This is part one of a two-part series.
This article covers theoretical knowledge of stretching and flexibility. Part two focuses on innovative practical applications. Together, they will give you a multi-dimensional look at stretching and flexibility programs including the benefits, terminology, methods and practical applications to help you implement a variety of programs for your classes or personal training clientele.
Flexibility is one of the five accepted health-related components of physical fitness (along with muscular strength and endurance, cardio-respiratory endurance and body composition). These components of physical fitness are deemed "health related" because an improvement in any or all of them will lead to improvements in health and well-being. Recently, flexibility programming has become a controversial topic. Questions have arisen over the best type of stretches to implement in a workout, if static stretching is appropriate in a warm-up, if stretching exercises enhance sports performance or reduce certain exercise injuries, and if flexibility work has a measurement of progressive overload or indicators of overtraining.
Why has flexibility received so little attention in an industry that has positioned it as a main component of human fitness? Part of the problem in the past has been that most instructors have stopped at the base level of knowledge in the area of flexibility training. We figure out what body position will put a muscle in its elongated or stretched position, throw a few of these positions into our warm-ups and cool-downs and hope we hit the major muscle groups by the end of the training session. This simple approach is only the beginning of a good flexibility program. What needs to be developed is a greater understanding and application of different methods of flexibility training to enhance the real-life and activity-specific demands we commonly place upon our bodies.
There are advantages to participating in a regular stretching program. It is believed by experts and athletes that stretching can improve not only sports performance, but also general health, well-being, body posture and aesthetics.
While it may be true that there are many highly successful sports performers who do not engage in a regular stretching program, such athletes are the exception rather than the rule. Stretching offers several advantages. Initially, as part of the warm-up process, when one is preparing the body for the more strenuous work to follow, a period of preparatory stretches will ensure that all muscles, joints and limbs have been carefully taken through their full range of movement. This reduces the risk of injuring muscles, joints and ligaments.
If correctly done, stretching also leads to an increase in normal range of movement. This leads to better flexibility. This is a benefit to the athlete in that the greater the range of movement a person has throughout the joints, the greater the amount of force that can be applied to the ground, water or objects used during a sport. Consider the runner who wants to increase speed. Running speed is determined by how quickly his or her legs move and how much ground is covered with each stride. The longer the force is applied and the more total force exerted, the more impressive the performance.
Stretching aimed at flexibility gains can help athletes correct certain deficiencies in technique. For example, excessively tight hamstring muscles may limit how effectively legs move through the range of movements required for sprinting or running activities. Performing appropriate stretching exercises can improve execution of the necessary movements which will improve sprinting or running technique. Deficiencies may also predispose a sports performer or enthusiast to injury, which may create an even stronger motivation toward including a thorough and balanced stretching regime in a sports program.
Although there is no scientific evidence to support it, many athletes argue a proper warm-up, including light stretching prior to vigorous activity, and a thorough cooldown, including longer held static stretching, can reduce some of the muscle soreness that results from a syndrome known as delayed onset muscle soreness (DOMS). This is the stiffness brought about through vigorous or unaccustomed exercise or strenuous physical activity, and can be acute. It will usually show up between 24 and 48 hours after exercise.
Even if you don't consider yourself an athlete or serious sports performer, it still makes good sense to structure an exercise session that contains a thorough and progressive stretching program to increase your range of movement. Unfortunately, the health aspects of improved range of movement are often only fully appreciated when normal range is lost due to age, illness or injury. Perhaps our renewed interest in flexibility training is a result of the baby boomer fitness generation reaching an age in which these types of losses are more common. Being flexible enables us to reach, bend, twist and turn with ease, making everyday tasks as well as exercise or sports-related skills much simpler to execute.
It is also the balance of flexibility and strength in all the major muscle groups, that enables the best possible posture to be maintained. This is critical whether standing, sitting, driving or performing an activity if you want to avoid strain and injury -- in particular to the muscles and joints of the back. Yet again, we often don't notice these problems creeping up until a more major problem has occurred. As a working generation, we tend to spend most of our time seated, which classifies us as "professional sitters." Slouching in front of keyboards and computer screens with our muscles and joints in odd positions for extended periods of time can habitually lengthen or shorten certain muscles. These changes create a domino effect that can lead to pressure being exerted upon other structures within the body, such as blood vessels, nerves and organs. Posture-related ailments, such as headaches and circulatory disorders, may result. Appropriate stretching may not solve all of the postural problems, but it can help get the body back into normal alignment and enable it to correctly function.
Keep in mind that the primary purpose of flexibility exercises is to preserve or attain greater range of motion (ROM). Flexibility varies from person to person depending on factors such as age, weight, lifestyle, arthritis and prior injuries to joints. Flexibility can also vary between different joints or even the same joint on opposite sides of the body. Flexibility or stiffness at a joint is determined by three components: the bone structure itself, connective tissues and surrounding muscles.
The bones permit or restrict movement according to their shape and articulation at the joint structure. We know from research by Corbin, et al., in 1990 that 47% of the restriction to movement is caused by the joint shape itself. This is, for the most part, unchangeable. What can be changed are the soft tissue elements. It is the elasticity in these structures that is vital to flexibility. The connective tissues include discs or cartilage within the joint, capsules and ligaments outside the joint, and the muscles with their tendons and connective fascia. Stiffness in connective tissue structures is rare in children, moderately common in adults, and common in older adults. The joint capsules and ligaments allow joint movement while preventing the bones from being displaced. Their elasticity is limited. If the capsule or ligaments are over-stretched, they don't readily return to their original length. This can result in a higher risk of joint sprains. This is why the fitness industry has been conservative in its recommendation of certain movements or positions that might unfavorably affect the ligaments of the knees and spine -- particularly during the warm-up.
In contrast to less elastic connective tissues are the muscles and muscle tissues associated with joints. They are contractile and elastic by nature. However, if not properly stretched on a regular basis, they can act as brakes on a certain movement -- either because their connective tissue covering (fascia) is tight, or their fibers are in chronic contraction and resist lengthening. According to researchers Wright and Johns in 1962, 41% of the resistance to ROM comes from the muscle and its fascia, and an additional 10% is attributable to the tendon which attaches the muscles to the bones. Flexibility exercises are typically designed to stretch the fascia and/or muscle fibers.
Since the best way to improve flexibility is through stretching, it is important to have a thorough knowledge of the different types of stretches and how to safely execute them. There are two main types of flexibility methods -- dynamic and static. Static flexibility training can be further subdivided into active and passive movements.
Dynamic flexibility refers to an active type of stretching exercise involving movement of varying degrees and speeds to meet or enhance the ROM typically used during specific activities or sports movements. Dynamic stretching at its extreme degree are bouncing or ballistic movements geared to replicate over-stretching movements that may occur during highly competitive sports. Although many athletes, such as gymnasts and skaters, may use these ballistic movements in their routines, the majority of experts would not recommend them due to the increased risk of injury. Static stretching and more moderate forms of dynamic stretching are generally recommended.
Static stretching has been defined as slow, sustained stretching exercises that hold a muscle in a lengthened position for a few seconds. It can be active or passive in nature. Active movements use unassisted stretches which require strength and muscular effort of the agonist muscle or prime mover. An example of this is the flexibility needed at the top of a high kick or split leap movement. To actively perform a static stretch, lift and hold your leg up as high as possible from a standing position without the help of arm hold or support. Passive movements are accomplished through the use of an external force such as that provided by a partner, hand hold or gravity. The body is placed in a position which increases the distance between the origin and insertion of the muscle, and held there until muscle release or relaxation is achieved. All other methods of stretching, such as proprioceptive neuromuscular facilitation (PNF), contract relax (CR), also commonly referred to as hold/relax method, or contract relax with agonist contraction, or CRAC, are variations of these.
Many of our stretching techniques are based on neurological factors that have implications on flexibility training. The three main neurological responses pertain to the myotatic stretch reflex, the golgi tendon organ reflex, and reciprocal innervation or inhibition.
The myotatic reflex occurs in every muscle when it is being stretched. It is a response to prevent damage to the muscle. When a muscle is stretched too quickly, an impulse is sent to cause a reflex contraction in that muscle. Since stretching will now work in opposition to the contraction, it is possible for damage to occur in the form of microscopic muscle tears, particularly with forceful ballistic stretching. An important thing to note is that the magnitude of the stretch reflex is proportional to the speed of movement. When stretches are statically held, whatever initial contraction there has been in the muscle will dissipate; this desensitization of the stretch reflex occurs in the first few seconds. Following this, there will be a greater movement or relaxation in the muscle as well as more permanent changes in tissues. It is the main reason experts recommend static rather than ballistic techniques for most flexibility programs.
The second neurological response relates to the golgi-tendon organ (GTO) reflex. GTOs, situated at the junction of the muscle and tendon, respond to and monitor tension in the muscle spindles. If tension in a muscle becomes great enough to stimulate the GTOs, they send a warning message which, in turn, produces a reflex relaxation in the tensioned muscle. This necessary tension is difficult to achieve through stretching.
Tension through contraction, however, is much easier to achieve and the basis for the PNF or CR and CRAC stretching techniques. In both cases, one stimulates a contraction, usually isometric in nature, in the muscle prior to a stretch or relaxation phase. This contraction then engages the GTO mechanism and results in a greater relaxation of the spindles and less resistance to stretching. This allows the muscle to stretch further than it normally would and thus permits a greater ROM in the joint.
In the CRAC method one further increases a stretch by following the isometric contraction and stretch with strong contraction in the opposing muscle group. This leads to the third neurological response known as reciprocal innervation or inhibition. In this neurological response, one muscle is innervated to contract and the opposing is inhibited so that it relaxes. This process occurs in all joints around the body, with only a few exceptions. If this response did not occur naturally we would not be able to move without injury. The CRAC method uses this helpful piece of neurological knowledge to further advance techniques in increasing flexibility and range of motion.
There has been some scientific debate focusing on the optimum duration to hold the isometric contraction used in both the CR and CRAC methods. Studies found no significant difference in improved ROM between contractions held for three as opposed to six seconds. Further studies using three-, six- and 10-second contractions again found no significant difference as far as ROM was concerned. The implication of this research might be that given the fact that long-duration isometric contractions elevate blood pressure significantly, the three- to 10-second parameter can safely be used with no detrimental side effects. It is important to mention the importance of proper supervision and application of these PNF techniques because they are most often done by a partner or practitioner who is manipulating ROM.
The most commonly used and recommended flexibility training method is passive static stretching, widely used in both the athletic and general fitness environments. The typical recommendation is to use a static technique held less than 12 seconds in the beginning of a workout once some movement has been performed to increase the tissue temperatures. Their primary objective is to facilitate a reasonable range of motion for the movements of the workout to follow. After the workout is completed, static stretching techniques are recommended, in which a position is held for 20 or more seconds to increase flexibility and decrease post exercise muscle tension.
Controversy has been raised over the appropriateness of stretches in the warm-up period of a workout. It is still believed that proper stretching techniques can be beneficial in neurologically and physiologically preparing the body for more vigorous movement. The key is to realize and utilize preparatory stretches in conjunction with movements that allow the connective tissue to warm up and further facilitate a gentle increase of active ROM. The only stretching that should be avoided in warm-up is ballistic or maximal range, long held techniques.
One type of stretching technique not given much attention in the past is dynamic stretching. Keeping in mind that dynamic flexibility is part of most activities, it makes sense to utilize or replicate movements in preparation to doing similar, more vigorous movements. The key is to prepare or slowly progress to similar ranges of motion without elevating momentum to the point of ballistic or jerky movement that could increase the risk of muscle injury. This type of active stretching also aids in raising the tissue core temperatures prior to static stretches to follow.
In many cases, some of the traditional rhythmic limbering exercises seen in fitness warm-ups already fit into the dynamic flexibility category. Examples are controlled torso reaches or arm punches, wide stance lunging, and side-to-side and low kicks. The key is to progressively duplicate movements that take your muscles near the end of their working ROM. If it is kept in control, without momentum taking over, movement will remain dynamic with minimal chance of incurring injury.
Active static stretches can also be helpful in creating better muscular balance within a ROM. By actively contracting a muscle to hold a position that requires flexibility in the opposing group, you are developing a more usable strength and flexibility ratio. If you increase flexibility on one side of a joint, it is only as functional as the strength you have to use it. On the flip side, if you increase the strength to place or hold a joint at a range that you are not flexible enough to reach, you may actually injure the muscle that cannot accommodate the range during strong or momentous movements. These types of exercises are often seen in yoga and dance positions or stances. They offer a unique blend of strength and flexibility demands, and are in many ways more relevant to the way our bodies need to function during real-life and sports-related activities.
Which methods are best for increasing sports or movement performance and preparedness is a question only answered by the specific needs of an individual. Knowing how and when to use passive, active, dynamic and neuromuscular stretching techniques will be discussed more fully in part two of this series.
"Stretching into the 21st Century: Part Two" will cover environmental and physiological factors that can influence connective tissue response, the sensation and indicators of flexibility intensity, and techniques for measuring existing flexibility levels and progression. It will also take a look at functional flexibility programs that can be designed to counter-balance existing injuries or reduce common skeletal muscular strains.
Author's Bio:
Kathy Stevens is a member of AFAA's board of certification and training, and a Reebok master trainer and program developer with 20 years experience in the fitness industry. She holds a B.A. in physical fitness and education.
[Part 2]
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