AGE AND CONTROL OF SKIN BLOOD FLOW: AGE AND LEAN BODY MASS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Purpose: To quantify core-to-skin thermal resistance during VC as a function of age and lean body mass, and refine models of human heat transfer in cold environments. Hypothesis a. The solution of heat balance equations will yield a lower derived core-to-skin thermal resistance (tissue insulation, IT) for older compared to young subjects of similar size and body composition. Hypothesis b. Controlling for age, subjects with decreased body mass and/or decreased lean body mass will exhibit a lower maximal IT. Age-groups consist of normal and lean/sarcopenic individuals. Young subjects are defined as 18-30 years; older subjects are 65-85 years old. Subjects are instrumented for measurement of the body's core and skin temperatures, forearm blood flow (FBF), skin blood flow (SkBF), blood pressure, and heart rate. Expired air is collected for the last 5 min of every 20 min period and analyzed for volume, O2 concentration, and CO2 concentration. After a 20-min baseline period at a dry bulb air temperature (Tdb) = 23 oC (73.4 degrees F) and relative humidity (RH) = 30%], Tdb are decreased to 12 degrees C (53.6 oF) and maintained for 40 minutes. Then, Tdb is lowered at a rate of 1degree C (1.8 degrees F)/20 min, until the onset of shivering or the subject wishes to discontinue. Shivering is determined by visual observation and self-report. During a 30-min recovery, the area around the laser Doppler probes is heated.