Loushin, Stacy R.

Abstract Background Tennis players often present with ulnar-sided wrist pain, which may reflect repetitive stress and/or faulty mechanics. There is a role for investigating the biomechanics of tennis strokes and how they may relate to wrist pathology. The purpose of this study was to investigate whether three-dimensional motion capture technology and dynamic electromyography (EMG), when used to study groundstrokes in elite junior tennis players, reveals patterns of upper extremity motion that may correlate with the development of clinically relevant pathology. Case Description Three-dimensional kinematic and EMG data were collected from two United States Tennis Association-ranked adolescent tennis players during groundstrokes. There were several observed differences in the two players' degree and timing of pronation/supination, ulnar/radial deviation, and flexion/extension during their strokes. Clinical Significance Advanced motion capture technology facilitates a nuanced understanding of complex movements involved in groundstroke production. This methodology may be useful for identifying athletes who are at risk for injury and guiding rehabilitation for players experiencing pain. Level of Evidence IV

Objectives: Baseball pitchers often participate in throwing programs that involve throwing at reduced effort levels to gradually increase the amount of stress experienced across the elbow. It is currently unknown how reduced effort pitching compares to maximum effort with respect to elbow stress and ball velocity. The purpose of this study is to determine whether elbow stress and ball velocity correlate with reduced effort pitching, whether elbow stress and ball velocity decrease proportionally while throwing at a reduced effort, and to assess intrathrower reliability. Methods: Ten healthy male high school baseball pitchers threw 5 pitches from a regulation pitching mound at 3 effort levels: maximum effort, 75% effort, and 50% effort. Elbow stress, specifically elbow varus torque, was calculated for all pitches using a marker-based 3D motion capture system. Ball velocity was measured using a Doppler radar gun. Intrathrower variability was calculated for each effort level. Results: Elbow stress and ball velocity decreased with reduced effort throws (p<0.001 and p=0.003, respectively). However, the reductions in elbow stress and ball velocity were not proportional. At 75% effort throws, elbow stress decreased only 19% and ball velocity decreased only 10%. At 50% effort throws, elbow stress decreased only 25% and ball velocity decreased only 15%. Intrathrower reliability was excellent for elbow stress and ball velocity, with intraclass correlation coefficients all greater than or equal to 0.80. Conclusions: Pitching at a reduced effort level resulted in decreased elbow stress and ball velocity. However, for every 25% reduction in perceived effort, elbow stress decreased by a mean of 13% and ball velocity decreased 8%. When baseball pitchers attempt to throw at a reduced effort of maximum, throwing metrics do not decrease proportionately. While pitching at a reduced effort of maximum decreases elbow stress and ball velocity, the decrease is not proportional, subjecting the elbow to more stress than intended. This has significant clinical importance to pitchers, coaches, and medical professionals in the setting of injury prevention and return to sport. [Table: see text]

Background: Baseball pitching injuries are on the rise. Inertial measurement units (IMUs) provide immediate feedback to players and coaches, allowing for collection outside of the traditional laboratory setting with real-world application. The 4D Motion system provides kinematics throughout the pitching motion and may be beneficial for individualized programs in the throwing athlete. A systematic analysis of these sensors has not been completed. Purpose: To evaluate the validity of the 4D Motion IMU system for analyzing the baseball pitching motion compared with marker-based motion capture, and evaluate the internal reliability and consistency of the device. Study Design: Controlled laboratory study. Methods: Ten high school pitchers participated in this study (10 male; 9 right-hand dominant; mean age, 16.6 ± 1.3 years; mean body mass index, 24.1 ± 3.9). Participants were simultaneously outfitted with six 4D Motion IMU sensors and retroreflective markers. The pitchers threw fastballs at maximum effort off a mound at the standard height and distance. A comparison was made between the IMUs and corresponding motion capture values for shoulder external rotation, elbow flexion, chest extension, pelvis and chest rotation velocity, and rotation acceleration. Results: Significant differences were found for 5 of 7 metrics analyzed. The IMU overreported most metrics, except for elbow flexion and pelvis rotation angular acceleration, where both positive and negative errors were observed. The root mean square error and percentage errors indicated smaller discrepancies for chest extension (4°± 5°) and pelvis (38 ± 19 deg/s) and chest (96 ± 42 deg/s) rotation velocity, with elbow flexion having the largest variance (21°± 9°). Conclusion: The values of the 4D Motion IMU system should not be considered equivalent when compared with marker-based motion capture studies. The system lacked internal consistency and reliability, with angular velocities being the most consistent. Caution should be used when using the metrics provided by an IMU-based system for individualized monitoring. Clinical Relevance: If found valid and reliable, IMUs could be used for longitudinal workload monitoring, individualized throwing and rehabilitation programs, and ultimately injury prevention. This study demonstrates that the data obtained from a 4D Motion system using Gen 3 sensors are not equivalent to the data obtained from a marker-based motion capture system.

Background: Baseball pitchers often participate in throwing programs that involve throwing at reduced effort levels to gradually increase the amount of stress experienced across the elbow. It is currently unknown how reduced effort pitching compares with maximum effort with respect to elbow stress and ball velocity. Purpose/Hypothesis: The purpose was to determine the correlation between elbow stress and ball velocity with reduced effort pitching. We hypothesized that decreased perceived effort would disproportionately correlate with elbow stress and ball velocity. Study Design: Descriptive laboratory study. Methods: Ten healthy male high school baseball pitchers threw 5 pitches from a regulation pitching mound at 3 effort levels: maximum effort, 75% effort, and 50% effort. Elbow stress, specifically elbow varus torque, was calculated for all pitches using a validated marker-based 3-dimensional motion capture system. Ball velocity was measured using a Doppler radar gun. Intrathrower variability was calculated for each effort level. Results: Elbow stress and ball velocity decreased with reduced effort throws ( P < .001 and P = .003, respectively). However, the reductions in elbow stress and ball velocity were not proportional. At 75% effort throws, elbow stress measured 81% (intraclass correlation coefficient [ICC], 0.95), and ball velocity measured 90% (ICC, 0.80) of maximum, respectively. At 50% effort throws, elbow stress measured 75% (ICC, 0.93), and ball velocity measured 85% (ICC, 0.87) of maximum. Intrathrower reliability was excellent for elbow stress and ball velocity, with all ICCs ≥0.80. Conclusion: Pitching at a reduced effort level resulted in decreased elbow stress and ball velocity. However, for every 25% reduction in perceived effort, elbow stress decreased by a mean 13%, and ball velocity decreased 7.5%. When baseball pitchers attempt to throw at a reduced effort of maximum, throwing metrics do not decrease proportionately. Clinical Relevance: While pitching at a reduced effort of maximum decreases elbow stress and ball velocity, the decrease is not proportional, subjecting the elbow to more stress than intended. This has significant clinical importance to pitchers, coaches, and medical professionals in the setting of injury prevention and return to sports.

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 ± 1.8 years, Height = 1.7 ± 1.1 m, BMI = 21.3 ± 3.4 kg/m2, 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.

» Ulnar-sided wrist pain is a common cause of debilitating wrist pain in stick-handling athletes. Due to the complexity of surrounding anatomy, the evaluation and diagnosis can be challenging. » Injury of the triangular fibrocartilage complex (TFCC) is the most common cause of ulnar-sided wrist pain. Repetitive, unrestricted pronosupination, wrist deviation, and axial-loading activity, such as in tennis, place substantial stress on the TFCC. » The ulnotriquetral (UT) ligament is a palmar thickening of the ulnar capsule arising from the palmar radioulnar (PRU) ligament of the TFCC. When injured, the UT ligament can be a source of acute or chronic ulnar-sided wrist pain. The ligament can avulse off bone, can rupture completely, or can split longitudinally. » Arthroscopic-assisted repair is a safe, reliable, and effective treatment for UT ligament split tears and peripheral TFCC tears. » Although the benefit of a team-based approach may be realized by most patients, high-performing, stick-handling athletes are part of a unique population who execute repetitive, extraordinary wrist movements. The high demand and functional requirement expected of the wrists require a uniquely tailored approach to return them to the same level of competitive play.

Background: In recent years, the prevalence of medial ulnar collateral ligament injuries has increased in throwers of all ages and skill levels. The motusBASEBALL sensor possesses an inertial measurement unit (IMU) that has been developed and applied to the throwing arm to allow for measurements of several objective parameters, which may prove beneficial for monitoring, rehabilitation, and injury prevention in the throwing athlete. However, the reliability, consistency, and validity of the IMU have not been independently assessed. Purpose: To evaluate the reliability, consistency, and validity of the motusBASEBALL sensor compared with the historic gold standard of marker-based motion capture. Study Design: Controlled laboratory study. Methods: A total of 10 healthy male baseball athletes with varsity-level high school experience volunteered to participate in this study. Participants were fitted with 37 retroreflective markers for motion capture and the motusBASEBALL IMU sensor. Participants threw 5 fastballs at maximum effort, with measurements recorded simultaneously by motion capture and the IMU. Arm slot, arm speed, arm stress, and shoulder rotation were measured and compared. Results: Of the 4 metrics generated by the IMU, significant differences were found for 3 of the throwing metrics compared with motion capture including arm slot (5.0°± 6.1°; P = .037), elbow varus torque (9.4 ± 12.0 N·m; P = .037), and shoulder rotation (6.3°± 6.1°; P = .014). Arm speed did not demonstrate a statistically significant difference (29.2 ± 96.8 rpm; P = .375). The IMU consistently underreported pitching performance values. Shoulder rotation exhibited excellent reliability with <5° of error, and arm slot demonstrated good reliability with <10° of error. Arm stress and arm speed were less reliable. Conclusion: The IMU was not accurate or valid for arm slot, arm stress, and shoulder rotation compared with marker-based motion capture. It was relatively accurate for arm speed. Despite its lack of validity, it was consistent and reliable for arm speed and shoulder rotation and relatively reliable for arm slot and arm stress. Caution should be used when comparing values provided by this IMU to the gold standard of marker-based motion capture. Clinical Relevance: IMU technology has potential to be used in monitoring, rehabilitation, and injury prevention in throwing athletes if valid. This study demonstrates that the values provided by the IMU should not be considered equivalent to those generated by the gold standard of marker-based motion capture; however, there may still be a role for this technology when relying on its internal consistency for intrathrower comparisons and tracking.