Homeostasis (6) , full

What is the primary focus of the discussion in chapter 6?

Homeostasis (Homöostase, maintenance of stable conditions) and the communication between different organs, specifically illustrated through the example of endurance exercise (Ausdauersport).

Why does cardiac output increase during exercise?

• To increase delivery of oxygen and metabolites to muscle

• To increase removal of heat from muscle

Does the respiratory system strongly adapt to increased exercise performance?

• It is generally thought that the respiratory system does not strongly adapt to increased exercise performance

When do anaerobic conditions occur in muscle exercise, and what is used for energy production?

• During strenuous muscle exercise, aerobic resynthesis of energy stores cannot keep pace with their utilization

• Under these anaerobic conditions:

  • Phosphocreatine is metabolized without oxygen

  • Glucose is metabolized without oxygen

What are the three specific reasons ATP is required for muscle contraction?

ATP is needed to break the association of myosin with actin, to remove calcium from the sarcoplasm (Sarkoplasma, the cytoplasm of a muscle fiber), and to establish ion gradients via the Na/K-ATPase to initiate action potentials.

How long does the amount of free ATP in skeletal muscle (Skelettmuskel) typically last?

The amount of free ATP is sufficient for only a few contractions.

What serves as an intermediate source of energy to replenish ATP in the muscle?

Phosphocreatine (Phosphokreatin), which allows the transfer of a phosphate group to ADP.

How is phosphocreatine created when the body is at rest?

ATP produced in the mitochondria transfers its phosphate group to creatine.

What is the process of glycolysis (Glykolyse, the metabolic breakdown of glucose)?

Under anaerobic (anaerob, without oxygen) conditions, glucose is metabolized into lactate (Laktat) without the use of oxygen to generate ATP.

What is required to sustain prolonged exercise?

A sufficient oxygen supply (Sauerstoffversorgung) is necessary to metabolize glucose or fatty acids via oxidative phosphorylation.

How long can the phosphocreatine (Phosphokreatin) available in muscle sustain contraction?

It typically lasts for less than a minute, depending on exercise intensity.

How long can the glucose available in the muscle sustain anaerobic ATP production?

It is sufficient for approximately one to two minutes.

What becomes the major source of energy after about one hour of exercise?

Fatty acids (Fettsäuren).

What causes blood vessels in the muscle to dilate during exercise?

The need to increase blood flow and the available oxygen supply (Sauerstoffzufuhr).

Why is the anaerobic pathway limited during strenuous exercise?

The increase of lactate results in an enzyme-inhibiting (enzyminhibierend) decline in pH.

What percentage of energy is derived anaerobically in a 100-meter dash?

Approximately 85% of the energy is derived anaerobically.

What percentage of energy is derived anaerobically in a 4 km race lasting 12 minutes?

Approximately 20% of the energy.

What percentage of energy is derived from anaerobic metabolism in a 60-minute long-distance race?

Only about 5% of the energy.

What is the purpose of consuming extra oxygen after exercise is over?

To remove excess lactate and to replenish ATP and phosphocreatine stores, a process known as oxygen debt (Sauerstoffschuld).

How is oxygen debt experimentally measured?

By determining oxygen consumption after exercise until a basal level is reached and subtracting that basal consumption from the total.

How high can oxygen debt be compared to basal oxygen consumption?

It may be as high as 6 times the basal consumption level.

What defines submaximal (submaximal) exercise intensity?

A steady state (Gleichgewichtszustand) of oxygen usage is established during the exercise.

What defines supramaximal (supramaximal) exercise intensity?

The oxygen required for oxidative phosphorylation is higher than what is supplied, so no steady state is established.

Which organ system requires most of the total energy during exercise?

Skeletal muscle (Skelettmuskel).

What is the main limiting factor for endurance exercise?

The capability of the body to provide the muscle with sufficient oxygen.

What does the term VO2 max represent?

Oxygen consumption (Sauerstoffverbrauch) under maximal aerobic conditions.

What is the linear relationship between power and oxygen consumption?

An increase in power by 1 Watt increases oxygen consumption by 10 ml/min.

What is the oxygen consumption rate per 100 Watts of power output?

Approximately 1 liter of O2 per minute.

How is VO2 max identified during a power-exertion test?

It is the point where oxygen consumption plateaus and no longer increases despite a further increase in power.

What is considered a good measure for the endurance capacity (Ausdauerleistung) of an athlete?

VO2 max/kg (oxygen consumption per kilogram of body weight).

What is the average VO2 max/kg for an untrained young male?

Approximately 45 ml/min x kg.

What VO2 max/kg values have been reported for professional cyclists?

Values as high as approximately 80 ml/min x kg.

Why must professional athlete VO2 max values be viewed with caution?

They are likely reached through the use of illegal substances, such as erythropoietin (EPO).

What adaptations occur after 6 weeks or months of endurance training?

There is a significant increase in overall performance, VO2 max/kg, and the anaerobic threshold (anaerobe Schwelle).

At what lactate level is the anaerobic threshold typically drawn?

At 4 mM lactate.

What are the likely causes for sustained power output increasing more than VO2 max?

A substantial increase in the number of mitochondria (Mitochondrien) in skeletal muscle and improved blood supply.

What is the typical oxygen consumption of a young man at rest?

Approximately 250 ml/min.

What is the maximal oxygen consumption for an untrained average male?

Approximately 3,600 ml/min.

What is the maximal oxygen consumption for an average male marathon runner?

Approximately 5,100 ml/min.

Are oxygen consumption limits usually reached before maximal breathing capacity?

Yes, there is normally a breathing reserve (Atemreserve) of approximately 50%.

What is the typical pulmonary ventilation (Lungenbelüftung) at maximal exercise compared to capacity?

It reaches 100-110 l/min, while maximal breathing capacity is around 150-170 l/min.

Under what conditions might the respiratory system become a limiting factor?

During exercise at high altitude, in very hot temperatures, or due to abnormalities like exercise-induced asthma.

What is a SpiroTiger?

A Swiss-invented device that allows training of the respiratory muscles (Atemmuskulatur) by breathing against high resistance without hyperventilation.

What medical conditions can be improved using the SpiroTiger?

COPD, myasthenia gravis, and cystic fibrosis, and it may also help against snoring.

What is the relationship between cardiac output (Herzzeitvolumen) and oxygen consumption?

They have a linear relationship.

What is the typical cardiac output for a young man at rest?

Approximately 5.5 l/min.

What is the maximal cardiac output for an untrained man versus a marathon runner?

Approximately 23 l/min for the untrained man and 30 l/min for the marathoner.

How many times can a marathoner increase their cardiac output compared to an untrained person?

A marathoner can increase it approximately 6 times, while an untrained person increases it about 4 times.

What is the main cause for increased cardiac output as an adaptation to exercise?

Hypertrophy (Hypertrophie, increase in organ size due to cell growth) of the heart, with the left ventricle increasing volume by up to 40%.

Why is the resting heart rate (Ruhepuls) significantly lower in endurance athletes?

The increased heart volume/stroke volume means resting cardiac output requirements can be met with fewer beats per minute.

Compare resting heart rates of a non-athlete versus a marathoner.

Non-athlete: 75 beats/min, Marathoner: 50 beats/min.

What is the increase in stroke volume (Schlagvolumen) for a marathoner from rest to maximal exercise?

It increases from 105 ml to 162 ml, an increase of about 50%.

What is the increase in heart rate (Herzfrequenz) for a marathoner from rest to maximal exercise?

It increases from 50 to 185 beats/min, an increase of about 270%.

Which factor contributes more to the increase in cardiac output during maximal exercise?

Heart rate contributes far more than the increase in stroke volume.

When does stroke volume normally reach its maximum during increasing exercise?

By the time cardiac output has increased only half way to its maximum.

How is any further increase in cardiac output achieved once stroke volume has maxed out?

By increasing the heart rate.

At what percentage of their maximal levels are heart rate and stroke volume during maximal exercise?

Approximately 95% of their maximal levels.

Why is the cardiovascular system (Herz-Kreislauf-System) considered the limiting factor for VO2 max?

Oxygen utilization cannot exceed the rate at which the cardiovascular system can transport oxygen to the tissues.