sustain life processes increases with altitude faster than indicated by the graph of oxygen partial pressure. 

This is an important clue to choose the optimal altitude at which we want to train to achieve something. The lower limit is about 1800 m above sea-level The upper limit is often referred to 3500 m above sea-level Some athletes prefer a mixed methods training at altitude, referred to "live high, train low". This is not the only right way, in fact one can meet the extreme opposite approach. 

                Every training camp in the mountains, should last no sorter than 3 weeks, because acclimation can take up to 10 days. The initial weeks should not be associated with great effort, because adaptive changes occur in the body. Often during the first 3 days, hematocrit increases significantly, but there is no polycythemia associated with an increase number of erythrocytes, but with a plasma volume decrease. There is the risk of thrombophlebitis (vein inflammation) , connected usually with a long journey in a seated position. 

The body can induce rapid and deep breath, as a reaction to the drop in oxygen partial pressure, leading to an excessive drop in carbon dioxide partial pressure and respiratory alkalosis. Compensation is the removal of metabolic bicarbonate and thus decrease the buffer plasma capacity. Hypocapnia (CO2 reduction), causes cerebral vasoconstriction. In practice, this means that persistent pain, dizziness, nausea, eating disorders, further decrease in exercise tolerance lasting consecutive days can show up.  

                After the initial few days of relative calmness, walking, light jogging, comes the time to increase exercise intensity. Acclimated organism performs certain changes, leading to increase the concentration of EPO in the blood, reticulocytes begin to emerge - a young red blood cells from the bone marrow indicating increase the pace of development and differentiation of red cell line. 

                There is a growing density of capillaries inside the muscles, which increases the total cross section vessel area and decreases vascular peripheral resistance. Unfortunately, one can observe decreasing density of mitochondria and glycogen level rise. Muscles adapt to glycolysis. There is a growing concentration of lactate. It is the direct reason why, after returning to the lowlands of performance may not be better than before departure. It takes about 2-3 weeks, to restore mitochondrial density. The muscles should regain the ability to use the newly developed red blood cells and the ability to carry oxygen. In addition, blood buffer capacity is recovered and even exceeded and lactate concentration accepted by the organism are much higher. 

                But do not be afraid of those few weeks, because the lifetime of erythrocytes in normal conditions is about 100 - 120 days. Moreover, at this time renewal may still be fast and the maximum number of red cells can be recorded even several weeks after returning from a mountain camp. 

                Some sports doctors believe that the philosophy of "live high, train low", mentioned earlier, enables a faster performance return after returning at the sea level, without impairing the growth of blood oxygen capacity. Special attention should be given to nutrition, taking into account the need for iron, folic acid and vitamin B12. You can even consider supplementation, taking into account the individual eating habits. 

Bibliography: 

1st Will Peveler, The Complete Book of Road Cycling & Racing 

2nd Knuttgen, Conconi, Handbook of Sports Medicine and Science Road Cycling