SEAL Physical Training Manual

Chapter 9 Flexibility Training
Although flexibility training is often overlooked, most coaches, exercise physiologists, and health care professionals recommend flexibility training because it is an important part of a strength and conditioning program.Especially when the athlete's muscular endurance and strength quality have reached a high level, stretching is even more important.If you want to get the best training effect, you must insist on flexibility training.

Section [-] The Significance of Flexibility Quality Training
Appropriate use of stretching training can improve flexibility and is of great significance.Mainly manifested in the following aspects:

Improve movement technique and improve athletic level

Reduce the risk of potential sports injuries (such as muscle pain and muscle damage)

relieve muscle soreness
Prevent or reduce lower back pain

Improve flexibility
Promote blood circulation around joints

In order to successfully complete combat missions and improve the corresponding combat level, scientific physical training must be carried out.Flexibility training is an integral part of the physical training program. The development of flexibility can not only expand the range of motion, but also facilitate the development of strength, endurance and other qualities, thereby improving the level of exercise.SEALs often undergo high-risk training that can easily lead to skeletal muscle damage.Therefore, through balanced physical training - simultaneously improve muscle strength and flexibility, enhance joint stability, and actively prevent training injuries.Both strength training and flexibility training are related to the activities of joints and surrounding tissues, and the two are closely linked and inseparable.

Muscle strength training can improve the body's flexibility, similarly, flexibility training can also increase muscle strength.Excessive strength training can easily cause minor muscle damage, and muscle fibers shorten during recovery.Stretching can make the muscles more active, avoid muscle shortening, and prevent muscle strain.Stretching also has the same preventive effect on other overtraining injuries (e.g. tendonitis, fasciitis).

Doing flexibility training without matching strength training can weaken muscle tissue and increase the risk of joint sprains, dislocations, and muscle sprains.Stretching stabilizes joints and activates surrounding muscles, thereby reducing the risk of training injuries.

Overstretching can also lead to injury.Only by carrying out balanced and scientific flexibility and strength training can excessive stretching be avoided.

Section [-] The concept of flexibility
Flexibility refers to the range of motion of each joint of the human body, as well as the stretching ability of soft tissues such as muscles, tendons and ligaments.

For special forces, flexibility refers to the maximum range of motion of a joint and the optimal stretching ability of muscles, tendons and ligaments in order to complete a specific task.Flexibility includes two points: the range of motion of joints and the stretching ability of muscles, tendons and ligaments.There are three main constraints:

Bone structure of the joint.It innately determines the range of motion of the joint;
The size of the soft tissue around the joint.Surrounding tissues include muscles, tendons, ligaments (see Chapter 1 for definitions), etc.;
The strength quality of the muscles around the joints.

Flexibility is generally divided into two types, dynamic (active) and static (passive).

Dynamic flexibility, also known as active flexibility quality, refers to the speed achieved by the joint range of motion in sports.This quality contains two meanings: the quality of muscles around the joints and the ability to overcome resistance to stretching.For example, actions such as throwing a baseball, attacking an opponent, and kicking in martial arts are all dynamic flexibility qualities.

Static flexibility, also known as passive flexibility, refers to the maximum range of motion when the joint passively bears this action under the action of external forces (competitors, fitness equipment, gravity), that is, the ability to use external forces to maintain stretching.

Static flexibility is generally greater than dynamic flexibility.

Stretch reflex and tendon reflex

Stretch reflex (Strength Reflex) and tendon reflex (Lengthening Reaction) are the results of the joint protection mechanism, which refers to the reflex movement that occurs when the muscles around the joint and the sensory organs in the tendon tissue are stimulated when the muscles around the joint are stretched. .As shown in Figure 7-1, there are two sensory organs in moving tense muscles: muscle spindle cells and tendon organs (GTOs, also known as Golgi tendon organs).

Muscle spindles are located inside the muscle, parallel to the muscle fibers.The basic process of the stretch reflex is as follows: When the muscle is stretched, it causes the muscle spindle to be excited, which sends a signal to the spinal cord, and the bone marrow sends a contraction signal to the muscle, causing the muscle to contract.The muscle spindles are the primary sensory organs of the stretch reflex.A classic example of a stretch reflex is the knee jerk reflex.When the doctor taps the patient's lower knee, the quadriceps muscles lengthen rapidly, and the muscle spindles send a signal, which causes the quadriceps muscles to contract rapidly again, causing the knee jerk reflex.The faster the tapping speed, the faster the muscle spindles react and the faster the muscles contract.When the muscle is initially stretched, the frequency of the signal transmitted by the muscle spindle is high, but as the muscle adapts to the stretched length, the transmission frequency gradually decreases.

The tendon organ is the main organ of the tendon reflex, which is located at the junction of the muscle and tendon; when the muscle contracts, the muscle is stretched, or both, the tendon organ is stimulated, triggering the tendon reflex.When the muscle tension increases, the tendon organ will send out inhibitory neurons, causing the muscles to relax and protecting the muscles and tendons from damage.Understanding the process of stretch reflex and tendon reflex is conducive to correct stretching exercises.

Stretching slowly is the most effective stretching method, and each movement is held for 15-30 seconds.

Stretching slowly will avoid irritating the muscle spindles and causing the muscles to contract.When doing stretching exercises, hold each position for a certain period of time, which can make the muscle spindles adapt to the longer muscle length and help to open the ligaments; moreover, it can also fully stimulate the tendon organs to make stretch reflexes, protecting the muscles and The role of tendons.

Section [-] Flexibility training methods

There are many training methods for developing flexibility, which can be roughly divided into the following categories:

dynamic stretching
static stretching
elastic stretching
Proprioceptive Neuromuscular Stretch (PNF)

1.dynamic stretching
Dynamic stretching means that the trainer relies on his own strength to perform fast, rhythmic, and gradually increasing range of stretching training.By controlling the range of motion and stretching soft tissues such as muscles, tendons, and ligaments, the trainer can increase the flexibility of the joint and the stretchability of the surrounding tissue.For example, frontal kicks, side kicks, arm swings, lower back exercises.Usually used for warm-up activities before competitions and sports.

The views of the academic circle on dynamic stretching and its efficacy are not uniform, and there are pros and cons.Some experts believe that short-duration, intermittent stretching exercises can cause stretch reflexes, causing muscle contractions, which are not conducive to physical training.And some experts insist that active stretching has invaluable benefits for faster, more explosive sports (eg, martial arts, gymnastics).In conclusion, static stretching should not be used to develop static flexibility, nor should it be used for excessive flexibility stretching.Performing dynamic stretching exercises similar to activities before a sport or competition can improve performance.

2.static stretching
Static stretching method refers to the method of increasing joint flexibility by relying on external force.Used to develop static flexibility, usually with slower, fixed-position exercises.Training is often also done with the help of a partner or external (wall or floor) forces, for example, lifting one leg and holding it with the hand, doing leg presses.Slow static stretching training can help reduce muscle spasms and muscle fatigue, and is often used for relaxation and finishing activities after training.

3.elastic stretching
Resilient stretching is the self-protective contraction of the body or joints due to sudden hyperextension.Resilient stretching is often used in strenuous exercises such as jumping training and should not be confused with dynamic stretching.Typical examples of elastic stretches are sudden squatting to touch the toes, or sudden upward kicks, and up and down arm swings are also typical elastic stretches.This type of stretching does not improve flexibility. Instead, repeated stretch reflexes can cause muscle strain and cause sports injuries.Therefore, this method of stretching is not recommended.

4. PNF stretching method

PNF stretching method, that is, proprioceptive neuromuscular stretching method, stimulates the body's proprioceptive organs to activate and recruit the largest number of motor muscle fibers to participate in activities, promote paralyzed muscle contraction, and at the same time adjust the excitability of sensory nerves to change Muscle tension, relieve muscle spasms.It is an advanced stretching technique, the best muscle training method that is popular at home and abroad, and is widely used in the healthcare industry.Before performing sports with high flexibility (such as martial arts, ballet, gymnastics, boxing, etc.), you need to do PNF stretching. There are many training techniques in the PNF stretching method, but it is usually completed in three steps: passive stretching - muscle isometric contraction exercises - the third set of stretching exercises (both static stretching and dynamic stretching).With the help of a partner or object, perform PNF stretching: passive stretching-muscle isometric contraction (meaning that the length of the muscle does not change during contraction, but only the contraction with increased tension) training, PNF with the help of stretch reflex and tendon reflexes to maximize joint flexibility.

As mentioned earlier, when a certain muscle tissue is stretched slowly and keeps this posture unchanged, the muscle will have a tendon reflex to prevent the muscle from contracting; the following isometric contraction training will cause the following changes in the muscle tissue: PNF in In training practice, the exercise form is similar to the static stretching method, but the mechanism is essentially different.

The physiological theory of PNF is based on the use of anti-stretch reflex (when the muscle contraction reaches a certain strength, the tension acts on the tendon organ to excite it, and the same muscle is reflexively inhibited through the class Ib afferent fiber, so that the muscle contraction stops and relaxation occurs) and To achieve the purpose of muscle relaxation, the isometric contraction of the muscle will generate strong stimulation to the muscle, and the tendon organ in the muscle will transmit the signal to the central nervous system, which reflexively relaxes the muscle, resulting in the generation of anti-stretch reflex.That is to say, the active contraction of the stretched muscle can counteract the stretch reflex produced, and the relaxation after contraction will increase, and the contraction of the antagonistic muscle can also increase the relaxation of the active muscle.

When a muscle contracts isometrically, some muscle fibers contract while others continue to lengthen.At the end of the contraction, the contracted muscle returns to its original length, while those fibers that continue to elongate remain the same length (due to the stretch reflex) and can be stretched even longer.

When a muscle contracts isometrically, the muscle becomes more tense, stimulating the tendon organ, triggering a tendon reflex, and inhibiting neurons that inhibit the muscle, preventing further contraction from occurring.When the isometric contraction ends, the inhibition does not recede and the muscle can be stretched longer.

After training after isometric contraction, the third step of muscle stretching is to use the ability of muscles to be stretched to a greater length to adapt muscles, tendons, ligaments and other sensory organs to longer stretching distances.

It is best to do PNF stretches with a partner.

There are many variations of the PNF stretching method, some of which are very complex.The most common is the "shrink-relax" method.This method has three steps: passive stretching, muscle isometric contraction, and passive stretching to increase the stretched length of the muscles and joint flexibility.

Let’s take the biceps femoris as an example to introduce the specific training process, as shown in Figure 7-2: First, statically stretch the target muscle and hold on for a few seconds; Do an isometric contraction of the muscles and hold for a few seconds; then relax the muscles and perform a static stretch again for a few seconds.

The above exercises can be performed alternately, completing sets of 1 to 5, always ending with static stretching.You will find that the static stretch after each repetition is a little deeper and the muscles are stretched better than the previous one.Like weight training, the PNF method should not be used too frequently, with a maximum of 2 to 3 training sessions per week.

Please note that several stretching methods introduced in this chapter can be used as active stretching exercises, passive stretching exercises, and PNF stretching methods.Trainers can use reasonable stretching methods according to their own needs.

Section [-] Warm-up and stretching exercises
Stretching is not the same as warming up.

Many people think of stretching as a warm-up, however, the two are completely different activities.Warm-up exercise refers to moving the limbs first with a lighter amount of activity before the main physical activity to prepare for the subsequent more intense physical activity.Warm-up exercises are usually divided into two categories: general warm-up exercises and specific warm-up exercises.Exercise warm-up is an important part of all training. The importance of warm-up is that it can reduce the risk factor of injury, help the body increase muscle temperature, increase heart rate and breathing depth and frequency, increase blood flow, improve blood oxygen delivery capacity, and provide Muscles provide more nutrition, which helps the tendons and joints of the muscles receive more hard training.

Before any stretching, sports, athletic competition, or military physical training,

Do warm up exercises.

Muscles with a low temperature usually cannot be stretched, and stretching without warming up can easily lead to sports injuries.Stretching is not a substitute for a warm-up, and active stretching is usually the last part of the warm-up, or it can sometimes be done after the warm-up is over.

Do stretching exercises only after you have fully warmed up.

1.general warm up

General warm-up refers to light physical activities that have nothing to do with the physical activities to be performed, mainly including running in place, air jumping and other aerobics.General warm-up exercises are usually performed before high-intensity sports (such as weightlifting, extreme physical training, gymnastics, etc.) to reduce the risk of joint and muscle damage.

2.Special warm-up exercise

Specific warm-up exercises are warm-up activities to meet the physical demands of specific sports, and can reflect the characteristics of specific sports.Before the start of exercise, usually 10-30 minutes of low-intensity special warm-up exercise.For example: before long-distance running, slow down for jogging warm-up; before cycling competition, slow down for cycling warm-up; before karate competition, slow down for related movement exercises.According to the exercise intensity, reasonably formulate the corresponding warm-up intensity.In general, the more intense the exercise, the longer the warm-up time is usually.

Any warm-up should be thorough enough to increase body temperature;

Sweating is a good sign that you are fully prepared for the next exercise,
Sports activities are now available.

Whether it is a general warm-up exercise or a special warm-up exercise, it should be combined with a certain amount of stretching exercise, especially those exercises with higher intensity and are prone to injury.After the warm-up exercise, before the official start of physical activity, the muscles should be stretched.Table 7-1 lists several special warm-up methods.Stretching may not be done after warming up if time is limited; however, stretching must be done after exercise to relax the muscles.

Serious relaxation after exercise can make people have a buffering process between exercising and stopping.Stretching slow motion and correct breathing can gradually relax the tense muscles, slow down the rapid pulse and return to normal, gradually reduce the elevated blood pressure to normal, gradually calm down the excited mood, and help to discharge Metabolize waste in the body and promote blood circulation in the muscles.

At the same time, relaxation and finishing activities can improve the training effect and promote the recovery of body muscles and various organs. Therefore, corresponding stretching exercises must be carried out after exercise.Stretching is an effective way to relax and help reduce muscle fatigue, muscle cramps, and muscle soreness.

After stretching, you can stand in cold water or jog in cold water. This method has the function of reducing and eliminating muscle soreness, and is often used for rapid recovery between games.

The ideal relaxation and finishing exercise should be interspersed with static stretching exercises, slowly relax the muscles, hold each stretching position for 15-30 seconds, and then stretch further.

Section [-] Recommended Stretching Exercises
1.dynamic stretching

During physical training, there should be appropriate dynamic stretching exercises (Dynamic Stretching) after warm-up exercises to stretch the main muscle groups.Dynamic stretching is not violent and fast stretching, but slowly pulling the muscles to the maximum range, stimulating the relevant muscles and joints, so that they can enter the state of motion faster; each stretching action can be held for about 2 seconds to achieve preparation Effect, the stretching action should be consistent with the fitness exercise to be carried out.Chart 7-1 introduces several commonly used dynamic stretching exercises.

2.static stretching

Most of the gains in flexibility training can be attributed to the consistent static stretching exercises during finishing activities.After a day's training, static stretching exercises can relax the muscles, accumulate energy, and fully prepare for the next day's training.

Table 7-2 summarizes the static stretching movements for each part of the body. Trainers can choose 1 to 3 movements from each part for training according to their own needs. (Pay attention to balance exercises for muscles such as hip flexors and hip extensors, biceps femoris and quadriceps.)
跑步、游泳过后，要多选择几个动作充分伸展相应肌肉群。每个动作重复2～5次，每个姿势保持15～30秒钟，然后放松10～15秒钟。

Note: None of these practice methods have a tempo limit.

Stretching program for the main muscle groups of the whole body after training in the seventh section

Table 7-3 introduces the stretching methods for the main muscles of the whole body after training, and the specific stretching methods are classified according to the stretching position (such as standing position, sitting position, etc.).If each stretching action is held for 15 seconds, it takes 10 minutes to complete the exercise on one side of the body (such as the left side), preferably 2 times on each side.

(End of this chapter)