Skip to page content Mission Information


The Effect of Increasing Mass upon Locomotion (ROI_TMLS)
Principal Investigator
Research Area:
Exercise physiology
Muscle physiology
Skeletal physiology
Species Studied
Scientific Name: Homo sapiens Species: Human

Astronauts perform locomotive exercise on the International Space Station (ISS) as a countermeasure to the physiological losses associated with space flight. The locomotive-related ground reaction forces may provide mechanical loading that is a sufficient stimulus for bone adaptation and thus reduce the bone loss that occurs. However, recent investigations have shown that the ground reaction forces developed during locomotion in microgravity are less than those occurring in normal gravity. Specifically, peak ground reaction forces measured in microgravity were less than those developed in normal gravity even when subjects were loaded at external load levels equal to or greater than their body weight.

The ground reaction force occurring between the foot and ground is equivalent to the resultant force applied to the body's center of mass. Since force is the product of mass and acceleration, an increase in body mass with a given acceleration should result in an increase in ground reaction force. The loading mechanisms used on the ISS to date, appear to be limited in allowing astronauts to achieve normal-gravity-like levels of peak ground reaction force. Thus, other approaches may be necessary to effectively create normal-gravity-like ground reaction force using the current treadmill onboard the ISS. Adding mass to the astronaut could result in an increased ground reaction force. The addition of mass to the subject, however, may also affect the kinematics, kinetics, and adaptations in normal locomotion.

Increasing the mass of the astronaut through a weighted vest offers a potentially economical and easily modifiable enhancement to current exercise countermeasures. The use of a harness capable of providing different levels of mass could save resources by reducing the need to develop new exercise devices. More importantly, the health and well-being of astronauts could be improved efficiently and inexpensively. Furthermore, exercise with body weight support and a weighted vest to increase overall mass may be useful during the rehabilitation process for individuals who are at risk for osteoporosis.

The goal of this study is to determine whether or not increasing subject mass can create more effective exercise countermeasures during long-term space flight and to better understand the motor accommodations made to gait. The primary purpose of this investigation is to determine how the manipulation of mass affects the ground reaction force during treadmill locomotion. The secondary purpose is to examine the kinetic adaptations to increased body mass during locomotion.

++ -- View more

De Witt JK, Hagan RD, Cromwell RL. The effect of increasing inertia upon vertical ground reaction forces and temporal kinematics during locomotion. Journal of Experimental Biology. April 2008 211(Pt 7):1087-92.[]

DeWitt JK, Cromwell RL, Hagan RD. The effect of manipulating subject mass on lower extremity torque: Paper presented at: American Society of Biomechanics Annual Meeting; August 22-25, 2007; Palo Alto, CA. NASA Technical Memorandum NASA-TM 2007-0019365.

Dewitt JK, Hagan RD. The effect of increasing mass upon locomotion. Houston TX: National Aeronautics and Space Administration, Lyndon B. Johnson Space Center; 2007 June. NASA Technical Publication NASA/TP-2007-0022350.

Musculoskeletal physiology
++ -- View more

Data Information
Data Availability
Archive is complete. Some data sets are online.
Data Sets + View data

Some data sets are not publicly available but can be requested.
Data Sets+ Request data

Dorsiflexion, ankle
Extension, ankle
Extension, hip
Extension, knee
Flexion, ankle
++ -- View more

Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
ROI 01/01/2002 12/31/2012 In Progress

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Jessica Keune
Institutional Support
National Aeronautics and Space Administration (NASA)
Alternate Experiment Name