SEAL Physical Training Manual

Chapter 3 Introduction to Physical Training
This chapter introduces the basic concepts and related terms of Physical Fitness.The concept of fitness is commonly used to define, measure levels of fitness, and other basic terms related to physical training.Technical terms such as: aerobic and anaerobic will be used throughout the chapters of the book, so this chapter first introduces such basic terms, and subsequent chapters will further explain specific physical training techniques.We recommend readers to read the content of this chapter in detail. These basic terms and concepts will help you better understand the content of the book and enable you to master training skills faster.

An overview of exercise physiology
Exercise physiology is one of the basic disciplines of sports science, which aims to study the changes in the structure and function of the human body under the influence of physical activity and exercise training, as well as the response and adaptation of the human body to exercise.The research results are applied to the design of physical education curriculum, organization of physical exercise and sports training.Physical fitness includes cardiorespiratory endurance, body shape, muscle strength and endurance, reaction sensitivity, etc.

Basic Concepts and Terminology

The following are the basic concepts and common terms of exercise physiology, these terms throughout the book, please read carefully.

Aerobic exercise: A process that requires oxygen to produce energy.

Aerobic exercise capacity: the maximum amount of aerobic exercise that can be completed per unit time.

Aerobic metabolism: Most exercises longer than 3 minutes require oxygen to deliver energy to them (oxidative process), in other words, energy must be produced through oxygen metabolism.

Sensitivity quality: refers to the ability to quickly and accurately change the body position.

Anaerobic exercise: A process that does not require oxygen to produce energy.

Anaerobic exercise capacity: the maximum amount of anaerobic exercise that can be completed per unit time.

Anaerobic Glycolysis: The process by which glucose or glycogen is broken down into lactic acid in the absence of oxygen.Lactic acid is a by-product of this process.

Anaerobic metabolism: the conversion process of anaerobic substances and energy, that is, the process in which the oxygen supply cannot meet the needs during exercise, and the muscles use other components to release energy to meet the exercise needs.

Anaerobic threshold: The anaerobic threshold is the anaerobic limit. When the oxygen required by the muscles cannot be fully supplied by the respiratory and circulatory system during exercise, the energy will come from anaerobic metabolism; at this time, the amount of lactic acid in the arteries begins to increase.

Adenosine triphosphate (ATP): Adenosine triphosphate stores and converts energy in muscles.After food is decomposed into muscles, energy is stored in the form of ATP; ATP is decomposed during exercise to release energy.

Balance Quality: The ability of the body to maintain balance when the body is static or dynamic.

Cardiopulmonary function: refers to the ability of the heart, lungs, and blood vessels to deliver oxygen to the muscles in motion and expel waste from the body.

Concentric contraction: also known as concentric contraction, shortening contraction, also known as "active movement", refers to the contraction that causes the muscle to shorten when it tightens.

Coordination: The ability to use one of the senses in conjunction with the musculature to accurately perform a movement; for example, hand-eye coordination in shooting.

Dynamic Movement: The contraction and relaxation of skeletal or other muscles that cause joint movement.

Eccentric contraction: Also known as elongation contraction, also known as "passive exercise", refers to the contraction of muscles that makes them lengthen.Muscles lengthen and contract when gravity is overcome, as occurs when descending a hill or stair.

Electrocardiogram (ECG): It uses an electrocardiograph to record the changes in electrical activity of the heart during each cardiac cycle from the body surface.

Dynamometer/dynamometer: An instrument for measuring power or force.

Dynamometer: The process of measuring strength during physical activity.

Physical exercise: Refers to organized and planned physical activities for the purpose of developing the body, improving health, and enhancing physical fitness.Including cardiopulmonary function, muscle strength and endurance, agility, body shape and other physical fitness exercises (see the introduction for details).

Fartlek Training: Also known as "speed game", the training method of alternating acceleration running and jogging is an intermittent training method to improve speed quality without a specific organizational form.

Flexibility: the ability to control the range of motion of a joint, specifically the sensitivity of tendons, ligaments, and surrounding soft tissues; the ability to control and respond under any activity intensity, especially during extreme exercise.

Glycogen: A carbohydrate (sugar) stored in the liver and skeletal muscle.

Glycolysis: The fermentation-like degradation reaction process of glucose or glycogen in tissues.Eventually, lactic acid or pyruvate is formed, and at the same time, part of the energy is released to form adenosine triphosphate (ATP) for tissue utilization.This process is an anaerobic metabolic process.

Glycolytic: Prepares or promotes glycolysis.

Heart rate: The number of times the heart beats per minute.

Interval training: resting after a bout or set of strenuous exercise, or reducing the intensity of the exercise.Interval training is primarily used for anaerobic exercise.

Isokinetic Contraction: A maximally exerted contraction of a muscle at a constant rate throughout the joint's range of motion; eg, an arm swing exercise in freestyle swimming.

Isometric contraction (static): Muscles neither lengthen nor shorten during contraction, while muscle tension is equal to external resistance, and its function is to support, fix, and maintain a certain body posture.In this type of activity, there is no joint movement.

Isotonic contraction (dynamic): When a muscle contracts, tension is maintained and the muscle can either lengthen or shorten.

Lactic Acid: A by-product of anaerobic metabolism.

Ligaments: Cords of connective tissue that connect bones to each other and function to strengthen joints.

Maximum oxygen uptake (VO2max): It is an important indicator for measuring aerobic metabolism capacity, the maximum amount of oxygen that the body can take in per unit time.Usually expressed in L/min or ml/kg/min.

Metabolic Equivalent (MET, Metabolic Equivalent Unit): A unit used to estimate the body's metabolic expenditure during physical activity.A metabolic equivalent refers to the energy consumed by an individual in a resting state, which is equivalent to consuming 3.5 milliliters of oxygen per kilogram of body weight.

Metabolism: The process of physical and chemical reactions that sustain life.

Minute Ventilation: The amount of air inhaled per minute.

Muscular Endurance: The ability to perform multiple movements against a certain resistance (usually 50% to 60% of the maximum resistance) over a long period of time.

Muscle Strength: The maximum force a muscle or group of muscles can produce.

Myoglobin: It is the main protein that composes skeletal muscle and cardiac muscle, has the function of transporting and storing oxygen, and is an important indicator for judging muscle strain.

Physical activity: Movement of skeletal muscles that expends energy.

Fitness/Physical Capacity: The ability to perform physical activity.

Muscle strengthening training: usually also called "explosive jumping ability training", it is used to exercise the ability of muscles to stretch and contract suddenly, including standing jump and mixed jump.

Power: The ability of a muscle to move as far as possible in a short period of time.Such as the explosive power shown in sprint, high jump and boxing.

Perceived effort grading (RPE): Perceived exertion is an index used by Borg to measure the relative exercise intensity according to the degree of self-perceived fatigue of the exerciser. It is a reliable indicator for measuring the level of physical strength in continuous intensity exercise and can be used to evaluate exercise. Intensity; it is usually related to indicators of cardiorespiratory metabolism, such as oxygen uptake, heart rate, etc.

Reaction time: The time to react after receiving a signal.

Ventilation ratio: The ratio of carbon dioxide produced to oxygen consumed is an important indicator of initial energy in sports.

Speed ​​quality: the ability to complete a certain movement in a short period of time.

Strength quality: the ability of muscles to overcome resistance and to effectively control the range of motion.

Stroke Volume: The amount of blood pumped by the heart per beat.

Tendon: A bundle of fibers attached to the end of a muscle through which it connects to bone or other tissue.

Tidal Volume (Tidal Volume, TV): The volume of air inhaled or exhaled each time in a resting state, like tidal fluctuations, hence the name tidal volume.

Section [-] Muscle structure and function
There are three main types of muscles:

Myocardium
Skeletal muscle

smooth muscle

This section focuses on skeletal muscle, which converts chemical energy into mechanical kinetic energy to carry out human activities.The following describes the basic composition of skeletal muscles and their respective characteristics and functions.Although some scholars make different divisions of skeletal muscle fibers, skeletal muscles can be roughly divided into the following three categories:

Slow-twitch red muscle (Class I)
Fast-twitch red muscle (class IIa)

Fast-twitch white muscle (class IIb)

1. Type I skeletal muscle fibers
Type I skeletal muscle fibers usually play an important role in endurance exercise.This type of fiber is usually called slow-twitch fiber, which has high aerobic capacity and anti-fatigue capacity. The main energy source is fat, but its glycolytic (anaerobic) capacity is poor, the contraction speed is slow, and the motor unit muscle strength Low, belonging to the low-intensity, long-term exercise muscle type.Slow-twitch muscle fibers are rich in myoglobin and are red in color, so they are also called slow-twitch red muscles; myoglobin refers to the iron-containing protein that stores and transports oxygen in muscles.Slow-twitch fibers are tonic motor neurons responsible for maintaining tension posture, also known as slow motor units.Slow-twitch fibers contain more myoglobin and cytochrome, and less myofibrils. During exercise, slow-twitch fibers contract slowly, and their explosive power is not strong, but they can last for a long time.

2. Type II skeletal muscle fibers
Class II skeletal muscle fibers can be divided into at least two classes: class IIa (fast-twitch red muscle) and class IIb (fast-twitch white muscle).These fibers are mainly used in strength and explosive activities. Type II a fibers are rich in myoglobin, so the color is slightly red, and they are called fast-twitch red muscles.It is located between the fast-twitch and slow-twitch fibers, and although faster than the slow-twitch fibers, it is also not suitable for endurance activities.

On the contrary, type II b fibers are the real fast-twitch fibers, which contain more myofibrils and less myoglobin and cytochrome, so some scholars call it "white" muscle.It contracts quickly and powerfully during exercise, and has strong explosive power, but poor endurance.Fast-twitch white muscle has the highest glycolytic (anaerobic) capacity and motor unit muscle strength, but is poor in aerobic capacity, contraction speed, and fatigue resistance, and belongs to the type of high-intensity, short-term exercise muscles. Type II b fibers tend to accumulate lactic acid. If lactic acid is not discharged in time, it will eventually lead to body fatigue.

Type I a fibers have the advantages of both muscle types at the same time, and can perform both aerobic and anaerobic exercises.It should be noted, however, that the two types of skeletal muscle fibers possess different properties.Generally speaking, when the human skeletal muscles are exerting force, if the force is relatively mild, only the slow-twitch red muscles participate in the contraction and generate force; as the strength of the skeletal muscles increases, the fast-twitch red muscles will also participate in the contraction force.However, the fast-twitch white muscles (type II b fibers) participate in the contraction force only when the force intensity of the skeletal muscle is at its maximum.However, physical exercise can change the properties of bone fibers.Therefore, endurance quality training can make fast-twitch red muscles show more characteristics of slow-twitch red muscles.Table 1-1 details the types of skeletal muscle fibers.

3.Skeletal muscle fiber distribution
Each individual has an innate number of fast-twitch and slow-twitch fibers, and all normal skeletal muscles contain all three types of fibers.However, the specific distribution of these fibers varies from person to person and from muscle tissue to muscle tissue. Even in the same person, different muscle tissues have different fiber distributions.Physical training can switch muscle fiber types, and can improve the metabolic capacity of fast-twitch and slow-twitch fibers through endurance training and explosive training.It should be noted that the training effect is not only affected by the distribution of muscle fibers in the body, but also restricted by other factors such as specific training conditions and diet.Figure 1-1 summarizes the average distribution of slow-twitch fibers in various athletes.

As shown in Figure 1-1, people who regularly participate in endurance sports have higher levels of slow-twitch muscles than sprinters and wrestlers.Figure 1-1 also shows us the highest aerobic metabolism of these groups of people: the higher the content of slow muscle fibers in the body, the stronger the aerobic metabolism.Note that in amateur athletes the situation may be slightly different.Specific physical training alters the distribution and properties of skeletal muscle fibers in the body.

Section [-] Principles of Physical Training

The goal of fitness training is to increase the level of fitness.Everyone who makes up his mind to do physical training has a unique physical quality.This chapter discusses four basic principles that apply to all forms of strength and conditioning training.

1.Appropriate load principle
The human body must be stimulated by a certain intensity to improve its function. Therefore, the trainer must carry out physical training with a higher intensity than usual, so that the body can gradually adapt to the intensive training.After the body adapts to higher-intensity exercise, it can effectively improve physical function.You can carry out load training through repeated training, increasing exercise intensity, and extending exercise time.These approaches can significantly improve the training effect of running, swimming and cycling, while increasing resistance and repeated training can significantly improve the effect of strength training.

2.Principles of special training

This principle refers to improving the corresponding metabolic and physiological functions of the human body through specific sports.For example: Running improves physical fitness but not swimming, and vice versa.Therefore, in order to achieve a good training effect, specific special training items must be specified to improve related muscle functions.

3.Principle of Differential Treatment

Exercise training effects vary from person to person.Appropriate training content should be selected according to individual differences in physical fitness, and a training plan with a corresponding load should be formulated.

4.Principles of Suspension of Training and Physical Decline
Regular training is a prerequisite for maintaining fitness.After a week or two of detraining, the fitness benefits obtained will gradually fade, and this issue will be discussed in detail later in this chapter.

According to the attributes of special operations, SEALs must comprehensively improve their physical fitness: strength, speed, agility, and endurance.Therefore, FITT (Frequency, Intensity, Time, Type) principles have played an important role in physical training, and training must be carried out in accordance with these principles.

FITT: frequency, intensity, time, type

The FITT principles will help you reap the best results from your workout.Alternate training should fully consider the three elements of exercise intensity, exercise volume, and exercise duration (see Chapter 3 for details). The next section will explain how to measure exercise intensity.

Section [-] How to measure training heart rate

This section focuses on exercise intensity, a term that will be used in subsequent chapters of this book.The exercise intensity here refers to the intensity of the exercise.If you work out in the gym, the fitness equipment will control the intensity of the exercise.Measuring heart rate is a relatively simple and convenient way to measure exercise intensity. By measuring heart rate, you can check whether your heart rate during exercise is within the target heart rate range.

Take the pulse rate at the carotid or wrist artery for 15 seconds and multiply it by 4 to get the number of heartbeats in 1 minute (heart rate).Compare this value with your target heart rate. If the value is low, you need to increase the intensity of exercise; otherwise, reduce the intensity of exercise.

Calculation method of target heart rate for physical fitness training
In order to maintain aerobic metabolism capacity, the exercise intensity needs to be moderate or above, that is, 70% to 90% of the maximum heart rate (Max HR).

Note: This is only an estimate of your maximum heart rate.

Due to individual physiological differences and differences in physical fitness, the actual maximum heart rate should be higher than this estimated value.However, the world usually uses this method to calculate the maximum heart rate.

Maximum heart rate per minute = 220 - age

Multiply the resulting values ​​by 0.7 and 0.9, respectively, so that you can get the target heart rate zone.Your heart rate should be in this zone during physical activity.Table 1-2 serves as an example to teach you how to use this method to determine your target heart rate range.

You can calculate your maximum heart rate by the method above or the method in Figure 1-2.A word of caution: in swimming and arm sports, the maximum target heart rate is usually low, if you do this type of training, please subtract 13 from the maximum heart rate.Table 1-3 will give the specific algorithm.

Section [-] Three major energy supply systems of skeletal muscle during exercise
Before explaining the physical training methods, let's discuss the three major energy supply systems of skeletal muscles.All three systems are very important as they provide energy to the moving muscles.Different types of sports have different main energy supply systems.

1.Energy supply system in speed motion
During exercise, material metabolism is accompanied by energy conversion, and since adenosine triphosphate (ATP) is the direct energy source for human muscle contraction during exercise, the release and utilization of energy is centered on ATP. ATP is the only direct energy source for converting chemical energy into mechanical energy during muscle exercise. The conversion rate of ATP is greatly accelerated during exercise, which is proportional to the speed of exercise.However, the ATP content in skeletal muscle is very small, and it can only maintain the maximum intensity exercise for a short period of time. When ATP releases energy, they are converted into adenine nucleoside diphosphate (ADP). In order to make ADP secondary to ATP and provide more energy for muscles, creatine phosphate (CP) is needed to promote the conversion of the two.Therefore, the way to activate CP is particularly important.Without CP, ADP can only provide energy for the body for a few seconds, but with the "help" of CP, the phosphagen functional system (ATP-CP) can provide energy for 30 seconds.Therefore, the ATP-CP system in speed exercise, also known as the phosphate storage pool, provides immediate anaerobic energy for muscle contraction.

ATPADP + phosphoric acid + energy
ADP+CPATP+creatine
2.Energy supply system in anaerobic exercise

The functional system in anaerobic exercise is called the mixed metabolic functional system of glycolysis and phosphagen (ATP-CP).The energy supply system is a transitional system.

When vigorous exercise lasts for more than 30 minutes, glucose is the only substance that can provide ATP to the muscles.Muscle obtains glucose through glycogen, and the process of anaerobically decomposing glucose or glycogen into lactic acid in muscle and synthesizing ATP to release energy is called glycolysis.During exercise, skeletal muscle relies on the regeneration of glycolysis for energy supply and utilization, which is called the glycolysis functional system.However, lactic acid is produced during the conversion of glucose into ATP.Under normal circumstances, there is only a small amount of lactic acid in the blood and muscles. When lactic acid accumulates in the muscles and blood, the muscles will feel tired unless the lactic acid is excreted in time.The reason why the human body can excrete lactic acid in time is because the muscles undergo oxidative metabolism, which provides the body with the ability to maintain exercise.If you continue to exercise strenuously, your muscles will inevitably feel tired after three to five minutes.

3.Energy supply system for aerobic exercise
The aerobic metabolism energy supply system of aerobic exercise provides energy for long-term, stable and continuous exercise, such as long-distance running, swimming and other sports.Muscles can obtain energy from glucose and fatty acids, the muscles themselves can store these glycogen, and they can also obtain these energy sources through blood circulation.Glucose is stored in the muscles as glycogen, while fatty acids are stored in the muscles as triglycerides.When the body performs prolonged slow exercise, triglycerides will replace glucose to provide energy for the muscles.

In different types of sports, these three energy conversion systems will play different roles at different times.The amount of energy they produce during energy metabolism is related to exercise time, exercise intensity, and exercise type.

Generally speaking, high-intensity, short-time sports mainly rely on anaerobic metabolism to obtain energy.Tables 1-4 summarize energy supply systems for various types of physical activity.

Section [-] Skills and Methods of Physical Training
Most people think of physical activity as either purely aerobic or purely anaerobic, or either.In fact, many sports are a combination of the two.For example: In a 1500-meter track and field race, the starting and sprint stages are anaerobic exercises, while the middle stages are aerobic exercises.Using proper physical training techniques can improve the body's aerobic and anaerobic metabolism.Table 1-5 lists the application of the three major metabolic systems in various physical training methods. Let's discuss which techniques can improve physical fitness and how to use these techniques.

1.interval training
Interval training is a training method in which physical training and rest are alternated.Active rest is usually used, such as jogging, walking and other relaxation training.According to different training needs, set different exercise time, exercise intensity, number of repetitions, as well as rest time and active rest exercise types.Interval training helps athletes increase exercise intensity.Through different types of interval training, the body's speed, anaerobic and aerobic functional capacity can be improved.

2.sprint training
The sprint training method helps to improve the quality of speed and muscle strength.It is necessary to repeatedly perform acceleration running exercises at the fastest speed.Under normal circumstances, the fastest speed can be reached after 6 seconds of starting, that is, the fastest speed can only be reached after starting 55-60 meters.

3.Interval training for sprints
This training method means that after 45-55 meters of sprint practice, cross-over jogging and relaxation exercises of 55-65 meters, and then sprint exercises, so as to perform repeated exercises of 4800 meters.Interval sprint training can help improve aerobic capacity.

4.accelerated running method
加速跑训练有助于提高速度素质和力量素质。具体做法是从慢跑到大步跑、再到冲刺的1组练习，然后进行1组走路的放松训练，重复进行训练。跑步距离可以设定成50～100米，例如可以依次进行50米慢跑、50米大步跑、50米冲刺、50米走路放松练习。

5.fartlek training
"Fartlek" in Fartlek Training means "accelerated running" in Swedish.This acceleration workout consists of alternating fast and slow runs on flat ground and inclines.Unlike interval training, fartlek training does not include dedicated relaxation and specific exercises.For example, you say to your friend: "Did you see that bus stop? Let's compare and see who gets there first." Then you run to the stop sign as fast as you can, and after reaching the end, you run a few steps forward , but the speed of these steps is significantly slower than the former.In other words, there is no preprogrammed running pace in this exercise.This method is very suitable for regular fitness, and you can adjust the training intensity according to your own needs.

6.continuous training
The continuous training method refers to the method of continuous training with low load intensity and long load time without interruption.Usually used to develop endurance qualities, such as endurance sports such as long-distance running or outdoor swimming.Athletes can perform both slow sustained training and fast sustained training.It can effectively improve the energy supply capacity of aerobic exercise and the intensity of aerobic exercise in this energy supply state.Chapters 4 and 5 of this book will explore the continuous training method further.

7.repetitive running training

This method is similar to the interval training method, the difference is that each group runs a longer distance, usually between 800 and 3200 meters.Do not begin repetitions until your heart rate drops below 120 beats per minute, or 60 percent of your maximum heart rate, during intervals.

Section [-] training and suspension
Physical training (Conditioning/Training) will increase the physical level, and after stopping the training (Deconditioning/Detraining), the physical level will decrease.However, training is a gradual process, and it takes about 6 weeks for obvious training effects to appear; and suspension of training can reduce physical fitness levels in a relatively short period of time.Tables 1-6 are physical training effect tables, showing the metabolic changes and cardiopulmonary changes of the human body after physical training.

After you stop training, your fitness level will drop within 1-4 weeks.After physical training, the body's metabolic capacity, cardiopulmonary function, and muscle enzyme levels are all significantly improved. However, after the training stops, the improved physical fitness will decline again.The impact of suspension of training on physical fitness mainly includes the following points:
Reduced aerobic metabolism - increased heart rate after exercise, reduced unilateral atrium pumping blood;
During exercise, blood lactic acid accumulation is accelerated, causing premature muscle fatigue;
Reduces levels of key muscle enzymes (enzymes that control muscles to maximize energy gain);
Reduced lung capacity, resulting in less oxygen available to muscles during exercise;
Reduce stamina - the time to resist fatigue is shortened;

Reduce the ability to burn calories during exercise; reduce the level of exercise in a difficult environment (such as high temperature environment).

After the suspension of training, in order not to let the physical fitness fade, it is necessary to continue training to maintain the improved physical quality.However, in the case of reducing training volume and training time, it is possible to maintain fitness levels and avoid physical decline by maintaining the intensity of normal training.Physical training at normal intensity two or three times a week can maintain aerobic capacity and the ability to inhibit lactic acid accumulation.Doing strength-specific training once or twice a week can maintain strength quality.Specialized training on military bases and post-injury recovery training are discussed in detail in Chapters 11 and 12 of this book.

Section [-] Positivity Recovery

积极性恢复是指在日常训练结束后，应该继续进行小幅或中幅（最大心率的30%～50%）的放松训练。例如：跑步训练结束后，应该继续走5-10分钟。本书Chapter 3（心肺功能训练）将对其具体内容和积极作用做进一步讨论。

(End of this chapter)