Chapter5 Fundamental Knowledge of Sports Science

1) Nature of muscle

Muscle does not have nature like compression spring. Muscle is rather similar to extension spring. Namely, a muscle always generates the power by contraction, not by extension. That is, muscle is different from compression spring. However, misunderstanding about that can often be seen among people not having interest in sports science. Probably, that misunderstanding comes from the impression of vertical jump because its motion reminds us of compression spring. But in actuality, in vertical jump, leg muscles generate the power by contracting. And its mechanism can be understood easily by following figure. Anyway, muscle always generates the power by contraction.

Muscle is similar to rubber band.

2) Voluntary and involuntary muscle contraction

When we lift up a baggage, we use our arm muscle consciously. In this case, command of muscle contraction comes from our brain. This kind of Muscle contraction is called as voluntary muscle contraction.

mechanism of voluntary muscle contraction

On the other hand, when we snoozing on a chair, our head often drop and jump it up. In this case, stretch reflex occurs in back neck muscles and it causes our neck to jump up. Incidentally, stretch reflex is a phenomenon that muscle contracts unconsciously right after it is stretched by some external force like gravity or centrifugal force.

By the way, as for in the stretch reflex, brain does not give a command of muscle contraction. And its mechanism is as follows: when signal of muscle extention arrives at spinal nerve from "sensor cell" of the muscle, spinal nerve gives a command of contraction to that muscle without concerning command of brain. That's the mechanism of stretch reflex. Brain does not have concern in this mechanism.

Mechanism of stretch reflex

From above reason, stretch reflex can be said as an unconscious and automatic muscle contraction. By the way, besides the stretch reflex, there are various types of muscle reflex and all of muscle reflex occur without brain's command. Therefore, muscle contraction due to the muscle reflex can be called as involuntary muscle contraction.

3) The word "automatic motion"

Wrist roll is one of the motion that is caused by stretch reflex. So muscle contraction in wrist roll occurs in unconscious. However we can feel and recognize that motion with our brain. Because signal of the wrist-roll-motion is sent from terminal cells to brain.

In our body, there are various kind of cells that acts like a sensor. For example, some cells sense temperature, some cells sense pain, some cells sense taste, and some cells sense articular movement.

"Unconscious" but "recognizable".....  It's too complexity. So I called this kind of motion as "automatic motion". "Automatic" is an useful word because it can expresses two means at once ”unconscious" and "recognizable”

4) Two Cases of Automatic Motion

Automatic motion can occur due to following two causes.

1) muscle reflex

As mentioned above, muscle reflex occurs without command from brain. So that, a motion as a consequence of surgery can be said as the automatic motion.

2) physical force

Various physical forces (Gravity, counteraction, centrifugal force, etc..) can cause various body movements. And that body movement also occurs without command from brain. So, this case can be said as an automatic motion too.

By the way,  there is a complicated problem that automatic motion can be recognized in many cases. Therefore, many coaches will often teach young players the automatic motion as a conscious motion. For example, "rotate your hip" and "squash the bug" are examples of that misleading coaching. In these cases, many players will try to perform those motions as a conscious motion. As a result, their performance will become different from coaches aim. This is the most common mistake in coaching baseball.

5) Oblique Rotation Theory of Hip Joint

Hip joint has oblique joint line and ball-and-socket-structure.

So primary movement of hip joint is oblique rotation along its oblique joint line.

And there are two kinds of oblique rotation, namely, upward rotation and downward rotation.

I named upward rotation as "hip-joint-open".
Hip joint open consists of flexion, abduction, and external rotation.

I named downward rotation as "hip-joint-close".
Hip joint close consis of extension, adduction, and internal rotation.

By the way, main work of legs are walking and running.
And these movement is led mainly by flexion and extension.
Therefore, hip joint's movement should be thought centering on flexion and extension.
In other words, hip-joint-open is natural form of flexion.
And hip-joint-close is natural form of extension.

These facts are evidenced by next examples.

1) hip joint open

If you squat down with close your both knees, you will get tired more than doing it with hip-joint-open. So, catching stance of infielder (especially catcher's it) is using the hip joint open. And of course, stability is also one of the important effect of hip joint open.

屈伸と股割りの写真

2) hip joint close

When you push a pedal of bicycle, you will slightly feel the internal rotation of hip joint. And in breaststroke of swimming, kicking the water back, you will slightly fell the internal rotation of hip joint. And it is impossible to do those (push a pedal, kick the water back) with external rotation of hip joint. These matters prove that hip joint close (including internal rotation) is the natural form of hip joint extension.

自転車の写真

Thus, movement of hip joint can be understood easily and clearly by regarding hip-joint-open and hip-joint-close as the key element. And this is the oblique rotation theory of hip joint. 

As mentioned above, hip-joint-open is the natural form of flexion and hip-joint-close is the natural form of extension. So considering this theory, we can know the correct method of hip joint training.

Flexion occurs when hip joint receives one's weight and extension occurs when pushing it back. Therefore training of hip-joint-open should be performed in movement of receiving the weight. And training of hip-joint-close should be performed in movement of rebounding the weight. Following clips are examples of hip joint training that is in accordance with oblique-rotation-theory of hip joint.

● training of hip-joint-open

● training of hip-joint-close

※) Hip joint training should be performed in the next order : firstly hip-joint-open, secondly hip-joint-close.  Because if it finishing with hip-joint-open training, hip joint will be loose.  This order can be said as same as "If you open the door, close it".

So then let us watch following videos paying attention to the back leg shifting from hip-joint-open to hip-joint-close. And relation between back leg's hip-joint-close and hip rotation will be understood clearly by those videos.

Bryce Harper  (0.36~)
http://www.youtube.com/watch?v=KYg9CmSqtks&feature=plcp
Adam Jones  (0.41~)
http://www.youtube.com/watch?v=dAYdu2UUfjQ&feature=channel_video_title
Alex Rodriguez  (0.52~)
http://www.youtube.com/watch?v=J4KbE5MDGrY&feature=plcp
Craig Kimbrel  (0.01~)
http://www.youtube.com/watch?v=aWO9kaaltdc&feature=plcp
Aroldis Chapman  (0.07~)
http://www.youtube.com/watch?v=cAlnLfkppm0&feature=plcp

hip joint open and close in batting

hip joint open and close in pitching

6) Hamstrings 

As is well known, hamstrings is important for sprint. And not just for sprint, hamstrings plays an important role in various sports scene. Of course, it can also be seen in batting and pitching motion. Simply put,  hamstrings is used for kicking and pushing the ground. In other words, it is "power of legs" just itself.

In this part, I will write about importance of hamstrings in more detail.

In the first place, hamstrings causes hip joint extension and knee flexion. Particularly, hip joint extension is important in this theme because hip joint extension is used in kicking the ground. And hip joint extension is a movement of swinging the leg back.

Therefore, If you put your left leg in front of your body and extend its hip joint, your body will be moved forward by ground reaction force.  Because you kicked the ground back with hip joint extension. In other words, hip joint extension is a motion for moving forward by kicking back the ground. This is the reason why hamstrings is important in sprint.

Extending the hip joint, Whole body will be carried forward by ground reaction force. 

Not to change the subject, quadriceps-femoris-muscle (QFM) has just the opposite function of hamstrings' it. That is, quadriceps-femoris-muscle causes hip joint flexion and knee extension. In short, Hamstrings and quadriceps-femoris-muscle antagonize each other.

    

By the way, knee extension also is used for kicking and pushing the ground as same as hip joint extension. But there is a great difference between "hip joint extension" and "knee extension".

That is, knee extension is a movement of swinging forward the leg region. So, if you put your left leg in front of body and extend its knee joint, your body will be moved back by ground reaction force.  Because you kicked forward the ground with knee extension.

In other words, knee extension is a motion for moving back (or stoping) by kicking the ground forward. As an evidence of it, football players tend to have much developed quadriceps-femoris-muscle trained in many opportunity of sudden stopping.

Now, we got the answer of question "Why hamstrings is important for sprint?". On the other had, in the case of batting and pitching motion, back leg kicks the ground back for pushing hip forward. And this motion causes hip rotation. Thus, in the case of batting and pitching motion, hip joint extension is used for generating the torque power. So, hip joint extension due to the hamstrings contraction is important for batting and pitching motion as same as sprint.

So then, what should we do for using power of hamstrings effectively? As a premise of this theme, extended muscle can generate more large power than loosened muscle. It can be explained in metaphor of rubber string.

And if pelvis tilts forward, hamstrings is extended and quadriceps-femoris-muscle is loosened. And if pelvis tilts back, hamstrings is loosened and quadriceps-femoris-muscle is extended. So, for using hamstrings effectively, pelvis tilts forward is very important.

Thus, pelvis-tilt-forward makes it  easy to use the power of hamstrings. And this is the reason why african people have been producing many medalist in sprint. In general, african people's pelvis are tilted forward more than other races' it. For example, James Brown has well tilted forward pelvis.

James Brown


And according my observation, following players have well tilted forward pelvis.

Michael Pineda (http://www.youtube.com/watch?v=PTDJk8lZ71c&feature=plcp)
Andrew McCutchen (http://www.youtube.com/watch?v=Stl3QK4UBcc&feature=plcp)
Adrian Beltre (http://www.youtube.com/watch?v=0kDIBEkUd5Q&feature=plcp)
Johnny cueto (http://www.youtube.com/watch?v=WbQI2INt49U&feature=plcp)
Justin.Upton (http://www.youtube.com/watch?v=0J4P0X2oJf4&feature=plcp)
Aroldis Chapman (http://www.youtube.com/watch?v=O705rxi5MBo&feature=plcp)

So why african people's pelvis tilt more forward than other race's it? The answer is that their iliopsoas muscle is much developed more than other races' it.  Iliopsoas muscle has a function of tilting pelvis forward. (Pelvis tilts forward by contraction of iliopsoas muscle.) And hamstrings is extended by tilting forward of pelvis.

iliopsoas muscle

So, next can be said.

African people have much developed iliopsoas muscle. → Their pelvis are tilted forward by iliopsoas muscle.→ Their hamstrings are much extended by tilted forward pelvis. → They can extend their hip joint strongly by contraction of hamstrings. → African people tend to be able to run fast.

As this video indicates, African people hold an unchallenged position in top ranked 100 meter sprint.


However, it is important that don't tilt the pelvis consciously.

In the first place, african people does not tilt their pelvis consciously. Their pelvis is tilted forward by nature. And if you tilt your pelvis forward consciously, your vertebral column will make warp like a heated board. Because conscious pelvis-tilt-forward is led by erector-spinae-muscles contraction.

Originally, vertebral column (spine) has a "S" curve like a figure below and it is called as "natural S curve of spine". On the other hand, Conscious pelvis-tilt-forward is led by erector-spinae-muscles contraction. And it makes a warp on whole of vertebral column. So, in the case of conscious pelvis-tilt-forward, you cannot keep the natural "S" curve of spine. This is the reason why you should not tilt your pelvis forward consciously.

On the other hand, African people's pelvis-tilt-forward is caused by iliopsoas muscle contraction. So their spine can keep the correct "S" curve because iliopsoas muscle pulls only lumbar spine front. For example, Dexter fowler's, Alex Rios's, and Michael Brantley's vertebral column clearly shows the natural "S" curve of spine.

As indicated in above illustration, iliopsoas muscle contraction causes lumbar-spine-lordosis by pulling lumbar spine front.

Watching these two guys dancing in following video, you can clearly see the natural "S" curve of spine on the both of them.


And because lumbar-spine-lordosis was caused and emphasized by iliopsoas muscle contraction, thoracic-spine-kyphosis is also emphasized by weight of head and upper torso. This is the mechanics of forming the correct "S" curve in spine. So, in many cases, thoracic-spine-kyophosis can clearly be sean in people having well tilted forward pelvis.

Ray Charles has a good "S" curve of spine too. Though he is sitting, he can step strongly because of he can effectively use the power of hip joint extension due to pelvis-tilt-forward.

good and bad way of sitting

Further, according my observation, following players clearly show the thoracic-spine-kyophosis which seems to be with pelvis-tilt-forward.

Alex Rios (http://www.youtube.com/watch?v=-mSc-GuCiiE&feature=plcp)
Carlos Lee (http://www.youtube.com/watch?v=v_GrS3A-hRQ&feature=plcp)
Robinson Cano (http://www.youtube.com/watch?v=qCHEbrmeBzY&feature=plcp)
Brandon Belt (http://www.youtube.com/watch?v=9xSDKP-lmHk&feature=plcp)
Hunter Pence (http://www.youtube.com/watch?v=zLHfeMVHas4&feature=plcp)
David Ortiz (http://www.youtube.com/watch?v=-3h4QOKwHMM&feature=plcp)
Scott Podsednik (http://www.youtube.com/watch?v=ac8XIkl4pI0&feature=plcp)
Jeff Francoeur (http://www.youtube.com/watch?v=vUQCXO3MLz4&feature=plcp) 
Drew Stubbs (http://www.youtube.com/watch?v=RjvP8nGGcRg&feature=plcp)
Carlos Pena (http://www.youtube.com/watch?v=xngkA4XgiF4&feature=plcp)
Michael Brantley (http://www.youtube.com/watch?v=OF_xx0WO7ys&feature=plcp)
Jeff Bianchi (http://www.youtube.com/watch?v=htW7qAEkZFw&feature=plcp)
Dexter Fowler (http://www.youtube.com/watch?v=sG0T60dXIVQ&feature=plcp)

By the way, as mentioned above, hamstrings and iliopsoas muscle are keystone of high performance in various sports.  So should we train these muscles with weight training? Needless to say, it has been attempted already in japan, mainly in track and field world. But that attempt couldn't produce remarkable results at least. And that failure gives us an important suggestion about this theme.

~ difficulty of training of hamstrings and iliopsoas muscle ~

In general, weight training causes muscle becoming hard and short. If hamstrings become short by weight training like leg curl, pelvis will tilt back by tension of hamstrings. As a result of pelvis-tilt-back, hamstrings become loose and it makes difficult to produce the power of hip joint extension.  In short, it has the opposite effect.

Then, what about iliopsoas muscle? Iliopsoas muscle has a function of folding body down like a scissors. Consequently, well known trainings of iliopsoas muscle are divided into two types : high-knee type exercise and sit-up type exercise.

First, high-knee type exercise is a training of quadriceps-femoris-muscle. So, in this training, antagonize muscle of hamstrings will be developed. It is the opposite effect too.

Next, sit-up type exercise is a training of abdominal muscle. If abdominal muscle becomes short by sit-up exercise, pelvis will be tilted back by tension of abdominal muscle. So, it also is the opposite effect too.

Thus, weight training of hamstrings and iliopsoas muscle have the opposite effect in many cases. So, how to train these two important muscles?  I will explain those mainly in chapter ●.