Archives of Physical Medicine and Rehabilitation

Archives of Physical Medicine and Rehabilitation

6 I4 HUMAN RESPONSE TO VIHRA'IION A. B. Broderson and H. E. van Cierke 1971 ASME Puper II-WA/BHF-S. ASME Winter Annual Meeting, Wushiugton, D.C. N...

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6 I4

HUMAN

RESPONSE

TO VIHRA'IION

A. B. Broderson and H. E. van Cierke 1971 ASME Puper II-WA/BHF-S. ASME Winter Annual Meeting, Wushiugton, D.C. Norember 2%DrccwJm 2. Mechanical impedance and it., variation in the restrained primate during prolonged bibration. (9 pages, 15 figures, 12 references) Authors’ Summary. Driving point mechanical impedance and phase angle were measured in two restrained, alert rhesus monkeys during 1.0 R sinusoidal vibrations: tests included both frequency sweep and extended duration (1 hr) exposure throughout a 6 to 30 Hz range. Impedance gives restricted, but useful, information for body subsystems near the driving interface. The sweep tests demonstrate abdominal and spinal resonances at 6 and 8 Hz; at higher frequencies, mass effects predominate because of restraint and ischial hardness. During extended exposure, resonances initially occur over a 60 to I2 Hz range but only at 6 Hz after an hour; average impedance drops over I2 ‘;, and phase angle over 8 Y; during the hour. Much more significantly, these changes are 50”,, complete within IO min and appear largely a result of increased damping and decreased stiffness with muscle fatigue. The primary resonance and high-frequency mass characteristics are closely approximated by a two-mass, single-degree-of-freedom model with half the total mass constrained. The high-frequency mass characteristics can be seen on other investigatori’ data and suggest alternate possibilities for modeling and calculation of stiffness and damping coefficients. Increased accuracy would aid in modeling the physiological consequences of prolonged vibration such as the core temperature rise demonstrated. The temporal changes demonstrated in biomechanic parameters and, therefore, energy exchange should not be overlooked when evaluating physiologic and performance alterations in man exposed to extended vibration environments. Topics : Biodynamic (Mechanical Impedance) ; Non-hunm Suhjecrs; Ph_vsiological E#ects (General).

F. U. Steinberg and A. L. Graber 1963 Archives of Ph_vsical Medicine and Rehabilitation 44, 645-650. The effect of age and peripheral circulation on the perception of vibration. (6 pages, 2 figures, 3 tables, I7 references) Authors Summary. The vibratory threshold was determined in the lower extremities of 98 subjects, ranging in age from 20 to 90 years. All were free of any disease which may affect vibratory perception; 69 had a normal arterial peripheral circulation as determined by palpation of the pulses and oscillometry and 29 had impaired arterial circulation. The threshold of vibratory sensation rose with age. The logarithms of the thresholds were directly proportional to the age. In the normal controls the spread of threshold values increased with age. Impairment of the peripheral circulation raised the vibratory threshold, compared to the normal control group of the same age. The difference was statistically significant. In 9 subjects in whom the peripheral circulation was impaired in one leg but not the other, the vibratory threshold was significantly higher in the affected leg. T- )ics: Vibration Sense (Thresholds); Diagnostic Applications; Subject Tvpe (ilge). R. N. Stiles and J. E. Randall 1967 Journal of Applied Physiology 23, 324-330. Mechanical factors in human tremor frequency. (7 pages, 5 figures, 3 tables, 15 references) Authors' Abstract. Acceleration measurements ofhand and finger tremor contain reproducible peaks in their power (variance) spectra. Muscle tension and moment of inertia of the hand and of the finger were systematically varied and the corresponding frequencies of the spectral peaks were observed. When average muscle tension was held constant, as monitored by a modified electromyogram signal, adding increments of mass to the finger lowered the 25 cycle/s spectral peak. The 9 cycle/s peak did not change. Adding mass to the whole hand lowered the frequency of 9 cycle/s spectral peak. The relationship between tremor frequency