Foot Reaction Forces During Space Flight (Foot) - 01.09.14
Science Objectives for Everyone The Foot/Ground Reaction Forces During Space Flight (FOOT) experiment studies the load on the lower body and muscle activity in crewmembers while working on the International Space Station (ISS). This study will provide a better understanding of the bone and muscle loss in the lower extremities experienced by astronauts in microgravity. The results of this experiment will help in future space flights, as well as have significance for understanding, preventing and treating osteoporosis on Earth.
Science Results for Everyone
Do these pants make me look fit? ISS crew members might ask that when wearing the Lower Extremity Monitoring Suit, pants with devices measuring muscle exertion, leg-joint movement, and force on the feet while using exercise equipment. For the Foot/Ground Reaction Forces During Space Flight (FOOT) investigation, the pants collected data showing significant reduction in foot forces during an activity in space versus the same activity on Earth. This result suggests that the previous generation of onboard exercise equipment is not giving enough resistive load against muscles, meaning exercise may be inadequate for maintaining muscle tone and strength on long missions. The latest onboard exercise equipment is currently addressing this issue and showing vast improvements over their predecessors.
Johnson Space Center, Human Research Program, Houston, TX, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration:
November 2002 - April 2006
Previous ISS Missions
This type of research has never been conducted on the ISS. Research aboard shuttle flights and the Russian Mir studied muscle and bone, but this is the first experiment of its kind. The Foot experiment has not flown on any mission prior to Expedition 6.
- Stress on lower extremity bones and muscles during daily life in microgravity is thought to be markedly reduced compared to Earth gravity, although no measurements have previously been made to quantify this reduction.
- The purpose of this experiment is to measure the load applied to the feet, the muscle activation, and joint range of motion of astronauts as they conduct routine daily activities both on Earth and in the microgravity environment of the ISS.
- Tests conducted during this study also measure the degree to which muscle volume, muscle strength, and bone mineral density change during spaceflight. The daily load, which is reduced in space because of the lack of gravity, is then correlated to muscle and bone fitness after the astronauts return to Earth.
- The results are used to directly compare the daily load experienced with changes in bone mineral density, muscle mass and muscle strength.
The human body is designed to bear weight. Without the stimulation caused by placing weight on lower extremities, whether due to the microgravity environment or lack of use on Earth, bones lose mass and muscles lose strength. The Foot experiment characterized the load placed on lower extremities during daily activities on Station and examined to what degree mechanical load stimulus, via an in-flight exercise routine, could prevent the muscle atrophy and bone loss associated with space flight.
To achieve this objective, Foot had several sensors mounted in a special pair of Lycra exercise pants known as the lower extremity monitoring suit (LEMS). The total force-foot ground interface (TF-FGI) served as an insole that, when placed inside a shoe, measures the amount of force placed on the bottom of the foot. Joint excursion sensors (JESs) record joint angles at the ankle, knee, and hip. Electromyography (EMG) electrodes recorded muscle activity, including net neural drive, along the leg (the vastus medialis, rectus femoris, biceps femorics, gastrocnemius, and tibial anterior) and in the right arm (the biceps brachii and triceps brachii). Information was collected by an ambulatory data acquisition system and downloaded into the Human Research Facility (HRF) laptop on board ISS after each session.
The loss of bone mineral in the lower extremities is widely viewed as one of the critical factors that may limit long-term human habitation of space (upper extremity changes in BMD appear to be minimal or to increase). Deficiencies in lower extremity muscle function as a result of prolonged exposure to microgravity also have implications for performance and safety during space missions. The information derived from this study is expected to shed new light on possible solutions to bone mineral loss and drops in muscle function of the lower extremities. These results will lay an important foundation for the further development of countermeasures for lower extremity muscle and bone loss.
The Foot sensors (the TF-FGI, JES, and EMG electrodes) and the ADAS1 all operate on batteries. The information collected by the ADAS1 is downloaded into the Human Research Facility (HRF) laptop after each session. When not in use, all Foot hardware is stored in the HRF.
A baseline for each participant is created preflight: a Dual Energy X-ray Absorptiometry (DEXA) image establishes bone mineral density; a muscle cross-sectional area is measured via Magnetic Resonance Imaging (MRI); and joint strength is determined using Cybex, an isokinetic dynamometer.
During their stay on ISS, the participants wear the LEMS and accompanying armband for approximately 8 hours as they go about their daily activities, including exercise. Data is taken for four days evenly spaced throughout the Expedition. The FGI-FCU is used to calibrate the insoles; a nitrogen source keeps a neoprene bladder inflated to maintain contact with the surface of the insole. The data is transferred from the ADAS1 to the HRF laptop after each session.
After flight, additional DEXA and MRI images and Cybex measurements are taken on each participant. The preflight, inflight, and postflight data are compared to create a complete dataset of activity, muscle strength, and bone density changes.
The objective of the Foot experiment was to quantify and explore the relationship between loading of the human body and changes in the homeostasis of the musculoskeletal system during space flight compared to Earth. This objective was achieved by studying the foot-ground reaction forces, lower extremity muscle activity, and joint movements at the hip, knee and ankle during normal daily activities on Earth and in the International Space Station (ISS). The Foot experiment also examined changes in strength, bone mineral density (BMD), and muscle volume.
The Foot investigation, led by Peter Cavanagh, collected data from four crewmembers before and during their six-month missions over the period from Increments 6-12 (November 2002 and April 2006). Normal daily activity ground-reaction forces on the feet were measured for each crewmember for 4 days prior to going to space, and approximately 4-7 days worth of data were recorded while the subject performed daily activities on the ISS (Pierre 2006).
Data was collected using the Lower Extremity Monitoring Suit (LEMS) system. The LEMS is an Ambulatory Data Acquisition System (ADAS) consisting of the electromyography (EMG) module, the Joint Excursion System, and the Total Force-Foot Ground Interface system, which were all integrated into a pair of pants worn by a crewmember. The integrated system was evaluated for data validity and performance readiness of the instrumentation, software, and data collection procedures prior to flight. Results indicate that the LEMS is capable of providing valid and useful biomechanical information on long-term exercise activities on board the ISS (Cavanaugh, 2009).
The Treadmill with Vibration Isolation and Stabilization (TVIS), Cycle Ergometer with Vibration and Stabilization (CEVIS), and Interim Resistance Exercise Device (iRED) are stationary exercise equipment located on board the ISS. They provided a means for crewmembers to maintain muscle tone and strength as well as valuable platforms for studying the effects physical exercises may have had on mitigating muscle atrophy and bone loss during long-duration space missions. The Foot study utilized a number of sensors to measure muscle exertion, leg-joint movement, and the amount of force applied to the feet during exercises with the TVIS, CEVIS, and iRED (Gopalakrishnan 2010).
Experimental data showed that foot forces, based on direct in-shoe force measurements, are greatly reduced, upward to nearly a half in some cases, compared to the same activity as on Earth. These mechanical loading reductions on weight-bearing bones are used to correlate the rate of bone loss of the most affected areas of the skeleton. The results demonstrate that exercise countermeasures performed during these missions were not adequate to prevent significant bone degradation over long-duration space flights. It is concluded that the reduced amount of force applied to bones and muscles during exercise and daily activities on board the ISS plays a crucial role in the reduction of BMD (Cavanagh, 2010).
In a paper by Genc et al. 2010, results showed that foot loads over a range of hardware settings were reduced by at least two-thirds even while performing exercises at the highest device capabilities on the TVIS and iRED. The study concluded that the TVIS, CEVIS, and iRED, as designed, were not generating enough resistive loads equal to that on Earth, and the need for greater loading should be addressed for upgrades and the next generation of exercise equipment for the ISS (Genc, 2009, 2010).
Precise measurement of the forces exerted by the muscles and bones in microgravity provides a means to quantify the relationship between force reduction and the rate of atrophy of the musculoskeletal system. Researchers are optimistic that the hypothesis of minimum-loading stimulus, in terms of exercise repetition and the amount of force being applied, can be confirmed and the threshold to maintain fitness can be accurately pinpointed. Already, the latest generation of exercise equipment with improved mechanical loading, individually tailored exercise programs, and crew-friendly setup and maintenance is being implemented on the ISS. The Combined Operational Load Bearing External Resistance Treadmill (COLBERT) and Advance Resistive Exercise Device (aRED) are now collecting data during high-intensity workouts and future studies will determine if these new exercise regimens are sufficient to allow crew members to remain healthy over the course of their mission.
Genc KO, Gopalakrishnan R, Kuklis MM, Maender CC, Rice AJ, Bowersox KD, Cavanagh PR, Cavanagh PR. Foot forces during exercise on the International Space Station . Journal of Biomechanics. 2010 November 16; 43(15): 3020-3027.
Cavanagh PR, Cavanagh PR, Gopalakrishnan R, Rice AJ, Genc KO, Maender CC, Nystrom PG, Johnson MJ, Kuklis MM, Humphreys BT. An Ambulatory Biomechanical Data Collection System for Use in Space: Design and Validation. Aviation, Space, and Environmental Medicine. 2009; 80(10): 870-881. DOI: 10.3357/ASEM.2266.2009.
Genc KO, Humphreys BT, Cavanagh PR, Cavanagh PR. Enhanced Daily Load Stimulus to Bone in Spaceflight and on Earth. Aviation, Space, and Environmental Medicine. 2009; 80: 919-926. DOI: 10.3357/ASEM.2380.2009.
Pierre MC, Genc KO, Litow M, Humphreys BT, Rice AJ, Maender CC, Cavanagh PR, Cavanagh PR. Comparison of Knee Motion on Earth and in Space: An Observational Study. Journal of Neuroengineering and Rehabilitation. 2006; 3(8). DOI: 10.1186/1743-0003-3-8.
Gopalakrishnan R, Genc KO, Rice AJ, Lee SM, Evans HJ, Maender CC, Ilaslan H, Cavanagh PR, Cavanagh PR. Muscle Volume, Strength, Endurance, and Exercise Loads During 6-Month Missions in Space. Aviation, Space, and Environmental Medicine. 2010; 81(2): 91-102. DOI: 10.3357/ASEM.2583.2010.
Cavanagh PR, Cavanagh PR, Genc KO, Gopalakrishnan R, Kuklis MM, Maender CC, Rice AJ. Foot forces during typical days on the international space station. Journal of Biomechanics. 2010; 43: 2182-2188. DOI: 10.1016/j.jbiomech.2010.03.044.
Ground Based Results Publications
Cavanagh PR, Cavanagh PR, Licata AA, Rice AJ. Exercise and Pharmocological Countermeasures for Bone Loss During Long-Duration Space Flight.Gravitational and Space Biology. 2005; 18(2): 39-58. PMID: 16038092.
- Life Sciences Data Archive
- Lerner Research Institute: Exercise in Microgravity
- International Space Station Medical Project (ISSMP)
NASA Image: ISS006E11018 - Expedition Six Mission Commander Kenneth Bowersox, wearing a body harness, runs on the Treadmill Vibration Isolation System (TVIS) while conducting the Foot/Ground Reaction Forces During Spaceflight (Foot) experiment in the Zvezda/Service Module.
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NASA Image: ISS006E11011 - View of the body harness for the Treadmill Vibration Isolation System (TVIS) and the Lower Extremity Monitoring Suit (LEMS) for the Foot/Ground Reaction Forces During Spaceflight (Foot) experiment in the Zvezda/Service Module. Both apparatus are being worn by Expedition Six Mission Commander Ken Bowersox.
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NASA Image: ISS008E20918 - Donned in the customized Lower Extremity Monitoring Suit (LEMS), Expedition 8 Mission Commander and Science Officer Michael Foale balances on the footplate of a special track attached to the Human Research Facility (HRF) rack in the Destiny U.S. Laboratory to perform Foot/Ground Reaction Forces During Spaceflight (Foot)/ Electromyography (EMG) calibration operations.
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NASA Image: ISS011E09829 - ISS Expedition 11 Science Officer, John Phillips, performing a Foot session in the U.S. Lab wearing the Foot LEMS pants.
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NASA Image: ISS011E09822 - ISS Expedition 11 Science Officer, John Phillips, performing a Foot session while exercising on the Cycle Egrometer with Vibration Isolation System (CEVIS) wearing the Foot LEMS pants.
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NASA Image: ISS012E18576 - Astronaut William S. (Bill) McArthur, Expedition 12 commander and NASA space station science officer, uses the Cycle Ergometer with Vibration Isolation System (CEVIS) while participating in the Foot/Ground Reaction Forces During Spaceflight (Foot) experiment in the Destiny laboratory of the International Space Station. McArthur wore the specially instrumented Lower Extremity Monitoring Suit (LEMS), cycling tights outfitted with sensors, during the experiment.
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ASA Image: ISS012E20120 - Astronaut William S. (Bill) McArthur, Expedition 12 commander and NASA space station science officer, equipped with a bungee harness, exercises on the Treadmill Vibration Isolation System (TVIS) while participating in the final run of the Foot experiment in the Zvezda Service Module of the International Space Station. McArthur was attired in the specially instrumented Lower Extremity Monitoring Suit (LEMS), cycling tights outfitted with sensors, during the experiment.
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