Smartphone games and competitive gaming are becoming increasingly recreational and Olympics activities with blooming popularity worldwide [2, 3, 17]. However, a number of occupational factors, including prolonged screen time, repetitive movements, poor posture, and sedentary behaviour have been identified to increase the potential risk for the development of chronic diseases and possibly all-cause mortality [8, 18]. This study aimed to examine the training behaviour, fatigue profile, and location of pain/discomfort among professional smartphone athletes. The present findings revealed that most professional eSport athletes would induce physical fatigues and dry eyes after half-day (4-hour) and full-day (8-hour) training. Furthermore, similar to previous demographic studies, eSport athletes are required to sit with the same position for 5.5 to 10 h/day [3, 5] or up to 14 h/day , leading to a sedentary lifestyle with an increased chance of fatigue and chronic injury as well as increased all-cause mortality [8, 18]. The physical fatigue may be due to poor workplace practices (prolong posture, repetitive movement), competition stress, and burnout; while eye fatigues could also be related to prolonged visual attention to the screen and poor lighting environment .
Fatigue is a common symptom of many medical conditions, from mild-to-severe. It can cause various physical, mental, and emotional symptoms, including headaches/dizziness, sore muscles, muscle imbalance, poor concentration, impaired decision-making, and hand-to-eye coordination . Our data indicated that nearly half of the athletes were actively performed regular relaxation/recovery after eSport training and competition, which agrees with the previous study showing a 29.2% and 34.2% of the videogame athletes had relaxation/recovery and physical fitness sessions, respectively . Therefore, a regular fatigue monitoring and management session were recommended to pertain to the athlete's maximal physical performance, injury, and illness risk, especially after half-day and full-day training.
Over 30% of the eSport athletes reported cervical spondylosis, headache/dizziness, phalanx tenosynovitis, and rhinitis. They could be related to the specific ergonomic and activity demand. In typical smartphone game athletes, maintaining posture with the prolonged inferior viewing angle and hand-held smartphone position would induce head flexion, repeated or sustained wrist bending, and repeated twisting or pushing thumb motions . Athletes may develop muscle imbalance between agonist and antagonist muscles and thus poor balance and muscle soreness. Additionally, our results indicated the highest prevalence rates of professional smartphone gaming athletes were neck (40%), finger (38%), and headache (32%), which were slightly different from the rates from the video gaming athletes [Neck (42%), back (42%), wrist (36%), and hand (32%)] and from the sedimentary office workers [lower back (72%) and neck (55.2%)] . The differences in prevalence rates and locations could be due to the unique workplace environment and task intensity in smartphone eSport, which affect fine-tuning of postural control and postural adaptation21 and thereby develop chronic injuries [2.9].
Interestingly, our results indicated that while career duration had no significant association with the fat ratio and total confirmed injury, but it showed a marginal negative association with BMI instead, which did not support our original hypothesis. It is expected that prolong sitting time in smartphone game training could be similar to sedentary lifestyles , which could lead to physical inactive that is related to an increased BMI and fat ratio and health risks such as hypertension and diabetes. One plausible explanation is due to a relatively short lifespan of the career in professional athletes, officially start at 18 and normally retire at 24 years old. Young sport athletes could be more likelihood to attain superior eye-hand coordination (500 to 600 action moves/min) and rapid decision making and reaction times [3, 6]. Another explanation is due to the movement intensity of eSport is as high as combat sports and might develop only mild injuries, which may not be easily recurrence over years as other traditional sports such as basketball, soccer and badminton. To our best knowledge, this is the first work that shows the fatigue and injury profiles of professional smartphone eSport athletes.
Some limitations should be considered when interpreting our results. First, only a single group of elite male smartphone athletes from Mainland China top teams was recruited in this study. The results may not be generalized to lower-level game players as well as recreational smartphone gamers. Second, only the self-report and orthopaedic examination report were provided. Other comprehensive physiological and performance indicators (e.g., eye-hand coordination, decision-making capacity, visual attention) should also be considered to facilitate the identification of talented players. Third, the small sample size in this study had low frequency distribution and therefore we used likelihood ratio instead of Chi-square with less statistical powerful. Forth, the fatigue and injury profiles are rather game-content specific, which may affect the decision-making and motor skill control (thumb vs. index finger) to attain the best results in a game. Although all the participants were trained with the same game-content in this season, more game-content should also be investigated to determine how game-content would influence the health injury. This can be served as the game design guidelines (e.g., length of each game set, use of control setting) for game designers and policy makers.