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Biomedical subjects

D Riebe

Publications and source records attributed to D Riebe.

16 recordsLinked to original sources
PubMed2005

Physical activity staging distribution: establishing a heuristic using multiple studies.

The purpose of this study was to identify the population prevalence across the stages of change (SoC) for regular physical activity and to establish the prevalence of people at risk. With support from the National Institutes of Health, the American Heart Association, and the Robert Wood Johnson Foundation, nine Behavior Change Consortium studies with a common physical activity SoC measure agreed to collaborate and share data. The distribution pattern identified in these predominantly reactively recruited studies was Precontemplation (PC) = 5% (+/- 10), Contemplation (C) = 10% (+/- 10), Preparation (P) = 40% (+/- 10), Action = 10% (+/- 10), and Maintenance = 35% (+/- 10). With reactively recruited studies, it can be anticipated that there will be a higher percentage of the sample that is ready to change and a greater percentage of currently active people compared to random representative samples. The at-risk stage distribution (i.e., those not at criteria or PC, C, and P) was approximately 10% PC, 20% C, and 70% P in specific samples and approximately 20% PC, 10% C, and 70% P in the clinical samples. Knowing SoC heuristics can inform public health practitioners and policymakers about the population's motivation for physical activity, help track changes over time, and assist in the allocation of resources.

Behavioral Research↗
PubMed2001

Blood glucose responses to carbohydrate feeding prior to exercise in the heat: effects of hypohydration and rehydration.

This study assessed the plasma glucose (PG) and hormonal responses to carbohydrate ingestion, prior to exercise in the heat, in a hypohydrated state versus partial rehydration with intravenous solutions. On separate days, 8 subjects (21.0 +/- 1.8 years; 57.3 +/- 3.7 ml x kg(-1) x min(-1)) exercised at 50% VO2max in a 33 degree C environment until a 4% body weight loss was achieved. Following this, subjects were rehydrated (25 ml x kg(-1)) with either: 0.45% IV saline (45IV), 0.9% IV saline (9IV), or no fluid (NF). Subjects then ingested 1 g x kg(-1) of carbohydrate and underwent an exercise test (treadmill walking, 50% VO2max, 36 degrees C) for up to 90 min. Compared to pre-exercise level (294 mg x dl(-1)), PG increased significantly (>124 mg x dl(-1)) at 15 min of the exercise test in all trials and remained significantly elevated for 75 min in NF, 30 min more than in the 2 rehydration trials. Although serum Insulin increased significantly at 15 min of exercise in the 45IV trial (7.2 +/- 1.2 vs. 23.7 +/- 4.7 mIU x ml(-1)), no significant differences between trials were observed. Peak plasma norepinephrine was significantly higher in NF (640 +/- 66 pg x ml(-1)) compared to the 45IV and 9IV trials (472 +/- 55 and 474 +/- 52 pg x ml(-1), respectively). In conclusion, ingestion of a small solid carbohydrate load prior to exercise in the 4% hypohydration level resulted in prolonged high PG concentration compared to partial IV rehydration.

Adult↗
PubMed2001

Comparison of two progressive treadmill tests in patients with peripheral arterial disease.

In a vascular rehabilitation program, 28% of our frail elderly patients are unable to be tested with traditional progressive exercise protocols at program entry due to the high (2.0 miles/h or 3.2 km/h) initial treadmill speeds. The purpose of this investigation was to compare a new progressive treadmill protocol which has a reduced initial speed (1.0 mile/h or 1.6 km/h) to an established protocol performed at 2.0 miles/h (3.2 km/h) to determine the comparability and reproducibility of the new protocol. Eleven patients with arterial claudication performed three symptom-limited exercise tests in random order. Two tests used the new protocol while the remaining trial used the established protocol. Claudication pain was measured using a 5-point scale. Oxygen consumption, heart rate, minute ventilation, respiratory exchange ratio and blood pressure at peak exercise were similar among the three trials. There were strong intraclass correlations for peak oxygen consumption (r = 0.97), onset of claudication (r = 0.96) and maximum walking time (r = 0.98) between the two trials using the new protocol. There was also a significant correlation between the new protocol and the established protocol for peak oxygen consumption (r = 0.90) and maximum walking time (r = 0.89). The new progressive treadmill protocol represents a valid, reliable protocol for patients with arterial claudication. This protocol may be useful for testing patients with a low functional capacity so that clinically appropriate exercise prescriptions can be established and the efficacy of treatments can be determined.

Aged↗
PubMed2000

Interactive communication strategies: implications for population-based physical-activity promotion.

Physical inactivity is a recognized independent risk factor for the development of cardiovascular disease. However, a large proportion of the U.S. population does not participate in regular physical activity, and research has shown that without intervention, most people remain sedentary. Thus, an urgent need exists for developing effective interventions to promote physical-activity adoption and maintenance. Additionally, it is important that these interventions can be disseminated to the large population of sedentary individuals. To be disseminable, physical-activity interventions must move beyond reliance on strictly face-to-face modes and begin to more fully use newer technologies, such as the Internet. This article summarizes the progress made in promoting physical activity with interactive communications. We also delineate areas for future research.

Cardiovascular Diseases↗
PubMed2000

Plasma vasopressin and aldosterone responses to oral and intravenous saline rehydration.

This investigation examined plasma arginine vasopressin (AVP) and aldosterone (Ald) responses to 1) oral and intravenous (IV) methods of rehydration (Rh) and 2) different IV Rh osmotic loads. We hypothesized that AVP and Ald responses would be similar between IV and oral Rh and that the greater osmolality and sodium concentration of a 0.9% IV saline treatment would stimulate a greater AVP response compared with a 0.45% IV saline treatment. On four occasions, eight men (age: 22.1 +/- 0.8 yr; height: 179.6 +/- 1.5 cm; weight: 73.6 +/- 2.5 kg; maximum O(2) consumption: 57.9 +/- 1.6 ml. kg(-1). min(-1), body fat: 7.7 +/- 0.9%) performed a dehydration (Dh) protocol (33 degrees C) to establish a 4-5% reduction in body weight. After Dh, subjects underwent each of three randomly assigned Rh (back to -2% body wt) treatments (0.9 and 0.45% IV saline, 0.45% oral saline) and a no Rh treatment during the first 45 min of a 100-min rest period. Blood samples were obtained pre-Dh, immediately post-Dh, and at 15, 35, and 55 min post-Rh. Before Dh, plasma AVP and Ald were not different among treatments but were significantly elevated post-Dh. In general, at 15, 35, and 55 min post-Rh, AVP, Ald, osmolality, and plasma volume shifts did not differ between IV and oral fluid replacement. These results demonstrated that the manner in which plasma AVP and Ald responded to oral and IV Rh or to different sodium concentrations (0.9 vs. 0.45%) was not different given the degree of Dh (-4.5% body wt) and Rh and amount of time after Rh (55 min).

Administration, Oral↗
PubMed1998

Endocrine responses during exercise-heat stress: effects of prior isotonic and hypotonic intravenous rehydration.

Exercise following exercise-induced dehydration (EID) has been shown to elevate concentrations of plasma norepinephrine (NE) and hypothalamic-pituitary-adrenal axis hormones. However, it is not known how intravenous (i.v.) rehydration (Rh) with isotonic (ISO) or hypotonic (HYPO) saline affects these hormone concentrations. It was hypothesized that HYPO, versus ISO, would lead to lower plasma NE and cortisol concentrations ([CORT]) during subsequent exercise following EID due to a decrease in plasma sodium concentration [Na+]. Eight non-heat acclimated men completed three experimental treatments (counterbalanced design) immediately following EID (33 degrees C) to -4% body mass loss. The Rh treatments were i.v. 0.9% NaCl (ISO, 25 ml x kg[-1]), i.v. 0.45% NaCl (HYPO, 25 ml x kg[-1]), and no fluid (NF). After Rh and rest (2 h total), the subjects walked at 53-54 percent of maximal O2 uptake for 45 min at 36 degrees C. After Rh, the following observations were made before/during exercise: percentage change in plasma volume (PV) was lower in NF compared to ISO and HYPO but similar between ISO and HYPO; delta[Na+] was similar between ISO and NF and higher in ISO compared to HYPO; delta plasma NE was higher in NF compared to ISO and HYPO, but similar between ISO and HYPO; delta plasma [CORT] was higher in NF compared to ISO and HYPO and higher in ISO compared to HYPO; rectal temperature was higher in NF compared to ISO and HYPO. These data would suggest that sympathetic nervous activity and [CORT] during exercise, subsequent to EID and Rh, was affected by lower PV (probably through cardiopulmonary baroreflexes) as well as core temperature. Furthermore, [CORT] was affected by delta[Na+] after Rh through an unknown mechanism.

Adult↗
PubMed1997

Effects of oral and intravenous rehydration on ratings of perceived exertion and thirst.

The purpose of this investigation was to compare the effects of oral and intravenous saline rehydration on differentiated ratings of perceived exertion (RPE) and thirst. Eight men underwent three randomly assigned rehydration treatments following a 2- to 4-h exercise-induced dehydration bout to reduce body weight by 4%. Treatments included 0.45% saline infusion (i.v.), 0.45% saline oral ingestion (ORAL), and no fluid (NF). Following rehydration and rest (2 h total), subjects walked at 50% VO2max for 90 min at 36 degrees C (EX). Central RPE during ORAL was lower (P < 0.05) than i.v. and NF throughout EX. Local RPE during NF was higher (P < 0.05) than i.v. and ORAL at minutes 20 and 40 of EX and overall RPE during NF was higher (P < 0.05) than ORAL at minutes 20 and 40 of EX. Significant correlations were found between overall RPE and mean skin temperature for i.v. (r = 0.72) and NF (r = 0.75), and between overall RPE and thirst ratings for i.v. (r = 0.70). Thirst ratings were not different among trials at postdehydration. Following rehydration, thirst was higher (P < 0.05) during NF than i.v. and ORAL and lower (P < 0.05) during ORAL than i.v. at all subsequent time points. Results suggest that oral rehydration is likely to elicit lower RPE and thirst ratings compared with intravenous rehydration.

Adult↗
PubMed1997

Bioimpedance spectroscopy technique: intra-, extracellular, and total body water.

The purpose of this study was to test the validity of a multiple frequency bioimpedance spectroscopy (BIS) technique that estimates extracellular fluid volume (ECV), intracellular fluid volume (ICV), and total body water (TBW). Thirteen healthy males (mean +/- SD: age, 23 +/- 3 yr; body mass, 80.6 +/- 14.7 kg) had their TBW and ECV measured by ingesting dilution tracers (7.27 g deuterium oxide, 1.70 g sodium bromide; blood samples at 0 and 4 h). ICV was calculated as TBW minus ECV. Impedance was measured (50-500 kHz) at rest, on a nonconducting surface, with a BIS analyzer. Electrode placement, posture, exercise, food/fluid intake, and ambient temperature were controlled. Dilution measures (TBW, 51.00 +/- 9.30; ECV, 19.88 +/- 3.14; ICV, 31.12 +/- 6.80 L) and BIS volumes (TBW, 50.03 +/- 7.67; ECV, 20.95 +/- 3.33; ICV, 29.04 +/- 4.51 L) were significantly different for ECV (P < 0.01) and ICV (P < 0.05); some individual differences were large. The correlation coefficients of dilution versus BIS volumes (r = 0.93 to 0.96) were significant at P < 0.0001; SEEs were: TBW, 2.23 L; ECV, 1.26 L; and ICV, 1.71 L. We concluded that BIS is valid for between-subject comparisons of body fluid compartments, is appropriate in clinical settings where change in ECV/ICV ratio is important, and should be used by comparing the required level of accuracy to the inherent technique error/variance.

Adult↗
PubMed1997

Intravenous vs. oral rehydration: effects on subsequent exercise-heat stress.

This study compared the influence of intravenous vs. oral rehydration after exercise-induced dehydration during a subsequent 90-min exercise bout. It was hypothesized that cardiovascular, thermoregulatory, and hormonal variables would be the same between intravenous and oral rehydration because of similar restoration of plasma volume (PV) and osmolality (Osmo). Eight non-heat-acclimated men received three experimental treatments (counterbalanced design) immediately after exercise-induced dehydration (33 degrees C) to -4% body weight loss. Treatments were intravenous 0.45% NaCl (iv; 25 ml/kg), no fluid (NF), and oral saline (Oral; 25 ml/kg). After rehydration and rest (2 h total), subjects walked at 50% maximal O2 consumption for up to 90 min at 36 degrees C. The following observations were made: 1) heart rate was higher (P < 0.05) in Oral vs. iv at minutes 45, 60, and 75 of exercise; 2) rectal temperature, sweat rate, percent change in PV, and change in plasma Osmo were similar between iv and Oral; 3) change in plasma norepinephrine decreased less (P < 0.05) in Oral compared with iv at minute 45; 4) changes in plasma adrenocorticotropic hormone and cortisol were similar between iv and Oral after exercise was initiated; and 5) exercise time was similar between iv (77.4 +/- 5.4 min) and Oral (84.2 +/- 2.3 min). These data suggest that after exercise-induced dehydration, iv and Oral were equally effective as rehydration treatments. Thermoregulation, change in adrenocorticotropic hormone, and change in cortisol were not different between iv and Oral after exercise began; this is likely due to similar percent change in PV and change in Osmo.

Adult↗
PubMed1995

Local cooling in wheelchair athletes during exercise-heat stress.

Wheelchair athletes with spinal cord injuries (WA) face challenges to thermal homeostasis, including reduced cutaneous vasoaction and sweat production. The purpose of this study was to evaluate the efficacy of local cooling to reduce heat strain in WA. Six elite, endurance-trained male WA (33 +/- 3 yr, 64 +/- 4 kg) performed three strenuous exercise tests in a hot-humid environment (32.9 +/- 0.1 degrees C, 75 +/- 3% RH) by pushing a racing chair on a stationary roller (30 min, 16.5 km.h-1, 704-766 W metabolic heat) while wearing shorts and socks. The three treatments involved an ice-packet vest (V) (0.14 m2 of skin surface), a refrigerated headpiece (H) (0.16 m2), or no cooling (C) (control). The vest and headpiece offered potential cooling of 388 W and 266 W. Mean body heat storage for trials V (117 +/- 26 W), H (117 +/- 22 W), and C (164 +/- 40 W) were statistically similar, partly because V (117 +/- 47 W) and H (75 +/- 59 W) cooled inefficiently (30 and 28%, respectively). Repeated measure ANOVA indicated no significant between-treatment differences (P > 0.05) for any variable in trials V, H, and C. We concluded that local cooling during V and H was ineffective because heat storage decreased, but was not prevented.

Adult↗
PubMed1994

Urinary indices of hydration status.

Athletes and researchers could benefit from a simple and universally accepted technique to determine whether humans are well-hydrated, euhydrated, or hypohydrated. Two laboratory studies (A, B) and one field study (C) were conducted to determine if urine color (Ucol) indicates hydration status accurately and to clarify the interchangeability of Ucol, urine osmolality (Uosm), and urine specific gravity (Usg) in research. Ucol, Uosm, and Usg were not significantly correlated with plasma osmolality, plasma sodium, or hematocrit. This suggested that these hematologic measurements are not as sensitive to mild hypohydration (between days) as the selected urinary indices are. When the data from A, B, and C were combined, Ucol was strongly correlated with Usg and Uosm. It was concluded that (a) Ucol may be used in athletic/industrial settings or field studies, where close estimates of Usg or Uosm are acceptable, but should not be utilized in laboratories where greater precision and accuracy are required, and (b) Uosm and Usg may be used interchangeably to determine hydration status.

Adult↗
PubMed1992

The blood pressure response to exercise in anabolic steroid users.

We measured blood pressure at rest and during exercise in nine weight lifters using anabolic steroids, 10 weight lifters not using these drugs, and 10 sedentary controls. BP was measured using standard sphygmomanometry and an appropriately sized cuff. Maximal treadmill tests and leg press exercise were conducted in random order on separate days. Systolic blood pressure in the anabolic steroid users was higher at rest and during both forms of exercise. Diastolic blood pressure during exercise was also higher in the anabolic steroid users than in the other two groups. The maximal systolic and diastolic blood pressure change from rest to exercise was not different among the groups, suggesting that the higher exercise pressure in the drug users was primarily due to higher resting values. Body weight and biceps circumference were greatest in the anabolic steroid users. Adjusting rest and exercise blood pressure for body weight or biceps size eliminated statistically significant differences between groups, but had little impact on the absolute group differences. We conclude that the higher rest and exercise blood pressure values noted in anabolic steroid users may be related to their larger body mass or may be an artifact of the larger arm circumference in these subjects. Other factors may also be operative, however, because blood pressure remained nonsignificantly higher even after body weight and biceps size were adjusted for statistically.

Adult↗
PubMed1991

Influence of carbohydrate moieties of human serum transferrin on the determination of its molecular mass by polyacrylamide gradient gel electrophoresis and staining with periodic acid-Schiff reagent.

The influence of carbohydrate moieties of transferrin (Tf) on the determination of its molecular mass (MM) by polyacrylamide gradient gel electrophoresis (PAGGE) was investigated. Iron-free native human serum transferrin (Tf) of 99% purity and partly or completely carbohydrate- and N-acetylneuraminic acid (NANA)-free molecule forms were analyzed. The MM differences before and after enzymatic cleavage were found not to agree with the theoretical difference. From amino acid and carbohydrate analysis the MM of Tf was determined to be 79,570 Da whereas by denaturing and nondenaturing PAGGE MM of 77,000 Da +/- 1000 Da were found. After enzymatic cleavage of the two carbohydrate chains of Tf the difference between the calculated MM and the value reported in literature increased to 7000 Da (nondenaturing PAGGE) and 9200 Da (denaturing PAGGE). Following enzymatic cleavage of the 4 NANA molecules (MM 1237 Da) we obtained the relatively largest difference between the value given in the literature and that determined by PAGGE, namely MM 3300 Da on nondenaturing and 4000 Da on denaturing PAGGE. The differences due to the removal of the other carbohydrates were negligible. In addition we tested the periodic acid-Schiff reagent to stain iron-free Tf, containing different carbohydrate residues. The shortest carbohydrate moiety necessary for Tf staining corresponds to two identical carbohydrate chains of the structure (Asn)-GlcNAc-GlcNAc-beta-Man-(alpha-Man-)-alpha-Man.

Amino Acids↗
PubMedDate not supplied

Cortisol and testosterone concentrations in wheelchair athletes during submaximal wheelchair ergometry.

It is yet unknown how upper body exercise combined with high ambient temperatures affects plasma testosterone and cortisol concentrations and furthermore, how these hormones respond to exercise in people suffering spinal cord injuries. The purpose of this study was to characterize plasma testosterone and cortisol responses to upper body exercise in wheelchair athletes (WA) compared to able-bodied individuals (AB) at two ambient temperatures. Four WA [mean age 36 (SEM 13) years, mean body mass 66.9 (SEM 11.8) kg, injury level T7-T11], matched with five AB [mean age 33.4 (SEM 8.9) years, mean body mass 72.5 (SEM 13.1) kg] exercised (cross-over design) for 20 min on a wheelchair ergometer (0.03 kg resistance.kg-1 body mass) at 25 degrees C and 32 degrees C. Blood samples were obtained before (PRE), at min 10 (MID), and min 20 (END) of exercise. No differences were found between results obtained at 25 degrees C and 32 degrees C for any physiological variable studied and therefore these data were combined. Pre-exercise testosterone concentration was lower (P < 0.05) in WA [18.3 (SEM 0.9) nmol.l-1] compared to AB [21.9 (SEM 3.6) nmol.l-1], and increased PRE to END only in WA. Cortisol concentrations were similar between groups before and during exercise, despite higher rectal temperatures in WA compared to AB, at MID [37.21 (SEM 0.14) and 37.02 (SEM 0.08) degrees C, respectively] and END [37.36 (SEM 0.16) and 37.19 (SEM 0.10) degrees C, respectively]. Plasma norepinephrine responses were similar between groups. In conclusion, there were no differences in plasma cortisol concentrations, which may have been due to the low relative exercise intensities employed. The greater exercise response in WA for plasma testosterone should be confirmed on a larger population. It could have been the result of the lower plasma testosterone concentrations at rest in our group.

Adult↗
PubMedDate not supplied

The major components of human energy balance during chronic beta-adrenergic blockade.

PURPOSE: The authors compare the major components of energy balance--dietary food intake, resting metabolic rate, and physical energy expenditure--in patients receiving beta-blocking medications and healthy controls. METHODS: The authors recruited subjects who were receiving beta-blocking agents (n = 22) from local hospitals and clinics. Twenty-two healthy controls were matched to each patient based on age, weight, and gender. Resting metabolic rates were determined using indirect calorimetry. Three-day dietary intakes and physical activity assessments were analyzed. RESULTS: There were no between-group differences in calories ingested or self-reported physical activity patterns. However, resting metabolic rates were lower in the beta-blocked subjects (beta-blocked = 1,541 +/- 464 kcals/day; controls = 1,817 +/- 426 kcals/day; P < 0.05). CONCLUSIONS: beta-adrenergic blockade causes a reduction in resting metabolic rate. Therefore, beta-blocked individuals should increase physical activity, decrease dietary intake, or both to maintain daily energy balance and prevent weight gain that accompanies a reduction in metabolic rate.

Adrenergic beta-Antagonists↗