Search PubMed⌕ Search

Biomedical subjects

R J Robertson

Publications and source records attributed to R J Robertson.

At least 91 records · Page 5Linked to original sources
PubMed1986

Activity in the spinal cord-injured patient: an epidemiologic analysis of metabolic parameters.

Individuals with traumatic spinal cord injury (SCI) represent a population with extreme inactivity. The purpose of the current research was to investigate the metabolic differences between extremely inactive disabled individuals (SCI sedentary group), active disabled individuals (SCI athletes), and able-bodied individuals. Fasting morning blood samples were obtained for the determination of high density lipoprotein cholesterol (HDLc) subfractions, glucose, and insulin. The sedentary SCI group was comprised of 77 consecutive male admissions to a rehabilitation center. The 17 SCI athletes were recruited prior to competition at the annual National Wheelchair Games. Total HDLc and both its subfractions were significantly lower (P less than 0.01) in the male SCI sedentary population than in the SCI athletes or able-bodied controls. HDL2 was significantly elevated (P less than 0.01) in the SCI athlete compared to the SCI sedentary group (42.7 vs 34.1 mg X dl-1) and was similar to the control population (46.1 mg X dl-1). Glucose levels were similar in the two SCI groups but were both significantly lower (P less than 0.05) than in the able-bodied controls. These data suggest that the extreme inactivity observed in disabled populations is associated with lower HDLc concentrations and presumably an increase in coronary heart disease risk if these values were to persist over time. Additionally, it appears that physical activity is associated with increases in total HDLc, primarily through the HDL2 subfraction. Glucose and insulin were similar for both SCI groups despite the marked difference in activity levels, suggesting that these parameters may not be associated with activity.

Adult↗
PubMed1986

Effect of blood pH on peripheral and central signals of perceived exertion.

Ten male subjects underwent exercise testing in three modes, arms (A), legs (L), and arms + legs (A + L), after ingesting 0.3 g X kg-1 body weight of either NaHCO3 to induce alkalosis or CaCO3 as a placebo (i.e., six exercise trials). Ratings of perceived exertion (RPE: Borg, 15-pt scale) for the arms (RPE-A), legs (RPE-L), chest (REP-C), and overall body (RPE-O) did not differ between acid-base conditions at 20, 40, or 60% VO2max for all three exercise modes. At 80% VO2max, 1) RPE-A was lower (P less than 0.01) during A; 2) RPE-L was lower (P less than 0.01) during L; and 3) RPE-A and RPE-L were lower (P less than 0.01) during A + L under the NaHCO3 as compared to the CaCO3 condition. Differences were not found for RPE-L during A or for RPE-A during L. RPE-C and RPE-O were lower (P less than 0.01) under NaHCO3 during A, L, and A + L. Blood acid-base, VO2, and cardiorespiratory responses were not differentially influenced by exercise mode. Blood pH was significantly higher under NaHCO3 than CaCO3 at pre-exercise and 80% VO2max. VO2, heart rate, and tidal volume did not differ between acid-base conditions at any exercise intensity. VE and respiratory rate did not differ between acid-base conditions at 20, 40, or 60% VO2max but were significantly lower under NaHCO3 at 80% VO2max. RPE-A and L were positively related to blood [H+], and RPE-C was positively related to VE for all exercise modes.

Acid-Base Equilibrium↗
PubMed1985

Exercise and subsequent sleep in male runners: failure to support the slow wave sleep-mood-exercise hypothesis.

10 male joggers participated in a 3-week experimental protocol designed to look at the effects of three levels of energy expenditure (no exercise, regular exercise, and double exercise) on mood and subsequent nocturnal sleep focusing on REM sleep and delta sleep parameters. Exercise conditions were well discriminated by daily (F(2,18) = 65.8, p less than 0.0000) mean hip activity counts during monitored field exercise and by the mean weekly body weights (F(2,14) = 7.24, p less than 0.007). Subjects slept for 2 nights in the laboratory following each exercise condition and filled out two brief, clinical self-rating scales each night prior to sleep. These two self-rating instruments together index 105 somatic and psychobiological symptoms that are subsumed by the five major clinical symptom clusters of: Depression, Mania, Anxiety, Cognitive Disorganization, and Organicity. There were no significant differences in manually scored whole-night sleep parameters with the exception of REM latency (F(2,18) = 3.63, p less than 0.05), and there were no significant differences in self-ratings of psychobiological symptoms by night or exercise condition. These results are discussed in the context of failure to support either the slow wave sleep-exercise hypothesis or the exercise-mood elevation hypothesis.

Adult↗
PubMed1985

Field dependence as a limiting factor in solving a complex learning problem.

Subjects in a prior study of complex learning often experienced difficulty in mastering the task because of an apparent reluctance to release one perceptual field and reconstrue the task on a higher cognitive level. It was hypothesized that were this the correct explanation, the faster learners would be more field independent on a measure of field dependence, since independence has been defined in terms of ease in releasing one's attention from the immediate perceptual field. This hypothesis was tested with 22 undergraduate subjects for whom Group Embedded Figures Test scores were correlated with the number of trials to completion on the complex learning task. A moderate but significant correlation supported the hypothesis.

Female↗
PubMed1984

Immediate closed antegrade Ender nailing of femoral fractures in polytrauma patients.

Fifty-four trauma patients with 61 femoral fractures stabilized within the first 24 hours of admission by closed antegrade Ender nailing were included in this study. This technique involves the insertion of Ender nails from a portal at the proximal end of the femur through the piriformis fossa. The curved distal ends of the nails were distributed throughout the distal femur to achieve greater purchase in the enlarged medullary canal of the distal fragment. This technique was used in one proximal, 20 midshaft, 37 distal, and three segmental fractures. There were 51 closed fractures, eight Grade I open, and two Grade II open fractures. The average age of the patient was 26 years, and the majority had polytrauma. The operative procedure was well tolerated by this group of patients. Pulmonary care was improved by avoidance of traction and enhanced capability for mobilization. Forty-two patients with 49 femoral fractures were available for complete follow-up. Forty-five fractures healed with the average time to appearance of bridging callus being 33 days, and average time to full union remodeled callus being 5.9 months. There were four nonunions, one delayed union, and eight malunions. There were nail protrusions in 22 cases (19 proximal and three distal). Fourteen patients required a second operation for reimpaction of the protruding nails or premature nail removal. These results were inferior to those obtained with the use of the retrograde Ender nailing technique or the Kuntscher nail. This technique should be used only if other techniques are unavailable or inappropriate, and only for stable, noncomminuted fractures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Hemoglobin concentration and aerobic work capacity in women following induced erythrocythemia.

The effect of induced erythrocythemia on hemoglobin concentration ([Hb]) and aerobic work capacity was determined for nine women. Cycle tests were performed at prereinfusion (T1), 2 days after a placebo infusion (T2), 2 days postreinfusion of 334 ml of red blood cells (T3), 8 days postreinfusion (T4), and 14 days postreinfusion (T5). T1 and T2 responses did not differ, negating a placebo effect. [Hb] increased from 12.7 g X dl at T1 to 14.7 g X dl at T3 and then remained constant at T4 and T5. Hematocrit increased from 38.1% at T1 to 44.9% at T3 and then remained constant at T4 and T5. Submaximal O2 uptake (VO2) and stroke volume (SV) did not change from T1 through T5. Submaximal cardiac output (Q) and heart rate (HR) decreased from T1 to T3 and then remained constant at T4 and T5. Arteriovenous O2 difference increased from T1 to T3 and then remained constant at T4 and T5. Maximal VO2 was greater at T3 (2.65 l X min-1), T4 (2.66 l X min-1), and T5 (2.60 l X min-1) than at T1 (2.41 l X min-1). Physical work capacity was greater at T3 (10,740 kg X m), T4 (10,980 kg X m), and T5 (10,380 kg X m) than at T1 (8,747 kg X m). Maximal values for Q, HR, and SV were unchanged from T1 through T5. At maximum, arteriovenous O2 difference and Hb flow rate increased from T1 to T3 and then remained constant at T4 and T5. The greater postreinfusion [Hb] improved O2 transport capacity and appeared to regulate circulatory responses.

Adult↗
PubMed1982

Differentiated perceptions of exertion and energy cost of young women while carrying loads.

Differentiated local ratings of perceived exertion from the legs and central ratings from the chest, and oxygen consumption, were determined during load carriage in seven young women. Subjects walked for 6 min at 3.22, 4.83, 6.44, or 8.05 km X h-1 carrying (1) no load, (2) a load equal to 7.5% of body weight (mean: 4.66 kg) or (3) a load equal to 15% of body weight (mean: 9.32 kg). Thus, each subject underwent 12 separate tests. The external loads were in the form of lead pellets carried in a plastic scuba belt worn around the waist. A differentiation threshold was found at 6.44 km X h-1 for the 0% and 7.5% loads and at 4.83 km X h-1 for the 15% load. At speeds below the threshold, the perception of exertion was similar in the legs, chest and overall. At higher speeds, exertion was perceived to be more intense in the legs than overall and less intense in the chest than overall, suggesting that the local legs signal was the dominant factor in shaping the overall sensation of exertion. The oxygen uptake was greater for the 15% load than for either the 0% or 7.5% loads, but was similar for the 0% and 7.5% loads. Findings suggested a critical weight limit for external loads that could be transported without increasing the metabolic cost beyond that required to move the body weight alone. This limit fell between 7.5% and 15% of the body weight. When oxygen uptake was expressed per kg of total weight transported, there was no loss of metabolic efficiency while carrying loads up to 15% of the body weight.

Adult↗
PubMed1982

Effect of induced erythrocythemia on hypoxia tolerance during physical exercise.

The effect of induced erythrocythemia on hypoxia tolerance during physical exercise was determined for five male mountain climbers. Treadmill testing was performed under four conditions: 1) prereinfusion, normoxia (Pre-N); 2) prereinfusion, hypoxia (Pre-H); 3) postreinfusion, normoxia (Post-N); and 4) postreinfusion, hypoxia (Post-H). An altitude of 3,566.2 m was simulated by having subjects breath a gas mixture of 13.5% O2-86.5% N2 at normal barometric pressure. Tests were administered immediately before and 24 h after autologous transfusion of 750 ml of red blood cells. Hematocrit increased from 43.3% at prereinfusion to 54.8% at postreinfusion. Hemoglobin concentration increased from 13.80 g X 100 ml-1 at prereinfusion to 17.63 g X 100 ml-1 at postreinfusion. Maximal O2 uptake (VO2 max, 1 X min-1) increased (P less than 0.05) by 12.8% (3.28 to 3.70) from Pre-N to Post-N and 13.0% (2.62 to 2.96) from Pre-H to Post-H. Treadmill performance time (s) increased (P less than 0.05) by 15.8% (793 to 918) from Pre-N to Post-N and 8.9% (687 to 748) from Pre-H to Post-H. VO2 max decreased by 20.1% from Pre-N to Pre-H and by 9.8% from Pre-N to Post-H. Treadmill time decreased by 13.4% from Pre-N to Pre-H and 5.7% from Pre-N to Post-H. The calculated change in hypoxia tolerance following reinfusion indicated that physiological altitude was improved by 463.6 m. It was concluded that induced erythrocythemia increased hypoxia tolerance during physical exercise.

Adult↗
PubMed1982

Central signals of perceived exertion during dynamic exercise.

The purpose of this review is to examine the evidence that links specific physiological processes with central signals of perceived exertion during dynamic exercise. The physiological processes thought to be associated with a central signals of exertion include heart rate (HR), ventilation (VE), respiratory rate (RR), and oxygen uptake (VO2). Parallel changes in HR and ratings of perceived exertion (RPE) were not apparent when HR was manipulated experimentally. Heart rate does not appear to be associated with a strong central signal of exertion. Sensations of ventilatory function and discomfort are the only central signals that are consciously monitored. Corresponding changes in VE and RPE were noted when ventilatory drive was altered by hypnosis, induced erythrocythemia, hypoxia, or hyperoxia. Ventilation begins to provide potent sensory signals between 45-70% VO2max. Both the absolute and relative (percent VO2) oxygen uptake have been proposed as central signals. For a fixed VO2, RPE differed when comparisons were made between various experimental conditions. In contrast, RPE did not differ between conditions when expressed as a function of percent of VO2max. The relative VO2 is more likely to be associated with a strong sensory signal. Central signals involving VE and the relative VO2 are proposed to act as an amplifier that potentiates local signals in proportion to the aerobic metabolic demand.

Aerobiosis↗
PubMed1979

Differentiated perceptions of exertion: part I. mode of integration of regional signals.

The mode of sensory integration of differentiated perceptions of exertion from the legs and chest was determined during sub-maximal cycle ergometer exercise. 50 male subjects performed three separate cycle ergometer tests. Power output was held constant at 840 kpm/min., while pedalling rate was randomly set at 40, 60, or 80 rpm. The over-all rating of perceived exertion was significantly lower than the rating for the legs and higher than that for the chest at each pedalling rate. Local signals from the legs dominated the sensory process. Central signals were less pronounced. The mean of the ratings for the legs and chest was slightly but significantly higher than the over-all rating at each pedalling rate. Therefore, the integration process at the superordinate level of sensory processing appeared as a weighted average of the involved regional signals.

Adult↗
PubMed1979

Differentiated perceptions of exertion: part II. relationship to local and central physiological responses.

Differentiated ratings of perceived exertion in the legs and chest were compared to local and central physiological adjustments during submaximal cycle ergometer exercise. 50 male subjects performed three separate cycle ergometer tests. Power output was held constant at 840 kpm/min., while pedalling rate was randomly set at 40, 60, or 80 rpm. Differentiated reports of exertion from the legs were considered to be local signals and reports from the chest to be central signals. Ratings of exertion for the legs, chest and over-all body were each significantly higher at 40 rpm than 60 or 80 rpm. Heart rate, oxygen uptake, ventilation and respiratory rate were also higher at 40 rpm. Lactic acid, pH, and pCO2 were similar between pedalling rates. Lactic acid did not operate differentially to influence local perceptual signals from the legs. Central measures of respiratory and aerobic metabolic adjustments were consistent with the more intense regional report of chest exertion at 40 rpm.

Adult↗
PubMed1978

Perceived exertion and the field-independence--dependence dimension.

Perceived exertion responses were compared between field-independent and field-dependent perceivers at three cycle-ergometer pedalling rates. 50 male subjects were classified according to mode of field approach on the basis of their performance on an embedded-figures test. Power output was held constant at 840 kpm/min., while pedalling rate was randomly set at 40, 60, or 80 rpm. Significant differences between the field-independent and -dependent groups were not found at the three pedalling rates for any of the physiological variables or for over-all, legs and chest ratings of perceived exertion. The extent of differentiated psychological functioning did not account for individual differences in perceptual reactance during muscular exertion.

Adult↗
PubMed1977

Perceived exertion and stimulus intensity modulation.

Perceptual augmentation and reduction were considered contrasting styles of Stimulus Intensity Modulation. Differences in perceived exertion between augmenters and reducers were determined for three cycle ergometer work loads. Subjects were 20 males having similar physiological characteristics. Stimulus Intensity Modulation was determined by kinesthetic figural aftereffect. Augmenters rated their perceptions of physical exertion to be more intense than reducers at 450, 750 and 1050 kpm/min. Differences in physiological responses between augmenters and reducers were not significant at the three work loads. Style of Stimulus Intensity Modulation appeared differentially to influence perceived exertion at the work levels studied.

Blood Chemical Analysis↗
PubMed1976

Aerobic exercise as a therapeutic modality in the relief of stress.

This paper reviews the pathophysiologic influences of 20th century emotional stress. The physiologic consequences of cardiovascular conditioning by aerobic techniques are also reviewed. It would appear that cardiovascular conditioning has physiologic characteristics which would counterbalance those induced by such stress. Accordingly, it appears logical that cardiovascular conditioning by aerobic exercise techniques is an effective therapeutic and prophylactic tool. Future investigative efforts must take two directions. First, the extent to which exercise may be used in ameliorating the pathologic consequences of chronic stress must be scientifically documented. Secondly, in those instances where exercise is undertaken imprudently, evidence must be gathered as to the extent that physical activity precipitates maladaptive responses in humans.

Adaptation, Physiological↗