# Upper Extremity Kinematics and Electromyographic Activity in Uninjured Tennis Players
###### Abstract  
There has been an increase in ulnar-sided wrist pain among tennis players. The purpose of this study was to establish a normative dataset of kinematic and electromyography (EMG) data during the forehand and two-handed backhand groundstrokes. In total, 20 adolescent United States Tennis Association (USTA) ranked tennis players (11/20 Male, Age = 15.0 \(\pm\) 1.8 years, Height = 1.7 \(\pm\) 1.1 m, BMI = 21.3 \(\pm\) 3.4 kg/m\({}^{2}\), 18/20 right-arm dominant) participated in this study. Kinematics (range of motion and angular velocity) and EMG data were simultaneously acquired during the forehand and two-handed backhand groundstrokes. Minimal differences were found between groupings of age, sex, and USTA ranking. The two-handed backhand groundstroke is characterized by bilaterally flexed elbows and ulnarly deviated wrists, with a flexed wrist and pronated forearm on the non-dominant side and an extended wrist and supinated forearm on the dominant side. EMG activation occurs bilaterally by peak backswing. The forehand groundstroke is characterized by a flexed elbow, pronated forearm, and ulnarly deviated and extended wrist. The wrist is at maximum ulnar deviation at ball impact. This study established an initial foundation for normative data for the forehand and two-handed backhand groundstrokes, which can be used for injury detection, rehabilitation, prevention, and ultimately performance improvement of tennis athletes. tennis; biomechanics; forehand; two-handed backhand; kinematics +
Footnote †: journal: _Sci._  
Footnote †: journal: _Sci. The wrist and hand play predominant roles in tennis strokes, functioning as the final link between kinetic energy generated by the lower body, trunk, and upper extremity at the time of ball contact [5]. In a recent review, the incidence and prevalence of wrist pain, specifically unnar-sided, as well as wrist injury, were noted to account for a higher percentage of total injuries than ever previously described [6]. Extensor carpi ulnaris (ECU) pathology represents the most common etiologies of ulnar-sided wrist pain [7]. Generating topspin during the forehand groundstroke requires the player to grip the racket in excessive ulnar deviation, predisposing the ECU to injury [8]. Additionally, the same injury pathology occurs in the non-dominant wrist during the two-handed backhand groundstroke, specifically the wrist closest to the racket head [7]. This injury mechanism impacts both elite and less experienced players alike. Less experienced players may subject themselves to larger stress due to poor technique and increased vibration loads in the elbow and wrist during stroke production [9]. Elite tennis players experience increased volumes of play, which has been suggested as positively correlated with injury rate [10; 11; 12]. While many studies have examined the kinematic characteristics of the tennis serve [13; 14; 15; 16], limited information exists regarding the mechanics of the forehand and two-handed backhand groundstrokes. [PERSON] et al. recently analyzed the non-dominant wrist during the two-handed backhand [17], but no electromyographic (EMG) recordings were acquired. To allow for the development of rehabilitation, return to play, and ultimately injury prevention strategies, normative movement patterns must be characterized. To date, to our knowledge, kinematic and EMG normative data for the forehand and two-handed backhand do not exist. To address the lack of data, this study examined kinematic and electromyographic (EMG) data during the forehand and two-handed backhand groundstrokes for the creation of a normative database. It was hypothesized that uninjured adolescent United States Tennis Association (USTA) ranked tennis players, regardless of age, sex, or USTA ranking, produce consistent stroke mechanics in the forehand and two-handed backhand groundstrokes to allow for the creation of a single normative database for both kinematic and EMG data.