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Biomedical subjects

J Iwamoto

Publications and source records attributed to J Iwamoto.

64 records · Page 4Linked to original sources
PubMed1988

Effect of pressure on thermal insulation in humans wearing wet suits.

The present work was undertaken to determine the critical water temperature (Tcw), defined as the lowest water temperature a subject can tolerate at rest for 3 h without shivering, of wet-suited subjects during water immersion at different ambient pressures. Nine healthy males wearing neoprene wet suits (5 mm thick) were subjected to immersion to the neck in water at 1, 2, and 2.5 ATA while resting for 3 h. Continuous measurements of esophageal (T(es)) and skin (Tsk) temperatures and heat loss from the skin (Htissue) and wet suits (Hsuit) were recorded. Insulation of the tissue (Itissue), wet suits (Isuit), and overall total (Itotal) were calculated from the temperature gradient and the heat loss. The Tcw increased curvilinearly as the pressure increased, whereas the metabolic heat production during rest and immersion was identical over the range of pressure tested. During the 3rd h of immersion, Tes was identical under all atmospheric pressures; however, Tsk was significantly higher (P less than 0.05) at 2 and 2.5 ATA compared with 1 ATA. A 42 (P less than 0.001) and 50% (P less than 0.001), reduction in Isuit from the 1 ATA value was detected at 2 and 2.5 ATA, respectively. However, overall mean Itissue was maximal and independent of the pressure during immersion at Tcw. The Itotal was also significantly smaller in 2 and 2.5 ATA compared with 1 ATA. The Itissue provided most insulation in the extremities, such as the hand and foot, and the contribution of Isuit in these body parts was relatively small. On the other hand, Itissue of the trunk areas, such as the chest, back, and thigh, was not high compared with the extremities, and Isuit played a major role in the protection of heat drain from these body parts.

Adult↗
PubMed1988

Critical water temperature during water immersion at various atmospheric pressures.

The present work was undertaken to determine the effect of atmospheric pressure [ranging from a high altitude of 4,300 m above sea level or 0.6 atmospheres absolute (ATA) to depths of 10 m deep or 2 ATA] on the critical water temperature (Tcw), defined as the lowest water temperature a subject can tolerate at rest for 2 h without shivering, of the unprotected subject during water immersion. Nine healthy males wearing only shorts were subjected to immersion to the neck in water at 0.6, 1, and 2 ATA while resting for 2 h. Continuous measurements included esophageal (Tes) and skin (Tsk) temperatures, direct heat loss from the skin (Htissue), and insulation of the tissue (Itissue). The Tcw was significantly higher at 0.6 ATA than 1 and 2 ATA: however, Tcw at 1 ATA was identical to that at 2 ATA. The metabolic heat production remained unchanged among the pressures. During the 2-h immersion in Tcw, Tes was identical among all atmospheric pressures: however, Tsk was significantly higher (P less than 0.05) at 0.6 ATA and was identical between 1 and 2 ATA. The overall mean Itissue was near maximal during immersion in Tcw in each pressure, and no difference was detected among the pressures. However, Itissue at the acral extremities (arm, hand, and foot) decreased significantly at 0.6 ATA, and subsequently heat loss from these parts was increased, which elevated an extremity-to-trunk heat loss ratio to 1.4 at 0.6 ATA from 1.1 at 1 and 2 ATA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Modification of a conventional bicycle ergometer for underwater use.

With a few simple modifications, a conventional row-bicycle ergometer could be made suitable for underwater use. By attaching three sizes of fins to the pedal cranks of the ergometer, work load in water could be achieved to an oxygen consumption (VO2) level range of 400 to 2000 ml/min. The preferable range of pedaling speeds was 30-40 rpm to maintain a constant speed for a prolonged time. When using three different fins VO2 was found to be: VO2 = 254.3 + 4.50n - 0.12n2 + 0.0030n3 for no fins, VO2 = 250.1 + 8.30n - 0.32n2 + 0.0062n3 for small fins, VO2 = 254.0 + 6.10n - 0.24n2 + 0.0068n3 for medium fins, and VO2 = 256.4 + 13.77n - 0.72n2 + 0.0131n3 for large fins, when n is the number of pedaling rate. Major advantages of this modified ergometer for underwater exercise are 1) the modification is simple and the size of the device is small enough to place in a tank of a climatic chamber, 2) the ergometer can be biologically calibrated and used for a wide range of exercise oxygen uptakes, and 3) a subject can exercise in a comfortable upright position.

Exercise Test↗
PubMedDate not supplied

Bone mineral density of metatarsus in hemiplegic subjects.

The cortical bone mineral density (BMD) of the first metatarsus was measured using computed x-ray densitometry in 84 hemiplegic subjects (35 men and 49 postmenopausal women) and 49 healthy age-matched controls (23 men and 26 postmenopausal women), and the determinants of paralysis-induced cortical osteopenia were investigated. In the hemiplegia group, ages were 63.9 +/- 9.8 yr (mean +/- standard deviation) for men and 66.6 +/- 11.0 yr for women. The duration of hemiplegia was 25.3 +/- 19.8 mo for men and 26.0 +/- 26.3 mo for women. The Brunnstrom stage (lower limb) was 4.0 +/- 1.1 for men and 3.8 +/- 1.4 for women. The walking ability, evaluated by walking score, was 3.6 +/- 1.3 (range, 1-5) for men and 3.2 +/- 1.5 (range, 1-5) for women. The time since menopause was 14.8 +/- 10.0 yr. The age and time since menopause were similar in the hemiplegia and control groups. On the paralyzed side, the BMD of men and women in the hemiplegia group was significantly lower than that of the control group on the nondominant side (by 6.1% and 11.6%, respectively). In hemiplegic men, Brunnstrom stage and walking score showed a significant positive correlation to the BMD (r = 0.418 and r = 0.349, respectively). In hemiplegic women, on the other hand, age, duration of hemiplegia, and years since menopause showed a significant negative correlation to the BMD (r = -0.260, r = -0.478, and r = -0.506, respectively), and Brunnstrom stage and walking score showed a significant positive correlation to the BMD (r = 0.526 and r = 0.406, respectively). These findings suggest that the determinant of metatarsal cortical BMD loss on the paralyzed side of the hemiplegic subject might be different according to gender. That is, although the degree of paralysis and walking ability could be a determinant of metatarsal cortical BMD loss on the paralyzed side of hemiplegic men, additional factors such as age, duration of hemiplegia, and years since menopause could play an important role in the determination of metatarsal cortical BMD loss in postmenopausal hemiplegic women.

Activities of Daily Living↗