Diving

Diving refers to the sport of performing acrobatics while jumping or falling into water from a platform or springboard of a certain height. Diving is an internationally-recognized sport that is part of the Olympic Games. In addition, unstructured and non-competitive diving is a common recreational pastime in places where swimming is popular.

While not a particularly popular participant sport, diving is one of the more popular Olympic sports with spectators. Successful competitors possess many of the same characteristics as gymnasts and dancers, including strength, flexibility, kinaesthetic judgment and air awareness.

Diving tower at the 2008 Euros

In the recent past, the success and prominence of Greg Louganis led to American strength internationally. China came to prominence several decades ago when the sport was revolutionized by national coach Liang Boxi and after intense study of the dominant Louganis. China has lost few world titles since. Other noted countries in this sport include Australia and Canada.

Mechanics of diving:

At the moment of take-off, two critical aspects of the dive are determined, and cannot subsequently be altered during the execution. One is the trajectory of the dive, and the other is the magnitude of the angular momentum.

The speed of rotation - and therefore the total amount of rotation - may be varied from moment to moment by changing the shape of the body, in accordance with the law of conservation of angular momentum.

The center of mass of the diver follows a parabolic path in free-fall under the influence of gravity (ignoring the effects of air resistance, which are negligible at the speeds involved).

Trajectory

Since the parabola is symmetrical, the travel away from the board as the diver passes it is twice the amount of the forward travel at the peak of the flight. Excessive forward distance to the entry point is penalized when scoring a dive, but obviously an adequate clearance from the diving board is essential on safety grounds.

The greatest possible height that can be achieved is desirable for several reasons:

• The height attained is itself one of the factors that the judges will reward.
• A greater height gives a longer flight time and therefore more time to execute moves.
• For any given clearance when passing the board, the forward travel distance to the entry point will be less for a higher trajectory.

Control of rotation

The magnitude of angular momentum remains constant throughout the dive, but since

angular momentum = rotational velocity × moment of inertia,

and the moment of inertia is larger when the body has an

increased radius, the speed of rotation may be increased by moving the body into a compact shape, and reduced by opening out into a straight position.

Since the tucked shape is the most compact, it gives the most control over rotational speed, and dives in this position are easier to perform. Dives in the straight position are hardest, since there is almost no scope for altering the speed, so the angular momentum must be created at take-off with a very high degree of accuracy. (A small amount of control is available by moving the position of the arms and by a slight hollowing of the back).

Notice that the opening of the body for the entry does not stop the rotation, but merely slows it down. The vertical entry achieved by expert divers is largely an illusion created by starting the entry slightly short of vertical, so that the legs are vertical as t

hey disappear beneath the surface. A small amount of additional tuning is available by 'entry save' techniques, whereby underwater movements of the upper body and arms against the viscosity of the water affect the position of the legs.

Twisting

Dives with multiple twists and somersaults are some of the most spectacular movements, as well as the most challenging to perform.

The rules state that twisting 'must not be generated manifestly on take-off'. Consequently, divers must use some of the somersaulting angular momentum to generate twisting movements. The physics of twisting can be explained by looking at the components of the angular momentum vector.

As the diver leaves the board, the total angular momentum vector is horizontal, pointing directly to the left for a forward dive for example. For twisting rotation to exist, it is necessary to tilt the body sideways after takeoff, so that there is now a small component of this horizontal angular momentum vector along the body's long axis. The tilt can be seen in the photo.

The tilting is done by the arms, which are outstr

etched to the sides just before the twist. When one arm is moved up and the other is moved down (like turning a big steering wheel), the body reacts by tilting to the side, which then begins the twisting rotation. At the completion of the required number of twist rotations, the arm motion is reversed (the steering wheel is turned back), which removes the body's tilt and stops the twisting rotation.

An alternative explanation is that the moving arms have precession torque on them which set the body into twisting rotation. Moving the arms back produces opposite torque which stop the twisting rotation.

Entry

The rules state that the body should be vertical, or nearly so, for entry. The arms must be beside the body for feet-first dives, which are typically competed only on the 1m springboard and only at fairly low levels of competition, and extended forwar

ds in line for "head-first" dives, which are much more common competitively. It used to be common for the hands to be interlocked with the fingers extended towards the water, but a different technique has become favoured during the last few decades. Now the usual practice is for one hand to grasp the other with palms down to strike the water with a flat surface. This creates a vacuum between the hands, arms and head which, with a vertical entry, will pull down and under any splash until deep enough to have minimal effect on the surface of the water (the so-called "rip entry"). Once a diver is completely under the water they may choose to roll or scoop in the same direction their dive was rotating to pull the splash away from the channel which they have just created.

Personal Diving Equipment

Scuba life support

• Open-circuit Scuba consisting of diving cylinder(s) and diving regulator(s)
• Rebreather, closed-circuit or semi-closed-circuit Scuba

Alternative life support

• Liquid breathing systems are extremely rare and at an early experimental stage. It is hoped that some day practical systems allow very deep diving.
• Snorkel allows breathing at the surface with the face submerged.
• Standard diving dress - mostly used in professional diving. Merely of historical interest now.
• Surface supplied diving - mostly used in professional diving, except recreational forms like snuba.

Thermal, sting and abrasion protection

• In cold water, a diving suit such as a dry suit or a wet suit
• In very warm water, many types of tough, long, everyday clothing provide protection, as well as purpose made garments such as dive skins and shorty wetsuits
• Diving gloves, neoprene is often used for thermal insulation
• Diving boots, often made of neoprene and rubber
• Safety helmet for scuba diving. Not air-holding. May have a built-in forehead light. Images at .

In-water stabilisation and movement

• A backplate is a structural device linking the buoyancy of the wing with the weight of the diving cylinders and harnessed around the diver's body
• Buoyancy compensator, Buoyancy Control Device, BCD or BC - many names for a buoyancy adjusting and life-saving buoyancy device
• Diver Propulsion Vehicle - to increase the range of the diver undwerwater
• Diving weighting system - to counteract the buoyancy of the diving suit and diver to allow descent
• Fins for efficient propulsion

Measurement and navigation

• Compass for underwater navigation
• Decompression tables to avoid decompression sickness
• Depth gauge is used with watch for decompression monitoring on decompression tables
• Distance line is used to navigate back to the start point in poor visibility
• Dive Computer to avoid decompression sickness
• Watch is used with depth gauge for decompression monitoring on decompression tables

• Mask allows the diver to see clearly underwater and protects the eyes.
• Full face mask protects the face from dirty or cold water and increas es safety by securing the gas supply to the diver's face. If it contains no mouthpiece, the diver can talk allowing the use of communications equipment.
• Diving helmets are often used with surface supplied diving. They provide the same benefits as the full face mask but provide a very secure connection of the gas supply to the diver and additionally protect the head.
• Underwater writing slates and pencils are used to transport pre-dive plans underwater, to record facts whilst underwater and to aid communication with other divers.
• Torchs / flashlights are essential for safety in low visibility or dark environments such as night diving and wreck and cave penetration. They are useful for communication and signalling both underwater and on the surface at night. Divers need artificial light even in shallow and clear water to reveal the red end of the spectrum of light which is adsorbed as it travels through water.
  

Tools

• Airlift - a gas "powered" tube that is used in nautical archaeology, which vacuums small objects, sand and mud from the sea bed
• Camera and housing - for underwater photography or underwater videography
• Decompression trapeze consists of one or more horizontal bars, suspended at decompression stops by buoys
• Diving reel to transport a distance line or line for a surface marker buoy
• Diving shot consisting of a weight, line and buoy used to mark the location of a dive site, allowing divers to navigate to and from the surface and to do decompression stops at a safe location
• Dry box to hold objects the diver needs to keep dry at depth (wallet, cell phone)
• Knife to cut lines, nets or to pry or dig. Can also be used for personal protection against underwater predators if needed, however not recommended.
• Lifting bag - to lift heavy objects underwater activated by adding air

Surface detection aids

• The purposes of this class of personal equipment are to:

• allow the support boat to monitor and find divers on the surface during or after a dive
• prevent the diver being struck by boat traffic
• mark the diver's position when drift diving or while at the decompression stop
• help rescue services in lifeboats and helicopters to locate the diver

Surface detection aids (with cheapest and most effective towards the top) include:

• Surface Marker Buoy, Decompression buoy, Delayed SMB, safety sausage or blob
• Red or yellow collapsible flag - high visibility, robust, bungeed to cylinder
• Whistle - cheap, will only be heard by people far from engine noise
• Torch/flashlight - if at sea after night fall
• Strobe light - needs long-lasting batteries
• High pressure whistle - expensive but effective
• Orange water dye - increases diver's visibility from search helicopters
• Mirror such as a used Compact Disc - to reflect sunlight or searchlights
• Red pyrotechnic flares - for helicopters and lifeboats
• Emergency position-indicating rescue beacon
• Glow stick - for night diving

Surface equipment

• Diver down flag is flown warning others that divers are underwater
• Diving air compressor to fill diving cylinders with high pressure air or other gasses
• Boats such as the rigid-hulled inflatable boat
• Echo sounder - a SONAR depth measuring and profiling device used for dive site location
• GPS receiver - for locating dive sites
• Proton magnetometer - for locating ferrous wrecks
• Remotely Operated Underwater Vehicle - for locating dive sites
• Marine VHF radio - for communicating with rescue services and other boats

Water Polo

Water Polo:-

Water polo is a team water sport. It is the oldest continuous Olympic team sport. The playing team consists of six field players and one goalkeeper with a maximum of six substitutes. The winner of the game is the team that scores more goals. Gameplay involves swimming, players passing the ball while being defended by opponents, and scoring by throwing into a net defended by a goalie. Water polo, therefore, has strong similarities to the land-based game of team handball. The frequency of 'man-up' (or 'power play') situations also draws comparisons with ice hockey.

Water polo equipment:

Little player equipment is needed to play water polo. Items required in water polo include:

Ball:
A water polo ball is constructed of waterproof material to allow it to float on the water. The cover has a special texture so it won't slip from the hands of a player. The size of the ball is different for men's and women's games.

Caps:

A water polo cap is used to protect the players' heads and ears, and to identify them. Home team field players wear numbered light or dark caps, and visiting team field players wear contrasting caps. Both starting goalkeepers wear (quartered) red caps, numbered "1", and substitute goalies caps are numbered either "1-A" in NCAA play or "13" for FINA international play. Caps are fitted with ear protectors.

Goals:
Two goals are needed in order to play water polo. These can either be put on the side of the pool, or in the pool using floaters.

Swimwear:
Male water polo players often wear swim briefs. Some players prefer to wear 2 briefs for more security during play. Female players must wear a one-piece swimsuit. Most of these suits do not have straps as normal suits, but are zipper-backed.

Gymnastics (other)

Rhythmic gymnastics:

Rhythmic gymnastics is a sport in which single competitors or pairs, trios or even more (generally five) manipulate one or two apparatus: rope, hoop, ball, clubs and ribbon. Rhythmic Gymnastics is a sport that combines elements of ballet, gymnastics, theatrical dance, and apparatus manipulation. The victor is the participant who earns the most points, as awarded by a panel of judges, for leaps, balances, pivots, flexibility, apparatus handling, and artistic effect.
The governing body, the Fédération Internationale de Gymnastique (FIG), changed the Code of Points in 2001, 2003 and 2005 to emphasize technical elements and reduce the subjectivity of judging. Before 2001, judging was on a scale of 10 like that of Artistic Gymnastics. It was changed to a 30-point scale in 2003 and in 2005 was changed to 20. There are three values adding up to be the final points—technical, artistic and execution.
International competitions are split between Juniors, under sixteen by their year of birth; and Seniors, for women 16 and over again by their year of birth. Gymnasts typically start training at a very young age and those at their peak are typically in their late teens or early twenties. The largest events in the sport are the Olympic Games, World Championships, and Grand-Prix Tournaments.

Trampoline:

A trampoline is a gymnastic and recreational device consisting of a piece of taut, strong fabric stretched over a steel frame using many coiled springs to provide a rebounding force which propels the jumper high into the air. In a trampoline, the fabric is not elastic itself; the elasticity is provided by the springs which connect it to the frame.Apparatus made up of a bed stretched by springs; the gymnasts perform acrobatics by jumping and bouncing on it.

Gymnastics

Gymnastics is a sport involving performance of exercises requiring physical strength, flexibility, agility and coordination. Artistic Gymnastics is the best known and most popular of the gymnastics sports governed by the Fédération Internationale de Gymnastique (FIG). Artistic Gymnastics typically involves the women's events of uneven parallel bars, balance beam, floor exercise, and vault. Men's events include floor exercise, pommel horse, still rings, vault, parallel bars, and high bar. Gymnastics evolved from exercises used by the ancient Greeks, that included skills for mounting and dismounting a horse, and from circus performance skills. Other forms of gymnastics are rhythmic gymnastics, various trampolining sports, and aerobic and acrobatic gymnastics.

Artistic gymnastics:

Artistic gymnastics is usually divided into Men's and Women's Gymnastics. Each group does different events; Men compete on Floor Exercise, Pommel Horse, Still Rings, Vault, Parallel Bars, and High Bar, while women compete on Vault, Uneven Bars, Beam, and Floor Exercise. In some countries, women at one time competed on the rings, high bar, and parallel bars (for example, in the 1950s in the USSR). Though routines performed on each event may be short, they are physically exhausting and push the gymnast's strength, flexibility, endurance and awareness to the limit.
Traditionally, at the international level, competitions on the various apparatus consisted of two different performance categories: compulsory and optional. For the compulsory event, each gymnast performing on a specific apparatus executed the same required routine. At the optional level, the gymnast performed routines that he or she choreographed. Nowadays, each country may use compulsory and optional routines at their discretion in the training of young gymnasts.

Women's events:-

Vault
In the vaulting events gymnasts: sprint down a 25 meter (about 82 feet) runway, jump onto a beatboard - a kind of springboard, (run/ take-off segment), land momentarily, generally inverted on the hands, on the vaulting horse or vaulting table, (pre flight segment), then spring or block off of this platform to a two footed landing (post flight segment). The post flight segment may include one or more multiple saltos or somersaults, and or twisting movements.
In 2001, the traditional vaulting horse was replaced with a new apparatus, sometimes known as a tongue or table. The new apparatus is more stable, wider, and longer than the older vaulting horse - approx. 1m in length and 1m in width, gives gymnasts a larger blocking surface, and is therefore safer than the old vaulting horse. With the addition of this new, safer vaulting table, gymnasts are attempting more difficult and dangerous vaults.

Uneven Bars
On the uneven bars (also known as asymmetric bars, UK), the gymnast navigates two horizontal bars set at different heights. The height is generally fixed, but the width may be adjusted. Gymnasts perform swinging, circling, transitional, and release moves,that may pass over, under, and between the two bars. Movements may pass through the handstand. Gymnasts often mount the Uneven Bars using a beatboard (springboard).

Balance Beam
The gymnast performs a choreographed routine from 60 to 80 seconds in length consisting of leaps, acrobatic skills, somersaults, turns and dance elements on a padded sprung beam. Apparatus norms set by the International Gymnastics Federation (used for Olympic and most elite competitions) specify the beam must be 125 cm (4' 1") high, 500 cm (16' 5") long, and 10 cm (4") wide. The event requires in particular, balance, flexibility and strength.

Floor
The floor event occurs on a carpeted 12m × 12m square, usually consisting of hard foam over a layer of plywood, which is supported by springs or foam blocks generally called a "sprung" floor. This provides a firm surface that will respond with force when compressed, allowing gymnasts to achieve extra height and a softer landing than would be possible on a regular floor. Female gymnasts perform a choreographed exercise 70 to 90 seconds long. In levels 4 and up, they can choose an accompanying music piece, which must be instrumental and cannot include vocals. In the United States, the other levels must perform a routine that is choreographed for them by USAG and these routines come with music. The routines of a female gymnast consist of tumbling passes, series of jumps, dance elements, acrobatic skills, and turns. A gymnast usually performs three or four tumbling passes that include three or more skills or "tricks". Elite gymnasts can have up to six or seven tumbling passes.
At the compulsory levels (1-6) gymnasts are judged on a scale of 10, but as they reach the higher levels, particularly levels 9 and 10, the gymnasts' start-values may vary depending upon a number of different factors such as skill level and skill combinations. Also, every skill has a letter grade describing its difficulty. At level nine, to reach a start value of ten, the gymnast has to acquire bonus points, which she can achieve by connecting two or more skills of a certain high level of difficulty.
Compulsory levels of gymnastics have choreographed routines, and all women competing at that level do the same routines. In the United States, compulsory levels go from 1-6; most gymnasts start at levels 1-4 . In optional level competitions, however, all routines are different and have different floor music. Optional levels in the U.S. include levels 7 - 10 (elite). The Olympics, and college level gymnastics are also optional. In the Olympics, gymnasts are considered elite level gymnasts, which is higher level than the U.S. level 10.

Men's events:-

Floor Exercise
Male gymnasts also perform on a 12m. by 12m. spring floor. A series of tumbling passes are performed to demonstrate flexibility, strength, and balance. The gymnast must also show strength skills, including circles, scales, and press handstands. Men's floor routines usually have four passes that will total between 60–70 seconds and are performed without music, unlike the women's event. Rules require that gymnasts touch each corner of the floor at least once during their routine.

Pommel Horse
A typical pommel horse exercise involves both single leg and double leg work. Single leg skills are generally found in the form of scissors, an element often done on the pommels. Double leg work however, is the main staple of this event. The gymnast swings both legs in a circular motion (clockwise or counterclockwise depending on preference) and performs such skills on all parts of the apparatus. To make the exercise more challenging, gymnasts will often include variations on a typical circling skill by turning (moores and spindles) or by straddling their legs (Flares). Routines end when the gymnast performs a dismount, either by swinging his body over the horse, or landing after a handstand.

Still Rings
Still Rings is arguably the most physically demanding event. The rings are suspended on wire cable from a point 5.75 meters off the floor, and adjusted in height so the gymnast has room to hang freely and swing. He must perform a routine demonstrating balance, strength, power, and dynamic motion while preventing the rings themselves from swinging. At least one static strength move is required, but some gymnasts may include two or three. A routine should have a dismount equal in difficulty to the difficulty of the routine as a whole.

Vault
Gymnasts sprint down a runway, which is a maximum of 25 meters in length, before hurdling onto a spring board. The body position is maintained while "punching" (blocking using only a shoulder movement) the vaulting platform. The gymnast then rotates to a standing position. In advanced gymnastics, multiple twists and somersaults may be added before landing. Successful vaults depend on the speed of the run, the length of the hurdle, the power the gymnast generates from the legs and shoulder girdle, the kinesthetic awareness in the air, and the speed of rotation in the case of more difficult and complex vaults.

Parallel Bars
Men perform on two bars slightly further than a shoulder's width apart and usually 1.75m high while executing a series of swings, balances, and releases that require great strength and coordination.

High Bar
A 2.4cm thick steel bar raised 2.5m above the landing area is all the gymnast has to hold onto as he performs giants (revolutions around the bar), release skills, twists, and changes of direction. By using all of the momentum from giants and then releasing at the proper point, enough height can be achieved for spectacular dismounts, such as a triple-back salto. Leather grips are usually used to help maintain a grip on the bar.
As with the women, male gymnasts are also judged on all of their events, for their execution, degree of difficulty, and overall presentation skills.

Tennis

Tennis is a sport played between two players (singles) or between two teams of two players each (doubles). Each player uses a strung racquet to strike a hollow rubber ball covered with felt (most of the time Optic Yellow, but can be any color or even two-tone) over a net into the opponent's court.
The modern game of tennis originated in the United Kingdom in the late 19th century as "lawn tennis" and had heavy connections to the ancient game of real tennis. After its creation, tennis spread throughout the upper-class English-speaking population before spreading around the world. Tennis is an Olympic sport and is played at all levels of society at all ages. The sport can be played by anyone who can hold a racket, including people in wheelchairs. In the United States, there is a collegiate circuit organized by the National Collegiate Athletics Association.
Except for the adoption of the tiebreaker in the 1970s, the rules of tennis have changed very little since the 1890s. A recent addition to professional tennis has been the adoption of "instant replay" technology coupled with a point challenge system, which allows a player to challenge the official call of a point.
Along with its millions of players, millions of people worldwide follow tennis as a spectator sport, especially the four Grand Slam tournaments (sometimes referred to as the "majors"): the Australian Open, the French Open, Wimbledon, and the US Open.





Tennis Equipment:-







Choosing a tennis racquet:
Choosing the right racquet will often boost a player's game. Racquet manufacturers such as Head, Wilson, Prince, Yonex, and Babolat, just to name a few, constantly introduce new lines of racquets each year. Depending on the budget, there are plenty of racquets to choose from; however, choosing the right one for a player's game is the key. There are several guidelines such as grip size, head size, length, flex, string patterns, weight, and balance to take into considerations before making the investment. The best thing to do is to demo different type of racquets to feel the difference before deciding on which one to buy. Most tennis equipment shops provides a demo program for their customers.

Grip size:
Choosing the right size of grip is essential. The grip size is measured as the length of the perimeter of the octagonal cross-section of the handle. Grip sizes 3⅞ and 4 are for juniors where 4¼, 4⅜, 4½, and 4⅝ are for adults. The average size for female is 4¼, while the average size for male is 4⅜. A method for determining the right grip size is to hold the racquet where the palm is on the same bevel as the string face. It should be possible to comfortably fit the index finger of your non-racquet hand into the space created between the ring finger and the palm that is holding the racquet. If there is not enough space for the index finger, then the grip is too small. If there is too much space then the grip is too big. If one is in between two grip sizes, the advice is to pick the smaller one. It is always possible to make the grip bigger by adding an overgrip which will increase the size by 1/16 or half a grip size.

Head size:
Head size is the measure of the hitting area. A midsize racquet has a hitting area of 85–95 square inches, mid-plus 95–105 square inches, and oversize greater than 105 square inches. Bigger head size racquet offer more power and spin, however; they lack maneuverability and stability. Smaller head size racquet offer more control and less power. In general, more accomplished players tend to use mid-size and mid-plus racquet because they can generate more power on their own and need a racquet that they can control their power with. Larger racquets usually appeal more to beginner and intermediate players who are looking for more power and larger sweet spot.



Racquet length:
The standard length of a tennis racquet is 27 inches. However, in recent years, manufacturers introduced extra long or stretch racquets which ranges from 27.5 to 29 inches long. These racquets, called extended length racquets, can give players more power and slightly extra reach. Usually, the extra long racquet is lighter in weight compared to its standard length counterpart to keep it maneuverable.

Flex:
The flex or stiffness of a tennis racquet is the racquet’s resistance to bending or deforming upon impact with the ball. A stiffer racquet bends less, thus depleting less energy from the ball and offers more power. A flexible racquet bends more, resulting in more energy loss and less power, but more control of the ball. Players with short swing would want to have stiffer racquets since it will give the most power. A much less stiff racquet give less power and would suit players with longer swing who can generate their own power. Stiff racquets also offer solid feel while less stiff racquets have a softer feel. One thing to keep in mind is the highly stiff racquets tend to give players tennis elbow.

String pattern:
String pattern is measured by how many strings go up and down (called mains) and how many strings go side to side (crosses) when the racquet is fully strung. An “open” string pattern is one where there is a lot of empty space in the string bed because there are fewer strings. A 16 x 18 is a common "open" string pattern where 18 x 20 is an example of a “closed” string pattern.
Open string patterns are popularly thought to allow for more spin potential, as the ball can embed itself into the strings more, due to their wider spacing. However, recent scientific studies have found that stringbed properties do not directly affect spin potential of a racquet. A more open string pattern does make for higher deflection angles, which results in higher arch in ball's trajectory — this difference in deflection angle may give an impression of more spin.[6]
One drawback of open string pattern is it reduces the string’s durability. Open string patterns place more impact stress on individual strings and also allow the strings to move more freely, increasing abrasion which causes string breakage.

Weight:
Technology has played a large role in racquet weights. Until the 1990s, tennis racquets weighed an average of 12–13 ounces. When Hammer technology was introduced by Wilson, it reduced the weight to 10–11 ounces. Nowadays, most manufacturers offer sub 10 ounces racquets. Heavier racquets are less maneuverable but more powerful and more stable than the lighter counter part. Lighter racquets generally are best suited for beginner and intermediate players because of their maneuverability. More accomplished players tend to prefer heavier racquets. When examining the weight of the racquet, it is also important to understand the weight balance.

Balance:
Racquets with the same weight could have different balance. A racquet with more weight distributed on the head rather than the handle is called a head heavy racquet, and the opposite is called a head light racquet. Head heavy racquets give players more power but lack maneuverability because of weight distribution. On the other hand, head light racquets provide more control and maneuverability. Most accomplished players tend to choose head light racquets.








Tennis ball:


A tennis ball is a ball designed for the sport of tennis, approximately 6.7 cm (2.7 in.) in diameter and is normally yellow in color.

Squash

quash is a racquet sport game played by two players (or four players for doubles) in a four-walled court with a small, hollow rubber ball. Squash is characterized as a "high-impact" exercise that can place strain on the joints, notably the knees[citation needed]. Squash is recognized by the IOC and remains in contention for incorporation in a future Olympic program.
The game was formerly called squash racquets, a reference to the "squashable" soft ball used in the game (compared with the harder ball used in its parent game Racquets (or rackets; see below)).

Standard rackets are governed by the rules of the game. Traditionally they were made of laminated timber (typically Ash), with a small strung area using natural gut strings. After a rule change in the mid-1980s, they are now almost always made of composite materials or metals (graphite, kevlar, titanium, boron) with synthetic strings. Modern rackets have maximum dimensions of 686 mm (27.0 in.) long and 215 mm (8.5 in.) wide, with a maximum strung area of 500 square centimetres (approx. 90 sq. in.), the permitted maximum weight is 255 grams (approx. 9 oz.), but most weigh between 110 and 200 grams (4-7 oz.).

Squash balls are 39.5 mm and 40.5 mm in diameter, and weigh between 23 and 25 grams. They are made with two pieces of rubber compound, glued together to form a hollow sphere and buffed to a matte finish. Different balls are provided for varying temperature and atmospheric conditions and standards of play: more experienced players use slow balls that are smaller and have less bounce than those used by less experienced players (slower balls tend to die in court corners, rather than standing up to allow easier shots). Depending on its specific rubber composition, a squash ball has the property that it bounces more at higher temperatures. Small coloured dots on the ball indicate its dynamic level (bounciness), and thus the standard of play for which it is suited. The recognised speed colours indicating the degree of dynamism are:

Balls are manufactured to these standards by Prince, Dunlop, Pointfore, Wilson, Black Knight and others. The "double-yellow dot ball", introduced in 2000, is currently the competition standard, replacing the earlier "yellow-dot" that was long considered the competition standard. There is also a high-altitude "orange dot" ball, used in places such as Mexico City, Calgary, Denver, and Johannesburg. In North America, the Dunlop "green dot" ball is often used at high altitude, as well.

Other balls available are:

a. Dunlop "Max Blue" (aimed at beginners), which is 12% larger and has 40% longer "hang time" than a "double-yellow dot ball" and has "instant bounce"

b. Dunlop "Max Progress" (red) (for players wishing to improve their technique), which is 6% larger with a 20% longer hang-time than a "double-yellow dot ball" and has instant bounce

Given the game's vigorousness, players wear comfortable sports clothing and robust indoor (non-marking) sports shoes. In competition, men usually wear shorts and a t-shirt or a polo shirt. Women normally wear a skirt and a t-shirt or a tank top, or a sports dress. Towelling wrist and head bands may also be required in humid climates. Polycarbonate lens goggles are recommended, as players might be struck with a fast-swinging racket or the ball, that typically reaches speeds exceeding 200 km/h (125 mph). In the 2004 Canary Wharf Squash Classic, John White was recorded driving balls at speeds over 270 km/h (170 mph). Many squash venues mandate the use of eye protection and some association rules require that all juniors and doubles players must wear eye protection.

Racquetball

Racquetball is a racquet sport played with a hollow rubber ball in an indoor or outdoor court. Earl Riskey developed paddleball in the 1920s. Joe Sobek is credited with inventing the sport afterward in 1950[citation needed], adding a stringed racquet to the game to increase velocity and control. Unlike most racquet sports, such as tennis or badminton, the court's walls, floor, and ceiling are legal playing surfaces (sometimes, depending on the rules), rather than out-of-bounds.
Normally, a racquetball game is played between two opposing players, though three- and four-player variations exist. Two-player games are called singles or "one-up" (1-on-1 for the entire game); three-player games are called "Ironman" or "Cut-throat" (2-on-1 for the entire game) where each player takes turns serving to the other two; the "California," or "In-and-Out" variation is a 3-player game where in it is played as a three-way singles game, except that the losing player of the previous rally remains in the back court, out of play, while the other two play the next point; the four-player game is called "doubles" and is played as teams.

Equipment:

This court and equipment are required for playing racquetball:-

a. A racquetball court; fully enclosed indoor or outdoor with forward wall
b. A racquetball; a dynamic (bouncy) rubber ball of 2.25 in. (57 mm) diameter
c. Two racquetball racquets; no longer than 22 inches
d. Racquetball goggles (Optional - Some clubs mandate goggles, while others do not.)

Other useful, optional equipment includes the following: a racquetball glove for firmly gripping the sweat-slicked racquet handle, avoiding callouses, and protecting the racquet-hand knuckles from the playing surfaces, (i.e. floor, wall, the other player[s]); racquetball court shoes and sweatbands, snug-fitting, absorbent cotton shorts and shirt, to control and contain sweat from the court floor.

Racquetball equipment varies greatly in quality and intended use. Lighter racquets are preferred to heavier ones in order to increase response time; however, lighter racquets usually cost more. Nicer racquets also embody long-string technology, where some of the strings run from the top of the racquet all the way through the handle, thus increasing the "sweet spot." Different racquetball ball colors also usually indicate different ball specifications and benefits. The speed of play and visibility of the ball usually increase from blue to green to violet. Depending upon the supplier different colored balls have different characteristics. Black balls are faster, more bouncy and yet less durable than the standard blue ones, and red balls are specifically engineered for outdoor play.

Badminton

Badminton is a racquet sport played by either two opposing players (singles) or two opposing pairs (doubles), who take positions on opposite halves of a rectangular court that is divided by a net. Players score points by striking a shuttlecock with their racquet so that it passes over the net and lands in their opponents' half of the court. A rally ends once the shuttlecock has struck the ground, and the shuttlecock may only be struck once by each side before it passes over the net.
The shuttlecock (or shuttle) is a feathered projectile whose unique aerodynamic properties cause it to fly differently from the balls used in most racquet sports; in particular, the feathers create much higher drag, causing the shuttlecock to decelerate more rapidly than a ball. Shuttlecocks have a much higher top speed, when compared to other racquet sports. Because shuttlecock flight is affected by wind, competitive badminton is best played indoors. Badminton is also played outdoors as a casual recreational activity, often as a garden or beach game.
Since 1992, badminton has been an Olympic sport with five events: men's and women's singles, men's and women's doubles, and mixed doubles, in which each pair is a man and a woman. At high levels of play, the sport demands excellent fitness: players require aerobic stamina, agility, strength, speed, and precision. It is also a technical sport, requiring good motor coordination and the development of sophisticated racquet movements.

Equipment:-

Racquets:

Badminton racquets are light, with top quality racquets weighing between 79 and 91 grams including the strings. They are composed of many different materials ranging from carbon fibre composite (graphite reinforced plastic) to solid steel, which may be augmented by a variety of materials. Carbon fibre has an excellent strength to weight ratio, is stiff, and gives excellent kinetic energy transfer. Before the adoption of carbon fibre composite, racquets were made of light metals such as aluminium. Earlier still, racquets were made of wood. Cheap racquets are still often made of metal, but wooden racquets are no longer manufactured for the ordinary market, due to their excessive mass and cost.
There is a wide variety of racquet designs, although the racquet size and shape are limited by the Laws. Different racquets have playing characteristics that appeal to different players. The traditional oval head shape is still available, but an isometric head shape is increasingly common in new racquets.

Strings:

Badminton strings are thin, high performing strings in the range of about 0.65 to 0.73 millimeters thickness. Thicker strings are more durable, but many players prefer the feel of thinner strings. String tension is normally in the range of 80 to 130 newtons (18 to 36 lbf). Recreational players generally string at lower tensions than professionals, typically between 18 and 25 lbf (110 N). Professionals string between about 25 and 36 lbf (160 N).
It is often argued that high string tensions improve control, whereas low string tensions increase power. The arguments for this generally rely on crude mechanical reasoning, such as claiming that a lower tension string bed is more bouncy and therefore provides more power. This is in fact incorrect, for a higher string tension can cause the shuttle to slide off the racquet and hence make it harder to hit a shot accurately. An alternative view suggests that the optimum tension for power depends on the player the faster and more accurately a player can swing their racquet, the higher the tension for maximum power. Neither view has been subjected to a rigorous mechanical analysis, nor is there clear evidence in favour of one or the other. The most effective way for a player to find a good string tension is to experiment.

Grip:

The choice of grip allows a player to increase the thickness of his racquet handle and choose a comfortable surface to hold. A player may build up the handle with one or several grips before applying the final layer.
Players may choose between a variety of grip materials. The most common choices are PU synthetic grips or toweling grips. Grip choice is a matter of personal preference. Players often find that sweat becomes a problem; in this case, a drying agent may be applied to the grip or hands, or sweatbands may be used, or the player may choose another grip material or change his grip more frequently.
There are two main types of grip: replacement grips and overgrips. Replacement grips are thicker, and are often used to increase the size of the handle. Overgrips are thinner (less than 1 mm), and are often used as the final layer. Many players, however, prefer to use replacement grips as the final layer. Toweling grips are always replacement grips. Replacement grips have an adhesive backing, whereas overgrips have only a small patch of adhesive at the start of the tape and must be applied under tension; overgrips are more convenient for players who change grips frequently, because they may be removed more rapidly without damaging the underlying material.

Shuttlecock:

A shuttlecock (often abbreviated to shuttle and also commonly known as a bird) is a high-drag projectile, with an open conical shape: the cone is formed from sixteen overlapping goose feathers embedded into a rounded cork base. The cork is covered with thin leather or synthetic material.
Synthetic shuttles are often used by recreational players to reduce their costs as feathered shuttles break easily. These nylon shuttles may be produced with a cork made of a hard sponge instead of natural cork.
Additionally, nylon shuttlecocks come in three varieties, each variety for a different range of temperatures. These three varieties are known as green (slow speed), blue (middle speed), and red (fast speed). The colours, and therefore speeds, are indicated by coloured strips fastened around the cork. In colder temperatures, a faster shuttle is used, and in hotter climates, a slower one is chosen.

Shoes:

Badminton shoes are lightweight with soles of rubber or similar high-grip, non-marking materials.
Compared to running shoes, badminton shoes have little lateral support. High levels of lateral support are useful for activities where lateral motion is undesirable and unexpected. Badminton, however, requires powerful lateral movements. A highly built-up lateral support will not be able to protect the foot in badminton; instead, it will encourage catastrophic collapse at the point where the shoe's support fails, and the player's ankles are not ready for the sudden loading, which can cause sprains. For this reason, players should choose badminton shoes rather than general trainers or running shoes, because proper badminton shoes will have a very thin sole, lower a person's centre of gravity, and therefore result in fewer injuries. Players should also ensure that they learn safe and proper footwork, with the knee and foot in alignment on all lunges. This is not only a safety concern, as proper footwork is critical in order to effectively move around the court.

Table Tennis

Table tennis, also known as ping pong, is a sport in which two or four players hit a lightweight, hollow ball back and forth with rackets (also known as 'bats' or 'paddles'). The game takes place on a hard table divided by a net. Players must allow a ball played toward them only one bounce on their side of the table and must return it so that it bounces on the opposite side. Points are scored when a player fails to return the ball within the rules. Play is fast and demands quick reactions. A skilled player can impart several varieties of spin to the ball, altering its trajectory and limiting an opponent's options to great advantage.
The game is controlled by the International Table Tennis Federation (ITTF), founded in 1926. Since 1988, table tennis has been an Olympic sport which includes four events. From 1988 until 2004, the events were men's singles, women's singles, men's doubles and women's doubles. Since 2008 the doubles have been replaced by the team events (Beijing was the first time where table tennis had an Olympic team event).

Equipment:->

Ball:-


The international rules specify that the game is played with a light 2.7 gram, 40 mm diameter ball. Generally, it is the most-used ball. The rules say that the ball shall bounce up 23 cm when dropped from a height of 30 cm thereby having a coefficient of restitution of 0.88. The 40 mm ball was introduced after the 2000 Olympic Games. However, this created some controversy as the Chinese National Team argued that this was merely to give non-Chinese players a better chance of winning[citation needed]. A 40 mm table tennis ball is slower and spins less than a 38 mm one. The ball is made of a high-bouncing gas-filled celluloid, colored white or orange, with a matte finish. The choice of ball color is made according to the table color and its surroundings. For example, a white ball is easier to see on a green or blue table than it is on a grey table. Stars on the ball indicate the quality of the ball. 3 stars indicates that it is of the highest quality, and is used in official competitions.

Table:-

Diagram of a table tennis table showing the official dimensions
The table is 2.74 m (9 ft) long, 1.525 m (5 ft) wide, and 76 cm (30 inch) high with a Masonite (a type of hardboard) or similarly manufactured timber, layered with a smooth, low-friction coating. The table or playing surface is divided into two halves by a 15.25 cm (6 inch) high net. The table surface can either have a green or blue color.

Racket:-

Players are equipped with a laminated wooden racket covered with rubber on one or two sides depending on the grip of the player. This is called either a paddle, racket, blade or a bat depending on where in the world the game is being played. In the USA the term "paddle" is common, in Europe the term is "bat," and the official ITTF term is "racket." This section will use the ITTF term.
Table tennis regulations allow different surfaces on each side of the racket. The different types of surfaces provide various levels of spin or speed, or in some cases, nullify spin. For example, a player may have a rubber that provides much spin on one side of his racket, and no spin on the other side of the racket. By flipping the racket in play, different types of returns are possible. To help a player distinguish between different types of rubber used by his opposing player, international rules specify that one side must be red while the other side must be black. The player has the right to inspect his opponent's racket before a match to see the type of rubber used and what color it is. Despite high speed play and rapid exchanges, a player can see clearly what side of the racket was used to hit the ball. Current rules state that, unless damaged in play, the racket cannot be exchanged for another racket at any time during a match.
Recent years have seen an advancement in technology of table tennis blades. Materials of different properties may be combined with the wood in the blade to enhance its playing performance. Many blades today feature one or more carbon layers within them to enhance their 'sweet spot', and to give the player a greater margin of error when playing powerful shots. Materials incorporated into table tennis blades today include titanium, acrylate, aramids, fiberglass, and aluminium.
The rubber coating may be of pimpled rubber, with the pimples outward, or it may be a rubber that is composed of two materials, a sponge layer, covered by a pimpled rubber, with the pimples pointed inwards or outwards. Some rackets are not covered with rubber at all, because a "naked" racket is more resistant to a spin. However, it is illegal to use these types of racket in competition as they are not approved by the ITTF. Some types of rubbers are also not approved. Approved rubbers have the ITTF emblem on the base of the rubber. Players have many choices and variations in rubber sheets on their racket. Although a racket may be purchased with rubber by the manufacturer, most serious tournament players will create a customized racket. A player selects a blank blade (i.e. a racket without rubber), based on his playing style. The type of wood and synthetic layers used to make up the blade will provide a slower or faster blade. The player can choose from different types of rubber sheets which will provide a certain level of spin, speed and specific playing characteristics.
Normally, a sheet of rubber is glued to a blade using rubber cement and not removed until the rubber wears out or becomes damaged. In the 1980s, a new technique was developed where the player would use a special glue called speed glue to apply the rubber every time he played. The glue would help provide more spin and speed by providing a "catapult" effect. This technique is known as "regluing" and has become a standard technique for top players.
The surface of a racket will develop a smooth glossy patina with use. The rubber surface needs to be regularly cleaned to ensure it retains a high friction surface to impart spin to the ball. Players use a commercial cleaner, or just water and detergent as cleaning agents.
Racket construction and new rubber technology (skilled elite players typically select and attach the rubber to their own rackets and glue them before every match) contribute significantly to the amount of deviation from the expected ball flight path. The fairly recent development of speed glue speeds up the departure of the ball from the rubber considerably, though at the cost of some ball control on touch shots where little or no spin is put on the ball. Speed glue was allowed for the last time in the 2008 Summer Olympics. From the 2012 Summer Olympics on speed glue will be banned at the Olympic games.