Changes in Shoulder Kinematics Following an Isokinetic Fatigue Protocol in Tennis Players
Condition: Fatigue
MeSH terms: Fatigue
Study type: Observational

Summary: 
      A typical tennis match can take 1 to 5 hours. Tennis serve can be divided into eight stages
      and three phases. Injuries usually happen in the cocking stage and acceleration phase of the
      serve, where it requires large shoulder range of motion and proper scapular motion, including
      sufficient scapular upper rotation, external rotation, and posterior tilt to produce a
      powerful serve. Altered shoulder kinematics are associated with shoulder injuries in tennis
      players, including delayed shoulder horizontal adduction, and early external rotation. Due to
      the long duration and repetition of activity in a match, fatigue may happen and result in
      decreases in sensory input, passive range of motion, ball speed, and muscle strength. These
      changes may further lead to altered glenohumeral and scapular kinematics. However, previous
      studies mainly focused on the effects of fatigue on scapular kinematics in constrain
      movements and applied different fatigue protocols, which lead to inconsistent results. Tennis
      serve in cocking stage and the acceleration phase require high activation of shoulder
      external rotators and internal rotators, including infraspinatus, pectoralis major,
      subscapularis, latissimus dorsi and serratus anterior. However, to our knowledge, no study
      has investigated how fatigue of shoulder rotators influences shoulder kinematic as well as
      scapular kinematics during the late cocking stage and acceleration phase of tennis serve.
      Therefore, the investigators aim to investigate whether fatigue of shoulder rotator affects
      shoulder kinematics in healthy tennis players during the late cocking stage and acceleration
      phase of tennis serve.This is a single group, pretest-posttest measurement study. In a
      fatigue protocol, investigators use an isokinetic dynamometer to induce fatigue of shoulder
      rotators. Outcome measures will be tested before and after the fatigue protocol, including
      peak torque of shoulder rotators, humerothoracic kinematics, scapulothoracic kinematics, and
      median power frequency recorded by a surface electromyography. Peak torque of shoulder
      rotators will be measured with an isokinetic dynamometer. Surface electromyography will be
      used to measure peripheral muscle fatigue by maximum voluntary isometric contraction.
      Humerothoracic kinematics and scapulothoracic kinematics during a functional tennis serve and
      scaption will be collected with a motion capture system.
    


Intervention name(s): isokinetic dynamometer
Intervention type(s): Device
Intervention description(s): We will use an isokinetic dynamometer to conduct the concentric isokinetic fatigue protocol. The start position is shoulder abduction 90°, elbow flexion 90°and range of motion is set from 0 ° (internal rotation) to 90 ° (external rotation) under 120°/s. To calculate maximum torque of shoulder external and internal rotation, the subject will perform maximum isokinetic test 5 times before fatigue. Fatigue protocol include 10 sets, and each set include 32 repetitions with 30 seconds of rest between sets. The fatigue protocol will be stopped under three conditions: 1. the torque decreases 50% of maximum torque three times in one set or 2.rating of perceived exertion (RPE) abrove 15 and players can not perform the fatigue protocol or 3. finish the whole test.
Observational model: Other
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        All of the subjects are healthy during the test to avoid the risk of injury.
      
Keywords: tennis player; shoulder kinematics; scapular kinematics; serving biomechanics; isokinetic dynamometer