Equilibrium Dynamic & static & center of Gravity and its application in sports

Definition: Equilibrium: has been defined broadly as a stateofrestorbalanceduetotheequalactionofopposingforces. Balance: ability to control equilibrium Equilibrium: state of no acceleration (no change of speed or direction) of body Static Equilibrium: body at rest or motionless Dynamic Equilibrium: body in motion with unchanged acceleration created by balanced applied and inertial forces Stability: resistance to disturbance of equilibrium (change of acceleration) Center of Gravity: point at which all body's mass is equally balanced or equally distributed in all directionsIntroduction: For any sport, the optimal method to improve balance, proprioception, and core stability is to practice the skill itself on the same surface on which the skill will be performed during competition. There is little transfer between balancing skills because balance is skill specific. For example, having a gymnasts practice on a wobble board balance will not be improved balance on the beam. Similarly, having a baseball pitcher stand on a foam roller while throwing a medicine ball may not improve proprioception when throwing from a mound. Likewise, having a football player stand on a stability disks while performing squats may not improve core stability when running through a defensive line. Performing resistance exercises on stability balls, foam rollers, wobble boards, and variations of such equipment has not been shown to enhance sports related skills.Stability has both advantages and disadvantages, depending upon the functional goal. If the objective were to remain stationary, for example, a high degree of stability would be advantageous. On the other hand, if one wanted to move quickly from one position to another, too much stability would hinder displacement, and would be a disadvantage. Often, finding just the right amount of stability is essential to successful function.To a large extent, ones stability is a product of their movement goals, the nature of their position in space, and the relative displacement of their center of gravity. This reflects the types of functions in which we engage. Functional activities may be divided into two broad classifications. In the first, the goal is to establish body stability, a product of static equilibrium. In the second, the objective is to transport the body through space, an action involving dynamic equilibrium. Thus, to appreciate the challenges that one faces in maintaining balance, and the applications that would best improve ones ability to do so, one should first understand the difference between static and dynamic balance.In a static balance function, the objective is to remain still, even if parts of the body are in motion. An example is reaching up to change a light bulb. Here, the performer has to create an elongated posture with arms held over head. Then, of course, there are the actions of grasping the bulb and rotating the wrist. Despite the fact that the goal is to maintain a fixed position, the subtle movements of the arms and hands and the postural shifts that naturally occur, cause motion at the center of gravity, which may affect stability and disrupt balance.Static equilibrium is influenced by two additional factors. First, as already discussed, is the base of support. Even in a body stability task, there is some movement of the center of gravity. A small base of support, therefore, doesnt allow for much movement error because the distance from any edge of the base to the center of gravity has decreased. Thus, the task becomes more difficult as the size of the base shrinks.The other influence on static equilibrium is the application of an external force. If one, while maintaining a stable position, were to be pushed or pulled by another object or person, then their balance could be jeopardized. Maintenance of static equilibrium would then depend on how effectively one could reposition their center of gravity towards a pushing force or away from a pulling force, and generally, how well they could resist the force that would otherwise cause a fall.Dynamic equilibrium is created during body transport tasks. In body transport, the objective is to displace the center of gravity in order to move the body through space. This usually involves moving the center of gravity beyond the base in order to initiate motion, and then forming a new support base to re-establish equilibrium. Its worth emphasizing that the center of gravity is deliberately moving, hence the dynamic nature of the task. Some movements are more dynamic than others, determined by the amount of mass being moved and the velocity of the movement, or in other words, the momentum. Simply stated, the more momentum created during body transport, the greater its dynamic state. The resulting challenge to equilibrium, therefore, is a product of a tasks inherent momentum, the size of the supporting base, and the direction of movement.Movement of the body may occur vertically, as in vertical jumping; horizontally, when walking or running; or some combination of both, as in leaping, or long jumping. Vertical tasks are challenging from the perspective of having to generate enough force to leave the ground and return smoothly. But in terms of maintaining equilibrium, this dynamic movement is relatively simple, so long as the supporting base remains large. Since, by definition, the center of gravity is moving vertically, its position relative to any edge of the supporting base, once established, remains fairly constant. Only when the base becomes much smaller, such as landing on one foot, or if the center of gravity is too close to the bases edge, does the task become demanding, as there is now greater potential for a shift in the center of gravity beyond the limits of the base.One might surmise, then, that horizontal movements at the center of mass have greater demands on balance control. If the center of gravity is moving horizontally, across the base of support, then at some point, it will pass beyond the boundary of the base and balance will be lost. Of course, this too is influenced by the momentum of the center of gravity and the size of the base. Consider the possibilities, starting with a slow movement over a large base, and then ultimately, a rapid motion over a small base. The demands on the performer become increasingly difficult.Lets, consider, for example, a leap, which is defined as jumping off of one leg and landing on the other. Envision someone leaping over a puddle, thus creating movement at the center of mass which is both vertical and horizontal. This is a fairly dynamic task, since the performer must generate enough force to get off the ground, thus creating quite a bit of momentum at the center of gravity.

Interestingly, while the performer is airborne, he is technically falling, but the real challenge occurs the instant the lead foot touches the ground. At the moment of contact, a new base of support is established, but being the size of the foot, it is a pretty small support surface. At that same instant, the center of mass is actually well behind the base, but moving rapidly in that direction. The problem for the performer is to gradually arrest the movement of the center of gravity so that it continues its motion until it is over the base, where it must stop in order to preserve equilibrium. Stop it too soon, or too late, and the result is a fall. This only gets harder as speed increases.Conclusion:The truth is, balance is not simply the ability to stand quietly on one foot while moving slowly up and down. Static and dynamic conditions test us constantly, whether during normal daily activities or in sporting events. These tasks require some degree of strength, power, timing, and coordination. Its no wonder that even very fit people sometimes struggle with these challenges.Bibliography: Dictionary.com., Answers.com, Willardson JM (2004). The effectiveness of resistance exercises performed on unstable equipment. Strength and Conditioning Journal; 26 (5), 70-74.; The Truth on Fitness: Balance (Part 2), Paul M. Juris, Ed.D.Executive Director, CybEx Institute.

Centrifugal and Centripetal Force and its application in Sports.

Definition: centripetal force and centrifugal force,action-reaction force pair associated with circularmotion.According to Newton's first law of motion, a moving body travels along a straight path with constant speed (i.e., has constantvelocity) unless it is acted on by an outsideforce. For circular motion to occur there must be a constant force acting on a body, pushing it toward the center of the circular path. This force is the centripetal ("center-seeking") force. For a planet orbiting the sun, the force is gravitational; for an object twirled on a string, the force is mechanical; for an electron orbiting an atom, it is electrical. The magnitudeFof the centripetal force is equal to the massmof the body times its velocity squaredv2divided by the radiusrof its path:F=mv2/r.

According to Newton's third law of motion, for every action there is an equal and opposite reaction. The centripetal force, the action, is balanced by a reaction force, the centrifugal ("center-fleeing") force. The two forces are equal in magnitude and opposite in direction. The centrifugal force does not act on the body in motion; the only force acting on the body in motion is the centripetal force.The centrifugal force acts on the source of the centripetal force to displace it radially from the center of the path. Thus, in twirling a mass on a string, the centripetal force transmitted by the string pulls in on the mass to keep it in its circular path, while the centrifugal force transmitted by the string pulls outward on its point of attachment at the center of the path. The centrifugal force is often mistakenly thought to cause a body to fly out of its circular path when it is released; rather, it is the removal of the centripetal force that allows the body to travel in a straight line as required by Newton's first law. If there were in fact a force acting to force the body out of its circular path, its path when released would not be the straight tangential course that is always observed.

The Benefits of Pilates

"I must be right. Never an aspirin. Never injured a day in my life. The whole country, the whole world, should be doing my exercises. They'd be happier." -- Joseph Hubertus Pilates, in 1965, age 86.Runner or golfer, tennis player or new mom, chances are you've heard someone talking about the benefits of Pilates. Many types of people, at many levels offitness, who have begun doing Pilates exercises say they've seen improvements in range of motion, flexibility, circulation, posture, and abdominal strength -- and decreases in back, neck and jointpain.Forty years after his death, the system of exercises developed by Joseph Pilates has never been in such demand. But can the benefits of Pilates (puh-LAH-teez), the system of strengthening andstretchingexercises designed to develop the body's core, mobilize the spine and build flexibility, really be that far-reaching?Pilates Benefit No. 1: Body AwarenessCelebrity Pilates teacher Siri Dharma Galliano says Pilates -- when performed correctly and with the proper supervision -- can do all that and more."It is an education in body awareness," says Galliano, who owns Live Art Pilates studio in Los Angeles. "It changes your shape by educating you in daily life. When you're cooking, brushing your teeth -- the lessons are coming home to pull your stomach in and pull your shoulders down. There is an attention required (in doing the exercises) that changes your awareness" even after class."It teaches you how to train your mind and build symmetry and coordination in the body," adds Galliano. "And when you can get control of the little things, that's practicing willpower."Aliesa George, a Pilates teacher in Wichita, Kan., agrees."The biggest benefit in my eyes would be personal awareness -- awareness of how you sit or how you stand or how you move and being able to relate those habits to the aches and pains and injuries you have or have had in the past," she says.For example, she says, it can help make you aware of that chronic tweak in the neck you get from sitting at the computer all day with rounded shoulders and a phone cradled between ear and shoulder.As a Pilates-trained physical therapist, Dan Westerhold says he sees a lot of clients with injuries or weakness of the postural muscles, as a result of work, lifestyle, or not exercising the right way."People sit slouched at computers all day, then go to the gym and work their extremities," says Westerhold, of Pilates Seattle. "They don't use their core."Think of a tree, Pilates experts say. Does it have all its strength in its limbs? No. The tree is only as strong as its trunk and roots. Without a strong trunk, the tree would topple over.It's the same for human bodies, say Pilates experts. If we don't concentrate on building a good foundation and a strong trunk or core, we'll end up tight in some places and weak in others, injury-prone and susceptible to the pitfalls of our occupation or chosen form of exercise.But how about flattening the abs? Can Pilates exercises really give you a washboard stomach?Experts warn that it's important not to equate a stronger core with a flatter stomach."When people want 'flat abs,' they are usually looking forweight loss, not abdominal strength and core support," says George. "More than touting the benefits of Pilates for flat abs, we should be touting the benefits of Pilates for a stronger, healthy back and body. If along the way, you do the other components of fitness and trim the body down, yes, you're going to have a flatter midsection."As you develop body awareness, stand straighter, and gain flexibility, "Pilates will shift your shape," says Galliano. "But just attending a group mat class may or may not change your body."Kevin Bowen, co-founder of the Pilates Method Alliance and director of special projects, says it is important that abdominals are flexible, not just hard."A flexible muscle is a strong muscle," says Bowen. "A hard muscle may feel good and give an interesting look, but if you don't have the flexibility and the balance and the functionality that you need to allow your body to function properly, sooner or later, it's going to show up someplace else."Pilates Benefit No. 3: Body ControlGalliano, who has sculpted the bodies of Madonna, Cameron Diaz, Sting, Carrie-Anne Moss, and Uma Thurman, says Pilates works because it teaches you how to move."Unless you are taught how to move and discover with your teacher what is blocking you (for example, keeping your shoulders up too high), you will never achieve body symmetry," Galliano says. "When you start getting control of your body, it gives you a great degree of satisfaction."There's an intrinsic relevance to it, says Little Rock, Ark.,internist Hoyte Pyle, MD, who has been practicing Pilates for five years. Instead of working major muscle groups in isolation, he says, "Pilates works the whole body in synergy," which is how we should be moving on a daily basis.The Roots of Pilates ExercisesThe discipline was created by German-born Joseph H. Pilates a century ago. A sickly child plagued withasthmaandrickets, he grew up to be obsessed about the perfect body. He sought a discipline to combine the physique of the ancient Greeks with the meditative strength of the East.The result was a system of exercises he called "contrology," requiring intense concentration and centered on a strong abdomen, deep stretching, and focused breathing. It worked for him. Joseph Pilates became a boxer, diver, skier, gymnast,yogadevotee -- and an incredible physical testament to his method.Pilates taught his method to wounded English soldiers during World War I, using springs he removed from their hospital beds to assist them as he developed techniques to increase their range of motion. It was from these crude devices that he developed the equipment still used today, including the reformer, Cadillac, Wunda chair, ladder barrel, and spine corrector.Pilates emigrated to the U.S. in 1926, teaching his method first to boxers and later ballet dancers, until the rest of the world caught on.Apparatus or Mat?Pilates himself rarely worked with groups. Most of his work was done one on one, so each person's exercises were tailored to meet his or her needs. But he used both mat exercises and equipment with his clients."Pilates was developed as a system," says George. "People will get the best benefits if they utilize it as a system, doing exercises on the mat and the equipment.""The equipment can offer more variety of movement," adds Bowen, "but it's important to have experience in the mat work as well. It's portable, for one thing."For someone who has limitations, equipment is a great place to begin, says Galliano."The equipment was really designed to help people do the mat work. It supports them while they do the action," she says, which is something they can't get in a mat class.Bottom line? If you can afford it, teachers recommend doing both mat classes and work on the equipment.Fusions of PilatesIt seems like everywhere you look, familiar exercise disciplines are taking on a new life with a Pilates twist. There are fusions of Pilates with everything from yoga andswimmingto ballroom dancing and boxing."Right now, Pilates is sort of a nice, hot word," says George. "Everybody wants to fuse Pilates with everything because it's going to help sell it."George's perspective?"Any movement or exercise that's done well should be beneficial to the body," she says, "but it doesn't necessarily mean you're doing Pilates."Pilates Is Not for EveryoneSome 50% of adults experienceback painat some time in their lives. At any given time, 25% of adults have acute or chronic back pain, says Jupiter, Fla., physical therapist Michael L. Reed, DPT.Pilates and other exercises that focus on the stability of the muscles that support the spine might seem like a perfect fit. But not all pain is the same, cautions Reed. Without a diagnosis for your back pain from a physician or health care professional, Pilates could do more harm than good, he says."You can't go to a non-medical practitioner that teaches Pilates and think that will resolve your back pain," says Reed. "That's the mistake people make."That's not necessarily to say that Pilates won't help, says Reed, who uses Pilates in his rehabilitation studio. Movement training is a sensible way tomanage pain, and non-weight-bearing exercises like Pilates can be done even by those struggling with pain, he says.However, he warns, "it's advantageous to have a better idea what may be generating theirsymptomsfirst."As any well-trained Pilates teacher will attest, without a proper diagnosis for the pain, even the best instructor cannot design a safe and effectiveexercise program.

Bibliography.The Columbia Electronic Encyclopedia,6th ed . Barbara Russi Sarnataro, WebMD Weight Loss Clinic-Feature