“Exposes the dangers of some well-known and often-used stretches.” —Calgary Herald
The Stark Reality of Stretching: For All Activities and Every Sport Focusing on the Weight Bearing Muscles of the Lower Extremitiesby Dr. Steven D. Stark
A comprehensive operator’s manual for the body, this newly updated guide provides the science, anatomy, precise definitions, and illustrations necessary for the proper application of knowledge to help keep the body healthy. It provides a current and concise understanding of why people should stretch, what a stretch is, and how to stretch properly. The
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A comprehensive operator’s manual for the body, this newly updated guide provides the science, anatomy, precise definitions, and illustrations necessary for the proper application of knowledge to help keep the body healthy. It provides a current and concise understanding of why people should stretch, what a stretch is, and how to stretch properly. The accurate, science-based stretching information provided here will help prevent dangerous muscle imbalances and common, incorrect stretches that often cause or contribute to functional damage of the feet, knees, hips, pelvis, and spine.
- Dr. Steven D. Stark Podiatric Corp.
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The Stark Reality of Stretching
By Steven D. Stark, Diana C. Douglas
Dr. Steven D. Stark Podiatric CorpCopyright © 1997 Dr. Steven D. Stark
All rights reserved.
Essentially, there are three types of joints:
1. Extremely stable and virtually immovable joints, like the cranium.
2. Slightly movable joints, like the sacroiliac joints of the pelvis.
3. Freely movable or synovial joints, like the knee and ankle.
The joints of the lower extremities are: the hip, knee, ankle, and the numerous joints of the foot. All of these joints are synovial joints.
Joints are places of union or junction between two bones to allow motion. The two bones are joined together by ligaments, and there is articular cartilage between the bones to provide the smooth surface to allow gliding motion.
Joints allow motion in order to provide mobility for the body.
Joint stability is provided by the ligaments that connect the bones and limit abnormal motion of the joint, by the shape of the joint, and by other connective tissues such as the joint capsules.
Joint motion is produced by contraction of the muscles whose tendons cross that joint.
C. Potential Injuries
Stable joints, like the hips, provide limited movement. Less stable joints, like the wrist, allow a wide range of motion. Although less stable joints are more easily damaged, all joints and their connective tissues can be harmed when they are forced beyond their normal range of motion.
II. CONNECTIVE TISSUE
Tendons, ligaments and fascia are comprised of connective tissue. Connective tissue is a mixture of collagenous and elastin fibers. Connective tissues are the fibrous cords that bind the individual body structures together. The differences in structure and function of collagen and elastin are very important. These differences are explained below.
A. Composition of Connective Tissue
Connective tissue is composed of two kinds of fibers: collagenous and elastic fibers.
Collagenous fibers, rich in protein, are essentially non-elastic.
Elastic fibers are characterized by the presence of the elastin protein. These fibers can be stretched, and when tension is relaxed will shorten again. They are combined with the more numerous collagenous fibers in varying amounts in connective tissue. The increased elasticity of specific ligaments and muscle fascia results from an increased percentage of elastin protein mixed with the collagen fibers.
The greatest proportion of tissue in tendons, ligaments, and fascia is collagenous fibers. The amount of elastin fibers in these structures varies with the purpose of the structure.
Tendons are composed almost entirely of collagen fibers because they are not meant to stretch, while the muscle fascia has a higher concentration of elastin fibers so that it can elongate and contract.
As a person grows older, the elasticity of the connective tissue tends to deteriorate. This tendency is accelerated by inactivity, postural misalignment and muscle imbalances.
B. Types of Connective Tissue
Definition and Purpose
Tendons are the most inelastic connective tissue in the body. They are the tough connective tissue that attaches muscle to bone. All muscles have a tendon of origin (where they originate from a bone) and a tendon of insertion (where the other end attaches by tendon to bone). The tendon of origin is usually attached to the more stable bone, while the tendon of insertion is attached to the more moveable bone.
Tendons consist almost entirely of heavy, inelastic collagen fibers that are stronger than both the muscle and the bone covering (periosteum) that the tendon attaches to.
Tendons can be partially torn or completely ruptured if loaded beyond their tensile strength. However, since the tendon has a higher tensile strength than the muscle or the bone covering (periosteum), most excessive loads on the tendon result in tearing of the muscle tissue or the periosteum of the bone.
This means that TENDONS CANNOT BE STRETCHED. Composed of inelastic collagen fibers, a weight of ten thousand times the molecular weight of the tendon will not stretch the tendon (Verzar, 1963).
Research indicates that microscopic fibers of tendons can be stretched to a maximum of approximately 10% of their original length before they rupture. However, at the molecular level, the fibers (protofibrils) of the tendon undergo an extension of only about 3% (Ramachandran, 1967).
In another study, a stretch of 4% was significant and corresponds to the limit of reversibility, and therefore of elasticity. At this point, the tendon's surface waviness disappears, and if the stretch continues injury may result (Crisp, 1972).
The healthy tendon will not rupture with a major overload. Instead, the muscle belly will tear or rupture and separate from the tendon; and the tendon may tear the periosteum of the bone the tendon is attached to.
A classic example of this major overload is tearing the patella tendon (tendon avulsion) completely off the front of the shin bone (the tibial tuberosity) while jumping. NFL football players and NBA basketball players have suffered this type of functional injury.
Overstretching of muscle places a heavy load on the tendon. Since the tendon is inelastic (the maximum increase in length of the actual fibers of the tendon can only be 3–4%), what often results is a microscopic tearing of the muscle tissue or of the bone covering (periosteum).
The most common causes of damage and degeneration of tendons are extended stress due to postural changes, poor biomechanics, extended overuse, and excessive tightness in the muscle of that tendon.
Definition and Purpose
Ligaments are tough connective tissues that stabilize and reinforce joints by connecting bone to bone. They consist of almost pure collagenous fiber. The amount of elasticity is again determined by the amount of elastin protein the ligaments contain.
The ligaments of the spine and the foot contain the most elastin content, which is why they are the most elastic ligaments in the body. They are therefore the easiest to damage with over-extension.
The degree of elasticity in ligaments also varies with gender (in general, women have more ligament elasticity than men), age, and the level of physical fitness.
Although they are pliant and flexible, nearly all ligaments lose their ability to perform correctly when they are elongated by chronic over-extension. This is explained by the elastic and plastic properties of ligaments.
Elastic Deformity from Acute Overload
When a joint is forced into an abnormal position during movement, the ligament has an abnormal stress applied to it. The ligament can withstand enormous forces for a very brief time. If the force is not removed, or if it exceeds the tensile strength of the ligament, then the ligament tears or ruptures. This is an elastic deformity caused by acute or sudden overload.
A classic example of this is the ankle sprain (inversion injury of the ankle). Most of these injuries are tears or complete ruptures of one or more ligaments on the lateral aspect of the ankle joint. These injuries are more severe than commonly thought, and should have immediate and proper treatment with current therapy. It takes from eight to twelve weeks to regain tensile strength in a damaged ligament, and the joint must be protected during this period with taping or with a brace.
The torn part of the ligament heals by bridging the torn fibers with scar tissue (fibrosis). The ligament will always be slightly longer and less effective in stopping abnormal joint motion, and the scar tissue will never be as strong as the original tissue. This is often the site of more tearing, chronic weakness, and repeated injury.
Plastic Deformity from Chronic Overload
When a ligament is put under a continuous and protracted stress it will gradually elongate because of tearing, weakening and lengthening at a molecular level. This is called plastic deformity. A classic example is the damage done to the medial collateral ligaments of the knee in the incorrect "hurdler's stretch." This is explained in the section on Hamstring stretches in Chapter 16, Topic VI.
As the ligament elongates and weakens; the joint that should be stabilized by that ligament will have increased abnormal motion (hypermobility). The increasing joint hypermobility results in instability and chronic inflammation, which can cause joint damage and degenerative arthritis.
All ligaments can be permanently damaged and elongated if subjected to protracted stress from postural faults, poor biomechanics, or repetitive overstretching beyond their tensile strength.
Definition and Purpose
Fascia is the connective tissue which forms enveloping sheaths around the entire muscle and each individual muscle bundle (fasciculi).
Fascia consists principally of collagenous fibers, although the amount of elastic fibers varies with the functional activity of the muscle. The large muscles of the extremities have a limited amount of elastic tissue.
Fascia resist very high momentary tension stresses during body movement without rupturing. Protracted stress will result in permanent elongation. Fascia also has a strong tendency to shorten due to age, cold, poor posture, and muscular imbalance. This long-term shortening of the fascia shortens the muscle, reducing the range of motion across the joints of the body.
III. SKELETAL MUSCLE ANATOMY
There are three main types of muscle — skeletal muscle, smooth muscle (found in the internal organs) and heart muscle. In The Stark Reality of Stretching we are concerned with the skeletal muscles of the lower extremity: how they function, and how they stretch.
Skeletal muscles are the voluntary contractile tissues that move our skeletons about. They are attached directly via tendons to bones. There are more than 600 skeletal muscles in the body. These differ in size and shape according to their function.
There are six main muscle groups in the lower extremities that produce or stabilize motion:
1. the hip flexors
2. the muscles of the posterior hip (the gluteal muscles and external hip rotators)
3. the quadriceps
4. the hamstrings
5. the groin muscles (the adductors)
6. the calf muscles
Each of these muscles or muscle groups has tendons that cross a joint. The contractions of the muscles provide the movement of the joints.
This diagram illustrates that all skeletal muscle originates from a tendon, and the tendon attaches to the periosteum of the bone.
Muscles are made up of bundles called fasciculi.
The fasciculi are made up of a group of muscle fibers composed of myofibrils.
Myofibrils are made up of sarcomeres.
Each sarcomere contains two myofilaments.
Myofilaments are made up of units of overlapping proteins called myosin and actin.
Myosin molecules have a long rod-shaped tail, a shorter rod-shaped neck, and two globular heads which form the cross bridges that connect to the actin protein and produce the motion required for contraction of the muscle.
The action of the cross bridging and the energy cycle of muscle contraction is important. However, the molecular level of muscle function is very technical, and beyond the scope of this book. The purpose of this book is to give athletes, coaches, everyone, an accurate understanding of muscle function and stretching that have a practical application and that translates easily when taught to others.
How muscles function, the properties of muscles, and how muscles stretch are the subjects of the next chapters.CHAPTER 2
HOW MUSCLES FUNCTION
Muscles shorten and elongate in order to produce motion across a joint, or they contract without changing length to hold a body position. It is important to understand the different pathways nerves can use to produce contractions of the muscle in order to appreciate what a stretch is, and how to accomplish the stretch.
Skeletal muscle contractions are either conscious voluntary contractions when using the muscles to lift or move an object intentionally or involuntary contractions when the muscles contract in response to a loading force without conscious thought.
I. PATHWAYS OF NEUROMUSCULAR CONTROL
A. Voluntary Contractions
When a person lifts the lower leg using the hamstring muscles, the brain (upper motor neurons) sends a message (nerve impulse) down the spinal cord to the anterior horn cells (lower motor neurons).
The lower motor neurons are the anterior and posterior horn cells of the spinal cord. They are located throughout the spinal cord wherever the large nerve roots leave the spinal cord to enter the body.
The nerve impulse then travels from the spinal cord to the muscle fibers (the motor end plates). This nerve impulse causes the hamstring muscles to contract in order to produce motion and lift the leg. This is an example of the brain directing muscle contractions to produce conscious functions.
B. Involuntary (Reflex) Contractions
When a person bends forward from the waist in a standing position, the hamstrings contract to stabilize the pelvis against gravity. If the hamstrings relax, the person would fall forward. The person does not think about contracting the hamstrings, and CANNOT RELAX the hamstrings while in this position.
This is an example of a reflex contraction in response to gravity and balance; also known as a myotactic or proprioceptive reflex contraction.
This reflex contraction starts with a lengthening load on the hamstrings as the person leans forward. The nerve fibers in the muscle (the muscle spindles) react to the new load and lengthening caused by the forward bending. The muscle spindles send myotatic nerve impulses to the spinal cord (posterior horn cells), which direct the impulses to the anterior horn cells of the spinal cord, which route the impulses directly back to the motor end plates of the muscle, causing an involuntary contraction of the muscle. This is a "loop" of nerve cells from the muscle into the "back door" of the spinal cord, passed on through the "front door" of the spinal cord back to the muscles, causing them to contract.
There is no brain function (upper motor neuron) involved in the initial contraction of the hamstrings to stabilize the pelvis.
The involuntary contraction of the hamstrings continues in order to maintain a specific postural position against the pull of gravity. The involuntary contraction is maintained by the myotactic reflex caused by the proprioceptive sensors of the muscles and spinal cord. This becomes very important in the discussion on positioning in proper stretches.
C. Types of Contractions
All types of muscle contractions explained below can be caused by either voluntary or involuntary neuromuscular pathways.
Shortening (concentric) contractions are when
a muscle develops tension sufficient to overcome a resistance and produce work, causing the muscle to visibly shorten and move a body part against that resistance. In the individual sarcomeres of the muscles, the two myofilaments shorten by movement of the actin protein over the myosin protein toward the center of the sarcomere. This shortens the sarcomere from both ends, expends energy, and produces motion.
Example: When you lift your leg using the hamstring muscles, the individual sarcomeres are shortening. The muscles are shortening, expending energy and producing motion. This is a concentric contraction of the muscles.
Excerpted from The Stark Reality of Stretching by Steven D. Stark, Diana C. Douglas. Copyright © 1997 Dr. Steven D. Stark. Excerpted by permission of Dr. Steven D. Stark Podiatric Corp.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Meet the Author
Dr. Steven D. Stark was the first podiatrist appointed to the Sports Medicine Council of British Columbia. His medical practice specializes in the treatment and prevention of injuries that are the result of biomechanical problems caused by structural and functional changes. He lives in Surrey, British Columbia.
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