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Biomedical subjects

M S Sothmann

Publications and source records attributed to M S Sothmann.

At least 19 recordsLinked to original sources
PubMed2004

Performance requirements of physically strenuous occupations: validating minimum standards for muscular strength and endurance.

Employment rights legislative mandates passed in the USA over the last three decades emphasize the importance of validating performance standards for physically strenuous occupations. This study validated minimally acceptable standards for the muscular strength and endurance necessary to perform fire suppression activities. Incumbent firefighters (n=153) selected for key demographic characteristics completed a simulated set of firefighting tasks (Fire Suppression Evolution) and then a Predictor Test Battery of physical abilities tests. Regression analysis revealed that three predictor test items (hose drag/high rise pack carry; arm lift; arm endurance) combined to significantly predict performance time of the Fire Suppression Evolution (p < or =0.01). Firefighters (n=41) rating videotaped performance times of the Fire Suppression Evolution determined that more than one-half a standard deviation slower than the mean time established by the incumbents reflected unacceptable performance. Approximately 80% of incumbent firefighters passed the minimally acceptable performance standard. Use of the 3-predictor test battery would correctly identify 89% of successful performers and 72% of unsuccessful performers. This study demonstrates that validation of minimal physical performance standards will identify a cohort of individuals with a high probability of not being able to perform critical fire suppression activities. This finding has important implications for examining the relationship between physical performance standards and medical and economic outcomes.

Adult↗
PubMed1999

Brain norepinephrine changes with simulated weightlessness and relation to exercise training.

Maintenance of nervous system function during periods of a deconditioning syndrome is important to prevent diminished psychological/behavioral, and physiological function observed during periods of bed rest, physical inactivity, and weightlessness. A main neurotransmitter is norepinephrine (NE), and its regulation yields insight into nervous system function. This research tested the hypotheses that, 1) deconditioning syndrome induced by simulated weightlessness of 9 days via the head-down tilt (HDT) model results in a blunted noradrenergic turnover rate in selected brain tissue and, 2) that exercise training acts as a countermeasure for these changes in noradrenergic activity. Male Sprague-Dawley rats (3 months, n = 60) were divided into either a HDT (HDT, n = 20), cage control (CAGE-CN, n = 20) or an exercise trained HDT (HDT-EX, n = 20) group. Each group was further subdivided into a saline (n = 10) or alpha-methyl-tyrosine (AM, n = 10) (200 mg/kg) injected subgroup. Animals in the HDT groups were tail suspended in a 30 degrees head-down tilt position for 9 days. Norepinephrine turnover was determined 3 h following administration of saline or alpha-methyl-para-tyrosine. The NE turnover rate (ng gm(-1) x h(-1)) for the CN, HDT, and HDT-EX groups, respectively, were as follows: locus coeruleus, 63 +/- 33, *134 +/- 65, 85 +/- 61; hypothalamus, 195 +/- 50, *47 +/- 47; *93 +/- 34; cerebellum, 10 +/- 18, *65 +/- 15, *53 +/- 19; cerebral cortex, 6 +/- 20, *28 +/- 15, *68 +/- 22. (*Denotes significant difference from the control group at the p < or = 0.05 level of significance; +denotes significant difference from the HDT group at the p < or = 0.05 level of significance.) These findings suggest that: 1) norepinephrine turnover rate adapts in a tissue-specific manner following a 9-day tail suspension, 2) increased norepinephrine turnover rates and norepinephrine tissue content in the HDT group are consistent with neural adaptation to a chronic stress response.

Analysis of Variance↗
PubMed1995

Selected psychophysiological stress responses in men with high and low body fatness.

Previous research on catecholamine (CA) response to exercise has linked heightened adiposity to a hypostress syndrome. In the present study a cognitive/psychomotor stressor was employed to determine whether this association exists during less metabolically challenging tasks. Moreover, because stress is manifested in a multidimensional manner, measures of behavior and perceived distress were analyzed in addition to the physiological response. Men were selectively recruited for two body fatness groups (low, 12 +/- 4%, N = 9; high, 27 +/- 2%, N = 10) while being matched on age, lean weight, and peak absolute oxygen consumption. All men performed a modified Stroop task for 12 min to induce a psychophysiological stress response. Physiological changes included significant increases in heart rate, venous plasma norepinephrine, and epinephrine. Cognitive/psychomotor responses indicated no change in reaction time during the task but significant cognitive fatigue as indicated by post-task anagram performance. Perceived distress was suggested by elevated state anxiety. The high and low adiposity groups were similar on all measures of the psychophysiological stress response. These findings suggest that elevated adiposity is not characterized by a hypostress state during the relatively low metabolic challenge of a cognitive/psychomotor stressor.

Adipose Tissue↗
PubMed1993

Young and old subjects matched for aerobic capacity have similar noradrenergic responses to exercise.

Sympathetic nervous system activity as indicated by circulating norepinephrine has been demonstrated to increase with advancing chronological age both at rest and during submaximal exercise. Much of the earlier work investigating this aging phenomenon used a younger group that had a higher peak oxygen consumption (VO2) than did the older group, which made comparisons difficult. In the present study, young [n = 7, 36 +/- 1.0 (SE) yr] and old subjects (n = 8, 61 +/- 1.2 yr) were matched on peak VO2 and then exercised at approximately the same relative submaximal VO2 (75%) and power output on a cycle ergometer for 21 min. Blood samples were collected at rest and in the 7th, 14th, and last minute of a 21-min exercise bout via an indwelling catheter in an antecubital vein. The norepinephrine responses for the young and old groups, respectively, were as follows: rest, 486 +/- 111 vs. 673 +/- 108; 7 min, 1,258 +/- 255 vs. 1,185 +/- 172; 14 min, 1,639 +/- 316 vs. 1,528 +/- 288; and 21 min, 2,038 +/- 488 vs. 1,936 +/- 453 pg/ml. These responses were not significantly different between the groups at any time period. The epinephrine values for the age groups were not statistically different: rest, 115 +/- 60 vs 88 +/- 51; 7 min, 140 +/- 18 vs. 326 +/- 88; 14 min, 216 +/- 33 vs. 366 +/- 104; and 21 min, 324 +/- 100 vs. 447 +/- 113 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Sympathetic nervous system and behavioral responses to stress following exercise training.

This study tests the hypothesis that a short-term (16 weeks) exercise program modifies sympathetic nervous system (SNS) and selected behavioral responses to acute psychological stress. Twenty-four previously sedentary middle-aged men with maximal aerobic capacity (VmaxO2) values less than 40 ml.kg-1.min-1 were assigned to experimental (n = 12) and control (n = 12) groups. All subjects performed a modified Stroop test (18 min) at pre- and postexercise training during which intravenous blood samples were drawn at three time intervals for plasma catecholamine (CA) determination. Motor performance was continuously recorded for assessment of premotor (PMT) and motor (MOT) components of reactions time. A set of anagrams were administered immediately following the modified Stroop to determine the level of cognitive fatigue induced. At both pre- and postexercise intervention, the total group (n = 24) manifested significant (p less than or equal to 0.05) elevations in state anxiety, heart rate, and plasma norepinephrine. No significant changes occurred over time on PMT or MOT. There were significantly (p less than or equal to 0.01) lengthened anagram performance scores poststress compared to nonstress values. The experimental group exercise trained 3 days/week for 16 weeks, resulting in a 20% increase in VO2max. However, there were no group differences on the CA or behavioral responses to the modified Stroop at pre- or postintervention. These findings do not support the hypothesis that short-term aerobic training significantly alters SNS activity or behavioral measures of central processing in middle-aged men exposed to an acute psychological challenge.

Adult↗
PubMed1992

Heart rate response of firefighters to actual emergencies. Implications for cardiorespiratory fitness.

Heart rate (HR) and oxygen consumption (VO2) responses during actual fire-suppression emergencies were monitored in 10 male firefighters. These firefighters worked at 157 +/- 8 beats per minute (bpm) for 15 +/- 7 minutes. This was 88 +/- 6% of their previously determined HR max. Based on treadmill testing, the HR x VO2 relationship was established for each firefighter. The predicted VO2 derived from HR monitoring in actual emergencies was 25.6 +/- 8.7 mL.kg-1.min-1 or 63 +/- 14% of VO2 max (40.0 +/- 6.5 mL.kg-1.min-1). These values on the cardiorespiratory response to actual emergencies are very similar to results derived from studies employing fire-suppression simulations. Recommendations for the VO2 max of firefighters ranging from 33.5 to 42.0 mL.kg-1.min-1 that have been generated from simulation testing appear appropriate given the cardiorespiratory responses to actual emergencies.

Adult↗
PubMed1992

Age as a bona fide occupational qualification for firefighting. A review on the importance of measuring aerobic power.

Recent federal and judicial initiatives have led to controversy over the justification of mandatory retirement policies applied to public safety occupations. The Equal Employment Opportunity Commission has been mandated to study this issue, and a critical element of that study will be to determine the types of tests to be employed as substitutes for a mandatory retirement age. In this review, a rationale is presented for the measurement of aerobic power (VO2max) as a predictor of the physical performance capability of firefighters. We conclude that task simulations rarely replicate the environmental conditions present at structural fires that stress the cardiorespiratory capability of firefighters. VO2max is an important predictor of performance effectiveness of firefighters to be used in conjunction with task-specific testing.

Age Factors↗
PubMed1991

Relationship of regional fat distribution and obesity to electrocardiographic parameters in healthy premenopausal women.

Abdominal obesity is an independent cardiovascular risk factor. The coexistence of abdominal obesity and electrocardiographic abnormalities may facilitate the development of cardiac arrhythmias and sudden death. We determined the relationship of body fat distribution and obesity to ECG indices in 27 obese premenopausal women on an isocaloric diet. Intra-abdominal fat distribution was assessed by computerized tomography, and obesity was assessed by hydrostatic weighing. The PR, QRS, and QTc intervals, the P and QRS axes, and the P-QRS angle were determined from a resting electrocardiogram. Cardiovascular risk profile was assessed by systolic and diastolic blood pressure and plasma cholesterol and triglyceride levels. Increased deposition of intra-abdominal fat was significantly associated with prolongation of the QTc interval independent of obesity and other cardiovascular risk factors. The prolongation of the QTc interval seen with increasing intra-abdominal fat distribution may enhance susceptibility to cardiac arrhythmias. These subjects should have electrocardiographic monitoring during periods of weight loss achieved by intensive regimens.

Abdomen↗
PubMed1991

Plasma catecholamine response to acute psychological stress in humans: relation to aerobic fitness and exercise training.

Existing cross-sectional studies on plasma catecholamine activity provide no support for the concept that a markedly high level of aerobic fitness modifies sympathoadrenal response to an acute psychological challenge in humans. In contrast, compromised sympathetic nervous system activity has been observed in individuals with low aerobic fitness and the relationship probably reflects a global deconditioning syndrome involving both psychological and physiological processes. The relationship between low levels of fitness and plasma norepinephrine may appear as a blunted or augmented response depending upon the nature of the task. Short-term (3-4 months) exercise training studies conducted with humans have not indicated a substantial adaptation in the relative plasma catecholamine change from a preexisting baseline during exposure to acute psychological stress. Exercise training can lower basal circulating plasma norepinephrine, resulting in lower absolute concentrations during an acute challenge, but the studies in this area lack consistency and the absolute change tends to be modest. There is no evidence that fitness or exercise training is significantly associated with plasma epinephrine activity during short-term psychological stress.

Analysis of Variance↗
PubMed1990

Plasma free and sulfoconjugated catecholamines during sustained exercise.

Previous research established a relationship between circulating sulfoconjugated norepinephrine (NE-SO4) and oxygen consumption at various exercise intensities. In this study, the stability of the NE-SO4 response was examined during sustained exercise at a constant relative intensity. Seven trained men bicycled at 78 +/- 3% of their maximal O2 consumption for 28 min and then rested on the ergometer for a comparable duration. After a 30-min rest, plasma samples were collected through an indwelling catheter at 7-min intervals during the exercise and recovery periods. Free NE and epinephrine increased sixfold during exercise. These changes were accompanied by increases in sulfoconjugated catecholamines, but only NE-SO4 achieved statistical significance (rest, 712 +/- 602; exercise, 1,329 +/- 1,163 pg/ml). This occurred at three collection periods (14, 21, and 28 min). Approximately 35, 52, and 95% of NE, epinephrine, and dopamine, respectively, existed as sulfoconjugated during exercise. Subject variation was present in the sulfoconjugated catecholamine response that could not be attributed to corresponding differences in circulating free catecholamine release. These findings implicate blood flow as a factor in the sulfoconjugation of NE, but not epinephrine or dopamine.

Adult↗
PubMed1989

Adiposity, fat distribution, and cardiovascular risk.

STUDY OBJECTIVE: To determine the relative importance of adiposity and fat distribution to cardiovascular risk profile. DESIGN: A cross-sectional study. SETTING: Clinical research center funded by the National Institutes of Health. PATIENTS: Convenience sample of 33 healthy premenopausal women with a wide range of body weight who did not have diabetes mellitus, hirsutism and virilism, gynecologic disorder, cardiac disease, or hypertension. Women participating in exercise or dietary programs or taking medication were excluded. All subjects completed the study. INTERVENTIONS: Total body fat mass was determined by hydrostatic weighting, and fat distribution was assessed by subscapular skinfold thickness, subscapular-to-triceps skinfold ratio, the waist-to-hip ratio, and computed tomography. Cardiovascular risk was assessed by the serum insulin response during oral glucose stimulation; levels of triglycerides and total cholesterol; high-density lipoprotein cholesterol to total cholesterol concentrations; and systolic and diastolic blood pressures. MEASUREMENTS AND MAIN RESULTS: The anthropometric parameters chosen were significantly associated with the cardiovascular risk profile (P less than 0.001). Visceral fat distribution assessed by computed tomography accounted for a significantly greater degree of variance in the cardiovascular risk factors than the total body fat mass (P less than 0.05). The cumulative insulin response was the primary metabolic variable relating the anthropometric indices to cardiovascular risk. CONCLUSIONS: Intra-abdominal fat deposition constitutes a greater cardiovascular risk than obesity alone. Hyperinsulinemia may constitute an important component of the increased cardiovascular risk of abdominal obesity.

Adipose Tissue↗
PubMed1989

The relationship of insulin to sex hormone-binding globulin: role of adiposity.

The role of adiposity in the relationship of insulin to sex hormone-binding globulin (SHBG) concentration was examined in 31 healthy premenopausal women of varying body weight. Fat mass was estimated by hydrostatic weighing. Concentrations of SHBG and testosterone (T) and cumulative insulin response during an oral glucose tolerance test were measured. The cumulative insulin response was inversely related to SHBG (r = -0.56, P less than 0.01). The relationship between SHBG and cumulative insulin response remained significant (r = -0.47, P less than 0.01) after adjusting for fat mass and T. The fat mass correlated significantly with SHBG (r = -0.51, P less than 0.01). The relationship of SHBG to fat mass remained significant after adjusting for T (r = -0.45, P less than 0.01). However, the relationship between fat mass and SHBG was no longer significant (r = -0.34, P greater than 0.05) after adjusting for cumulative insulin response. Hyperinsulinemia may play an important role in the progressive reduction of SHBG observed with increasing adiposity.

Adult↗
PubMed1989

Relative contribution of obesity and body fat distribution to alterations in glucose insulin homeostasis: predictive values of selected indices in premenopausal women.

Obesity and fat topography are risk factors for hyperinsulinemia, insulin resistance, and diabetes mellitus. The relative contribution of obesity and body fat distribution indices to fasting and oral glucose-stimulated C peptide, insulin, and glucose concentrations were determined in 33 healthy premenopausal women. Obesity level was assessed by hydrostatic weighing and fat topography by computerized tomography-derived intraabdominal fat area, waist to hip ratio, subscapular skinfold thickness and the ratio of subscapular to triceps skinfold thickness. Both fat mass and regional fat distribution indices were associated closely with changes in insulin secretion. Fat topography indices were more closely correlated (p less than 0.001) to insulin response than were fat mass indices (p less than 0.01). The subscapular skinfold thickness had the greatest integrity for reflecting fat mass and fat distribution as they relate to the metabolic profile. The subscapular skinfold thickness may help identify individuals at risk for noninsulin dependent diabetes mellitus.

Adipose Tissue↗
PubMed1988

Cardiovascular fitness and selected adrenal hormone responses to cognitive stress.

Individuals manifesting high maximal oxygen consumption (VO2max) have augmented adrenal responsivity to physical stress. We subjected 17 males representing a wide range of VO2max to cognitive stress and measured their forearm venous plasma epinephrine, norepinephrine, and cortisol responses. Six repeated blood samples were collected at resting, stress, and recovery intervals. Significant increases were observed for epinephrine (X +/- SD; rest, 50 +/- 30; stress, 81 +/- 77 pg/ml; p less than or equal to 0.05) and norepinephrine (rest, 404 +/- 235; stress, 481 +/- 314 pg/ml; p less than or equal to 0.05). Cortisol changes were not significant. A positive association (r = 0.54; p less than or equal to 0.05) was observed between epinephrine and VO2max during the first collection of the stress period. An inverse association (r = 0.49; p less than or equal to 0.05) was present between VO2max and norepinephrine. No significant correlations occurred with cortisol. These results indicate that enhanced cardiovascular fitness is characterized by augmented epinephrine responsivity to cognitive stress. This association exists in the presence of an inverse relationship between plasma free norepinephrine response and VO2max.

Adult↗