Measuring and Modeling the Effects of Encumbrance on Seated Reach

Principal Investigator: Matthew Reed, University of Michigan, mreed(at)
Government: Rebekah Gruber, Harry Zywiol, U.S. RDECOM-TARDEC
Industry: Jeff Mayhugh, Navistar

Soldiers seated in military vehicles are being asked to perform an increasing variety of tasks, including communications and controlling weapons systems. Personal protective equipment (PPE), including body armor, and body borne gear (BBG) restrict the soldier’s ability to reach. The restrictions affect reaches to targets in the vehicle and “self-reach” to targets on the soldier. Currently available tools used to simulate soldiers for ergonomics analysis, such as the Jack human figure model, lack the ability to accurately represent the reach restrictions created by PPE and BBG.

A recent ARC study quantified the effects of PPE and BBG on soldier posture and body shape. For this Seated Soldier project, U-M led a team that measured 309 soldiers in a range of driver and crew (squad) seating conditions, and obtained whole-body scan data describing body shape and PPE/BBG locations with respect to the body. A companion project used the results of the Seated Soldier study to develop improved Jack manikins that better represent the postures and shapes of the encumbered soldier. The next step is to create the ability to simulate the effects of that equipment on ranges of motion.

We seek to conduct a laboratory study to quantify the effects of body armor and body-borne equipment on reach capability, including self-reach. This will be followed by developing a concise statistical representation of these effects for incorporation into human simulation software. Finally, using the Jack human modeling software, we will create a demonstration implementation of reach-restriction simulation.


  • Parkinson, M.B. and Reed, M.P. (2007).  Standing reach envelopes incorporating anthropometric variance and postural cost. Technical Paper 2007-01-2482. SAE Transactions: Journal of Passenger Cars - Mechanical Systems. 126(6):2073-2078.
    doi: 10.4271/2007-01-2482 (mirror site)
  • Parkinson, M.B., Reed, M.P., Kokkolaras, M., Papalambros, P.Y. (2007).  Optimizing truck cab layout for driver accommodation.  Journal of Mechanical Design, 129(11):1110-1117. doi: 10.1115/1.2771181 (mirror site)
  • Danker, J.S. and Reed, M.P. (2006).  Behavior-based model of clavicle motion for simulating seated reaches. SAE Transactions: Journal of Commercial Vehicles, 115:47-52. doi: 10.4271/2006-01-0699 (mirror site)