Cutaneous Hypersensitivity and Balance Control in Humans (Hypersole) - 07.29.14
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The Cutaneous Hypersensitivity and Balance Control in Humans (Hypersole) investigation studies the range of mechanisms that humans rely on to maintain balance while standing or walking. One of these mechanisms involves receptors in the sole of the foot, which for example, detect pressure changes as a person walks across the ground. Hypersole uses a vibration device and monofilaments (a single strand of manmade fiber similar to fishing line) to record the sensitivity of the receptors in eleven crewmembers. Researchers are documenting, for the first time, any changes in the skin sensitivity of each crewmember’s foot sole in order to identify which receptors may be influenced by a period of weightlessness. Coupled with tests that assess changes in crewmembers’ abilities to maintain their balance, these measures will help establish how increased skin sensitivity contributes to balance control.
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Help, I’ve fallen and can’t get up! Humans use receptors in the soles of our feet that detect pressure change to keep their balance. It is found that while most crew members had decreased sensitivity of these foot receptors after spaceflight, in some it increased. Those with this increased sensitivity also had a substantially reduced ability to balance. Weightlessness, known to affect balance control, may have triggered the increased sensitivity. The data help scientists to identify which receptors are involved to determine how increased skin sensitivity contributes to balance control, leading to ways to address post- spaceflight balance issues.
Canadian Space Agency (CSA), Saint-Hubert, Quebec, Canada
Sponsoring Space Agency
Canadian Space Agency (CSA)
ISS Expedition Duration
March 2010 - September 2011
Previous ISS Missions
This is the first mission for the Hypersole investigation.
- Anecdotal evidence from crewmembers suggests that the tingling sensation some feel in their feet while in space and for short periods back on Earth may be the response of different sensory receptors in the skin that naturally compensate for the re-weighting of sensory information due to the decreased input from the vestibular, or inner ear, system in an environment of microgravity.
- Project results are expected to add significantly to existing studies of the aging process, which includes reductions in information relayed by skin sensors that lead to a loss of balance control and, among the elderly especially, a greater incidence of falls. The data will also provide knowledge that benefits crewmembers as they perform their in flight and post-flight duties.
Information from the mechanoreceptors (sensory organs or cells that respond to mechanical signals such as touch) in the foot sole skin has a large impact on balance and postural control in the gravitational environment of Earth. Four different types of receptors provide information regarding skin contact, indentation pressure, slips and skin stretch to facilitate orientation of the body in the environment and for postural equilibrium. As we age, the fidelity of the information relayed by the sensors in the skin is decreased. With a reduction in skin information, there are deficits in balance control and an increased incidence of falls in the elderly. Current strategies to improve balance involve the augmentation of skin input through vibration devices.
Space flight provides a unique opportunity to further investigate the relationship between changes in balance control and skin contributions. During space flight, there are changes that occur with the postural control system due to the altered gravito-inertial (a process of mental rotation which involves three dimensions, rather than just one) environment. The specific changes that occur with skin have not been documented. The experiment aims to use Von Frey monofilaments (a set of fine nylon hairs used to measure sensitivity of the skin) and vibration testing to determine changes in skin sensitivity postflight. Crewmembers will indicate when sensations are present during the testing paradigm. Postflight values will be compared to those obtained preflight. Values will also be correlated to changes observed in whole body postural control. It is hypothesized that skin sensitivity will be increased post space flight. It is also hypothesized that increases in the sensitivity of the skin will correlate with balance deficiencies related to vestibular information.
The research has the potential to impact 1) investigators understanding of the mechanism by which skin contributes to balance control on Earth, and 2) future applications to further understand skin contributions to balance control in an altered gravito-inertial environment for space exploration. To date, the majority of work examining skin contributions to balance control has explored the removal of skin information and the resultant postural instability. Devices to augment cutaneous (relating to the skin) input have been proposed as a means of re-establishing balance. Insight into balance challenges as a result of heightened skin input will enhance current theories concerning skin contribution to postural control.
It is known that multiple sensory systems interact to develop a sense for body position and orientation within one’s environment. The removal or deficiency within one sensory system often leads to re-weighting, which results in a greater importance placed on the other reliable sources of input. Hypersole aims to understand the contributions that skin may play in providing information to establish orientation during and following a period of microgravity, when vestibular input is less reliable. The hope is to understand whether skin may be used to facilitate balance and orientation for the completion of tasks; a direct application would be extra vehicular activities. Equally important is how this information will help crew to regain stability as they transition back to a gravitational environment upon landing.
Information from the mechanoreceptors in the foot sole skin has a large impact on balance and postural control. As we age, we experience DECREASED information from foot sole skin input. One solution is to augment skin information with the intent of improving balance. Space flight provides a unique opportunity to examine a group of individuals with a potential INCREASE in skin sensation. Additionally, space flight provides an analog to aging with respect to the vestibular system and sensory re-weighting. It is not known on Earth how information from the skin is weighted in an elderly population and whether an increase in skin input will actually benefit postural stability. Therefore, research targeted at a healthy population of crewmembers will enable us to maximize on the physical changes of weightlessness to provide a model for balance investigations with aging. It is believed that knowledge will also be transferable to balance control in crewmembers.
A minimum of nine subjects are required for the Hypersole investigation.
This experiment collects data before and after space flight, but not during the flight.
Lowrey C, Perry S, Strzalkowski N, Williams DR, Williams DR, Wood SJ, Wood SJ, Bent LR. Selective skin sensitivity changes and sensory reweighting following short-duration space flight. Journal of Applied Physiology. 2014 March 15; 116(6): 683-692.
Ground Based Results Publications
The Ultimate Tickle Test
Plaster mold taken of subject’s foot.
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