********************************************* STRETCHING AND FLEXIBILITY: Everything you never wanted to know (Part 1 of 4) ********************************************* by Brad Appleton Version: 1.27, Last Modified 95/05/19 Copyright (C) 1993, 1994, 1995 by Bradford D. Appleton Permission is granted to make and distribute verbatim copies of this document provided the copyright notice and this permission notice are preserved on all copies. This document is available in ascii, texinfo, postscript, dvi, and html formats via anonymous ftp from the host `cs.huji.ac.il'. Look under the directory `/pub/doc/faq/rec/martial.arts'. The file name matches the wildcard pattern `stretching.*'. The file suffix indicates the format. For WWW users, the URL is: http://www.cs.huji.ac.il/papers/rma/stretching_toc.html. ------------------------------ Subject: What's New This Month There are no changes this month. However, I am looking for a new anonymous FTP site at which to archive this FAQ in its available formats. Please send me e-mail if you know of or can provide such a site. ------------------------------ Subject: Table of Contents All section titles in this document begin with the prefix "Subject: ". If you wish, you may scan ahead to a particular section by searching for the regular expression /^Subject: SECTION-NAME/. For example, to go to the unnumbered section named "Introduction", you could scan for /^Subject: Intro/; to go to section 1.1, you could scan for /^Subject: 1\.1/; and to go to appendix A, you could scan for /^Subject: Appendix A/. This document is organized into the following sections: PART 1: Introduction Disclaimer Acknowledgements About the Author 1 - Physiology of Stretching 1.1 - The Musculoskeletal System 1.2 - Muscle Composition 1.2.1 - How Muscles Contract 1.2.2 - Fast and Slow Muscle Fibers 1.3 - Connective Tissue 1.4 - Cooperating Muscle Groups 1.5 - Types of Muscle Contractions 1.6 - What Happens When You Stretch 1.6.1 - Proprioceptors 1.6.2 - The Stretch Reflex 184.108.40.206 - Components of the Stretch Reflex 1.6.3 - The Lengthening Reaction 1.6.4 - Reciprocal Inhibition PART 2: 2 - Flexibility 2.1 - Types of Flexibility 2.2 - Factors Limiting Flexibility 2.2.1 - How Connective Tissue Affects Flexibility 2.2.2 - How Aging Affects Flexibility 2.3 - Strength and Flexibility 2.3.1 - Why Bodybuilders Should Stretch 2.3.2 - Why Contortionists Should Strengthen 2.4 - Overflexibility 3 - Types of Stretching 3.1 - Ballistic Stretching 3.2 - Dynamic Stretching 3.3 - Active Stretching 3.4 - Passive Stretching 3.5 - Static Stretching 3.6 - Isometric Stretching 3.6.1 - How Isometric Stretching Works 3.7 - PNF Stretching 3.7.1 - How PNF Stretching Works PART 3: 4 - How to Stretch 4.1 - Warming Up 4.1.1 - General Warm-Up 220.127.116.11 - Joint Rotations 18.104.22.168 - Aerobic Activity 4.1.2 - Warm-Up Stretching 22.214.171.124 - Static Warm-Up Stretching 126.96.36.199 - Dynamic Warm-Up Stretching 4.1.3 - Sport-Specific Activity 4.2 - Cooling Down 4.3 - Massage 4.4 - Elements of a Good Stretch 4.4.1 - Isolation 4.4.2 - Leverage 4.4.3 - Risk 4.5 - Some Risky Stretches 4.6 - Duration, Counting, and Repetition 4.7 - Breathing During Stretching 4.8 - Exercise Order 4.9 - When to Stretch 4.9.1 - Early-Morning Stretching 4.10 - Stretching With a Partner 4.11 - Stretching to Increase Flexibility 4.12 - Pain and Discomfort 4.12.1 - Common Causes of Muscular Soreness 4.12.2 - Stretching with Pain 4.12.3 - Overstretching 4.13 - Performing Splits 4.13.1 - Common Problems When Performing Splits 4.13.2 - The Front Split 4.13.3 - The Side Split 4.13.4 - Split-Stretching Machines PART 4: Appendix A - References on Stretching A.1 - Recommendations A.2 - Additional Comments Appendix B - Working Toward the Splits B.1 - lower back stretches B.2 - lying buttock stretch B.3 - groin and inner-thigh stretch B.4 - seated leg stretches B.4.1 - seated calf stretch B.4.2 - seated hamstring stretch B.4.3 - seated inner-thigh stretch B.5 - psoas stretch B.6 - quadricep stretch B.7 - lying `V' stretch Appendix C - Normal Ranges of Joint Motion C.1 - Neck C.2 - Lumbar Spine C.3 - Shoulder C.4 - Elbow C.5 - Wrist C.6 - Hip C.7 - Knee C.8 - Ankle Index ------------------------------ Subject: Introduction This document is a modest attempt to compile a wealth of information in order to answer some frequently asked questions about stretching and flexibility. It is organized into chapters covering the following topics: 1. Physiology of Stretching 2. Flexibility 3. Types of Stretching 4. How to Stretch Although each chapter may refer to sections in other chapters, it is not required that you read every chapter in the order presented. It is important, however, that you read the disclaimer before reading any other sections of this document. (See "Disclaimer"). If you wish to skip around, numerous cross references are supplied in each section to help you find the concepts you may have missed. There is also an index at the end of this document. ------------------------------ Subject: Disclaimer Although every effort has been made to ensure that all information presented in this document is accurate, errors may still be present. If you notice any errors, please send corrections via e-mail to `Brad_Appleton@ivhs.mot.com'. THE AUTHOR MAKES NO WARRANTY OF ANY KIND IN REGARD TO THE CONTENT OF THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, OR FITNESS FOR ANY PARTICULAR PURPOSE. THE AUTHOR OF THIS DOCUMENT SHALL NOT BE LIABLE FOR ERRORS CONTAINED IN IT, OR FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES IN CONNECTION WITH THE FURNISHING OF, USE OF, OR RELIANCE UPON INFORMATION CONTAINED IN THIS DOCUMENT. In other words: "I'm not a doctor, nor do I play one on TV!" I can not be held liable for any damages or injuries that you might suffer from somehow relying upon information in this document, no matter how awful. Not even if the information in question is incorrect or inaccurate. ------------------------------ Subject: Acknowledgements Thanks to all the readers of the `rec.martial-arts', `rec.arts.dance' and `misc.fitness' newsgroups on Usenet who responded to my request for questions (and answers) on stretching. Many parts of this document come directly from these respondents. Thanks in particular to Shawne Neeper for sharing her formidable knowledge of muscle anatomy and physiology. Other portions of this document have been taken from the following books: `Sport Stretch', by Michael J. Alter (referred to as M. Alter in the rest of this document) `Stretching Scientifically', by Tom Kurz (referred to as Kurz in the rest of this document) `SynerStretch For Total Body Flexibility', from Health For Life (referred to as `SynerStretch' in the rest of this document) `The Health For Life Training Advisor', also from Health For Life (referred to as `HFLTA' in the rest of this document) `Mobility Training for the Martial Arts', by Tony Gummerson (referred to as Gummerson in the rest of this document) Further information on these books and others, is available near the end of this document. (See "Appendix A - References on Stretching"). ------------------------------ Subject: About the Author I am *not* an expert in anatomy or physiology! I do have over 6 years of martial arts training, and over 20 years of dance training in classical ballet, modern, and jazz. However, my primary "qualifications" to write this document are that I took considerable time and effort to read several books on the topic, and to combine the information that I read with the information supplied to me from many knowledgeable readers of Usenet news. I have tried to write this document for all audiences and not make it specific to any particular sport or art (such as dancing or martial arts). I have also tried to leave out any of my own personal opinions or feelings and just state the facts as related to me by the *real* experts. I am always interested in hearing about any new information which would be appropriate to add to this document. If you have any such information about a stretching technique, a book, or anything else you can think of, please feel free to contact me. All I ask is that you be prepared to provide me with at least one reputable and reliable source for your information. ------------------------------ Subject: 1 - Physiology of Stretching The purpose of this chapter is to introduce you to some of the basic physiological concepts that come into play when a muscle is stretched. Concepts will be introduced initially with a general overview and then (for those who want to know the gory details) will be discussed in further detail. If you aren't all that interested in this aspect of stretching, you can skip this chapter. Other sections will refer to important concepts from this chapter and you can easily look them up on a "need to know" basis. ------------------------------ Subject: 1.1 - The Musculoskeletal System Together, muscles and bones comprise what is called the "musculoskeletal system" of the body. The bones provide posture and structural support for the body and the muscles provide the body with the ability to move (by contracting, and thus generating tension). The musculoskeletal system also provides protection for the body's internal organs. In order to serve their function, bones must be joined together by something. The point where bones connect to one another is called a "joint", and this connection is made mostly by "ligaments" (along with the help of muscles). Muscles are attached to the bone by "tendons". Bones, tendons, and ligaments do not possess the ability (as muscles do) to make your body move. Muscles are very unique in this respect. ------------------------------ Subject: 1.2 - Muscle Composition Muscles vary in shape and in size, and serve many different purposes. Most large muscles, like the hamstrings and quadriceps, control motion. Other muscles, like the heart, and the muscles of the inner ear, perform other functions. At the microscopic level however, all muscles share the same basic structure. At the highest level, the (whole) muscle is composed of many strands of tissue called "fascicles". These are the strands of muscle that we see when we cut red meat or poultry. Each fascicle is composed of "fasciculi" which are bundles of "muscle fibers". The muscle fibers are in turn composed of tens of thousands of thread-like "myofybrils", which can contract, relax, and elongate (lengthen). The myofybrils are (in turn) composed of up to millions of bands laid end-to-end called "sarcomeres". Each sarcomere is made of overlapping thick and thin filaments called "myofilaments". The thick and thin myofilaments are made up of "contractile proteins", primarily actin and myosin. ------------------------------ Subject: 1.2.1 - How Muscles Contract The way in which all these various levels of the muscle operate is as follows: Nerves connect the spinal column to the muscle. The place where the nerve and muscle meet is called the "neuromuscular junction". When an electrical signal crosses the neuromuscular junction, it is transmitted deep inside the muscle fibers. Inside the muscle fibers, the signal stimulates the flow of calcium which causes the thick and thin myofilaments to slide across one another. When this occurs, it causes the sarcomere to shorten, which generates force. When billions of sarcomeres in the muscle shorten all at once it results in a contraction of the entire muscle fiber. When a muscle fiber contracts, it contracts completely. There is no such thing as a partially contracted muscle fiber. Muscle fibers are unable to vary the intensity of their contraction relative to the load against which they are acting. If this is so, then how does the force of a muscle contraction vary in strength from strong to weak? What happens is that more muscle fibers are recruited, as they are needed, to perform the job at hand. The more muscle fibers that are recruited by the central nervous system, the stronger the force generated by the muscular contraction. ------------------------------ Subject: 1.2.2 - Fast and Slow Muscle Fibers The energy which produces the calcium flow in the muscle fibers comes from "mitochondria", the part of the muscle cell that converts glucose (blood sugar) into energy. Different types of muscle fibers have different amounts of mitochondria. The more mitochondria in a muscle fiber, the more energy it is able to produce. Muscle fibers are categorized into "slow-twitch fibers" and "fast-twitch fibers". Slow-twitch fibers (also called "Type 1 muscle fibers") are slow to contract, but they are also very slow to fatigue. Fast-twitch fibers are very quick to contract and come in two varieties: "Type 2A muscle fibers" which fatigue at an intermediate rate, and "Type 2B muscle fibers" which fatigue very quickly. The main reason the slow-twitch fibers are slow to fatigue is that they contain more mitochondria than fast-twitch fibers and hence are able to produce more energy. Slow-twitch fibers are also smaller in diameter than fast-twitch fibers and have increased capillary blood flow around them. Because they have a smaller diameter and an increased blood flow, the slow-twitch fibers are able to deliver more oxygen and remove more waste products from the muscle fibers (which decreases their "fatigability"). These three muscle fiber types (Types 1, 2A, and 2B) are contained in all muscles in varying amounts. Muscles that need to be contracted much of the time (like the heart) have a greater number of Type 1 (slow) fibers. According to `HFLTA': When a muscle begins to contract, primarily Type 1 fibers are activated first, then Type 2A, then 2B. This sequence of fiber recruitment allows very delicate and finely tuned muscle responses to brain commands. It also makes Type 2B fibers difficult to train; most of the Type 1 and 2A fibers have to be activated already before a large percentage of the 2B fibers participate. `HFLTA' further states that the the best way to remember the difference between muscles with predominantly slow-twitch fibers and muscles with predominantly fast-twitch fibers is to think of "white meat" and "dark meat". Dark meat is dark because it has a greater number of slow-twitch muscle fibers and hence a greater number of mitochondria, which are dark. White meat consists mostly of muscle fibers which are at rest much of the time but are frequently called on to engage in brief bouts of intense activity. This muscle tissue can contract quickly but is fast to fatigue and slow to recover. White meat is lighter in color than dark meat because it contains fewer mitochondria. ------------------------------ Subject: 1.3 - Connective Tissue Located all around the muscle and its fibers are "connective tissues". Connective tissue is composed of a base substance and two kinds of protein based fiber. The two types of fiber are "collagenous connective tissue" and "elastic connective tissue". Collagenous connective tissue consists mostly of collagen (hence its name) and provides tensile strength. Elastic connective tissue consists mostly of elastin and (as you might guess from its name) provides elasticity. The base substance is called "mucopolysaccharide" and acts as both a lubricant (allowing the fibers to easily slide over one another), and as a glue (holding the fibers of the tissue together into bundles). The more elastic connective tissue there is around a joint, the greater the range of motion in that joint. Connective tissues are made up of tendons, ligaments, and the fascial sheaths that envelop, or bind down, muscles into separate groups. These fascial sheaths, or "fascia", are named according to where they are located in the muscles: "endomysium" The innermost fascial sheath that envelops individual muscle fibers. "perimysium" The fascial sheath that binds groups of muscle fibers into individual fasciculi (See "1.2 - Muscle Composition"). "epimysium" The outermost fascial sheath that binds entire fascicles (See "1.2 - Muscle Composition"). These connective tissues help provide suppleness and tone to the muscles. ------------------------------ Subject: 1.4 - Cooperating Muscle Groups When muscles cause a limb to move through the joint's range of motion, they usually act in the following cooperating groups: "agonists" These muscles cause the movement to occur. They create the normal range of movement in a joint by contracting. Agonists are also referred to as "prime movers" since they are the muscles that are primarily responsible for generating the movement. "antagonists" These muscles act in opposition to the movement generated by the agonists and are responsible for returning a limb to its initial position. "synergists" These muscles perform, or assist in performing, the same set of joint motion as the agonists. Synergists are sometimes referred to as "neutralizers" because they help cancel out, or neutralize, extra motion from the agonists to make sure that the force generated works within the desired plane of motion. "fixators" These muscles provide the necessary support to assist in holding the rest of the body in place while the movement occurs. Fixators are also sometimes called "stabilizers". As an example, when you flex your knee, your hamstring contracts, and, to some extent, so does your gastrocnemius (calf) and lower buttocks. Meanwhile, your quadriceps are inhibited (relaxed and lengthened somewhat) so as not to resist the flexion (See "1.6.4 - Reciprocal Inhibition"). In this example, the hamstring serves as the agonist, or prime mover; the quadricep serves as the antagonist; and the calf and lower buttocks serve as the synergists. Agonists and antagonists are usually located on opposite sides of the affected joint (like your hamstrings and quadriceps, or your triceps and biceps), while synergists are usually located on the same side of the joint near the agonists. Larger muscles often call upon their smaller neighbors to function as synergists. The following is a list of commonly used agonist/antagonist muscle pairs: * pectorals/latissimus dorsi (pecs and lats) * anterior deltoids/posterior deltoids (front and back shoulder) * trapezius/deltoids (traps and delts) * abdominals/spinal erectors (abs and lower-back) * left and right external obliques (sides) * quadriceps/hamstrings (quads and hams) * shins/calves * biceps/triceps * forearm flexors/extensors ------------------------------ Subject: 1.5 - Types of Muscle Contractions The contraction of a muscle does not necessarily imply that the muscle shortens; it only means that tension has been generated. Muscles can contract in the following ways: "isometric contraction" This is a contraction in which no movement takes place, because the load on the muscle exceeds the tension generated by the contracting muscle. This occurs when a muscle attempts to push or pull an immovable object. "isotonic contraction" This is a contraction in which movement *does* take place, because the tension generated by the contracting muscle exceeds the load on the muscle. This occurs when you use your muscles to successfully push or pull an object. Isotonic contractions are further divided into two types: "concentric contraction" This is a contraction in which the muscle decreases in length (shortens) against an opposing load, such as lifting a weight up. "eccentric contraction" This is a contraction in which the muscle increases in length (lengthens) as it resists a load, such as pushing something down. During a concentric contraction, the muscles that are shortening serve as the agonists and hence do all of the work. During an eccentric contraction the muscles that are lengthening serve as the agonists (and do all of the work). (See "1.4 - Cooperating Muscle Groups"). ------------------------------ Subject: 1.6 - What Happens When You Stretch The stretching of a muscle fiber begins with the sarcomere (See "1.2 - Muscle Composition"), the basic unit of contraction in the muscle fiber. As the sarcomere contracts, the area of overlap between the thick and thin myofilaments increases. As it stretches, this area of overlap decreases, allowing the muscle fiber to elongate. Once the muscle fiber is at its maximum resting length (all the sarcomeres are fully stretched), additional stretching places force on the surrounding connective tissue (See "1.3 - Connective Tissue"). As the tension increases, the collagen fibers in the connective tissue align themselves along the same line of force as the tension. Hence when you stretch, the muscle fiber is pulled out to its full length sarcomere by sarcomere, and then the connective tissue takes up the remaining slack. When this occurs, it helps to realign any disorganized fibers in the direction of the tension. This realignment is what helps to rehabilitate scarred tissue back to health. When a muscle is stretched, some of its fibers lengthen, but other fibers may remain at rest. The current length of the entire muscle depends upon the number of stretched fibers. According to `SynerStretch': Picture little pockets of fibers distributed throughout the muscle body stretching, and other fibers simply going along for the ride. Just as the total strength of a contracting muscle is a result of the number of fibers contracting, the total length of a stretched muscle is a result of the number of fibers stretched - the more fibers stretched, the more length developed by the muscle for a given stretch. ------------------------------ Subject: 1.6.1 - Proprioceptors The nerve endings that relay all the information about the musculoskeletal system to the central nervous system are called "proprioceptors". Proprioceptors (also called "mechanoreceptors") are the source of all "proprioception": the perception of one's own body position and movement. The proprioceptors detect any changes in physical displacement (movement or position) and any changes in tension, or force, within the body. They are found in all nerve endings of the joints, muscles, and tendons. The proprioceptors related to stretching are located in the tendons and in the muscle fibers. There are two kinds of muscle fibers: "intrafusal muscle fibers" and "extrafusal muscle fibers". Extrafusil fibers are the ones that contain myofibrils (See "1.2 - Muscle Composition") and are what is usually meant when we talk about muscle fibers. Intrafusal fibers are also called "muscle spindles" and lie parallel to the extrafusal fibers. Muscle spindles, or "stretch receptors", are the primary proprioceptors in the muscle. Another proprioceptor that comes into play during stretching is located in the tendon near the end of the muscle fiber and is called the "golgi tendon organ". A third type of proprioceptor, called a "pacinian corpuscle", is located close to the golgi tendon organ and is responsible for detecting changes in movement and pressure within the body. When the extrafusal fibers of a muscle lengthen, so do the intrafusal fibers (muscle spindles). The muscle spindle contains two different types of fibers (or stretch receptors) which are sensitive to the change in muscle length and the rate of change in muscle length. When muscles contract it places tension on the tendons where the golgi tendon organ is located. The golgi tendon organ is sensitive to the change in tension and the rate of change of the tension. ------------------------------ Subject: 1.6.2 - The Stretch Reflex When the muscle is stretched, so is the muscle spindle (See "1.6.1 - Proprioceptors"). The muscle spindle records the change in length (and how fast) and sends signals to the spine which convey this information. This triggers the "stretch reflex" (also called the "myotatic reflex") which attempts to resist the change in muscle length by causing the stretched muscle to contract. The more sudden the change in muscle length, the stronger the muscle contractions will be (plyometric, or "jump", training is based on this fact). This basic function of the muscle spindle helps to maintain muscle tone and to protect the body from injury. One of the reasons for holding a stretch for a prolonged period of time is that as you hold the muscle in a stretched position, the muscle spindle habituates (becomes accustomed to the new length) and reduces its signaling. Gradually, you can train your stretch receptors to allow greater lengthening of the muscles. Some sources suggest that with extensive training, the stretch reflex of certain muscles can be controlled so that there is little or no reflex contraction in response to a sudden stretch. While this type of control provides the opportunity for the greatest gains in flexibility, it also provides the greatest risk of injury if used improperly. Only consummate professional athletes and dancers at the top of their sport (or art) are believed to actually possess this level of muscular control. ------------------------------ Subject: 188.8.131.52 - Components of the Stretch Reflex The stretch reflex has both a dynamic component and a static component. The static component of the stretch reflex persists as long as the muscle is being stretched. The dynamic component of the stretch reflex (which can be very powerful) lasts for only a moment and is in response to the initial sudden increase in muscle length. The reason that the stretch reflex has two components is because there are actually two kinds of intrafusal muscle fibers: "nuclear chain fibers", which are responsible for the static component; and "nuclear bag fibers", which are responsible for the dynamic component. Nuclear chain fibers are long and thin, and lengthen steadily when stretched. When these fibers are stretched, the stretch reflex nerves increase their firing rates (signaling) as their length steadily increases. This is the static component of the stretch reflex. Nuclear bag fibers bulge out at the middle, where they are the most elastic. The stretch-sensing nerve ending for these fibers is wrapped around this middle area, which lengthens rapidly when the fiber is stretched. The outer-middle areas, in contrast, act like they are filled with viscous fluid; they resist fast stretching, then gradually extend under prolonged tension. So, when a fast stretch is demanded of these fibers, the middle takes most of the stretch at first; then, as the outer-middle parts extend, the middle can shorten somewhat. So the nerve that senses stretching in these fibers fires rapidly with the onset of a fast stretch, then slows as the middle section of the fiber is allowed to shorten again. This is the dynamic component of the stretch reflex: a strong signal to contract at the onset of a rapid increase in muscle length, followed by slightly "higher than normal" signaling which gradually decreases as the rate of change of the muscle length decreases. ------------------------------ Subject: 1.6.3 - The Lengthening Reaction When muscles contract (possibly due to the stretch reflex), they produce tension at the point where the muscle is connected to the tendon, where the golgi tendon organ is located. The golgi tendon organ records the change in tension, and the rate of change of the tension, and sends signals to the spine to convey this information (See "1.6.1 - Proprioceptors"). When this tension exceeds a certain threshold, it triggers the "lengthening reaction" which inhibits the muscles from contracting and causes them to relax. Other names for this reflex are the "inverse myotatic reflex", "autogenic inhibition", and the "clasped-knife reflex". This basic function of the golgi tendon organ helps to protect the muscles, tendons, and ligaments from injury. The lengthening reaction is possible only because the signaling of golgi tendon organ to the spinal cord is powerful enough to overcome the signaling of the muscle spindles telling the muscle to contract. Another reason for holding a stretch for a prolonged period of time is to allow this lengthening reaction to occur, thus helping the stretched muscles to relax. It is easier to stretch, or lengthen, a muscle when it is not trying to contract. ------------------------------ Subject: 1.6.4 - Reciprocal Inhibition When an agonist contracts, in order to cause the desired motion, it usually forces the antagonists to relax (See "1.4 - Cooperating Muscle Groups"). This phenomenon is called "reciprocal inhibition" because the antagonists are inhibited from contracting. This is sometimes called "reciprocal innervation" but that term is really a misnomer since it is the agonists which inhibit (relax) the antagonists. The antagonists do *not* actually innervate (cause the contraction of) the agonists. Such inhibition of the antagonistic muscles is not necessarily required. In fact, co-contraction can occur. When you perform a sit-up, one would normally assume that the stomach muscles inhibit the contraction of the muscles in the lumbar, or lower, region of the back. In this particular instance however, the back muscles (spinal erectors) also contract. This is one reason why sit-ups are good for strengthening the back as well as the stomach. When stretching, it is easier to stretch a muscle that is relaxed than to stretch a muscle that is contracting. By taking advantage of the situations when reciprocal inhibition *does* occur, you can get a more effective stretch by inducing the antagonists to relax during the stretch due to the contraction of the agonists. You also want to relax any muscles used as synergists by the muscle you are trying to stretch. For example, when you stretch your calf, you want to contract the shin muscles (the antagonists of the calf) by flexing your foot. However, the hamstrings use the calf as a synergist so you want to also relax the hamstrings by contracting the quadricep (i.e., keeping your leg straight). ------------------------------ Brad_Appleton@ivhs.mot.com Motorola PNSB, Northbrook, IL USA "And miles to go before I sleep." DISCLAIMER: I said it, not my employer!