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  Conditioning for Rowing 划船的調節

Conditioning is essentially about preparing the body for physical stress. It is generally achieved, one way or another,  by repeatedly stressing the body at progressively higher levels, or workloads, in order to bring about long-term changes in the bodies response to exercise and therefore, improve or increase, the time, power and efficiency with which the athlete can perform a given task.       

In rowing as in all physical activities, the bodies job is to perform work, i.e. pull on the oar to propel the boat down the course. All types of physical work require muscular contraction, the muscles pull on the bony skeleton to produce movement. Muscular contraction requires energy. Each muscle cell must have its own energy supply if it is to contribute to the overall movement of the body. It is important to have a basic understanding of the production of energy at the cellular level if you are to understand how different forms of training will affect your athletes.

Energy Systems
The energy source for all cells, including muscle cells, is a molecule called adenosine triphosphate, or ATP for short. Simply put, this molecule contains four parts, one adenosine molecule and three, high energy, phosphate groups. When this molecule is broken down by an enzyme, there is left adenosine diphosphate, ADP (one adenosine molecule with only two phosphate groups), one free phosphate group, and energy released by the breakdown that can now be used by the cell for contractile activity. Thus, the equation will read:

                                                         ATP ----> ADP + P + energy

Because ATP is the only energy source that can be directly used for muscle contraction, ATP must be constantly supplied for muscle activity to continue. However, there is only a very limited supply of ATP immediately available in muscle tissue, only enough to supply a maximal contraction for a few seconds at most. Hence, it is obvious that there must be ways of providing more ATP to keep a constant supply to working muscles to enable the athlete to continue performing beyond a few seconds. There are three different pathways for providing additional ATP during muscular contraction.

1) Creatine phosphate肌肉磷酸 (CP) is the first storehouse used at the start of exercise. CP is a molecule, like ATP, containing a high-energy phosphate group. Also like ATP, when the bond between creatine and phosphate is broken energy is released, i.e.

                                                           CP ----> creatine + P + energy

The energy and the free phosphate just created, can be directly donated to ADP to reform useable ATP, i.e.…

                                       CP (creatine + P + energy) + ADP ----> creatine + ATP

... ,which can then be used to provide energy for continued muscular contraction. For various reasons, most of the energy contained within resting muscle is in creatine phosphate (CP) pools. A rested muscle contains about five times as much CP as ATP. When contraction starts at the beginning of exercise, all the ATP stores are rapidly used, and additional ATP is formed from the CP stores via the reactions described above. ATP can be formed via this method in only a fraction of a second. Thus, CP is the immediate source of additional ATP when exercise begins. CP stores are also depleted quickly however, within about 10 seconds of commencement of high-intensity exercise, the whole CP within a rested muscle is effectively used up. For very short physical events such as sprints, jumping and throwing, this is fine, but for rowing however, it is clearly not.

2) Oxidative phosphorylation or Aerobic glycolysis is a process whereby glucose (refined from food intake) is combined with oxygen (from the air we breathe) to produce carbon dioxide, water and energy for the resynthesis of ATP. Simplified, the equation looks like this:

                                         glucose + O2 ----> CO2 + H2O + ATP

Unlike the ATP-CP system described earlier, oxidative phosphorylation involves a number of complex steps and it needs a constant supply of oxygen. Thus, it is relatively slow. Because of the need for oxygen, this type of metabolism is called aerobic (with air). It yields a great deal of ATP, in fact, most of the ATP used during any exercise lasting more than three or four minutes comes from this source, and its metabolites, carbon dioxide and water are relatively harmless to the body and can be easily used or excreted as necessary. It is, however, limited by two main factors; 1) amount of basic food source (glucose); and 2) amount and speed of O2 able to be delivered to the muscle by the heart and lungs. If the workload required by the exercise exceeds the ability of the heart and lungs to deliver that oxygen, as often occurs in the final stages of a race or during a surge, another method of supplying ATP must be found.

3) Anaerobic glycolysis is a method by which glucose can be broken down without the presence of oxygen (anaerobic = without air), thus providing the energy for resynthesis of ATP. However, instead forming the harmless end products of oxidative phosphorylation (i.e. carbon dioxide and water), the absence of oxygen means that the end product is the toxin, lactic acid. The equation, then, looks like this:    

                                         glucose ----> lactic acid + ATP

Oxygen is needed to complete the breakdown of lactic acid into the more neutral carbon dioxide (CO2) and water. This process has two main advantages over the aerobic metabolism described above: 1) it can form ATP in the absence of oxygen; and  2) it is much faster than aerobic metabolism, so, even though it extracts much fewer molecules of ATP per glucose molecule than oxidative phosphorylation, it proceeds so much more rapidly, that it can outpace oxidative phosphorylation over short periods of time. However, the cost is high. First, because each glucose molecule is not fully processed, this is an inefficient process and requires large amounts of nutrient fuel (glucose). Thus, the muscle stores of glycogen are rapidly depleted. Second, the by-product of this process is lactic acid. Accumulation of lactic acid has been implicated in the muscle soreness that occurs during intense exercise, causes a fall in body pH and generally hastens the onset of fatigue.

Thus, there are three methods of supplying ATP to working muscles.

These are called Energy Systems.

1.CP-ATP (creatine phosphate)
2.oxidative phosphorylation (aerobic glycolysis)
3. anaerobic glycolysis

They have certain advantages and disadvantages over one another:

CP-ATP system:

fast-acting - lasts only about 10 seconds;
>> good for fast, powerful - low yield of ATP per CP (contractions molecule)
–    no toxic by-products – doesn’t need oxygen

Oxidative Phosphorylation
–high  yield of ATP per (Aerobic Glycolysis) glucose molecule

–slow to initiate - requires oxygen to work

– low fuel consumption – can’t supply all the energy

>> long-lasting, can provide requirements for maximal ATP indefinitely as long muscle contraction
     (i.e. as there is O2 and glucose slow to work)

–no toxic by-products

Anaerobic Glycolysis - fast-acting - high fuel consumption
>> can supply ATP to - low yield of ATP
–    maximally working glucose molecule per muscles – toxic by-product (lactic acid)
>> can supply more ATP than oxidative phosphory – limited time-span due to
     relation for short periods build-up of lactic acid

Basic Equations for the Energy Systems: System Fuel Reactants End Products 基本能量系統等式

ATP CP-ATP Creatine Enzymes Creatine + 2ATP Phosphate /

Anaerobic Glycolysis Glucose Enzymes Lactic Acid + 2ATP /

Aerobic Glycolysis Glucose Enzymes CO2 + H2O + 32ATP + O2


What Energy Systems are used When and Why?

During a 2000 m rowing-race, all three of the energy systems are used. Initially, the CP-ATP system is used at the start of the race, because it is fast-acting and is most efficient for rapid, powerful muscular contraction. But, it is very short acting and is exhausted in about 10 seconds. The aerobic metabolism (oxidative phosphorylation) is slow and still starting up. So, anaerobic glycolysis must fill the gap. For the first minute or so, anaerobic glycolysis is the predominant supplier of ATP to the working muscles. But, lactic acid is building up and the muscles are starting to hurt and there is still 1600m to go! Fortunately, by now, aerobic metabolism is in full swing and can come to the rescue. It gradually takes over from the anaerobic glycolysis and the lactic acid stops accumulating. By about 1.5 to 2 minutes into the race, virtually all the ATP is supplied by aerobic metabolism and the athlete is cruising. However, now a surge is necessary, and more ATP is required, fast! The aerobic system is already at full stretch and CP-ATP is used up, so anaerobic glycolysis makes up that deficit of energy for the extra effort. Almost as soon as it began, the surge is over and aerobic metabolism takes over the whole job again.

But, a little bit more lactic acid has accumulated. 300m to go and the crew begins to wind up the rating and the effort. More ATP required, more lactic acid accumulates, as anaerobic glycolysis makes up the extra energy required. Finish, and exhaustion, Muscles are full of lactic acid and that hurts! The athlete now has an oxygen debt to pay off..
Oxygen Debt: An athlete will continue to breathe heavily for a period after ceasing exercise. This is due to a need for continued increased oxygen uptake to repay the oxygen debt incurred during exercise. The extra oxygen is required to complete the metabolism of lactic acid and other by-products, that were formed when ATP was required from non-aerobic sources such as creatine phosphate and anaerobic glycolysis.
*Overall, in a rowing race, the aerobic system supplies about 80% of the ATP to the working muscles, the anaerobic systems (CP-ATP and anaerobic glycolysis) supply the remaining 20%. A rough graph of the usage of the various systems is below:

Utilisation of the various Energy Systems in a 2000m Rowing Race

     CP-ATP /   Anaerobic /  Aerobic Percentage Glycolysis  of      Energy System Used
     100%     90%          80%        70%                60%                50 40 30 20 10 0 %
     Start                1500m              1000m                500m                   Finish

The Oxygen Transport System

Aerobic metabolism is the main supplier of energy during a rowing race. It is important, therefore, to understand what limits the aerobic metabolism, so we can train to improve its efficiency, capacity and overall effectiveness. The bottom line is, aerobic metabolism can only operate in the presence of oxygen. Thus, it is limited by how much oxygen can be delivered to the working muscle by the rest of the body - Oxygen Transport.
The oxygen transport system is made up of 2 main parts. Firstly the respiratory system, the nose/mouth, throat and lungs are responsible for taking in air (21% O2) to where oxygen can diffuse into the bloodstream. Secondly, the circulatory system, the heart, blood vessels and the blood itself, are responsible for transporting that oxygen from the lungs to them muscles. So we come to the ins and outs of oxygen transport. It can best be described in five steps:

1) The Lungs
The lungs can inhale 120-180 litres of air per minute in normal people during exercise. This can be over 200 in top rowers. Consider that normal air is 21% oxygen. That makes up to 42 litres of oxygen per minute that a top heavyweight athlete can inhale during hard exercise. This is considered enough O2 for the demands of the body and does not change significantly with training.

2) The Blood
The ability of the blood to carry oxygen is dependent on the volume of blood and the number of red blood cells in the blood. The red blood cells carry haemoglobin, which is the molecule that actually binds with oxygen to carry it in the blood. Trained athletes generally have a greater total blood volume and a greater number of red blood cells that untrained people. Studies have shown that endurance training can increase resting blood volume by up to 16%. The changes are caused by an increase in both plasma volume and red blood cell volumes.

3) The Heart
The cardiac output (CO) is a measure of the quantity of blood pumped by the heart, through the circulatory system in one minute. It is dependent on stroke volume (SV), which is the volume of blood ejected from the heart each beat, and the heart rate (HR) which is the number of heartbeats per minute. SV * HR = CO Cardiac output varies from about 5 litres per minute at rest to over 40 litres per minute with strenuous exercise. Increases in both heart rate and stroke volume are responsible. Maximum heart rate within individuals is relatively fixed and does not alter much with training. Stroke volume however, is extremely responsive to endurance training and can increase significantly. Reductions in exercise heart rate and resting heart rate that typically occur with training are indicators that stroke volume has increased. Blood on average has a haemoglobin level of 15 grams per 100 mls and carries about 200 mls of oxygen per litre. Consider then, some comparisons between a normal male, a lightweight rower and a heavy weight rower: Normal Male Lightweight Heavyweight Stroke Volume 110 mls 160 mls 200 mls Max. Heart Rate 200 bpm 200 bpm 200 bpm Cardiac Output 22 litres 32 litres 40 litres

O2 carrying capacity of blood is 200mls per litre, therefore ---> O2 to muscles 4.4 litres 6.4 litres 8.0 litres

4) Capillary density
Capillaries are very small blood vessels that surround muscle fibres. An increase in the number and density of the capillaries surrounding each muscle fibre will deliver more blood and therefore more oxygen to the muscle. Endurance training increases the total number of functional capillaries surrounding muscle fibres and thereby allows more oxygen to be available to the muscle.

5) Blood Flow to Working Muscles
During exercise, the flow of blood to working muscles does increase because arteries carrying blood to inactive areas (such as the intestines and other viscera), tend to constrict, whilst arteries carrying blood to working muscles tend to dilate as they require more oxygen. Research indicates that training will increase the speed and efficiency of the blood flow to working muscles.

• a number of more complex adaptations to training occur within the muscle cells themselves to increase the efficiency with which they consume oxygen. These are beyond the scope of this course, but be aware that they do occur.

How Training improves the Oxygen Transport System

Endurance training or aerobic training is training that uses predominantly aerobic metabolism to provide ATP. That is, it is of a low enough intensity, that anaerobic sources are not required to supply extra energy.

Aerobic training usually lasts a long time (from 20 minutes up to 2 to 3 hours) and includes activities such as slow running, low intensity ergos or rowing, long distance cycling or swimming. Anaerobic training is high intensity training that requires extra ATP to be supplied by anaerobic sources, the CP-ATP system and the anaerobic glycolysis system. It is usually broken up into several bouts of short, high intensity activities lasting from 5 seconds up to 2 to 3 minutes. It includes such things as interval training and circuit training. It can be done running, on the ergo, in the boat, on the bike or in the gym. Training of both aerobic and anaerobic systems are vital to the rower. Different types of training bring about different adaptations in the oxygen transport system.

It is important to understand which types of exercise create which adaptations.

1) A healthy respiratory system delivers more oxygen to the circulatory system than can be transported in the blood. Therefore, the lungs are not considered a limitation to a rowers performance.

2) The circulatory system can be improved with training. The most effective type of training is that,which places a demand on the heart to enlarge and strengthen itself. The best type of training to produce this effect is anaerobic or interval training. Interval training uses short periods of intense, anaerobic work, interspersed with periods of recovery. A larger, stronger heart has a larger stroke volume, resulting in higher cardiac output and more oxygen to the working muscles.

3) The muscles themselves can also be improved with training. The most effective type of training is that, which places a demand on the muscle fibres to utilize oxygen. The best type of training for this is endurance or aerobic training. Endurance training utilizes long periods of work at medium intensities with few or no rests. This type of training increases the number of functional capillaries around the muscle fibres and increases the activity and mechanisms in the muscle cells to utilize oxygen.

How to work out Training Intensity ----> Use the Heart Rate

As discussed above, there is a correlation between exercise intensity and the type of energy system used. Cardiac output is the major determinant of oxygen supply to the muscles. When the intensity of the exercise reaches a certain point, the cardiac output is no longer able to supply enough oxygen to the muscles, and anaerobic systems take over to supply the extra energy. Cardiac output is determined by stroke volume (relatively constant during exercise) and heart rate, which increases as exercise intensity increases. If we know the exercise intensity level at which the

cardiac output begins to fail in oxygen supply, we can work out which energy systems we are using at given exercise intensities. The heart rate is our indicator of exercise intensity.

It has been shown that at about 80-90% of maximum heart rate, there is no longer adequate oxygen supplied to working muscles. This figure is known as the Anaerobic Threshold, because, beyond this heart rate anaerobic glycolysis must be used to contribute the extra energy and lactic acid will start to accumulate in the working muscles. The actual percentage will vary slightly from person to person, but is relatively constant within the individual. Some useful observations can be drawn from the general figure.

1) If you desire to increase your athletes endurance capacity, you can simply take their heart rates and figure the percentage of each individuals maximum. Anywhere below 60-65% is not having much of a training effect, anywhere over 80-85% is too hard, they will be using anaerobic energy sources. So, a range of 65-80% of maximum heart rate will ensure they are training solidly within the bounds of aerobic metabolism.

2) If you desire to increase your athletes anaerobic capacity, they should be training with a heart rate of  more than 85% of maximum. They will not be able to keep this up for long, hence it is usually done as interval training, circuits, etc.

It is suggested that training with a combination of the above methods, it is actually possible over time to increase an athletes anaerobic threshold. Additionally, it is certain that with training over several months and /or years, athletes can increase the tolerance of their muscles to the effects of lactic acid and continue to function at high intensities with levels of lactic acid that would stop an untrained individual in their tracks.

                                                                                                                                                               1999 Sport is Life