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Biomedical subjects

E M Bernauer

Publications and source records attributed to E M Bernauer.

At least 37 records · Page 2Linked to original sources
PubMed1981

Plasma volume, osmolality, vasopressin, and renin activity during graded exercise in man.

Plasma volume (PV), renin activity (PRA), and osmotic (Osm), sodium (Na+), and arginine vasopressin (AVP) concentrations were measured in venous blood samples taken before and after three levels of cycle ergometer exercise (100, 175, and 225 W) in 15 young male volunteers. Plasma volume and solute concentrations changed significantly (P less than 0.05, denoted by *) with work intensity. The % delta PV was -3.7%* at 100 W, -8.8%* at 175 W, and -12.4%* at 225 W. Plasma Na+ concentration, Osm, and AVP increase were curvilinear with graded exercise and were significant only when work intensity exceeded 40% VO2max. PRA increase was linear and significant at all work levels. The % delta PV was significantly correlated with delta Osm (r = 0.99*) and delta Na+ (r = 0.89*) but had low correlations with delta AVP (r = 0.22, NS) and delta PRA (r = 0.12, NS). However, delta AVP was significantly correlated with delta Na+ (r = 0.86*) and delta Osm (r = 0.83*), whereas delta PRA had low correlations with delta Na+ (r = 0.33, NS), delta Osm (r = 0.29, NS), and delta AVP (r = 0.43, NS). The data support the hypothesis that a) with exercise, AVP release is a primary factor for fluid and electrolyte regulation as it is highly correlated with the plasma hyperosmolality produced by a net hypotonic plasma efflux; b) an exercise intensity greater than 40% VO2max is required to change plasma osmolality and, thus, stimulate significant AVP release; and c) the stimulation of the renin-angiotensin system is a more general stress response, which responds to increasing sympathetic nervous activity.

Adult↗
PubMed1980

Role of thermal and exercise factors in the mechanism of hypervolemia.

Our purpose was to determine whether the chronic increase in plasma volume (PV), resulting from heat exposure (HE) and exercise training (ET), was due only to elevated rectal temperature (Tre) or whether there were additional nonthermal factors related to the exercise. Eight men were divided into two groups. The HE group sat for 2 h/day (Tdb = 42 degrees C, 93% rh) for 8 consecutive days; Tre was raised by 1.72 +/- 0.04 degrees C to 38.5 degrees C each day. The ET group rode a bicycle ergometer for 2 h/day for 8 days (Tdb = 25 degrees C, 60% rh) at a load (60-65 Vo2max) that gave the same area under their Tre curve. PV increased by 177 ml (4.9%, P less than 0.05) in the HE group and by 427 ml (12.0%, P less than 0.05) in the ET group. This exercise-induced hypervolemia was associated with thermal factor(s) that contributed 40% and nonthermal factors that accounted for the remaining 60%. Some nonthermal, exercise-induced factors were twofold greater increases in plasma osmotic and vasopressin levels during exercise, and a fivefold increase in resting plasma protein (albumin) content.

Adult↗
PubMed1980

Exercise training-induced hypervolemia: role of plasma albumin, renin, and vasopressin.

To investigate the time course and mechanism of the increase in blood volume (BV) during isotonic exercise training, blood hemoglobin, hematocrit, and plasma volume (PV), osmotic, electrolyte, renin activity (PRA), vasopressin (AVP), and protein fractions were measured periodically in eight trained men 20-22 yr (Vo2max = 57 ml . min-1 . kg-1) before, during, and after ergometer exercise training (approximately 160 W, 65% Vo2max) for 2 h/day for 8 days. During training, plasma total osmolar and albumin contents increased to maintain a constant plasma osmolality and protein concentration during PV expansion. After training, BV increased by 457 ml (+8.1% P less than 0.05), due to an increase in PV of 427 ml (+12.1%, P less than 0.05); red cell volume was essentially constant (delta = +30 ml, NS). Plasma hypervolemia during training was associated with two major factors: 1) a ninefold elevation in PRA and AVP during exercise that facilitated Na+ and H2O retention, and 2) a progressive, chronic increase in plasma albumin content that provided increased H2O-binding capacity for the blood. Thus an efficient procedure for increasing PV is the daily performance of high-intensity isotonic leg exercise (65% Vo2max) for 2 h/day.

Adult↗
PubMed1979

Temperature changes during exercise measured by thermography.

The present study explores the dynamic changes of surface temperatures associated with peripheral vascular shifts during and following hand gripping, one-legged ergometric, and running exercise. An AGA 680 thermovision system, incorporating a Bolex 16-mm camera and displaying 10-colored isotherms on a slave monitor, generated synchronous infrared (IR) movies at 16 frame/s. Incremental increases in surface skin temperatures (Ts) were observed while gripping at 20, 50, and 80% of maximum with a peak rise of 1.7 degrees C. Thermographic recorded Ts changes during dynamic one-legged exercise were higher in the exercising leg than the resting leg. Surface temperatures dropped in both limbs following exercise. The advantages of the use of thermography during transient thermal states, as produced by dynamic exercise, is supported by comparative Ts data taken from thermograms and thermistors.

Hand↗
PubMed1977

Cardiorespiratory responses to exercise after bed rest in men and women.

The purpose of this study was to compare cardiorespiratory responses of men and women to submaximal and maximal workloads before and after bed rest (BR). Fifteen male college students (19-23 yr) and 8 female nurses (23-34 yr) underwent 14 d and 17 d, respectively of bed rest. The maximal work capacity test was performed in the supine position on a bicycle ergometer just before and immediately after bed rest. The women's maximal O2 uptake (maximal VO2) was 41% lower (P<0.05) than the men's before bed rest and 42% lower (P<0.05) after bed rest. During bed rest the women's maximal VO2 decreased from 2.06 to 1.86 liter/min (-9.7%, P<0.05), and that of the men decreased from 3.52 to 3.20 liter/min (-9.1%, P<0.05). Compared with pre-BR values, after bed rest the maximal ventilatory volume was essentially unchanged in the men (+1.8%) and women (+ 2.3%), but maximal heart rate was elevated from 185 to 193 b/min (+ 4.3%, P<0.05) in the men and from 181 to 187 b/min (3.3%, P<0.05) in the women. Submaximal VO2 was unchanged after bed rest in the men but was significantly reduced in the women; the women's Hct and RBC levels were lower (P<0.05) than comparable male data. Mean corpuscular volume was unchanged in both groups pre- and post-bed rest. It is concluded that the proportional deterioration in maximal VO2 following prolonged bed rest was essentially the same in young men and women.

Adult↗
PubMed1977

Fluid and electrolyte shifts during bed rest with isometric and isotonic exercise.

Fluid and electrolyte shifts were measured in seven men (19-21 yr) during three 2-wk bed rest (BR) periods, each of which was separated by a 3-wk ambulatory recovery period. During two of the three BR periods they performed isometric exercise and isotonic exercise. No prescribed exercise was given during the other BR period. On day 4 of BR, plasma volume decreased (P less than 0.05) 441 ml (-12.6%) with no exercise, 396 ml (-11.3%) with isometric, and 262 ml (-7.8%) with isotonic exercise; the decreases (NS) of extracellular volume were -4.4%, -2.6%, and -2.7%, respectively. By day 13 of BR, plasma volume stabilized at the lower level with isometric and isotonic exercise and continued to decline with no exercise; but the extracellular volume returned to or above control levels due to an overshoot of the interstitial volume of +320 to +430 ml (2.0-2.7%) that was about equal to the plasma volume loss. During BR there were isocontent losses from the plasma of protein, albumin, globulin, urea N2, uric acid, creatinine, Na, Cl, osmolarity, P, and glucose that were not influenced by either exercise regimen. However, the blood, red blood cell, and plasma volumes, and the Ca and K contents were stabilized during BR by both exercise regimens. The results suggest that during BR, preservation of the extracellular volume takes precedence over maintenance of the plasma volume, and this mechanism is independent of the effects of isometric or isotonic exercise.

Adult↗
PubMed1977

Fluid and electrolyte shifts in women during +Gz acceleration after 15 days' bed rest.

Twelve women (23-34 yr), comprising a bed-rest (BR) group of eight subjects and an ambulatory (AMB) group of four subjects, were centrifuged after 14 days of ambulatory control (C),after 15 days of a 17-day BR period, and on the third day of recovery (R). Venous blood was taken before and after the third +3.0 G acceleration run (1.8 G/min). Relative to (C), the +Gz tolerance after BR was reduced -49.0% (P less than 0.05) in the BR group and -38.7% (NS) in the AMB group; during (R) the BR group regained up to 89.4% and the AMB group up to 87.1% of their (C) tolerances. In each of the three test periods, the shifts in plasma Na, Cl, PO4, and osmotic contents, which accompanied +Gz, followed the outward shift of plasma volume (PV). The correlation of the shift of PV during acceleration with the +Gz tolerance was 0.72 (P less than 0.01). During acceleration, the PV and electrolyte loss for both groups after BR was about half the loss of (C) and (R). Compared with (C) and (R) values, potassium shifts were variable but the mean corpuscular volume and mean corpuscular Hb contents and concentrations were unchanged during all +Gz runs; The results indicate that: 1) the higher the (C) + Gz tolerance, the greater the tolerance decline due to BR; 2) relative confinement and reduced activity contribute as much to the reduction in tolerance as does the horizontal body position during BR; 3) bed-rest deconditioning has no effect on the erythrocyte volume during +3.0 Gz; and 4) about one-half the loss in tolerance after BR can be attributed to PV and electrolyte shifts.

Acceleration↗
PubMed1977

Combined effects of breathing resistance and hyperoxia on aerobic work tolerance.

Effects of three curvilinear inspiratory resistances (R1, R2, R3) on the cardiorespiratory responses of seven well-trained men during incremental cycling tests to exhaustion were studied by comparison to the low resistance R0 (at 1 l/s, R0 = 0.2; R3 = 6.5 cmH2O-s/l). Submaximal VO2 and the gas exchange anaerobic threshold (AT) were not affected by increasing resistance. Although maximal work rates were not significantly changed, highly significant reductions were observed for VE (R0 = 166.3; R3 = 99.7 l/min BTPS), VO2 max (R0 = 4,26; R3 = 3.74 l/min), HR (R0 = 185; R3 = 176 beats/min), and endurance (R0 = 17.3; R3 = 15.5 min) suggesting that aerobic work tolerance was dependent on ventilatory capacity. In additional tests removal of R3 at exhaustion abruptly increased VE and VO2, and permitted work to continue. Ventilation and work tolerance were therefore limited by R3 before the legs fatigued. Breathing 35% O2 against R3 produced significant, although small, increases in AT, VO2 max, peak HR, and endurance while decreasing the hyperventilatory response to work above AT. Thus, aerobic work tolerance reduced with high inspiratory resistance was partly restored by moderate hyperoxia, apparently because the ventilatory limit was delayed.

Airway Resistance↗
PubMed1977

Effects of exercise on fluid exchange and body composition in man during 14-day bed rest.

To determine the cause of the body weight loss during bed rest (BR), fluid balance and anthropometric measurements were taken from seven men (19-21 yr) during three 2-wk BR periods which were separated by 3-wk ambulatory recovery periods. Caloric intake was 3,073 +/- 155 (SD) kcal/day. During two of the three BR periods they performed supine isotonic exercise at 68% of VO2max on the ergometer for 1 h/day; or supine isometric exercise at 21% of maximal leg extension force for 1 min followed by a 1-min rest for 1 h/day. No prescribed exercise was given during the other BR period. During BR, body weight decreased slightly with no exercise (-0.43 kg, NS), but decreased significantly (P less than 0.05) by -0.91 kg with isometric and by -1.77 kg with isotonic exercise. About one-third of the weight reduction with isotonic exercise was due to fat loss (-0.69 kg) and, the remainder, to loss of lean body mass (-0.98 kg). It is concluded that the reduction in body weight during bed rest has two major components: First, a loss of lean body mass caused by assumption of the horizontal body position that is independent of the metabolic rate. Second, a loss of body fat content that is proportional to the metabolic rate.

Adult↗
PubMed1977

Exercise performance in 6-to-11-year-old boys with Duchenne muscular dystrophy.

To determine effects of severe muscular dystrophy on the performance of dynamic exercise, cardiorespiratory responses to incremental work on a bicycle ergometer and isokinetic limb strength measurements were compared for 13 dystrophic boys and 13 normal, untrained boys. The dystrophic boys (D) were matched to the normal boys (N) on the basis of age (8.4 yr), height (125 cm) and weight (25.7 kg). At rest, the dystrophic group had higher heart rates (HR) (D = 102; D = 31; N = 39 ml), with no difference in oxygen uptake (VO2), calculated cardiac output (Q), pulmonary ventilation (VE), or respiratory exchange ratio (R). During submaximal work, VO2, SV, Q and VE were lower in D. During maximal work, D had lower peak values for work rate (D = 400; N = 600 kg/min), endurance (D = 41; N = 60 ml), Q (D = 5.2; N = 11.0 liters/min), VE (D = 8.2; N = 36.9 liters/min), and R (D = 0.84; N = 0.99). Arm and leg strengths (four flexion and four extension motions) were lower in D, but muscle girths were not necessarily smaller. The findings indicate exercise performance in D was below normal and limited by low cardiorespiratory capacities, diminished leg strength, and perhaps reduced peripheral oxygen utilization. Duchenne muscular dystrophy, even in its early stages, apparently affects the work capacity of cardiac and pulmonary muscles as well as limb muscles.

Anthropometry↗
PubMed1976

Fibrinolytic and hemostatic changes during and after maximal exercise in males.

To evaluate changes in fibrinolytic activity, factor VIII and other hematological variables during and after a progressive step increment in work load, 10 healthy male subjects (22-27 yr of age) were exercised to exhaustion on an electromagnetic bicycle ergometer. Blood samples were drawn serially throughout the experiment. Little change in fibrinolytic activity was observed before 70-80% maximum heart rate (MHR) was achieved. Major changes occurred after 80% MHR. Peak values coincided with maximum exercise. In contrast major changes in factor VIII were observed between 95 and 100% MHR with peak values occurring 5-10 min postexercise. An increase in white blood cell count, platelet count, and retention was observed at maximum exercise. One individual failed to demonstrate an increase in either fibrinolytic or factor VIII activity. Relating the data to either the percent maximal oxygen uptake or percent maximal heart rate demonstrates the importance of the exercise protocol and exerting all subjects to the same relative level of physiological work.

Adult↗
PubMed1976

Cardiorespiratory deconditioning with static and dynamic leg exercise during bed rest.

Bed rest deconditioning was assessed in seven healthy men (19-22 yr) following three 14-day periods of controlled activity during recumbency by measuring submaximal and maximal oxygen uptake (VO2), ventilation (VE), heart rate, and plasma volume. Exercise regimens were performed in the supine position and included a) two 30-min periods daily of intermittent static exercise at 21% of maximal leg extension force, and b) two 30-min periods of dynamic bicycle ergometer exercise daily at 68% of VO2max. No prescribed exercise was performed during the third bed rest period. Compared with their respective pre-bed rest control values, VO2max decreased (P less than 0.05) under all exercise conditions; -12.3% with no exercise, -9.2% with dynamic exercise, but only -4.8% with static exercise. Maximal heart rate was increased by 3.3% to 4.9% (P less than 0.05) under the three exercise conditions, while plasma volume decreased (P less than 0.05) -15.1% with no exercise and -10.1% with static, but only -7.8% (NS) with dynamic exercise. Since neither the static nor dynamic exercise training regimes minimized the changes in all the variables studied, some combination of these two types of exercise may be necessary for maximum protection from the effects of the bed deconditioning.

Adaptation, Physiological↗
PubMed1975

Modeling static and dynamic human cardiovascular responses to exercise.

A human performance model has been developed and described [9] which portrays the human circulatory, thermo regulatory and energy-exchange systems as an intercoupled set. In this model, steady state or static relationships are used to describe oxygen consumption and blood flow. For example, heart rate (HTRT) is calculated as a function of the oxygen and the thermo-regulatory requirements of each body compartment, using the steady state work values of cardiac output (CO, sum of all compartment blood flows) and stroke volume (SV, assumed maximal after 40% maximal oxygen consumption): HTRT=CO/SV. The steady state model has proven to be an acceptable first approximation, but the inclusion of transient characteristics are essential in describing the overall systems' adjustment to exercise stress. In the present study, the dynamic transient characteristics of heart rate, stroke volume and cardiac output were obtained from experiments utilizing step and sinusoidal forcing of work. The gain and phase relationships reveal a probable first order system with a six minute time constant, and are utilized to model the transient characteristics of these parameters. This approach leads to a more complex model but a more accurate representation of the physiology involved. The instrumentation and programming essential to these experiments are described.

Analog-Digital Conversion↗
PubMed1975

Cardiorespiratory, hematological and physical performance responses of anemic subjects to iron treatment.

Twenty-nine adult iron-deficient anemis subjects (13 men and 16 women) with hemoglobin levels of 4.0 to 12.0 g/100 ml blood were divided into either an iron treatment or placebo group. Hematological, cardiorespiratory and performance data were collected before, during, and after treatment and compared with data from a control group of subjects (4 men and 6 women) from the same socioeconomic population. Hemoglobin levels for the iron treatment group improved from 7.7 to 12.4 g for the women and from 7.1 to 14.0 g for the men. Values for the control group were 13.9 g and 14.3 g for the women and men, respectively. The placebo group showed virtually no change over the 80-day period (8.1-8.4 g for women and 7.7-7.4 g for men). Peak exercise heart rates (5 min, 40-cm step test) were significantly reduced after treatment from 155 to 113 for the iron treatment men and 152 to 123 for the women compared with the placebo group which showed no changes. Values for the control group were 119 and 142 for the men and women, respectively. In response to the exercise test, no difference in oxygen consumption was found between the iron treatment and placebo group although 15% more O2 was delivered per pulse in the iron treatment group. Blood lactates were significantly highein the placebo than iron treatment group both at rest, 1.18 versus 0.64 mmole/liter, and 1 min after exercise, 5.30 versus 2.68 mmoles/liter. No changes in handgrip or shoulder adductor strength were observed following treatment. These results clearly support the concept that performance requiring high oxygen delivery is significantly affected by hemoglobin levels.

Adolescent↗
PubMed1975

Development of physical profiles for specific jobs.

Inherent risk of injury associated with heavy physical work tasks frequently obviates direct job analysis -- content validity -- for predictive or diagnostic purposes. A common alternative is an appraisal of the physical attributes manifest by the job requirements and the selection of tests of related physical factors. 241 job applicants were given a test battery composed of 40-items at the University of California Medical Center, Sacramento, California. A factor analysis reduced the initial 40-item test battery to an unweighted 6-item field test battery FTB. Standards scales were established for the FTB and applied to evaluate without prejudice a second group of 300 applicants. Since the present criterion for adequate job performance is simply the successful completion of climbing school, means for each test item of the FTB were evaluated for their predictive value. The mean scores for the step test and balance were found to be significantly different, smaller than .05 between the successful and unsuccessful applicants, whether male or female. Percent fat differed significantly only in the males and two strength tests and reaction times were not significant. Additional studies were conducted on two groups of young adults with known fitness levels to better characterize the strength factors which are considered essential to acceptable pole climb performance. Significant differences were found for both static and dynamic strengths, p equals smaller than .05. In summary, a FTB of simple, objective, job related test items can be identified and validated for predictive and diagnostic purposes. Probabilities for success can be established through a preliminary self-screening test program and administered by the employment office. The test items which comprise the FTB can be figuratively presented as a profile analysis and incorporated in the employee's medical file for longitudinalappraisal. If meaningful standards can be established for use in preemployment or job transfer screening, substantial financial benefits can accrue to the company in terms of reduced administrative and training costs and a reduction in "sick leave" and liability resulting from industrial accidents.

Adipose Tissue↗
PubMed1975

Effects of equivalent sea-level and altitude training on VO2max and running performance.

Twelve middle-distance runners, each having recently completed a competitive track season, were divided into two groups matched for maximal oxygen uptake (VO2max), 2-mile run time and age. Group 1 trained for 3 wk at Davis, PB = 760 mmHg, running 19.3 km/day at 75% of sea-level (SL) VO2max, while group 2 trained an equivalent distance at the same relative intensity at the US Air Force Academy (AFA), PB = 586 mmHg. The groups then exchanged sites and followed a training program of similar intensity to the group preceding it for an additional 3 wk. Periodic near exhaustive VO2max treadmill tests and 2-mile competitive time trials were completed. Initial 2-mile times at the AFA were 7.2% slower than SL control. Both groups demonstrated improved performance in the second trial at the AFA (chi = 2.0%), but mean postaltitude performance was unchanged from SL control. VO2max at the AFA was reduced initially 17.4% from SL control, but increased 2.6% after 20 days. However, postaltitude VO2max was 2.8% below SL control. It is concluded that there is no potentiating effect of hard endurance training at 2,300-m over equivalently severe SL training on SL VO2max or 2-mile performance time in already well conditioned middle-distance runners.

Adolescent↗