The relationship between postural components and muscle strength balance among 9 to 14-year old children

Study was to examine the differences between the strength of linked agonist and antagonist muscles according to their location and postural role. Study included 102 schoolchildren: age 11,28±1,55 (x±SD); BMI 18,87±3,71. Body posture was assessed visually in the sagittal plane (neck, chest, shoulders, upper back, trunk, abdomen, lower back position) and in the frontal plane (head, shoulders, spine, hips, feet, arches position) using the New York State Posture Rating Chart. Each component was rated on a scale 5 (normal), 3 (slightly deviated), 1 (markedly deviated). Maximal isometric muscle strength was measured with manual dynamometer on the muscles: neck fl exors and extensors, upper and lower part of pectoralis major, middle and lower part of trapezius, trunk fl exors and extensors, hip fl exors and extensors, hip adductors and abductors. Children were divided into two groups: normal posture and deviated posture. We found that the detrimental effect on the posture of the divergence in strength between opposing muscles was dependent on their location. There were cases of pronounced strength imbalance among children with normal posture, for example in relationship of hip extensors to hip fl exors, while deviated posture group showed negligent imbalance. On the other hand, children with postural deviation appear to have imbalances in other locations. For example, in the relationship of the pectoralis group to the trapezius. Likely explanation is that there are normal differences between anterior and posterior muscle groups, but posture related problems seem to be dependent on the strength imbalance of antagonistic muscle groups at a specifi c location.