Theoretical Approach to Function and Musculoskeletal Development in Human Anatomy

Abstract-Thesis

Muscular systems can be developed by applying specific training techniques and methods in order to accomplish goals. Understanding human anatomy leads to development of more efficient techniques and methods of training, which in turn results in increased physical health. Many people lack proper understanding of the musculoskeletal system, and human anatomy in general. This is true across a range of people, ranging from the average person, to athletes training at a competitive level. The results of this lack of knowledge varies, it might be that a person does not train at a high enough intensity to reach their goal of burning fat, or it might be that an athlete does not properly progressively overload, resulting in negligible increases in strength. Proper understanding of the human body is what shapes training routines and programs or methods. It is what helps trainers determine what exercises an athlete should use, and it helps regular exercisers determine the length and intensity of their workout. In this paper I will try to cover the function of the musculoskeletal system, as well as any systems working in conjunction with it. I will discuss how muscles respond to different environments and how they develop as a result of this. I will determine the relevance of this understanding and how it helps develop training methods and programs. Finally, I will discuss health benefits and recommended methods and programs that applies the theory and science to practice.

Biology of the musculoskeletal system

Muscles are organs belonging to the muscular system. The function of this system is to generate all movement in the body. There are three types of muscles, these being smooth muscle, cardiac muscle, and skeletal muscle.Smooth muscle is a non striated involuntary muscle type responsible for large parts of digestion, but it is also found in the walls of blood vessels. Cardiac muscle is found exclusively in the heart. It is a striated, involuntary muscle type that is responsible for pumping blood through the body. Skeletal muscle is the muscle type that is responsible for all voluntary movement. The remainder of this paper will focus on skeletal muscle.Skeletal muscle is mostly voluntary, meaning that one can voluntarily flex or relax the muscle, an exception to this is the diaphragm and some other respiratory muscles, which is classified as skeletal muscle, but is mostly moved involuntarily. Skeletal muscle is striated, and is technically each individual muscle, of which there are 460, functions as a separate unit. Each muscle also contains connective tissue, as well as an artery, vein and nerve to ensure proper functionality. Skeletal muscle has a complex structure. It consists of multiple strands of myofibril, which are bundled together to form a muscle fibre. Muscle fibres are the actual muscle cells, and these again group together to form fascicles. Multiple fascicles combine to form the muscle, which is connected to the bones by tendons and powered by arteries and veins, that provide nutrition and transportation of oxygen.
Muscle contraction and relaxation actually occurs within the myofibril. The strands of myofibril consist of segments of sarcomere separated by a z-line. Within the sarcomere there are two different types of myofilaments, namely actin and myosin. Contraction is basically achieved when actin and myosin react with eachother, contracting the sarcomere, which brings the z lines closer together, and ultimately contracts the muscle. The reaction between actin and myosin forms an action called the sliding filament model of muscle contraction. In a resting muscle actin is blocked from myosin by two proteins called tropomyosin and troponin. These proteins are released when ATP and calcium are present, which is exactly what happens when a muscle contracts. The ATP is obtained through the mitochondria when in a contraction process, and the sarcoplasmic reticulum surrounding muscle cells has walls with calcium pumps responsible for releasing calcium ions. It also has calcium channels linked to voltage sensitive proteins in the membrane of the muscle cell.

The entire process of muscle contraction starts when the brain sends out an action potential along the motor neuron to the targeted muscle cell. The neuron releases acetylcholine into a synapse of the muscle cell, which triggers a flow of sodium into the cell and causes nearby sodium channels to open. The action potential then travels down a T-tubule, where it triggers voltage sensitive proteins linked to the calcium channels in the sarcoplasmic reticulum.

Finally, calcium rushes into the cell through the now open channels, binding to the troponin proteins, which then moves the tropomyosin away. During this process, the myosin binds with a molecule of ATP, which it breaks down into ADP and a leftover phosphate ion. This allows the myosin to move into an extended position, from where it latches onto the actin, where it releases the stored energy from the ATP reaction, and changes shape. It essentially moves the actin forward, contracting the sarcomere. This cycle is repeated when the ADP binds with the phosphate ion and forms ATP again, in order to bind to the myosin that is still connected to the actin. This changes its shape back into the extended position, where the myosin yet again breaks down the ATP into ADP and the process is continued until the calcium pumps of the sarcoplasmic reticulum try to restock the calcium. This unbinds it from the troponin, allowing the tropomyosin to cover the actin again, protecting it from the myosin, and restricting further contraction.
(Crashcourse, muscle cells, web, 2015)

Skeletal Muscle: Cellular-Organismal Level
The actual uses and applications of the muscle contraction process and the sliding filament model of muscle contraction as covered above are many. In order to complete different actions and movements muscles contract in many ways. Some muscles fill different purposes, although they are all pretty much the same biologically. An example of this would be the actions of flexing and extending the elbow. These two actions fulfill quite different purposes, however they do this through a nearly identical process, the only major difference being their location in the musculoskeletal system. When the biceps contracts in order to move the forearm inwards the muscle receives an action potential, triggering the sliding filament model of muscle contraction, which contracts the muscle, shortening the distance between the origin and insertion of the muscle, and ultimately moving the elbow in flexion. One might think that in order to accomplish the opposite action, moving the elbow in extension, the biceps extends and pushes the forearm away in some sort of reverse contraction, however this is not the case. Muscles can only pull by contracting, they are not capable of extending themselves past their resting state. This means that the action of extending the arm is accomplished not by the biceps, but by the triceps, which also pulls by contracting, however from a different location with a different origin and insertion point.

When performing a movement or exercise, muscles are generally classified into 4 different groups. The agonist muscle is the muscle that generates the majority of the force needed to create the movement. It is the main muscle and often the targeted muscle of that exercise. Going back to the example of a biceps curl, the biceps is the agonist, as it is the muscle that applies the majority of the force to do the curl.

An antagonist muscle is the muscle opposing the agonist muscle. The antagonist usually relaxes while the agonist is under load, However this is not always the case, as in the eccentric portion of a movement, the antagonist can sometimes help control the weight. The antagonist muscle in a biceps curl is the triceps, as it relaxes while the biceps contracts to curl the weight. However, the triceps also assists in the eccentric portion of the curl, in order to prevent gravity from smashing the weight down into the elbow joint at the bottom of the movement.

The synergists are the muscles that often assist in generating force for the movement, but they also act to stabilise a joint around which the movement is occurring. In a biceps curl, the synergists are the M.brachioradialis, and the M.brachialis as they help stabilise the elbow joint, as well as generate some force in the biceps curl.

The last group are the fixators. These muscles help stabilise the origin of the agonist muscle, as well as the joint that the origin moves over. In the case of the biceps curl, the fixators would be rotator cuff muscles and the M.serratus anterior and pectoral muscles, as well as the trapezius, levator scapulae and other clavicular muscles. They stabilise the shoulder joint, which is the joint that the biceps origin spans over. (ptdirect, muscle roles and contraction types, web, 2017)

A motor unit is a group of muscle fibres that all get their signals from the same, single motor neuron. Due to the fact that all muscle fibres listen to the same motor neuron, they act as a unit. In large muscles that perform simple actions such as the quadriceps, there are many muscle fibres in one motor unit, as the muscle generally exerts a large amount of force and does not complete actions that require fine adjustments in force output. The muscles in a hand however have very few fibres in one motor unit, as there are large variations in the amount of force required to perform an action, as these range from typing gently on a keyboard, to grasping onto a heavy weight. This makes the hands and fingers quite nimble.
Muscles contract in a response to an action potential, however there are some more intricate phases and events in this process. When an action potential is sent and received, the muscle fibres quickly contract and release in a twitch. And each has three different phases. Namely, the Latent Period, Period of Contraction, and Relaxation Period.

The latent period is the period during the sliding filament model of muscle contraction where calcium pulls away the troponin and tropomyosin, exposing the actin. In other words, the latent period is when the stimulus has arrived, but no action has been taken yet. Following this, there is a period of contraction. This period is the phase where the myosin latches onto the actin, uses energy from ATP to move it forward, detaches and repeats, contracting the sarcomere and ultimately the muscle. Finally, comes the relaxation period, where the calcium is pumped back into the sarcoplasmic reticulum, putting troponin and tropomyosin back in their place, covering the actin and ending the contraction and relaxing the muscle.(Crashcourse, Muscles Organismal Level, web, 2015)

The strength of a movement, or how vigorously a muscle contracts is regulated by the motor neurons. The motor neurons increase force by firing multiple action potentials in rapid succession. The effect this has is that the targeted muscle does not have time to enter the relaxation phase before the next action potential triggers the flow of calcium again. Meaning that rather than calcium levels decreasing, even more is released, exposing even more actin, leading each successive twitch getting stronger and ultimately resulting in a stronger contraction. When these twitches build on each other, due to the absence of the relaxation phase, the contraction grows stronger, until a point where all the actin is exposed. This process is called Temporal Summation. The complete contraction, when all actin is exposed, is called Tetanus. When the muscle has reached tetanus, it is rapidly burning through ATP, and due to ATP being a finite resource, the muscle cannot maintain contraction indefinitely, and fatigues until the tension drops.

Due to muscle fibres operating in motor units, the only way to create a grade of force is by altering the frequency of action potentials. Therefore, the strength of the stimulus can be altered by sending action potentials to more motor units. Contractions intensify as the motor neurons stimulate more motor units. This process is called Multiple Motor Unit Summation, or Recruitment and is of utmost importance in the development of training programs for hypertrophy.
(Crashcourse, Muscles Organismal Level, web, 2015)

Skeletal muscle consists of three different types of muscle fibres that are recruited specific situations. First are the slow twitch, or red muscle fibres, Type ia. Type ia fibres are small in size, and red. These fibres have a slow contraction speed and output little force, but has a lot of mitochondria that use oxygen in order to generate energy. Type ia fibres are highly fatigue resistant, meaning that they tire very slowly, these fibres are mainly used for walking, jogging and similar low intensity, endurance focused exercises.

Type iia fibres, are moderate fast-twitch fibres, these are red, and moderate in size. They use oxygen and glucose as a source of energy and output moderate force. These fibres are however not as fatigue resistant as Type ia fibres, although they still are somewhat fatigue resistant. THese fibres are activated in activities that require moderate in duration and intensity, such as running, swimming and short distance cycling.

Type iix fibres are fast twitch fibres that are large and white in color. It uses high amounts of glucose stored as glycogen rather than oxygen as a source of energy, giving it a very high output force. This also means that it does has low fatigue resistance. Type iix fibres are activated during high intensity, low duration actions such as lifting weights and sprinting.
These muscle fibres are recruited or activated in a specific order called Henneman's Size Principle. Which states that slow twitch Type ia muscle fibres are always recruited first, and when these are maxed out, Type iia fibres are activated. Type iix fibres are only activated when the recruited Type iia fibres are maxed out, and are then used until failure. The purpose of this order is to minimise muscular fatigue by using motor control so the body does not use more force than necessary. The Size Principle states that the more motor units recruited, the greater the force generated. (PictureFit, Muscle Fibers Explained, web, 2015)

There are three different types of muscle contraction: isotonic, isometric and auxotonic.
An isotonic contraction is a contraction where the tonus of the muscle is constant and the length of the muscle changes. An isotonic contraction is almost impossible to perform because due to the gravity force and biomechanics of the body, it is very difficult to keep the tonus of the muscle constant during a movement. An isometric contraction is a contraction where the length of the muscle is constant and the tonus may vary or stay constant. An auxotonic contraction is a dynamic contraction where the length of the muscle changes and the tonus also changes. An isometric contraction is normally used in static strength training. An example of this is the Plank. This exercise is isometric, as the abdominal area and core are all activated and undergo contraction, however this contraction is isometric, as the length of the muscle does not actually change and there is no movement in the spine. Auxotonic contraction occurs in movements such as yet again, the biceps curl, but also in the majority of training exercises. In the biceps curl, the biceps contracts, shortening its length and pulling its insertion point towards the origin, meaning that the arm bends at the elbow joint. This movement is auxotonic as it physically shortens the biceps and moves the weight in a movement where the tonus of the muscle is at its peak at 90% flexion at the elbow.
Cellular Respiration
The stoichiometric reaction that occurs in the human body of adenosine triphosphate synthesis is vital to human survival. Adenosine triphosphate or ATP is a molecule that is synthesized through glucose, in order to provide energy to the muscles of the body, so that these can contract consistently, resulting in movement of limbs in the case of skeletal muscle, and the proper functioning of vital organs in the case of cardiac and smooth muscle.

Following the synthesis of ATP, this molecule, often referred to as the energy currency of the body, undergoes a variety of reactions, where it emits energy in a hydrolysis reaction, then is “recharged” by adding energy and removing water, while reforming the bond with the third phosphate ion. This cycle is repeated over and over, and is responsible for the successful contraction of muscle fibres animal anatomy.

The reaction that actually generates ATP however, is the actual stoichiometric reaction in this scenario. It is also referred to as cellular respiration.The first step in this cycle is the process of glycolysis. During glycolysis, one glucose molecule is broken down into two pyruvate molecules (4-carbon molecules also referred to as pyruvic acids.). This process requires the investment of two ATP molecules, but then the reactions products are amongst others, 4 ATP molecules, for a net profit of two ATP molecules. In addition the glycolysis results in two pyruvates, as well as two molecules of NADH (a powerhouse of energy utilised in the ETC), which are energy rich, and will later be utilised in the process to create further ATP molecules. Glycolysis is an anaerobic process, meaning that it does not require the presence of oxygen. When in an anaerobic state, the process of fermentation is initiated, resulting in accumulation of lactic acid. Lactic acid can build up inside of muscle tissue, and thereby result in fatigue.

The next two processes, these being the Krebs cycle also known as the Citric Acid Cycle, and the electron transport chain, are both aerobic, and require oxygen, which means that they cannot be completed once the body exceeds its anabolic threshold.

The Krebs cycle is a process that also generates ATP. It takes place inside the membrane of the mitochondria in a cell. This cycle utilises the products of glycolysis, namely the two pyruvate molecules, in order to form a further two ATP molecules, in addition to some energy, that comes in various forms. One of the carbon atoms in the pyruvate molecule is oxidized, resulting in CO2, which leaves the cell. What is left is a molecule of Acetyl Coenzyme A (a molecule whose main purpose is to give carbon atoms to the citric acid cycle.), which then again bonds with the previously formed NAD+(a coenzyme that exists in all living cells, called Nicotinamide adenine dinucleotide), as well as a hydrogen atom, forming NADH . Therefore, the products of the Krebs cycle are another two NADH molecules, which will later be utilised in order to create more ATP.

The enzymes here also react with ADP, or adenosine diphosphate (ADP, essentially an ATP molecule without its third phosphate attached), in order to create another ATP molecule per pyruvate, in this case that being two. These enzymes also assist in the process of creating a six- carbon molecule by joining the Acetyl Coenzyme A and a four-carbon molecule called oxaloacetic acid. This six-carbon molecule is Citric acid. The citric acid undergoes a process in form of a cycle, where it loses carbon atoms and undergoes various changes until it ends back up as oxaloacetic acid, and the cycle repeats. In the process of the Krebs cycle, there are a lot of leftover CO2 molecules, originating from the act of oxidising a carbon atom, which are exhaled first by the cell, then transported via veins to the alveoli, where they are finally exhaled by the lungs.

Each carbon atom removed by the Krebs cycle also generates some energy, although not in the form of atp. This energy is stored by B vitamins, in order for them to be utilised later in the electron transport chain. This part of the reaction includes NAD and FAD, which bond to hydrogen atoms and gain a positive charge, resulting in another six NADH atoms, and two FADH2 molecules, per glucose molecule, to be used in the electron transport chain.

Finally, comes the electron transport chain, or ETC. This process utilises all the previously formed NADH molecules in order to create ATP. The electron transport chain is a biological process where the electrons of the NADH and FADH2 molecules are used to power a pumping system, that makes these molecules undergo a variety of changes, until they finally are processed through a protein called ATP synthase, which ultimately utilises the energy generated by the electrons to power a mechanism that combines a ADP molecule with a phosphorus ion in order to create the end product, ATP. In a perfect scenario, a healthy cell is able to generate a maximum of 34 molecules of ATP through the ETC itself.

Training Techniques and Goals
-Muscular Endurance
There is a multitude of programs and training techniques used in order to reach a goal, and some of these are more effective than others. As previously established, goals are usually sorted into three types concerning muscular development. First is the endurance training. This training uses longer workouts with high reps and low weights, or low intensity and long duration. Training for muscular endurance is extremely beneficial to aerob sports such as long distance cycling, swimming and running.
-Muscular Strength
The next type is training for muscular strength. Basically what this training attempts to do is increase efficiency of neurological connections with muscles in order to increase max strength. This type of training operates within the 1-5 rep ranges. This type of training is often functional and beneficial to many sports that require explosive bursts of force. An example of this is athletics, powerlifting, acrobatics, and also to some extent football, soccer and wrestling.
-Muscular Hypertrophy
The final type of training is hypertrophy based training. Here, the main goal often is aesthetics of physique, as found in bodybuilding, but also muscular mass and healthy weight gain, which is useful for sports such as american football, where being heavy has benefits. Hypertrophy training is based around the process of protein synthesis, which occurs when muscle fibres break down due to continuous tension and strain. This increases the size of muscle fibres substantially, but does not increase strength as much. Hypertrophy training operates within the 8-12 rep ranges, but may change depending on what muscle groups are being targeted. This rep range, which often goes close to complete exhaustion or failure, recruits a high amount of of type iix fibres, which are the largest fibres in a muscle. A principle used in most hypertrophy based training is SPOT, short for Specific-Progressive-Overload-Training. Which is a pretty simplistic concept as it just tells athletes to train in a manner that progressively overloads a specific muscle. This is normally accomplished by adding small weight increases to lifts, but can also be slightly increasing target reps. If the muscle is progressively being overloaded, it will develop in response to this change in environment, and break down and become larger. Bodybuilders especially focus a lot on isolating exercises, that make it easy to overload a single muscle at a time, in order to limit other variables that could affect progression.
This means that a Bodybuilder will likely see easier progress in tricep growth by completing a tricep pushdown, which completely isolates the tricep, compared to a dip, which is a more compound movement that activates chest and shoulder muscles as well, making it more functional and attractive to powerlifters and crossfitters.

Finally, there are a range of methods that meet more than only one of the outcomes (strength, hypertrophy, endurance). This can be accomplished not only by including exercises that favour several of the different training types into one program, but also by combining the principles to form a program that should show progress in all areas. For example, if an athlete wanted to become large, and strong, in order to increase performance in a sport, he might want to consider a routine that has heavy compound lifts, increasing strength, as well as proceeding to include various isolated high volume hypertrophy exercises. Or he might want to consider a plan that has compound lifts that max out until failure with high volume (high reps-lower weight), around 8 reps. This will theoretically give significant increases in overall strength, due to it being a compound movement, but also hypertrophy, due to the large amount of type iix fibres recruited. This method does however make compromises on both sides, as the exercises will be good, but not optimal to both hypertrophy and strength training. Therefore, the most common method of increasing both strength and size simultaneously is a technique referred to as Powerbuilding.

As the name suggests, it includes elements of Bodybuilding workouts, with elements of Powerlifting programs.In contrast to the previously mentioned method, powerbuilding does not actually combine the principles int one exercise, but rather uses both consecutively. This means that a powerbuilding routine often has a compound powerlifting lift at the beginning, working with many sets, low reps (only 2-3), and a close to max weight. This increases strength in the same way as powerlifting does, but rather than concluding the workout, powerbuilding routines proceed to include a normal hypertrophy based bodybuilding plan afterwards. Due to muscular fatigue, the second part of the workout is slightly restricted volume wise, but the effect stays almost the same, and some research even shows that the increased strength directly correlates with volume, tension and hypertrophy increases.

Relevance and Application of Knowledge
All types of muscular development are extremely beneficial to most branches of sports. Muscular strength and/or muscular endurance form the supporting pillars of many popular sports. Often athletes that plateau at a certain level or experience slow progress, try to improve by increasing frequency of training in that sport and just end up banging their head into the same wall. This could quite likely be an effect of them not having a sufficient base of muscular development. Across a wide range of sports, athletes practice strength training in addition to their sport specific workouts. This is true in most sports ranging from golfing to football and beyond. A simple example of this is an experienced golfer that has hit a plateau and is unable to increase range of shots and overall performance. He might think that he should practice swinging and correcting technique and invest resources into this, although the technique is not the limiting factor in his swing. In this scenario, the golfer is likely in dire need of strength increase in order to increase range of shots and thereby performance. If the golfer is missing this fundamental pillar, he is guaranteed to underperform and never reach his true potential. Completing functional resistance training to develop muscular strength will increase output force per swing, and thereby his maximum and average length of shots. However, all types of resistance training are not suitable for this situation.

The golf swing requires a exceptional muscle-mind connection and coordination. In addition to this, overall explosive strength is essential. The exercises the golfer should perform are therefore functional compound movements, with high weight to increase explosive strength. He should have a rep range of 3-5 reps per set in order to avoid unnecessary build up of movement constricting muscle mass, and 3-5 sets in order to have maximum effect and fatigue out of the exercises. It is important that he includes compound exercises such as the bench press, shoulder press, chin-up, squat and deadlift, as these do not only increase strength in major muscle groups as well as stabilizing and core muscles, but also require correct form and coordination.

If the golfer had a hypertrophy based program, his performance would probably not increase at all.If the golfer included too many isolation exercises on which he used too little weight with too many repetitions resulting into high volume, he would not gain strength at a rapid rate, and rather than increasing coordination, he would acquire hypertrophy, which has little to no benefit to golfing. The isolation exercise would not increase his overall coordination, and the high volume would only provide small increases to explosive strength. The only significant outcome of this type of training would be an increase in muscle cell size and muscular hypertrophy. This is almost completely useless, as size is irrelevant in golfing, the only slight benefit would be added weight to drive the swing.

If the golfer applied a muscular endurance based program, he would likely see no improvements in strength, and only slight increases in coordination. Endurance based programs usually include isometric compound movements. This could be beneficial to the golfer, as he would work on coordination and strength in some minor supporting muscles, but he would not address the heart of the problem, namely a lack of explosive strength. Endurance training utilises high amounts of reps and very low weights at best. This would barely affect explosive strength required in a golf swing at all, as these exercises only recruit slow twitch muscle fibres and not the fast twitch type ii fibres required for explosive strength.

Muscular development is key in most sports, and often athletes are told by trainers to incorporate some resistance training in their plans already at a young age. As established, it is key to know what type of training is required. Muscular development is important, but so is a balance of the other supporting pillars, mobility and cardiovascular fitness. If all these pillars are in place, it is quite easy for an athlete to build upon this base with sport-specific exercise.

Muscular development is not only relevant to athletes. Understanding how the musculoskeletal system works confirms that it is also extremely useful for an average person depending on goals. The goal of many non-athletes is to lose weight by lowering body fat percentage. Some people tend to think that if they want to lose weight around the stomach and waist area they should do crunches and leg raises. This is a result of a spot-training method (not to be confused with SPOT-traing/specific-progressive-overload-training). Spot training assumes that a particular area of the body can be slimmed down or toned by doing exercises that target the underlying muscle groups. This is actually not true, as knowledge of bodily functions as well as specific studies show that the muscles require glycogen to burn oxygen, but the location of the glycogen storage is irrelevant and often purely up to genetics.

Bodyfat percentage is a pretty simple equation of calories in versus calories out. The calories only come in through food, so controlling nutrition is the key, and calories are burned through the basic metabolic rate, which is the calories used to breathe, keep the heart beating and vital organs functioning, as well as activity. Due to the BMR being purely genetic, the only two controllable variables are food intake and calories burnt as a result of activity levels. Low calorie intake and high activity levels, will result in a caloric deficit and thereby decrease body fat percentage. High calorie intake and low activity levels will cause a caloric surplus and increase in body fat percentage, which is not necessarily unhealthy, as a caloric surplus is also essential to gaining muscle mass. This means that calories are burnt relative to the exhaustion of the muscles, regardless of what muscles are active, and will decrease overall body fat percentage but not that of specific areas. This again means that in order to burn fat in the most efficient way, one should complete exercises that engage as many parts of the body simultaneously at an intensity that requires continuous supplies of glycogen. Most often the best answer is running, cycling, swimming and other exercises that exercise the cardiovascular system.
With that said, resistance training can be quite beneficial to people suffering from joint pain and want to avoid running. In this case, a plan with many compound exercises with moderate weight and low reps, short rest periods and overall high intensity is advisable. This will promote healthy development in both muscular strength, size and endurance, while being intensive enough to burn a significant amount of calories.

On the other end of the spectrum, many people start going to the gym with goals of getting bigger and looking better and more aesthetic, however, fail to do so, when they add too much weight, compromising form and volume or use too little weight and too many reps, effectively exercising for muscular endurance. If the goal of an individual is to gain muscle mass, Progressive Overload in a variety of both compound and isolating exercises with focus on both concentric and eccentric contraction is the best approach. Starting off, it usually is easiest to build a solid foundation using machine alternatives to compound lifts, such as chest press in place of bench press, as it makes it easier to overload the muscle without being restricted too much by underdeveloped synergist and fixator muscles before moving on to more challenging compound lifts.

In Hypertrophy based training, form of an exercise is crucial to development. Having proper form, and a good range of motion are essential for complete contraction and recruitment of type iix fibres. This means that starting off with lighter weights and then moving progressively up is the best approach. Actual weight lifted is almost completely irrelevant, as hypertrophy is obtained by successful breakdown and synthesis of type iix fibres, rather than motor unit synergy.

Having a balanced program for muscular development that includes primarily exercises specific to a person's goals is extremely healthy, and although in most cases not ideal to pure fat loss, it is still a pretty good solution. Increasing muscular endurance compliments an active lifestyle, and the ability to tire slowly in muscles promotes healthy habits such as standing and even sitting in a more ergonomic way to reduce strain on the body. Inactive lifestyle and poor posture are leading causes of injury and reducing the risk for this can only be described as extremely positive.

Hypertrophy based training is often looked down upon for not being as functional, however due to the significant improvements in appearance resulting from it, the psychological benefits should not be overlooked. Seeing progressive improvements in one's own physique is often extremely inspiring and the resulting increase in self-esteem lends positive effects to many other aspects of life. Obtaining a healthy and aesthetic physique by means of functional training for the most part also increases general happiness and motivation.

Increasing explosive strength is often very rewarding, as adding plates to big lifts and seeing progress is quite motivational. However, strength based training is also very relevant for day to day tasks. In many professions, being able to lift heavier weights has subtle benefits, increasing productivity slightly. Competition is also an important factor here. Competing with friends and within a powerlifting community is often rewarding for everyone, as it is motivational and fun to see progress in yourself and others. Strength based training is however possibly one of the least popular branches of muscular training due to a lack of greatly rewarding everyday effects, despite its pure functionality.
Approaches to Muscular Development Training
There are three main goals of within muscular development, namely muscular endurance, strength and hypertrophy. Each of these goals requires a different approach to training and programming. It is generally agreed upon that developing muscular endurance requires low resistance weight or tension with high reps or duration. Training for strength requires the opposite, high weight and low reps. Whereas hypertrophy training is most effective when overloaded by high volume as a result of moderate weight and reps.
-Muscular Endurance
When training for muscular endurance, based on the research, I would recommend training with a variety of compound movements as well as some isometric exercises. Cranking out reps and going to failure is important and intensity should remain high throughout the workout. Rest times can be relatively short and little to no weight is recommended. Generally speaking, emphasis should be on maintaining correct form, as this should activate synergist muscles properly, for a complete workout. Exercises depend greatly on the type of sport the individual is training for, ranging from push ups to planks and band training.
-Muscular Strength
If Increasing muscular strength is the goal, training with heavy weight is absolutely crucial. I would recommend staying within a rep range of 1-5 reps at the most, of 3-5+ sets. 3 to 5 sets on regular compound exercises, however having proper warm up sets and combining working sets with a back off set is often quite beneficial. Therefore, the total amount of sets in one of the big 3 lifts would lie around 7-8 sets. In order to continue improving, it is important to progressively increase volume. At first this might mean adding a rep to one or more of the sets, but eventually increasing actual weight on lifts is crucial. Doing alterations to a lift is also healthy, as swapping for example from a low bar squat to a front squat will change the movement and range of motion, to place more tension on quadriceps, thereby also increasing the overall strength in leg musculature.
The main focus however should be on improving in the Bench Press, Squat and Deadlift.
-Muscular Hypertrophy
Hypertrophy training, also referred to as bodybuilding is commonly based upon one key principle, progressive overload. This is the key to hypertrophy, gradually increasing volume by adding weight or reps, will increase tension on muscles progressively, forcing muscles to adapt and rebuild during protein synthesis. In this type of training, limiting variables is key, which is why form should always be the first priority. Also, including some accessory or isolation exercises is also of great value. Considering that functionality and form guidelines are not important here, “cheating” a little in some exercises to crank out a last rep is totally fine, as it increases tension on the muscle, and ultimately hypertrophy increases. Rest times should not be over 2 minutes, as this allows blood to escape the working muscle again and the “pump” is lost. Maintaining a pump in muscles throughout the workout seems to have slight benefits to hypertrophy, as it increases the rate at which type iix fibres are recruited. Some people even use a occlusion method to stop blood flow out of the muscle, resulting in an even more severe pump, however research does not give definitive proof of its effect, and is therefore not necessary. In order to increase rates of hypertrophy increase, training several days a week (preferably 4-6) is recommended. Due to the slow recovery of muscles, having a split that trains chest and triceps, one day, followed by a back and biceps day and complete legs and core day is optimal for recovery and progression.
-Powerbuilding
Many people seem to think that one can only have one of the previously mentioned goals. This is not completely true. Combinations of these plans can definitely work to increase overall muscular development, however due to recovery limitations, progress will be slightly restricted if you attempt to increase all areas of muscular development simultaneously.

One combination of programs does not suffer from these restrictions. Scientifically speaking, there is no limitation to completing a combination of bodybuilding and powerlifting. As mentioned previously, this combination, often referred to as powerbuilding, increases strength dramatically, maintaining the same hypertrophy increases as a normal bodybuilding routine. The concept of Powerbuilding is to go heavy on a compound lift at the beginning of the workout and then following up on this powerlifting exercise with a regular hypertrophy based program with a multitude of accessory exercises. In the first exercise, it is recommended to do work with a powerlifting structure, specifically, 2-5 reps, for 5-7 sets. This part of the workout can be quite challenging due to the heavy weight, but it should not restrict the bodybuilding workout afterwards, as the rest periods in the first exercise are quite long (90-120 sec).
Following the first part of the workout comes the hypertrophy based training. This part operates completely independently of the powerlifting part. If the lifter has a goal of increasing strength in the powerlifting exercises, it is advisable to incorporate some more compound exercises in the second part of the workout, as this helps to build up the muscles involved also in the big 3 lifts. Therefore, it is beneficial to replace an isolation exercise such as a tricep extension, with a corresponding compound lift, such as a weighted dip. The outcomes of a powerbuilding routine are significant increases in both strength and hypertrophy. The only drawbacks to this type of training will be slightly longer and more straining workouts. It also takes a decent amount of programming to figure out proper tension overload and weight increases especially for the powerlifting part.

Conclusion
Understanding how the musculoskeletal system functions on a cellular and organismal level, is essential to developing training programs and methods that target specific goals. Muscular systems can be developed by applying specific techniques and methods in order to accomplish goals. The research conducted leads me to conclude that there are three main goals within muscular development, each requires unique approaches to training. The core principles can be combined in order to develop programs that offer a more specialised training, as well as general training for the average person. Muscular development makes up one of the key pillars to developing the solid foundation required to excel at any branch of athletics. But is also essential to a healthy lifestyle and is beneficial to everyday tasks. Considering the vast range of benefits muscular development training has on the human body, it is strongly recommended to practice it on a regular basis.

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