This page contains ideas/documentation for a Sargent College project to vary the effective weight of a backpack carried by a subject walking on a treadmill.

Design Documents


Weight range is 10%-30% of subject body mass. 20% corresponds to the amount of weight which must be added/removed during the trial. The weight will be added/removed in 2.5% mass increments.

Subject Weight 10% 20% 30% 2.5%
50kg 5kg 10kg 15kg 1.25kg
115kg 11.5kg 23kg 34.5kg 2.9kg

For a 115kg subject (250lb) the maximum weight to be added/removed is 34.5kg (about 50lb).

'Baseline Design

Two water tanks are permanently mounted, one above and one below the treadmill. A third tank is mounted on the backpack. Water is delivered from the upper tank to the backpack to increase the simulated mass, and drained from the backpack to the floor tank to reduce the mass. A pump returns the water to the upper tank.

The controller allows the operator to deliver a specific volume of water from the upper tank to the backpack (to increase mass) or from the backpack to the lower tank (to decrease mass). Ideally, the controller would be calibrated by entering the subject mass in kg, and then would display the current mass and allow the operator to increment or decrement the mass by a specified amount.

Initially, the controller will be a software application running on a PC. A small interface board is required to connect the solenoids, sensors and load cell to the computer via the  U3

'Parts List

Omega  FPR-204-PS


Asco  8210G002
LabJack?  U3

'Reference Material