ACTN3 Essay

More hemoglobin allows the muscles to work harder for a longer period of time. The higher aerobic capacity, gives men the advantage over women when running events over 800 meters.

These are the smallest of the muscle fibres. These will be red in colour as they have a good blood supply and will also have a dense network of blood vessels. They also contain many mitochondria to make them more efficient at producing energy using oxygen. They contract slowly and also fatigue slowly suiting them best to aerobic endurance activities such as the 10,000m. These fibres are most effective during the middle part of the race when the athlete has found a constant speed, allowing the muscles to work for longer, as they are not being over-exerted. This is because they give there energy over a long period of time allowing the athlete to run for a sustained period of time. They are also slow to fatigue because they have an incredibly high aerobic capacity, meaning the athlete will be able to run long distances without feeling tired. To be able run a long distances, the

Rationale, Significance and Hypothesis. An extrinsic factor, which exerts a dominant influence on skeletal muscle fiber phenotype, is the nervous system. Buller et al. (1960) elegantly demonstrated the plastic nature of skeletal muscle fibers in response to changes in innervation type. Later, Lφmo and Westgaard (Lφmo and Westgaard, 1974; Westgaard and Lφmo, 1988) demonstrated that depolarization of muscle with specific patterns and frequencies of electrical activity are sufficient to cause changes in mature muscle fiber phenotypes. However, how myofibrillar gene expression and structural organization is affected by the frequency of impulses during activity, the amount of activity over time, or other characteristics of patterned activity is essentially unknown. To answer these questions will require the isolation and study of subsets of muscle-specific proteins in relation to different electrical activation patterns in vivo, an issue that cannot be easily addressed in preparations currently used in the study of muscle development and maintenance. However, using novel in vivo approaches can, in part, circumvent this difficulty.

These fibers are known as "white fibers" because they do not contain much blood. The major difference between a and b is type IIa uses oxidative glycolytic which uses oxygen to help convert glycogen to ATP. Type IIb fast glycolytic, which rely on ATP stored in the muscle cell to generate energy. These fast-twitch muscle fibers have a much high activation threshold than slow-twitch. These muscles are activated when slow-twitch are unable to sustain the force needed for the body. The major down fall of type IIa and type IIb is the ability to fatigue quickly. The fast-twitch muscle group is responsible for the growth and shape of particular muscles within the body. Fast-twitch fibers are better suited for weight lifting and sports such as football. Most bodily muscles are evenly made of slow-twitch and fast-twitch

Think of your national athletics team at the Olympics. All the individuals in it are exceptionally talented – but at different things. The javelin thrower is able to throw his javelin powerfully and release it from his grasp at exactly the right time; the marathon runner has phenomenal endurance; and the sprinter has powerful leg muscles so that she can explode out of the starting blocks.

Type II fibres are more susceptible to fatigue than type I fibres because, to begin with type II fibres have smaller and fewer mitochondrion unlike type I fibres that have more and larger mitochondrion, which in return results in greater oxidative enzyme activity, greater utilization of oxygen and will have a greater fatigue resistance compared to fast twitch fibres. Secondly, type II fibres have a lower myoglobin concentration which hinders its ability to store and facilitate oxygen diffusion which will cause type II fibres to fatigue more faster. Another factor is that type I fibres have a much smaller muscle fibre diameter, which means there is a smaller diffusion distance allowing for oxygen to be used faster since it doesn’t have to travel to far, unlike the large type II fibres. The last factor that causes for a large fatigue index being associated with a high percentage of fast twitch fibres is that type I fibres

The three primary muscle fiber types are Type I, Type IIA, and Type IIB. Type I or slow-twitch muscle fibers are predominantly used for aerobic activities, such as running and walking, and the main fiber type found in the body types of endurance athletes like marathon runners. These body types are characterized as ectomorphic or slim, linear body type. I would train an individual with a body type primarily of Type I muscle fibers, by encouraging exercises with higher repetitions (e.g., 12 repetitions or more, with 2 to 3 working sets), higher volume and shorter rest periods, in order to engage the greatest number of those muscle fibers. This is because Type I muscle fibers require more work to maximize growth or hypertrophy, take longer to fatigue and recover quickly.

Also black people have low body fat that also can be helpful for them in running. According to Sailor article “Muscle and tendon physiology also contribute to black “athleticism.” It is well publicized that blacks have a higher percentage of fast twitch muscle fibers and higher levels of glycotic and phosphogenic enzyme activity levels, when diet and activity levels are controlled for, which would provide an advantage in explosive, short-duration muscular exertions.“ Black people have short bellies as well; this is a great help for them for running. Since the muscles can be stretched and store energy that can be this energy can be retransferred during running that will cause them lose less energy. These are some physiological reasons that black people can do better in sports. Due to these biological advances they got with time, because of their genetic material that has been changed in evolution, they can do better in sport competitions in specific fields of sport compare to other races. However they do poor in some other sports such as swimming because of these differences as

Fast twitch fibers can be an aid to sprinter to quickly engender a lot of force (BUT can switch from fast through increase of training)

Physical activity is a key component in maintaining ones individual health and promoting longevity in life. In order for individuals to initially commence and continue being physically active, we are required to look at their motivation and attitude towards physical activity, as this plays a crucial role. A number of genes have been identified as affecting an individual’s level of physical activity. One of these genes is the ACTN3 gene, and is said to be the most highly researched sporting performance gene (Sessa et al., 2011). However the association between the ACTN3 gene and an individual’s motivation and attitude towards physical activity is poorly researched and inadequately understood.

Several gaps in the current body of knowledge have been indentified including, among others: small sample size of most athletic cohorts, lack of corroboration with replication cohorts of different ethnic backgrounds (particularly, made up of non-Caucasian athletes), the need of research accounting for the potential role of epigenetics in elite athletic performance, and also the need for future models that take into account the association between athletic status and complex gene gene and gene environment

There are three types of myosin fibers within a muscle and those are aerobic fiber 1a (slow-twitch), aerobic fiber 2a (fast-twitch), and anaerobic fiber 2x (fast-twitch). 1a is low intensity and it increases in intensity to 2x. 1a and 2a are aerobic, so they require oxygen for cell respiration to complete glycolysis, Kreb’s cycle, and the electron transport train. If they do not get enough oxygen, they start to create lactic acid because they can only complete glycolysis. Whereas 2x fibers immediately start to create lactic acid because they are anaerobic and can not use oxygen so they only do glycolysis. Everyone is born with these three types of fibers usually almost equally balanced throughout their muscles but some people will get an unequal

The age-related loss of muscle power is more rapid than the parallel loss of muscle strength which in turn is more rapid than the loss of muscle mass. Patients with sarcopenia manifested a reduction in the number of both type I/slow-twitch

twitch muscles. Fast twitch muscles have a fast form of myosin ATP and are very

Muscular endurance is very important for people playing sports and who have to sustain an activity for long periods of time. Muscular endurance is determined by how well your slow twitch muscle fibers are developed. In case your wondering what slow twitch muscle fibers are, I will explain. There are generally two types of muscle fibers in your body, slow twitch and fast twitch. Slow twitch muscle fibers cannot exert as much force as fast twitch, but can sustain an effort over a much greater period of time. Fast twitch muscle fibers can exert a great amount of force but for a very limited amount of time. Therefore, slow twitch equals endurance, while fast twitch equals strength.