The study discusses the reasons for the need to use exoskeletons on construction sites. However, modern models of exoskeletons are not very comfortable for human use. One reason is the application of absolutely rigid links. The authors address this setback by applying in exoskeletons the links with variable length and controlled stiffness via alterable strength of magnetic field. A 3-dimensional model of exoskeleton, including five variable-length links with adjustable stiffness, for human musculoskeletal system has been developed. The model uses magneto-rheological fluid to control link stiffness on the variable-length sections. The links connections are simulated with hinges, spherical or cylindrical, implementing required rotational motion. The developed model is closer to the human locomotion system. It can be applied for designing more comfortable exoskeletons compared to the currently existing ones. The use of comfortable exoskeletons will make the work of construction workers easier and will reduce the number of injuries and occupational diseases.