April 2022

Effect of Rounded and Hunched Shoulder Postures on Myotonometric Measurements of Upper Body Muscles in Sedentary Workers

Authors: Rama Krishna Reddy Guduru 1, Aurelijus Domeika 1, Aukse Domeikiene 2


  1. Institute of Mechatronics, Kaunas University of Technology, 51424 Kaunas, Lithuania
  2. Department of Preventive Medicine, Faculty of Public Health, Lithuanian University of Health Sciences, 44307 Kaunas, Lithuania

Journal: Applied Sciences - March 2022, Volume 12, Issue 7, Article no. 3333 (DOI: 10.3390/app1207333)

Background: Shoulder pain is prominent among sedentary employees who make motions of the upper limbs on a regular basis. Rounded shoulder posture (RSP) and hunched shoulder posture (HSP) are the most common clinical postural misalignments. These cause the spine to bend and raise tension on the nerve roots, which has a negative impact on upper-extremity muscular strength and function. Therefore, this study was carried out to investigate the effect of RSP and HSP on the mechanical parameters of the upper body muscles in clinically asymptomatic sedentary workers.

Methods: Twenty office workers with RSP, 20 with HSP, and 20 with normal shoulder posture (NSP) were matched for age, BMI, and type of job. Volunteers were split into groups based on photometric shoulder angle measurements. Mechanical properties such as muscle tone, stiffness, and elasticity of the upper trapezius (UT), middle trapezius (MT), posterior deltoid (PD), and pectoralis major (PM) were assessed in sedentary postures.

Results: The study revealed a significant decrease in muscle tone for the pectoralis major and a significant increase in muscle stiffness for the poster deltoid in both RSP and HSP as compared to NSP. Specifically, muscle tone decreased from 20.1 ± 4.0 to 12.4 ± 3.1 Hz (38.3%), (p ≤ 0.001) in RSP and from 20.1 ± 4.0 to 14.0 ± 4.8 Hz (30.3%), (p ≤ 0.001) in HSP. Muscle stiffness increased from 309.9 ± 70.7 to 348.15 ± 68.7 N/m (11%), (p ≤ 0.001) in RSP and from 309.9 ± 70.7 to 441.7 ± 45.9 N/m (29.8%), (p ≤ 0.001) in HSP.

Conclusions: RSP and HSP have an impact on the tone, stiffness, and elasticity of upper body muscles in healthy asymptomatic sedentary workers. These postures, on a regular basis, may affect physical health and decrease workers’ productivity. In addition, it is recommended for sedentary workers to take regular breaks and attend training that could help improve their physical health.


Keywords: upper body muscles, sedentary workers, muscle tone, elasticity, stiffness

In office workers, the biomechanical characteristics of the muscles during RSP and HSP have changed significantly. This study showed that RSP and HSP are more likely to impact the tone, stiffness, and elasticity of the upper body muscles. MT has higher muscle tone in RSP and lower in HSP, and vice versa. In the case of stiffness, for RSP, and HSP, the PD muscle has the highest value, and PM and MT the lowest. PM and UT have the highest logarithmic decrement during RSP and HSP. These postures, held on a regular basis, may affect physical health and decrease workers’ productivity. This shows that the postural changes associated with RSP and HSP could affect sedentary workers’ shoulder kinematics and muscle activity. Furthermore, it is recommended that sedentary workers take regular breaks and attend training that could help improve their physical health, and organizations should track postural changes and alerts by using monitoring devices.