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Biomedical subjects

R G Knowlton

Publications and source records attributed to R G Knowlton.

At least 91 records · Page 5Linked to original sources
PubMed1980

Physiological and performance characteristics of United States championship class orienteers.

The purpose of this investigation was to study the anaerobic and aerobic power of female and male United States championship orienteers and relate these data to competitive performance. In addition, it was considered valuable to obtain a general physical description of the athletes. Anthropometrically, neither the females (n=5) nor the males (n=13) conformed to a somatotype classification typical of endurance athletes. Although the mean anaerobic power values for the females (76.6 kg.m.sec-1) and the males (106.6 kg.m.sec-1) were consistent with what is known for distance runners, the respective aerobic powers of 46.1 and 61.6 ml.kg-1.min-1 were considerably below expectations for national class competitors. The explanation for this latter finding was attributed to their reported training programs. Partial residual plots and multiple regression procedures were used to determine the relationship between aerobic power and gender, respectively, with speed of competitive performance. The final equation to predict performance was P = -13.10 + 0.62(VO2max) + 0.26 (Experience, years) - 0.03 (Anaerobic power) + 1.21 (gender) - 0.01 (VO2max)2 with an R-square of 0.73 and P less than 0.01.

Adult↗
PubMed1980

Body temperature, respiration, and acid-base equilibrium during prolonged running.

The purpose of this investigation was to study respiratory responses related to acid-base equilibrium during two bouts of prolonged high intensity treadmill running, each at different body temperature levels. In an attempt to augment elevation in body temperature during prolonged running, incomplete rehydration procedures were employed. Rectal temperature was found to increase significantly during the course of each run. In addition, rectal temperature was found to be significantly higher during the second run at each respective time period. After the transition to exercise, plasma volume, arterial lactate concentration, arterial hydrogen ion concentration, arterial carbon dioxide partial pressure, arterial bicarbonate concentration, pulmonary ventilation, and ventilatory equivalent of carbon dioxide remained constant throughout each run. It was also found that arterial carbon dioxide partial pressure was lower and ventilatory equivalent of carbon dioxide was higher during the second run at each respective time period. For the studied population, these results indicate that after initial adjustments most of the examined variables remain fairly constant despite increasing rectal temperature during prolonged running.

Acid-Base Equilibrium↗
PubMed1979

Post-competition blood lactate concentrations in collegiate swimmers.

The purpose of this investigation was to quantitate post-competition lactate (LA) concentrations of swimmers during a competitive collegiate meet. Blood LA was measured by an enzymatic method on 23 subjects 5 min after each race event. The largest mean LA concentration of 25.7 mM/L was observed in swimmers after competing in the 200-yd individual medley. Swimmers in the 200-yd butterfly, back, breast and freestyle races had similar mean blood LA concentrations (ranging from 16.4 to 20.6 mM/L). Swimmers in the two longest events, the 500-yd and 1,000-yd free style races, had mean LA concentrations of 15.6 and 10.0 mM/L, respectively. To account for the effects of motivation, LA concentrations were measured following maximal effort noncompetitive 100 and 200-yd swims. LA concentrations were slightly greater in conjunction with faster performances for the competitive as compared to the noncompetitive 100 and 200-yd swims.

Adult↗
PubMed1979

Thermal and circulatory responses to repeated bouts of prolonged running.

The purpose of this study was to determine the thermal and circulatory responses of seven runners (X VO2max = 66 ml kg min) to two bouts of high intensity prolonged treadmill running (PTR) [each 80-min at 70% VO2max] spaced by a 90-min rest. After the transition to exercise, oxygen uptake (VO2) and percent change in plasma volume remained constant throughout each PTR. Rectal temperature (Tr) and heart rate (HR) increased while stroke volume (SV) and cardiac output (Q) decreased during the course of each PTR. The pattern of response for each variable was similar for both PTRs. However, Tr and HR were higher and SV and Q were lower during the second PTR when compared to the first of each respective time period.

Adult↗
PubMed1979

Effect of prolonged running on physiological responses to subsequent exercise.

The purpose of this study was to compare metabolic and cardiopulmonary responses for submaximal and maximal exercise performed several days preceding (pre-test) and 45 min after (post-test) 21 miles of high intensity (70% VO2 max) treadmill running. Seven aerobically trained subjects' oxygen uptake, oxygen pulse, respiratory exchange ratio, heart rate, pulmonary ventilation, ventilatory equivalent of oxygen, and blood lactate concentration were determined for exercise during the pre- and post-test sessions. No differences were found for submaximal oxygen uptake, oxygen pulse, pulmonary ventilation and ventilatory equivalent of oxygen between the pre- and post-test values. Generally, submaximal heart rate responses were higher, and respiratory exchange ratio values were lower during the post-test. Reductions of maximal work time (12%), maximal oxygen uptake (6%) and maximal blood lactate concentration (47%) were found during the post-test. Thermal stress and glycogen depletion are possible mechanisms which may be responsible for these observed differences.

Adult↗
PubMed1978

Metabolic responses of untrained individuals to warm-up.

Seven untrained male subjects were studied for the effects of mild warm-up on oxygen uptake and lactic acid production. Each subject completed two standardized workloads on a bicycle ergometer requiring 75% of their physical work capacity. Protocols of the two tests consisted of either no warm-up or a 4-min warm-up preceding a 5-min exercise at approximately 80% of their maximal oxygen uptake. The contrasting protocols did not reveal any significant differences between heart rate, lactic acid, and oxygen uptake. The dominant influence on the metabolic processes was the absolute workload of the tasks and not the presence or absence of preliminary related activity. It was concluded that an untrained individual lacks the cardiovascular and cellular adaptations necessary to demonstrate metabolic benefits from warm-up.

Adult↗
PubMedDate not supplied

A polymorphic DNA marker linked to cystic fibrosis is located on chromosome 7.

Although cystic fibrosis (CF) is among the most common inherited diseases in Caucasian populations, the basic biochemical defect is not yet known. CF is inherited as an autosomal recessive trait apparently due to mutations in a single gene, whence the efforts made to identify the genetic locus responsible by linkage studies. Two markers have recently been identified that are genetically linked to CF: one is a genetic variation in serum level of activity of the enzyme paraoxonase, and the other is a restriction fragment length polymorphism (RFLP) identified with a randomly isolated DNA probe. We report here that the genetic locus DOCRI-917 defined by the cloned DNA probe is located on chromosome 7.

Chromosome Mapping↗