Treadmill with Vibration Isolation and Stabilization System (TVIS) - 07.15.14
ISS Science for Everyone
Science Objectives for Everyone The Treadmill with Vibration Isolation and Stabilization System (TVIS) is an exercise system that is designed for use as a component of the CHeCS. In microgravity, astronauts do not exert as much force on their muscles as on Earth; without exercise, these muscles begin to atrophy. This can lead to bone density loss with symptoms similar to osteoporosis.
Science Results for Everyone
A treadmill in the ISS gives astronauts a way to exercise and so maintain muscle and bone health. Because exercise causes vibrations and micro-acceleration, the treadmill has stabilizing systems to minimize their transfer to the ISS structure and to keep the exercise surface relatively stable. The most powerful low frequency vibrations on the ISS come from air conditioning compressors and gyrodynes which are rotors that stabilize the spacecraft. Treadmill use typically causes frequencies of 11 Hz (beats per second) and less, with spikes from changes in exercise modes, such as switching from walking to running. The data show that horizontal vibrations typically exceed those along the ISS’s longitudinal axis, and distribution depends largely on where measurements are taken.
Developer(s) Information Pending
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
November 2000 - March 2013
Previous ISS Missions
- The Treadmill with Vibration Isolation and Stabilization (TVIS) was the first treadmill on the ISS, along with the Cycle Ergometer with Vibration Isolation System (CEVIS), and the Advanced Resistive Exercise Device (ARED) adding to a complement of three different exercise devices on board the ISS (TVIS is supplemented with the second generation Combined Operational Load Bearing External Resistance Treadmill (COLBERT) during expedition 19 during August 2009).
- TVIS is one of the critical countermeasure devices that is used to keep the ISS crewmembers fit while on-orbit and helps prepare them for return to Earth.
- During nominal on-orbit operations, data is recorded to the TVIS System PCMCIA cards that are inserted into the TVIS System Control Panel prior to exercise. Many parameters are recorded including temperatures, voltages, elapsed time, speed, heart rate and subject load. The crew downloads the TVIS System PCMCIA data to the SSC T61P for downlink to the ground for analysis. This allows scientists and doctors to evaluate how effective the treadmill exercise is in reducing the amount of bone and muscle density loss due to microgravity exposure, and allows for Engineering to monitor hardware performance and troubleshoot any anomalies.
- The TVIS is designed so that ground experts can track crew health on orbit to create individual exercise prescriptions and uplink them to the crew. The information sent down to the ground experts used in conjunction with other medical monitoring equipment is used to determine how well the crewmembers are being conditioned or lack thereof and to adjust exercise prescriptions accordingly.
The running surface of the treadmill is used in much the same way as any conventional treadmill, except the user is held to its surface by the Series Bungee Systems (SBS), which uses latex rubber tubes and/or by the Subject Load Device (SLD), which attach to a shoulder and waist Treadmill Harness to counter the microgravity (µg) environment. When used without the SLDs, the SBSs are considered the contingency loading configuration.
The SLDs are the primary subject restraint system. Prior to exercise, the crewmember dons the Treadmill Harness and clips the harness y-straps to the respective end stops on the SLD?s cables. The SLDs provide loading from 40 to 220 lb. The load variation of the SLD is approximately 6 lb/in. of cable extension. Each SLD makes use of 2 adjustable torsion springs tied to a cable-feed pulley. The crewmember used the Control Panel to enter the desired load. Mechanical limit switches in each SLD are used to prohibit over adjustment in either direction. Each SLD is instrumented with a load cell, which measures tension in the cable attached to the subject. This tension reading is used to determine the subject load supplied by the SLD. While the applied loads are continuously monitored and recorded every 5 seconds on the PCMCIA card, the system does not attempt to maintain constant load during exercise.
The TVIS System Electronics Box (EB) is responsible for distributing power and processing commands/data for the TVIS System. A battery circuit is used to maintain the real-time clock and maintain the relay configuration settings in case of a power failure or when the SM circuit breakers are turned off, e.g., for TVIS System maintenance. The battery has a 6-month operational life and can be changed out by the crew via a door located on the aft end of the EB. The Device Interface Board (DIB) provides subsystem interconnectivity and is used to transfer commands and data to and from the VIS System, SLDs, Control Panel, and Motor Box. TVIS System circuit breakers are located on the aft end of the EB for over current protection of the system. Weekly tasks of the TVIS include cleaning of the handrails, closeout panels, and display covers to remove any dust, debris, sweat (Dry Wipe). Additionally, routine maintenance tasks are done Monthly, Quarterly, and every 6 months to inspect several general TVIS components, verify torque on accessible fasteners, lubricate needed components, set time and date on Control Panel, perform Speed Characterization Tests, replace electronic box battery, check gyroscope ropes and pivot spacers and check corner wire ropes. The rack space is checked for vacuum accumulated debris. Checks are done on the drive belt, belt alignment, belt tension, and for sharp edges and burrs on the running surface. Annual maintenance tasks include grease lubrication of the front and rear drums as well as rear drive shaft. With humans currently occupying the International Space Station (ISS) for six months and space exploration missions of one to three years on the horizon, preservation of crewmember health and fitness is a major objective of the international space community. Exercise has been the primary utility used by the space agencies in an effort to protect cardio-vascular, bone, and skeletal muscle health while in space for extended stays.
- TVIS user can override any exercise protocols when desired. The PCMCIA card is used to store the following parameters: Tread Speed, restraint Force, distance, elapsed time, heart rate, gyro speed, pre-programmed exercise protocol, fault messages, actual protocol performed, real-time clock, electronics box temperature, motor box temperature.
- The Generalized Controller Module processes data from the Electronics Box for display and storage onto the LCD and PCMCIA card, processes heart rate data for storage and display, and processes commands to the Electronics Box. The Control Panel also provides a switch pad with membrane switches and LED indicators, which are located on top of the panel. The membrane switches control solid state relays which can be used to enable/disable power to the VIS Stabilizers, VIS Gyro, Treadmill Motor, and Treadmill Control Panel/Electronics Box assembly in case of a TVIS subsystem failure.
- The treadmill can be operated in the motorized or non-motorized modes. In the motorized mode, the belt speed is adjustable from 0.0 to 16 km?h-1 (0.1 to 10.0 mph) in 0.16 km?h-1 (0.1 mph) increments. In the non-motorized mode, the belt speed is dependent upon the effort provided by the exerciser, and the resistance to belt motion can be manipulated with a braking system.
- The treadmill belt will begin movement and the exercise session initiated via crew action. Prescribed exercise regiment is currently 30-40 min at 70-85% of maximum heart rate (HRmax) on TVIS. Aerobic Intervals of 20-30 second "all out sprints." Eight (8) sets of 20 sec sprint with 10 sec recovery 2 min interval is sometimes used on ISS with 7 minute warm up at 40% of maximal oxygen uptake (VO2max) , followed by 5x2 minute stages at 60, 70, 80, 90, 80% VO2max then 5 min cool down. Also, two-minute interval is sometimes used on ISS with 7 minute warm up at 40% of VO2max, followed by 5x2 minute stages at 60, 70, 80, 90, 80% VO2max then 5 min cool down.
Investigations of the influence of low frequency vibrations on the microgravity environment on the Russian segment of the ISS begun after the first partial replacement of sensors IMU_128 (small acceleration meter) on the service module in March 2003. The most powerful vibrations are those created by air conditioning system (ACS) compressors and gyrodynes of the ISS stabilization system. The magnitude of these background perturbations vary from several meter-kilogram (mkg) to tens of meter-gram (mg) depending on the modes of operation and locality of the disturbance. Crewmembers performing physical exercises (PE) on the suite of exercising equipment onboard also produce micro accelerations which are collected and analyzed by researchers.
The TVIS is located in the service module of the Russian segment. The treadmill’s damper system allows a maximum displacement of 12 cm and rotation of 2.5° relative to any axis and is designed to transfer minimal impact forces, however this does not provide for complete damping of movements. Vibrating frequencies of 11 Hz (cycle per second) and less can be attributed as frequencies characteristic for exercises on the treadmill. Periodic sharp increases of low frequency perturbations for approximately two minutes can be observed, within the greater power and higher frequency vibrations of ACS compressors and air-duct fans, and are indicative of changes in modes of exercises (walking, running, etc.). Significant differences in measurements are recorded when different compressors are operating along with the normal working activity of the crew and are responsible for greater perturbations than exercises on the treadmill. However, in all compartments and at various modes, characteristic frequencies are practically identical, but the amplitudes during physical exercises are several times higher than corresponding parameters of the background environment. In the Destiny module, perturbations below 1.0 Hz is dominated by treadmill exercises, but the total power of perturbations in the frequency band 0–6 Hz is approximately 2.5 times higher for the Russian bicycle ergometer than the treadmill. In the frequency band 0–10 Hz during PE on the service module (SM), perturbations in the American segment increase almost by an order of magnitude in comparison with the “quiet conditions.” Similarly disturbances were previously recorded on the Mir space station during exercise equipment operations.
Overall, the main power of perturbations, concentrated in the band 50–200 Hz, is caused both by crew vital activity and by functioning standard onboard systems. The microgravity and vibration conditions in different compartments of the ISS at various modes of station operation can vary by more than an order of magnitude as sensors in the American segment also indicate. The data presented above show that, practically in all cases, the perturbations in the transverse plane of the Destiny module exceed perturbations along the longitudinal ISS axis, and the distribution of perturbations substantially depends on the location of measurements (Belyaev et al. 2009).
Belyaev MY, Babkin EV, Ryabukha SB, Ryazantsev AV. Microperturbations on the International Space Station during physical exercises of the crew. Cosmic Research. 2011 April 16; 49(2): 160-174. DOI: 10.1134/S0010952511010011.
Ground Based Results Publications