Long term adaptations to exercise - Cardiovascular system

The second assignment we will be doing will be based around the long term adaptations that our 5 body systems go through as a result of regular exercise.

Long term = At least 6 weeks

Adaptations = Responses of the body as a result of a regular stimulus - in this case, exercise.

The 5 body systems we will be analysing are:

Cardiovascular
Muscular
Skeletal
Respiratory
Energy

Week 1 - Cardiovascular

There are lots of adaptations that the cardiovascular system goes through as a result of regular exercise. These adaptations help with better delivery of oxygen, and better removal of carbon dioxide and other metabolic products, such as lactic acid. There are 9 different responses:

1. Cardiac hypertrophy
2. Decreased resting heart rate
3. Decreased resting blood pressure
4. Increased stroke volume
5. Increased cardiac output
6. Increased blood volume
7. Increased capillarisation
8. Increased aerobic capacity
9. Decreased recovery time

I am going to be explaining 3 of these in depth.

1. Cardiac hypertrophy:

Cardiac hypertrophy is the process by which the heart muscle gets stronger as a result of regularly working harder.

As the heart works harder on a regular basis, the muscular walls get thicker (especially the left ventricle wall), and there is an overall increase in the amount of cardiac muscle.

The changes occur as a result of there being a regular increase in the amount of work the cardiac muscle has to do. It responds to this increase in load by increasing the size and number of muscle fibres in order cope with the load better.

This will have a positive effect on performance as it means that the heart muscle doesn’t have to work as hard to deliver the same amount of blood to the working muscles

Acute responses of the respiratory system to exercise

In this final week of acute responses to exercise we looked at the respiratory system.

As we start to exercise we breathe more often and more deeply, and these are the two responses I am going to explain.

Increase in breathing rate

When we begin to exercise a number of changes happen to our blood. These are related to the increased demand for energy. In our working muscles, oxygen is combined with nutrients to create ATP through aerobic respiration. One of the by-products of this process is carbon dioxide. Carbon dioxide is a toxic chemical in our blood, as it lowers the pH of it, disrupting homeostasis. We know that once our blood becomes more acidic the rate of reaction of our enzymes slows down, and if this was to continue for too long, our body processes would stop all together and we would die. Therefore, our body must have a mechanism for getting rid of carbon dioxide, and that mechanism is to breathe it out.

During exercise we must breathe this out more rapidly, and therefore our breathing must speed up. This is controlled by chemoreceptors in our aortic arch and carotid bodies. These detect the increase in carbon dioxide, and send signals to the medulla and pons. These, in turn, send neural signals to the respiratory muscles to tell them to increase the rate of breathing. Mechanoreceptors located in the working joints, tendons and muscles also send signals to the medulla and pons as a back up mechanism.

It is often thought that we breathe more rapidly during exercise in order to increase the amount of oxygen that we breathe in. Obviously we do need more oxygen in order to increase the amount of energy we can reproduce, but actually it is the body's sensitivity to elevated levels of carbon dioxide that are responsible for the increase in breathing rate, and not the depletion of oxygen. This is because even during prolonged exercise, our muscles are unable to use oxygen at the rate it is supplied in the blood.

Cardiovascular responses to acute exercise

This week we learned about the cardiovascular responses of acute exercise. These are basically the changes that occur in the heart and blood vessels when we take part in a single exercise session.

Heart rate anticipatory response

Even before we start to exercise our heart begins to beat faster. This is termed the anticipatory response, and is exactly what it sounds like - the anticipation of the heart to the exercise that is about to happen, by increasing its number of beats per minute. Our body does this in order to begin supplying more oxygen and nutrients to the working muscles. This response occurs through the release of adrenaline from the brain, which stimulates the nerve impulses in the heart and make it begin to beat faster. This is known as the fight or flight response, where the body is preparing for the activity it might be expected to go through.

Acute exercise and the energy systems

In todays lesson we have discussed the effects of acute exercise on the energy systems. The basis of the responses are formed around a concept called the 'energy continuum'. See below:

The energy continuum is a way of explaining which energy system is predominantly used during different durations and intensities of exercise. We can see that all energy systems are used to regenerate energy all the time, but the predominant one is based on a number of factors.

The ATP-PC system

This system is predominantly used during high intensity short duration activities of up to 10 seconds. The 100m sprint would be a good example. The system produces energy really rapidly, which is a major advantage, but it is limited to 10 seconds as the stores of phosphocreatine deplete rapidly.

The Lactic acid system

This is predominantly used between 10 and 90 seconds, and takes over as the dominant energy provider after out phosphocreatine stores are depleted. This system also creates energy over short duration high intensity exercise, and a good example of a sporting activity would be the 400m sprint. The limiting factor of this system is the build up of lactic acid in the muscles, which stops them from functioning properly. In order to carry on exercising after this time we must drop the intensity, so that our muscles can produce energy through the break down of oxygen and glucose/fat.

The Aerobic system

This system is predominantly used during low/medium intensity exercise, and can last for a long time. The reason why we can provide energy quickly using this system is that it needs to have enough availability of oxygen, and enough time to break it down for energy. A major advantage of this system is that it can provide energy for a really long time (hours, if required). A major limitation to this system is that it cannot produce energy quickly enough for high intensity activity. A marathon would be an example of the body producing most of its energy through the Aerobic energy system.

Using all 3

Our body never really uses just one energy system, and all the time that we are exercising, stores of PC are being regenerated, and lactic acid removal is taking place. This is why an individual playing a team sport such as football or hockey would be able to undertake more than one 10 second sprint in the game - they may have to drop their intensity for a little while, but as soon as their PC stores have regenerated (as little as 30 seconds later) they can then use those stores for another sprint.

Musculoskeletal responses to acute exercise

In this weeks lesson we looked at the musculoskeletal system responses to acute exercise.

The musculoskeletal system is made up of muscles, bones, joints, tendons and ligaments.

There are 4 acute responses to this system when we exercise, these are:

1. Increased blood supply
2. Increased pliability
3. Increased range of movement
4. Muscle fibre micro tears

1. Increased blood supply:

When we exercise vasodilation happens in the blood vessels that supply our muscles. This is a positive response to exercise and occurs for 2 reasons. The first is to transport more oxygen and nutrients to the muscle cells, and the second is to take away heat from the muscle cells.

When we exercise we need more oxygen and nutrients - such as carbohydrates and fat - in order to make ATP in the mitochondria of the muscles. The increased blood supply helps us to cope with this demand.

Also, when we exercise the friction from muscle contraction causes heat to build up in the muscle cells. We need to try and remove this heat, as it has a detrimental effect on our cells (they can cook, or the enzymes stop working properly). The blood is responsible for removing this heat, and taking it to the skin (the blood vessels at the surface of the skin vasodilate), where it is removed through the process of sweating.

Useful websites for acute responses

http://www.vcepehub.com/wiki/item/acuteresponses

http://www.ptdirect.com/training-design/anatomy-and-physiology/adaptations-to-exercise/physiological-responses-and-adaptations-to-exercise-2013-an-overview

Introduction to physiology of fitness

Week 1 - Overview week:

We discussed the definitions of the words 'chronic' and 'acute'.

Acute = Straight away/short term
Chronic = Over time/long term

We also discussed the learning outcomes for the unit:

1. Know the body's response to acute exercise - Including musculoskeletal, energy, cardiovascular, and respiratory systems

2. Know the long term effects of exercise on the body systems - Including muscular, skeletal, energy, cardiovascular and respiratory systems

3. Be able to investigate the physiological effects of exercise on the body systems.

We will need to write a blog entry during, or straight after every lesson with details what we have discussed during the lesson. This will either help us to complete assignments, or in the case of assignment 2 will be evidence and is actually the assignment itself.

As part of the unit I will need to go to the gym once a week at the least. I will need to choose at least 1 cardiovascular activity (treadmill, bike, cross trainer or rowing machine), and at least one muscular activity. The idea is that we will feel or see adaptations in our bodies over the next 6 weeks, and we will write about these in our blog, relating what is happening (or not happening) to the theory that we have been covering during the lessons.

Next weeks lesson will concentrate on the musculoskeletal system responses to acute exercise.