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Relationships Among Lower Body Strength, Power, and Performance of Functional TasksThere is a large degree of variability among crewmembers with respect to decrements in muscle strength and power following long duration spaceflight, ranging from 0 to approx.30% reductions. The purpose of this study was to investigate the influence of varying decrements in lower body muscle strength and power (relative to body weight) on the performance of 2 occupationally relevant tasks (ladder climb and supine egress & walk). Seventeen participants with leg strength similar to US crewmembers performed a leg press power test, an isokinetic knee extension strength test and they were asked to complete the 2 functional tasks as quickly as possible. On additional test days the participants were asked to repeat the functional tasks under 3 conditions where a different external load was applied each time using a weighted suit in order to experimentally manipulate participants strength/body weight and power/body weight ratios. The weight in the suit ranged from 20-120% of body weight and was distributed in proportion to limb segment weights to minimize changes in center of gravity. The ladder task consisted of climbing 40 rungs on a ladder treadmill as fast as possible. The supine egress & walk task consisted of rising from a supine position and walking through an obstacle course. Results show a relatively linear relationship between strength/body weight and task time and power/body weight with task time such that the fastest performance times are associated with higher strength and power with about half the variance in task time is accounted for by a single variable (either strength or power). For the average person, a 20% reduction in power/body weight (from 18 to 14.4 W/kg) induces an increase (slowing) of about 10 seconds in the ladder climb task from 14 to 24 seconds (approx.70%) and a slowing of the supine egress & walk task from 14 to 21 seconds (approx.50%). Similar relationships were observed with strength/body weight and task performance. For the average person, a 20% reduction in strength/body weight (from 2.1 to 1.7 Nm/kg) resulted in a slowing of the ladder climb from 10.5 to 24 seconds (approx.128%) and a slowing of the supine egress & walk from 11 to 20 seconds (approx.82%). These data suggest that the single variable of either low body muscle strength or power, relative to body weight is predictive of about 50% of the variance in task performance time, and that considerable slowing in task performance is associated with relatively typical decrements in muscle performance seen with long duration spaceflight. The observation of a relatively linear relationship between strength/power and task time suggests that across the full spectrum of initial crew strengths and typical decrements in strength previously observed, that task performance would be expected to be slowed following long duration spaceflight. These data will be confirmed in actual spaceflight with subsequent studies.
Document ID
20100012113
Acquisition Source
Johnson Space Center
Document Type
Presentation
Authors
Ploutz-Snyder, Lori
(NASA Johnson Space Center Houston, TX, United States)
Ryder, J.
(Universities Space Research Association Houston, TX, United States)
Hackney, K.
(Student Programs)
Scott-Pandorf, M.
(Wyle Labs., Inc. Houston, TX, United States)
Redd, E.
(Wyle Labs., Inc. Houston, TX, United States)
Buxton, R.
(Wyle Labs., Inc. Houston, TX, United States)
Bloomberg, J.
(NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 24, 2013
Publication Date
June 13, 2010
Subject Category
Life Sciences (General)
Report/Patent Number
JSC-CN-20152
JSC-CN-20873
Meeting Information
Meeting: Life in Space for Life on Earth
Location: Trieste
Country: Italy
Start Date: June 13, 2010
End Date: June 18, 2010
Sponsors: European Space Agency. Centre Spatial de Toulouse, International Society for Gravitational Physiology, Centre National d'Etudes Spatiales
Distribution Limits
Public
Copyright
Public Use Permitted.
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