We investigated the effect of upper limb and shoulder girdle alignment on cervical muscle hardness and range of motion. [Participants and Methods] The participants were 20 healthy adult males. The measurement posture was the sitting position, and the upper limb and shoulder girdle alignment measurements were performed under three conditions: loading of both upper limbs, no loading of both upper limbs, no loading of the left upper limb. A biological tissue hardness tester and an ultrasonic three-dimensional motion analysis system were used to measure the cervical muscle hardness and range of motion, respectively. [Results] The cervical muscle hardness of the left and right trapezius muscles significantly reduced when both upper limbs were loaded, and that of the left trapezius muscle significantly reduced when there was no load on left upper limb. The cervical range of motion significantly increased in extension, rotation, lateral flexion when both upper limbs were loaded, and left rotation and right flexion significantly increased when there was no load on the left upper limb. [Conclusion] The results suggest that the upper limb and shoulder girdle alignment affects cervical muscle hardness and range of motion.
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