Effect of Head-Neck Position on Arm Lifting Strength

The purpose of this study was to examine whether the muscle strength of the elbow flexors would be influenced by head and neck (HN) positions. Forty-one healthy male and female students between the ages of 19 and 32 years volunteered as subjects. A Force Evaluation and Testing System (FET 5000) was used to measure the arm lifting strength in the standing positions while each subject keeping his head in various prescribed positions (neutral, flexion, and extension). The mean force of two trials was determined for each HN position. At the same time, electromyographic activity of bilateral biceps brachii muscles was quantified during maximal voluntary isometric arm lifting. Repeated measures analysis of variance was used to analyze the effects of HN positions on the amount of elbow flexors force and integrated electromyographic (IEMG) values. The results showed that the highest mean lifting strength was recorded at extension position for both males and females. Significant differences were found between HN positions and arm lifting strength. In the other way, no significant difference of the IEMG values of bilateral biceps brachii muscles between HN positions were found. However, this study seemed to support the conclusion that HN position did influence on the production of isometric elbow flexors force. The actual clinical implication is limited due to the limitations of the study.