PSK4U
Introductory Kinesiology
Unit 4: Physiology
Activity 2: Energy Systems
Assignment 1: Would You Want To Know?
Imagine that when you were born, there was a machine that could scan your body and tell you what type of physical activities your body is best designed to perform. This machine could help you better understand if your body would excel at powerful, quick types of movements or slow, long endurance activities.
Would you want to know?
How would this information alter your decisions to take part in activities that you may not excel in but still enjoy?
Would this cause even more early specialization in young athletes if we could guarantee which sports or activities they would have a chance of becoming great at?
If you eat meat, you have at one time or another, come across different shades of meat. In some cases, especially with turkey, you may be asked at a restaurant which colour you prefer.
Did you know that the colour (usually classified as white or dark) of the meat tells you about its properties? The meat we eat is predominantly muscle, and muscle is made of fibres. These fibres are responsible for producing force when asked to contract and in turn, replenish energy stores used for that contraction.
It is generally accepted that muscle fiber types can be broken down into two main types:
- slow twitch (Type I)
- fast twitch (Type II) muscle fibres
- Type IIa fibres
- Type IIb fibres
These distinctions seem to influence the ways muscles generate force and energy. Human muscles contain, to a large extent, a genetically determined mixture, on average, 50% ST and 50% FT. The key difference between slow twitch or fast twitch fibres is the ability to use oxygen. Type 1 fibres use oxygen to generate energy; Type IIA also uses oxygen to produce energy but can also produce energy without it, whereas FT Type IIb fibres does not use any oxygen to produce energy.
As you will learn in the following activity, there are 3 energy systems in the body and only one of them uses oxygen, namely the Aerobic system (cellular respiration). If you were to look at muscle fibres that predominately use this form of energy production you will notice that it is dark in colour. Why?
In blood we have a protein called hemoglobin which is responsible for carrying oxygen around the circulatory system. Muscle fibres that use aerobic respiration for energy production contain a similar protein called myoglobin, which is responsible for carrying oxygen molecules in the muscle fibre. Hence, it’s this extra oxygen carrying protein that gives the muscle (meat) a darker colour. So the next time you are eating a chicken wing or piece of pork, take a look at the colouring of the meat and try to guess what kind of activity that muscle is best suited for. Remember, dark meat is for endurance (ie. walking, long flights) and white meat is for short, explosive bursts of power (ie. fast swimming, short flights)!
Resources
- verywell.com: Does muscle fiber type determine sports ability?
- The Science of Cooking: What Gives Meat its Colour?
A time for action, but first let’s eat! - Energy production and nutrients
When driving a car, to accelerate you have to press down on the gas pedal. This adds fuels to the engine and in turn, signals an increase in "work" to be done by the engine so it starts to pick up speed. If you drive a manual transmission car (often called a standard transmission) you physically have to change gears as the car accelerates, whereas in a vehicle with an automatic transmission the changing of gears is done for you. This automatic changing of gears allows you to drive at a higher speed.
Much like a car, your body needs fuel in order to move as a response to a "workload" being applied to it. Our fuel is Adenosine triphosphate, or ATP. Instead of going to a "refueling station" like a car does, we eat food, taking in different forms of fuels that in one way or another get converted into our universal fuel, ATP. It is these different forms of “conversions” and ingredients used for that conversion, that our body calls on when it is confronted with a demand for energy that allows it to perform tasks of varying intensities and durations.
Depending on the activity in which you are engaged, the body will make use of different fuels to help power energy systems (like gears in a car) which will produce the only form of energy needed for our muscles to work, ATP. These systems have been adapted for supplying energy at the required rate and in the necessary amount for that activity or "workload" placed on the body.
Let’s take a closer look at the main nutrients we must eat for our body to produce the needed ATP to tackle physical activities we may encounter. The three main nutrients are fats, carbohydrates, and proteins.
Break it down - Where do we get the building blocks for our energy?
Fats typically provide more than half of the body's energy needs. Fat from food is broken down into fatty acids, which can travel in the blood and be captured by hungry cells. Fatty acids that aren't needed right away are packaged in bundles called triglycerides and stored in fat cells, which have unlimited capacity. Fat is stored predominantly as adipose (fat) tissue throughout the body and is a substantial energy reserve which produces 9.3 kilocalories of energy per gram.
Fat is less accessible for cellular metabolism as it must first be reduced from its complex form, triglyceride, to the simpler components of glycerol and free fatty acids. So although fat acts as a vast stockpile of fuel, energy release is too slow for very intense activity but is a very important fuel for longer duration, low intensity activities such as walking, swimming, rollerblading and running a marathon.
Resources
- diabetesforecast.org: How the Body Uses Carbohydrates, Proteins, and Fats
The carbohydrates in food are digested into small pieces, turning into glucose, or a sugar that is easily converted to glucose, that can be absorbed through the small intestine's walls. After a quick stop in the liver, glucose enters the circulatory system, causing blood glucose levels to rise.
Once the cells have had their fill of glucose, the liver stores some of the excess for distribution between meals just in case blood glucose levels fall below a certain threshold. If there is leftover glucose beyond what the liver can hold, it can be turned into fat for long-term storage so none is wasted. A heavy training session can deplete carbohydrate stores in the muscles and liver, as can a restriction in food intake. Carbohydrate can release energy much more quickly than fat, however it only releases 4.1 kilocalories of energy per gram.
Resources
- diabetesforecast.org: How the Body Uses Carbohydrates, Proteins, and Fats
You can get energy from protein, but it’s not your best choice. Protein has other jobs to fill that take priority over using it as an energy source, such as building muscles and producing the protein-based substances that make muscles contract. It also takes your body longer to turn protein into energy compared to the quick boost you can get from carbohydrates.
Protein is used as a source of energy, particularly during prolonged activity; however, it must first be broken down into amino acids before being converted into glucose. As with fat, protein cannot supply energy at the same rate as carbohydrates, delivering only 4.3 kilocalories of energy per gram.
Resources
- livestrong.com: Does Protein Give You Energy?
Creatine Phosphate is a substance that really doesn’t always fall into the "nutrients needed for activity" column, however it is one of the fuels needed in explosive activities so it is important to understand its role.
Creatine phosphate is readily available and is stored in cells to rapidly produce ATP. However, it exists in limited concentrations and it is estimated that there is only about 100g of ATP and about 120g of creatine phosphate stored in the body, mostly within the muscles. Together ATP and creatine phosphate are called the high-energy phosphogens.
Resources
- Mayo Clinic Creatine
Assignment 2: Snowball It!
Examine "Break it down - Where do we get the building blocks for our energy?"
Hypothesize how the human body was designed to maximize its energy uses by its fuel choices. Justify your thinking.
In addition, suggest an explanation for how the human body has been designed to prepare itself for periods where energy input levels are lower (ie. starvation, famine).
You’ll get there! - The Three Metabolic Pathways
Energy production in the human body is both time and intensity related. Compare the three metabolic pathways to see how they are similar and how they differ.
Remember to consider the inquiry based approach as you read through the various pieces of information. Take notes on this material using this organizer.
| The ATP - Phosphocreatine (PC) system - (Anaerobic Alactic System) | Glycolysis - (Anaerobic Lactic System) | Cellular Respiration - (Anaerobic System) | |
|---|---|---|---|
| Fact: | This is the most immediate system of energy production which can produce very large amounts of energy for a short amount of time by using the small amounts of fuel that is naturally stored in muscle at rest. This is the system to get you started in any movement and/or when you need to make a fast, short burst of speed or movement. | This system produces ATP at a high rate but is mostly limited to the “burning” feeling you get in your muscles when you push them for a longer period of time. That “burning” feeling is the waste product, lactic acid, accumulating in your muscles. | Cellular respiration or the Aerobic system, is one of the most used and important energy systems in the body. Cellular respiration is reflective of the relationship between the cardiorespiratory system and muscular system as the ability to bring in oxygen and transport it to needed areas. This is pivotal to the efficiency and success of this form of energy production. |
| Where does it take place? | The ATP-PC system takes place in the cytoplasm of the muscle cell. | Glycolysis takes place in the cytoplasm. | Cellular respiration takes place in the mitochondria, the powerhouse organelle, of cells. |
| What fuel is used to produce ATP? | The first fuel used is the ATP that is stored in the muscle before the available phosphocreatine is used. | This system uses glucose (sugar) as its fuel source in the production of ATP. | This system uses all 3 nutrients (glycogen, fats, and proteins) in the production of ATP. |
| Does it use Oxygen? | This system is ANAEROBIC which means that it does not use oxygen to produce ATP. This system is also referred to as the “Anaerobic Alactic” system because it does not use oxygen (anaerobic) and does not produce the waste product of lactic acid (alactic). | The glycolytic system does not use oxygen and thus is considered ANAEROBIC, similar to the ATP-PC system. This system is known as the Anaerobic Lactic System as it does not use oxygen but it does produce lactic acid as a byproduct of the breakdown of sugars. | This system is known as the AEROBIC system reflecting the important use of oxygen in the production of ATP. |
| How many ATP does it produce? | The ATP-PC system produces 1 molecule of ATP at a very fast rate. | Glycolysis produces 2 molecules of ATP for every molecule of glucose. | 36 molecules of ATP are produced per molecule of glucose. |
| How long does it last? | This system only can produce energy from the creation of ATP for 10-15 seconds. | This system lasts from 15 seconds up to 180 seconds (3 minutes). | The aerobic system kicks in at around 120 seconds, or 2 minutes, and can last beyond that depending on the state of the athlete’s overall fitness. |
| How many chemical reactions are in the conversion? | The ATP-PC system is a simple process needing only 1-2 chemical reactions for ATP synthesis. | Glycolysis is a larger process involving 11 chemical reactions. | Cellular respiration involves the complex relationship between glycolysis, the Krebs cycle (a series of chemical reactions that occur in the mitochondria of the cell) and the electron transport chain (ETC). |
| What are the waste products produced? | There are no waste products from the ATP-PC system. | The waste product of glycolysis is lactic acid. This acid results from the breakdown of sugars and is the reason milk goes sour after a long period of time. | The simple waste products of cellular respiration are carbon dioxide (CO2) and water (H2O). This is the reverse reaction to photosynthesis in plants where they produce carbohydrates and oxygen (O2). |
| What types of physical activity is it good for? | Explosive power and speed events such as sprints, jumps, and lifting. | The glycolysis system is good for activities that are intermediate in length such as swimming a 100 meter butterfly race, sprinting for 200-800m and the average hockey shift. | This form of ATP production is good for long duration activities such as marathons, triathlons, hiking and endurance events. |
| What are the Pros and Cons of the system? | The largest benefit from the ATP-PC system is that it is a very quick surge of power but its largest limitation is that it depletes its ability to breakdown ATP and PC just as fast. So overall the ATP-PC system produces energy and runs out of ATP and PC extremely fast. | The advantage of the glycolytic system is that it produces a large surge of energy over a longer period of time than the ATP-PC system. The build up of the waste product, lactic acid, is the largest downside to this system, as it causes pain and fatigue. If an athlete can tolerate the pain and train their system to buffer the acid, they will be able to maintain a longer duration of activity at a higher energy output. | The benefit to cellular respiration is the long duration that the system can continue to produce ATP for. The downside to the aerobic system is that is requires large amounts of oxygen (O2) and is slow to react and reach its peak output. |
| How do you train this system? | Training the High Energy Phosphate System Interval training:
Sprint training:
|
The rate of lactic acid accumulation, which is higher at higher workloads, can be adapted in the trained individual. This rate can be decreased by:
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Endurance training is the most effective method (long duration several times per week):
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Introduction
Learning Goals and Success Criteria
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Rubric 1