A Descriptive Profile of Isometric Muscle Strength and Muscle Strength Imbalance in Young Tennis Players

Abstract

Background. Tennis is assumed as asymmetric sport, prolonged training practice could affect muscle strength
imbalance. Muscle strength functional ratio imbalance could be a reason for poor posture, physical weakness and
increased risk of injury. The purpose of the research was to evaluate young tennis players’ main muscle group
strength topography and to investigate the level of different muscles groups’ bi-lateral and contra-lateral imbalance.
Methods. The participants of the study were six young right handed competitive tennis players (girls, age 11.4 ±
0.5 years, tennis experience 4.7 ± 0.6 years). Examination of main muscles groups was performed with an isokinetic
dynamometer.
Results. Young  tennis  players  have  pronounced  bi-lateral  imbalance  between  shoulder  joint  extensors  and
flexors  (25%),  internal  and  external  rotators  (36%),  left  elbow  flexors  and  extensors  (58%),  wrist  pronator  and
supinator (the right hand 17%, left 48%), hip flexors and extensors (35%); knee joint flexors and extensors (60%);
ankle dorsal flexors and plantar flexors (59%); spine and abdominal muscles (48%). It was detected that young tennis
players have pronounced contra-lateral imbalance between right and left internal rotators of the shoulder joint (27%)
and external rotators (26%), wrist joint supinators (41%).
Conclusions.  To  avoid  the  increase  in  muscle  bi-lateral  imbalance  it  is  highly  recommended  to  pay  more
attention to shoulder adductors and shoulder external rotators, elbow flexors and extensors, wrist supinators and
extensors, knee extensors, ankle plantar flexors and spine flexors. For contra-lateral imbalance prevention in addition
to train non-dominant upper extremity muscles: shoulder internal and external rotators, wrist supinators.

Keywords:  bi-lateral imbalance, contra-lateral imbalance, maximal isometric torque, muscle functional ratio,  asymmetry.