Prevention and Care of Physical Injuries when Playing Table Tennis at Home during COVID-19 Quarantine

Table tennis is a sport suitable for different types of environmental conditions and can be carried out both indoor and outdoor with simple equipment. Due to the convenience and flexibility of this sport, it has become a globally favorite exercise for people who are confined at home due to COVID-19 outbreak. Unlike common misperceptions about table tennis being a light exercise, it is a fast sport with quick physical movement, posture changes, and even body rotations, which can easily get players injured. Particularly, people are prone to injuries in a home environment that often does not fully meet the standard of playing conditions. Common injuries caused by playing this sport are around the wrist, waist, knee, and shoulder areas. In this article, illustrations and discussed are centered on injury prevention, analysis, and therapeutic care. Cautious preparations in advance, both physically and environmentally, can effectively prevent much of the injuries.

improve one's immune system, which is particularly relevantin this pandemic. Regular participation in exercise enhances bone density, tendon and ligament intensity, range of motion, and lean body mass (muscular strength). The physical effects of exercise also include increase in cardiorespiratory efficiency, decrease in body fat, and protection against chronic diseases [5]. Improvements in psychological well-being have also been observed as a result of physical activities. Proper exercise and sport activities lead to a reduction in mental status of negative valence such as anxiety, depression, anger, and loneliness [4]. Nevertheless, caused by the virus pandemic, public places such as sport venues, fitness clubs, and parks and trails are shut down for an extended period of time.
Home-based exercise became a new fitness choice for people to maintain health conditions, improve immunity, and relieve negative emotions such as anxiety and depression. the cerebral cortex of the player is in an excited condition all the time with restrained alternant process, which exerts a very good exercising effect to the acuity that improves vision and the flexibility of nervous system. Because the ball moves fast and spins, the players are required to accurately observe the rotation and landing point of the ball instantly and quickly decide a strategy to return the ball play. This process helps improving the function of the nervous system and the coordination of the body [1,6,7] . Based  on these advantages of table tennis, during COVID-19 many people   choose to work out by playing table tennis in their living rooms or basements, and normally they get a good work-out from doing so.
Table tennis may be considered by many as a light exercise, and players are less prone to injuries. Yet, in reality, this is not true.
Table tennis is a fast sport with quick physical movement, posture changes, and even body rotations, which requires full attention and swift reaction [8,9]. The fast-paced game and regularly-rotating body movements can easily get players injured. Particularly, people are prone to injuries in a home environment that often does not fully

Wrist Injury and Prevention Measures
The wrist is mainly made up of eight small bones of different shapes, which is why the wrist can make rather flexible and accurate movements. In the meantime, small bones in the wrist are susceptible to injuries. The range of motion of the wrist is overall small. When players hitting the ball, their arms act as a lever and the wrist makes the inward rotation or abduction motion quickly.
If the wrist joint is lack of flexibility, it is prone to an injury or even repeated injures. There are three major measures to prevent a wrist injury: (a) warm up, stretch, and get the wrist ready for playing, (b) form a good habit of using protectors such as wrist band, and (c) avoid over exertion of strength and full range of motion. When the wrist is slightly injured, symptoms such as pain, limited movement, and swelling can appear. While ice pad helps reducing inflammation in early hours, fumigation with medicine and appropriate massage would promote blood stasis absorption after 48~72 hours of injury. As massage is an adjunctive therapy, the following specific methods of massage can be applied in a wrist injury: (a) wrist flexor: when the wrist is in dorsiflexion, massaging from the inside of the forearm can stretch the flexor of the wrist so as to accurately massage the muscle group. To do so, one can use the forearm and fist to effectively replace the thumb when massaging; and (b) wrist extensor: these muscles are usually more fibrotic than the flexors and an accurate massage of each muscle will yield a good effect when wrist flexion will put the extensor into a stretching state [9][10][11].

Waist Injury and Prevention Measures
When playing table tennis, the upper body of the player leans forward and the lumbar spine ligament is pressed forward also. can be an adjunctive therapy. The following is a specific method of massage for waist injury: Massage the quadratus psoas by using the fingers or knuckles, which allows more precise and deeper access to the quadratus psoas. When there is a major lumbar soft tissue or ligament tear, obviously facet joint dislocation, or lumbar disc herniation, the injured individual needs to rest in bed and seek for medical treatment [8,10,12].

Knee Joint Injury and Prevention
During the course of playing table tennis, the knee joint is individual intends to play for more than an hour, it is better to limit the consecutive playing time to half an hour. Players can walk for a while during the intervals to relax their muscles and eliminate fatigue. Massage can be an adjunctive therapy. Here is a method of sitting position to relax knee joint: sit next to the massage table, fix the sore spot or use one's fingers to restrict movement, and then stretch the knee joint. In more severe cases, full extension should be stopped to reduce the likelihood of inflammation, which can develop as a result of pressure on the patella [8,9,12].

Shoulder Joint Injury and Prevention
When playing table tennis, an individual develops the tendency of using the arm to smash the ball repeatedly. The repetitive movements involving over-using or over-exerting the shoulder and excessively pulling shoulder may easily cause an injury to the tendon in the long head of biceps brachia. The main reasons of injuries are that the shoulder joint is pulled repeatedly and rub with ligament when doing the activities of extension and rotation. In order to prevent injuries, some precautions should be taken while playing. First, it is important to warm up sufficiently before playing, including jogging, joint rotation, and stretching. Secondly, one should not only practice forehand or backhand strokes, which is unbalanced and prone to muscle strain. In addition, it is better for people to play for half an hour maximum in each round. Players should take a break afterwards, for instance taking a walk during the intervals to relax their muscles and eliminate fatigue. When feeling uncomfortable or slightly injured, one can self-massage shoulder blades on the back with fingers. These can be performed by using fingers or knuckles for physical therapy and manipulating arms to stretch the muscles on one's side. If the area is too tense or sensitive, the player can lower the arm to soften the muscle and make the area easier to access [8,9,10,11].