Seated buttock contours: a pilot study of Australian senior high-school students.

Both posture and comfort of a chair are influenced by the contour and characteristics of the seat. Knowledge of seat contours of a student population could thus be useful in the design of school chairs. This study investigated seated buttock contours of senior high-school students in order to determine: (a) their general characteristics, (b) the effect of gender and sitting posture and (c) the relationship between the contours and selected anthropometric variables (stature and mass). A contour measurement device was developed and used to measure buttock contours in five sitting postures (typing, sitting up, sitting back, slumping and writing). Buttock contours were quantified by constructing anterior-posterior (AP) and lateral profiles from which six discrete profile dimension measurements were made. AP and lateral profiles were found to have a consistent shape across all participants. Five out of six profile dimensions were significantly different between genders, with just one significantly different between sitting postures (typing and sitting back). Correlations between anthropometric measures and profile dimensions were relatively low (r < 0.34) with no clear patterns evident. Overall results of this study suggest that buttock contours are influenced by gender to a greater extent than sitting posture.

Preferred seat orientation of senior high-school students.

The height of the front of the seat is the primary determinant of appropriate seat size in the school setting. In the present study, this dimension was fixed at 445 mm and, using a brief adjustment period, students adjusted the angle of the seat to their preferred rear seat height (PRSH) under three fixed and one adjustable desk height conditions and for one desk height, under two time conditions. PRSH was significantly greater at an 800 mm desk height (454+/-14 mm) compared to 735 mm (447+/-15 mm) and 720 mm (444+/-16 mm). When desk height as well as rear seat height were adjustable, PRSH was 446+/-15 mm and preferred desk height 751+/-25 mm. Taller students or those with larger popliteal heights selected lower PRSHs at all desk heights, with PRSH more strongly related to popliteal height (r = -0.54 to -0.59) than stature (r = -0.44 to -0.50). No differences were found in PRSH between short (<5 min) and long (30 min) adjustment periods for the 735 mm desk height. The nearly horizontal seat positions found in this study were between those recommended by other authors.

Thermoregulatory responses to exercise and warm water immersion in physically trained men with tetraplegia.

OBJECTIVE: To compare thermoregulatory responses of highly trained men who are tetraplegic during 40 min exercise at 65% [Vdot]O(2) peak and 60 min immersion in 39 degrees C water. METHODS: Four physically trained men who are tetraplegic participated in three laboratory visits. The first visit involved familiarisation and then determination of [Vdot]O(2) peak using open circuit spirometry during an incremental test to exhaustion with each man propelling his sport wheelchair on a motor driven treadmill. The order of second and third visits was randomly allocated. Visit 2 involved 40 min of exercise at 65% [Vdot]O(2) peak propelling each man's sport wheelchair on treadmill. Visit 3 involved sitting immersed to nipple line in 39 degrees C water for 60 min. Venous blood was obtained pre, during and after each intervention and analyzed for haemoglobin, haematocrit and changes in plasma volume were calculated. Separated plasma was analyzed for noradrenalin and adrenalin (high performance liquid chromatography). Heart rate, rectal temperature, and sweat rate estimated from a sweat capsule placed on forehead (dew point hygrometry) were recorded throughout. RESULTS: [Vdot]O(2) peak and HR max of these subjects were 1.14+/-0.16 l.min(-1) and 99+/-4 b.min(-1) respectively. Heart rate preimmersion was 67+/-4 b.min(-1) rising to 75+/-4 b.min(-1) after 40 min and 87+/-3 b.min(-1) after 60 min immersion. Heart rate was 68+/-3 b.min(-1) pre-exercise rising to 91+/-5 b.min(-1) after 40 min exercise. Rectal temperature rose from 35.97+/-0.30 degrees C pre immersion to 37.32+/-0.51 degrees C after 60 min immersion, and from 36.42+/-0.20 degrees C pre-exercise to 36.67+/-0.19 degrees C after 40 min exercise. Haemoconcentration occurred during 40 min of exercise and haemodilution occurred throughout 60 min of water immersion. Three participants demonstrated no sweating on the forehead during immersion or exercise. One subject commenced sweating after 20 min exercise and after 5 min of immersion. CONCLUSION: Compared to exercise, immersion was associated with a lower heart rate, a lower plasma noradrenalin concentration and an expanded plasma volume. When considering exercise or warm water immersion as therapeutic modalities in men who are tetraplegic, attention should be paid to heat gain and changes in plasma volume.

Does endurance training affect orthostatic responses in healthy elderly men?

PURPOSE: To investigate the effects and time course of endurance training on the regulation of heart rate (HR), arterial pressure (AP), norepinephrine (NE), and plasma volume (PV) during orthostatic stress in healthy elderly men. METHODS: Thirty-one healthy men (65--75 yr) were randomly allocated into endurance training (N = 20, EX) and control (N = 11, CON) groups. The EX group cycled 3 d x wk(-1) for 30 min at 70% VO(2peak) for 12 wk x VO(2peak) was determined on an electronically braked cycle ergometer, before training and after 4, 8, and 12 wk of endurance training. The immediate (initial 30 s), early steady-state (1 min), and prolonged (5, 10, 15 min) beat-by-beat HR and AP responses during 90 degrees head-up tilt (HUT) were measured at least 3 d after each VO(2peak) test. Spontaneous baroreflex slopes were determined by application of linear regression to sequences of at least three cardiac cycles in which systolic blood pressure (SBP) and R-R interval changed in the same direction. Venous blood was collected during 90 degrees HUT and analyzed for changes in plasma NE concentrations, as well as hematocrit and hemoglobin to determine changes in PV. RESULTS: Endurance training significantly (P < 0.01) increased VO(2peak) (mL x kg(-1) x min(-1)) in EX by 10 +/- 2%. The immediate, early steady-state, and prolonged HR and AP responses and spontaneous baroreflex slopes during 90 degrees HUT were not significantly different (P > 0.05) between EX and CON groups before or after 4, 8, or 12 wk of endurance training. No significant differences (P > 0.05) were observed between EX and CON groups for peak changes in PV during orthostasis before (-15.0 +/- 1.4% vs -11.9 +/- 1.3%) or after 4 (-12.2 +/- 1.0% vs -12.7 +/- 1.4%), 8 (-13.7 +/- 1.2% vs -12.4 +/- 0.7%), and 12 wk (-10.8 +/- 1.6% vs -10.6 +/- 0.6%) of endurance training, suggesting a similar stimulus presented by 90 degrees HUT in both groups. Peak changes in NE concentrations during HUT were similar (P > 0.05) between EX and CON groups before (119 +/- 23 pg x mL(-1) vs 191 +/- 36 pg x mL(-1)) and after 4 (139 +/- 29 pg x mL(-1) vs 146 +/- 25 pg x mL(-1)), 8 (114 +/- 32 pg x mL(-1) vs 182 +/- 41 pg x mL(-1)), and 12 wk (143 +/- 35 pg x mL(-1) vs 206 +/- 42 pg.mL-1) of endurance training. CONCLUSIONS: These data indicate that in healthy elderly men, improvements in VO(2peak) can occur without compromising the regulation of HR, AP, NE, and PV during orthostatic stress.

Thermoregulatory responses to repeated warm water immersion in subjects who are paraplegic.

OBJECTIVE: To compare thermoregulatory responses to repeated warm water immersion (39 degrees C) between physically active subjects who are paraplegic or able-bodied in order to gain insight into rehabilitative and adaptive processes. METHODS: Five paraplegic (P) and six able-bodied (AB) males participated. VO2 peak was determined by open-circuit spirometry using a cycle ergometer (AB) and propelling a wheelchair on a motor driven treadmill (P). Subjects sat immersed to the nipple line in 39 degrees C water for 60 min for 5 consecutive days. Pre- and post-test measurements included heart rate (HR), oesophageal temperature (Tes), sweat onset and rate (dew point hygrometry). Venous blood was obtained before, and during immersion to estimate changes in plasma volume. RESULTS: The P group was older and lighter than AB group (P<0.05). VO2max, VCO2max and VE(max) were significantly greater in AB group. HR at rest and after 60 min immersion was not significantly different between the groups pre- or post-test. Tes significantly increased after 60 min immersion in both groups, at both pre- and post-testing sessions. Post-test Tes after 60 min immersion (AB) was significantly less than Tes after 60 min of immersion pre-test. The DeltaTes (Tes 60 min-Tes 0 min) was significantly higher in AB group than the P group at pre- but not post-testing. No significant changes in sweat onset or rate were found for the AB or P groups during the pre- or post testing sessions. Significant expansion of plasma volume occurred during immersion in both groups, pre- and post-immersion sessions. CONCLUSIONS: Repeated warm water immersion (39 degrees C) for 60 min per day for a total of 5 days did not produce a significant adaptive response in P group. In the AB group, Tes at the end of 60 min immersion was significantly lower after the adaptation period.

Norepinephrine and epinephrine responses during orthostatic intolerance in healthy elderly men.

In young individuals, orthostatic intolerance is associated with marked increases in plasma epinephrine (EPI) concentrations and attenuated rises in plasma norepinephrine (NE) concentrations. This study investigated the cardiovascular, EPI and NE responses of healthy elderly males during orthostatic stress. Twelve men (68 +/- 1 yr) with a recent history of orthostatic hypotension and who exhibited orthostatic intolerance (HYPO) during 90 degrees head-up tilt (HUT) were compared with 12 men (69 +/- 1 yr) without a history of orthostatic hypotension and who remained normotensive (NORMO) throughout 90 degrees HUT. Beat-by-beat recordings of heart rate (HR), mean (MAP), systolic (SBP), diastolic (DBP), and pulse (PP) pressures were made throughout 90 degrees HUT. Blood samples obtained during supine rest and 90 degrees HUT were analyzed for changes in EPI and NE concentrations, hematocrit, hemoglobin and plasma volume. Compared to supine rest, orthostatic intolerance was characterized by significant reductions (p < 0.0001) in MAP, SBP, DBP, and PP. The HR, MAP, SBP, DBP, and PP at the termination of 90 degrees HUT was significantly lower (p < 0.0001) for HYPO than NORMO. The 90 degrees HUT position resulted in significant increases (p < 0.01) in NE for both HYPO and NORMO, with the rise in NE significantly lower (p < 0.05) in HYPO. There were no differences between groups regarding EPI concentrations at the termination of 90 degrees HUT. These results suggest that the magnitude of arterial pressure (AP) reduction does not influence the EPI response during orthostasis in healthy elderly men. However, marked reductions in AP, leading to orthostatic intolerance, are associated with inadequate increases in NE in these individuals.

Testing the heterogeneity theory of late-life mortality plateaus by using cohorts of Drosophila melanogaster.

Variation among individuals in robustness has been posed as a general explanation for the lack of increase in late-life mortality rates. Here, we test corollaries of this heterogeneity theory. One is that populations that have undergone strong laboratory selection for differentiated stress resistance should show significant differences in their late-life mortality schedules. To test this corollary, we employed 40 410 flies from three groups of Drosophila melanogaster populations that differ substantially in their resistance to starvation. No significant differences between these groups were found for late-life mortality. Another corollary of the heterogeneity theory is that there should be late-life plateaus in stress resistance that coincide with the plateau stage of the mortality curve. In 20 994 flies from six replicate outbred laboratory populations, we measured mortality rates every other day and starvation and desiccation resistance every 7 days. Both male and female starvation and desiccation resistance clearly decreased with time overall. There was no late-life plateau in male desiccation resistance. A late-life plateau in male starvation resistance may exist, however. Together, these two experiments generally constitute evidence against heterogeneity as a major contributor to the phenomenon of late-life mortality plateaus.

VO2peak and the gas-exchange anaerobic threshold during incremental arm cranking in able-bodied and paraplegic men.

Resting energy expenditure, peak oxygen uptake (VO2peak) and the gas-exchange anaerobic threshold (Than) were measured during incremental arm cranking (15 W x min(-1)) in six able-bodied (AB) and six paraplegic (P) subjects. Only male subjects with traumatic spinal cord injuries in the area of the 10-12th thoracic segment were included in the P group. All AB and P subjects were physically active. Mean (SE) values for age and body mass were 28 (2) years and 78.9 (3.9) kg for the AB group and 32 (4) years and 70.8 (7.9) kg for the P group (P>0.05). Resting energy expenditure values were not found to be significantly different between AB [5.8 (0.2) kJ x min(-1)] and P [5.1 (0.3) kJ min(-1)] subjects. Mean VO2peak values were 29.3 (2.4) ml x kg(-1) min(-1) and 29.6 (2.2) ml x kg(-1) x min(-1) for the AB and P groups, respectively (P>0.05). Absolute oxygen uptake values measured at two gas-exchange anaerobic threshold (Than) were not significantly different between the two groups. However, the Than occurred at a significantly higher percentage of VO2peak in the P [58.9 (1.7)%] group than in the AB [50.0 (2.8)%] group (P<0.05). Moreover, respiratory exchange ratio (R) values obtained at the Than and at 15, 45, 60, 75 and 90 W of incremental exercise were significantly lower in the P group than in the AB group. Heart rates were significantly elevated at every submaximal work stage (15-120 W) in the P group compared to the AB group (P<0.05). These findings suggest that chronic daily wheelchair activity produces local adaptations in the functional upper-body musculature, which reduce glycogenolysis and increase the rate of lipid utilization (lower R) during arm exercise. These local adaptations may be in part responsible for the significantly higher Than observed for arm exercise in P subjects, even though VO2peak values were essentially the same for both groups.

Rectal and esophageal temperatures during upper- and lower-body exercise.

This study investigated the question: is core temperature measurement influenced by whether exercise involves predominantly upper- or lower-body musculature? Healthy men were allocated to three groups: treadmill ergometry (T) n = 4, cycle ergometry (C) n = 6 and arm crank ergometry (AC) n = 5. Subjects underwent an incremental exercise test to exhaustion on an exercise-specific ergometer to determine maximum/peak oxygen consumption (VO2max). One week later subjects exercised for 36 min on the same ergometer at approximately 65% VO2max while temperatures at the rectum (T(re)) and esophagus (T(es)) were simultaneously measured. The VO2max (1 x min(-1)) for groups T [4.76 (0.50)] and C [4.35 (0.30)] was significantly higher than that for the AC group [2.61 (0.24)]. At rest, T(re) was significantly higher than T(es) in all groups (P < 0.05). At the end of submaximal exercise in the C group, T(re) [38.32 (0.11) degrees C] was significantly higher than T(es) [38.02 (0.12) degrees C, P < 0.05]. No significant differences between T(re) and T(es) at the end of exercise were noted for AC and T groups. The temperature difference (T(diff)) between T(re) and T(es) was dissimilar at rest in the three groups; however, by the end of exercise T(diff) was approximately 0.2 degrees C for each of the groups, suggesting that at the end of steady-state exercise T(re) can validly be used to estimate core temperature.

The antagonists RU486 and ZK98299 stimulate progesterone receptor binding to deoxyribonucleic acid in vitro and in vivo, but have distinct effects on receptor conformation.

Three types of transfection experiments were used to detect the abilities of different classes of antagonists to stimulate binding of progesterone receptor (PR) to progesterone response elements (PRE) in intact mammalian cells. These included a promoter interference assay, in which PR binding to PREs positioned between the TATA box and the start of transcription is detected as a reduction of expression of a constitutively active reporter gene, competition of PR antagonist and glucocorticoid receptor agonist for a common glucocorticoid response element/PRE-controlled reporter construct, and activation of a chimeric receptor (PR-VP16) containing the constitutive trans-activation domain derived from the VP16 protein of herpes simplex virus. By each approach, all antagonists tested were equally effective in stimulating PR binding to PREs in the cell. This included previously designated type I (ZK98299) and type II (RU486, ZK98734, and ZK112993) 11beta-aryl substituted steroid analogs. Stimulation of PR binding to PREs in the cell by ZK98299 was of interest because this antagonist has been reported to lack the ability to stimulate PR-DNA binding in vitro by electrophoretic gel mobility shift assay compared with RU486, which promotes efficient binding of PR to PREs. To clarify the apparent discrepancy between intact cell and in vitro results with ZK98299, we altered electrophoretic gel mobility shift assay conditions to allow detection of less stable DNA complexes. Under these conditions, ZK98299 induced the formation of specific PR-PRE complexes. Further analysis of the ZK98299-induced DNA complexes revealed that they exhibited an electrophoretic mobility different from that of the complexes induced by RU486, and the off-rate of PR from DNA was faster than that of the PR bound to agonist. This suggests that ZK98299 promotes a conformational change within PR distinct from that induced by RU486. The present results are consistent with the conclusions that ZK98299 stimulates PR binding to target DNA sequences and that ZK98299 and RU486 represent two mechanistic classes of antagonists based on inducing different conformational changes in PR.

Maximal physiological responses during arm cranking and treadmill wheelchair propulsion in T4-T6 paraplegic men.

The aim of the study was to compare the exercise responses during maximum wheelchair propulsion on a motor driven treadmill (TM) and maximum arm cranking (AC) in a homogenous group of nine paraplegic men with clinically complete spinal cord lesions between T4 and T6. The test order for each ergometer was random and time between the two ergometer tests was 3-7 days. All experiments were conducted in an air conditioned environment (23 degrees C DB, 18 degrees C WB). The highest VO2 recorded during the final minute of arm cranking (1.65 +/- 0.14 l min-1) and wheelchair propulsion on the treadmill (1.72 +/- 0.10 l min-1) was not significantly different. There were no significant differences in heart rate during the final minute of arm cranking (177 +/- 3 b min-1), and wheelchair propulsion on a motor driven treadmill (177 +/- 4 b min-1), nor were there any significant differences in minute ventilation (STPD) between AC (52 +/- 6.6 l min-1) and TM (56.1 +/- 4.8 l min-1). The VCO2 l min-1 for AC (2.00 +/- 0.20 l min-1) and TM (2.00 +/- 0.12 l min-1) was also not significantly different. The present study found that, unlike previous studies, no significant differences in VO2 (l min-1, ml kg-1 min-1) VE (l min-1), VCO2 (l min-1) or heart rate (b min-1) were found between the two modes of ergometry during the last minute of incremental exercise to exhaustion in a homogenous group of T4-T6 paraplegic men.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of sauna on tetraplegic and paraplegic subjects.

Six tetraplegic (T) and 4 paraplegic (P) subjects underwent a 20-minute pre sauna phase (30 degrees C DB; 65% RH), and an up to 15-minute sauna (85 degrees C DB; less than 10% RH), followed by a 15 minute post sauna phase (30 degrees C DB; 65% RH). During all phases subjects wore a bathing suit and remained supine on a hospital trolley. Heart rate (HR) and blood pressure (BP) were recorded during all phases. Rectal temperature (Trec) was measured by a probe (AD590) inserted approximately 14 cm into the rectum. Oral temperature (Toral) also utilising (AD590) circuitry was recorded simultaneously with Trec. Skin temperature (Tsk) (AD590) was measured on the head, chest, right thigh and right calf. Forehead sweat rate (SR) was determined from dew point temperature (Tdp). A catheter was inserted into a dorsal hand or foot vein and venous blood was withdrawn at selected times and analysed for haemoglobin (Hb) and haematocrit (Hct), and the separated plasma was analysed for glucose (Glu), sodium (Na+), potassium (K+) and chloride (C1-). Venous blood sampled just prior to entering and just prior to leaving the sauna, was analysed for adrenalin (A) and noradrenalin (NA) using high performance liquid chromatography. For both groups HR rose significantly during the sauna with a significant decline in HR for the P group during the post sauna phase. There were no significant changes in systolic BP for either group. A significant decline in diastolic BP was found for the T group during the post sauna phase. There were no episodes of syncope.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prolonged exercise at a similar percentage of maximal oxygen consumption in trained and untrained subjects.

Six trained male cyclists and six untrained but physically active men participated in this study to test the hypothesis that the use of percentage maximal oxygen consumption (%VO2max) as a normalising independent variable is valid despite significant differences in the absolute VO2max of trained and untrained subjects. The subjects underwent an exercise test to exhaustion on a cycle ergometer to determine VO2max and lactate threshold. The subjects were grouped as trained (T) if their VO2max exceeded 60 ml.kg-1.min-1, and untrained (UT) if their VO2max was less than 50 ml.kg-1.min-1. The subjects were required to exercise on the ergometer for up to 40 min at power outputs that corresponded to approximately 50% and 70% VO2max. The allocation of each exercise session (50% or 70% VO2max) was random and each session was separated by at least 5 days. During these tests venous blood was taken 10 min before exercise (- 10 min), just prior to the commencement of exercise (0 min), after 20 min of exercise (20 min), at the end of exercise and 10 min postexercise (+ 10 min) and analysed for concentrations of cortisol, [Na+], [K+], [Cl-], glucose, free fatty acid, lactate [la-], [NH3], haemoglobin [Hb] and for packed cell volume. The oxygen consumption (VO2) and related variables were measured at two time intervals (14-15 and 34-35 min) during the prolonged exercise tests. Rectal temperature was measured throughout both exercise sessions. There was a significant interaction effect between the level of training and exercise time at 50% VO2max for heart rate (fc) and venous [la-].(ABSTRACT TRUNCATED AT 250 WORDS)