Bowling refers to a series of leisure activities in which a player rolls or throws a bowling ball. In indoor bowls, the target is usually to knock over pins. In outdoor variations, the aim is usually to get the ball as close to a target ball as possible. The indoor version of bowling is often played on a flat wooden or other synthetic surface, while outdoor bowling the surface may be grass, gravel or a synthetic surface. The most common types of indoor bowling include ten-pin, nine-pin, candlepin, duckpin and five-pin bowling, while in outdoor bowling, bowls, petanque and boules are popular. There are many forms of bowling, with one of the most recent being ten-pin bowling, also known as the norm. The earliest most primitive forms of bowling can be dated back to Ancient Egypt and the Roman Empire. Indeed, about 2,000 years ago a similar game evolved between Roman legionaries: it entailed tossing stone objects as close as possible to other stone objects (this game became popular with Roman soldiers, and eventually evolved into Italian Bocce, or outdoor bowling). The first standardized rules for pin were established in New York City, on September 9, 1895. Today, bowling is enjoyed by 95 million people in more than ninety countries worldwide and continues to grow through entertainment media such as video games for home consoles and handheld devices. Bowling is an anaerobic type of physical exercise, similar to walking with free weights. Bowling helps in burning calories and works muscle groups not usually exercised. The flexing and stretching in bowling works tendons, joints, ligaments, and muscles in the arms and promotes weight loss. While most sports are not for elderly people it is possible to practice bowling very well at advanced ages. Apart from the physical benefits, it also has psychosocial benefits, strengthening friendships or creating new ones in groups Like any other physical activity, warming up helps to prevent injuries. Bowling balls are heavy with varying weight ranges; to avoid back and wrist injury, they should be picked up with both hands. Its also recommended to bend ones knees while picking up bowling balls to avoid back injuries. Most bowling ball return mechanisms use a power-lift that includes a spinning wheel, and bowlers should keep their hands clear of it. Bowlers should also warm up their fingers before inserting them into a bowling ball, to ensure that their fingers do not get stuck in the ball. Even in small ball bowling, balls should be picked up with one hand on each side of the ball - small balls return to the rack with enough force to smash fingers. It is imperative to keep the soles of bowling shoes dry. If the bowling shoe sole gets wet, it can stick like glue on an approach and result in the bowler suffering a wipeout or blown knee. The most common causes of wet bowling shoes tend to be spilled beverages, drips in washrooms and near concessions, and snowmelt or rainwater tracked into the bowling center. Outdoor footwear should be removed at the bowling center entrance. All spills should be reported to bowling center staff and cleaned immediately. The lane surface carries a high amount of oil (lane conditioner) and is extremely slippery. A bowler should never cross the foul line at the approach. Only authorized personnel should step past the foul line, even if it is to pick up a loose item that fell onto the lane.