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Biomedical subjects

K Klausen

Publications and source records attributed to K Klausen.

At least 37 records · Page 2Linked to original sources
PubMed1989

Forearm oxygen uptake during maximal forearm dynamic exercise.

This study was undertaken in an attempt to determine the maximal oxygen uptake in a small muscle group by measuring directly the oxygen expenditure of the forearm. Five healthy medical students volunteered. The subjects' maximal forearm work capacity was determined on a spring-loaded hand ergometer. Exercise was continued until exhaustion by pain or fatigue. Two weeks later intra-arterial and intravenous catheters were placed in the dominant arm. Blood samples for measurement of oxygen concentration were collected via the catheters. Forearm blood flow was measured by means of the indicator dilution technique. Oxygen uptake was determined according to the Fick principle. The forearm oxygen uptake attained at maximal work loads was a mean of 201 (SD +/- 56) mumol.min-1.100 ml-1. It was impossible at maximal exercise to discern a plateau of the oxygen uptake curve in relation to work output. It is suggested that a plateau in the oxygen uptake curve is not a useful criterion for maximal oxygen uptake in a small muscle group. Skeletal muscle may have an unused capacity for oxygen consumption even at maximal exercise intensity where muscle work cannot be continued due to muscle pain and fatigue.

Adult↗
PubMed1988

Effects of acute hypoxia and CO2 inhalation on systemic and peripheral oxygen uptake and circulatory responses during moderate exercise.

The effect of acute hypoxia and CO2 inhalation on leg blood flow (LBF), on leg vascular resistance (LVR) and on oxygen supply to and oxygen consumption in the exercising leg was studied in nine healthy male subjects during moderate one-leg exercise. Each subject exercised for 20 min on a cycle ergometer in four different conditions: normoxia, normoxia + 2% CO2, hypoxia corresponding to an altitude of 4000 m above sea level, and hypoxia + 1.2% CO2. Gas exchange, heart rate (HR), arterial blood pressure, and LBF were measured, and arterial and venous blood samples were analysed for PCO2, PO2, oxygen saturation, haematocrit and haemoglobin concentration. Systemic oxygen consumption was 1.83 l.min-1 (1.48-2.59) and was not affected by hypoxia or CO2 inhalation in hypoxia. HR was unaffected by CO2, but increased from 136 beat.min-1 (111-141) in normoxia to 155 (139-169) in hypoxia. LBF was 6.5 l.min-1 (5.4-7.6) in normoxia and increased significantly in hypoxia to 8.4 (5.9-10.1). LVR decreased significantly from 2.23 kPa.l-1.min (1.89-2.99) in normoxia to 1.89 (1.53-2.52) in hypoxia. The increase in LBF from normoxia to hypoxia correlated significantly with the decrease in LVR. When CO2 was added in hypoxia a significant correlation was also found between the decrease in LBF and the increase in LVR. In normoxia, the addition of CO2 caused a significant increase in mean blood pressure. Oxygen consumption in the exercising leg (leg VO2) in normoxia was 0.97 l.min-1 (0.72-1.10), and was unaffected by hypoxia and CO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Metabolism of exercising skeletal muscle during beta 1-selective adrenoceptor blockade.

Concentrations of glycogen, glucose, glucose-6-phosphate and lactate in the lateral vastus muscle were measured in seven subjects before and after dynamic muscle exercise at a work load of 75% of each subject's maximal working capacity, and with and without intravenous administration of the beta 1-selective beta-adrenoceptor blocking agent, atenolol. Pulmonary oxygen uptake was measured during exercise. Heart rate and arterial blood pressure were measured throughout the study. Arterial concentrations of glucose, lactate and free fatty acids were measured at rest and during exercise. The muscle concentration of glycogen and the extent of glycogen depletion with exercise were not influenced by the beta 1-adrenoceptor blocker. Similarly, there was no change in the muscle concentrations of glucose, glucose-6-phosphate and lactate. Heart rate decreased at rest and during exercise. Arterial blood pressure was not influenced by beta-blockade. Pulmonary oxygen uptake decreased by 6.5%. The exercise induced rise in arterial blood concentration of free fatty acids was abolished by beta 1-selective beta-blockade. It is concluded that the decrease in lactate release from exercising muscles during beta 1-adrenoceptor blockade seen in other studies cannot be explained by an impaired breakdown of muscle glycogen. It may be inferred, however, that a reduced availability of free fatty acids in the exercising muscles during beta 1-selective (and non-selective) beta-blockade may enhance the combustion of pyruvic acid and thereby decrease the production of lactate.

Adult↗
PubMed1985

Activity of mono- and biarticular leg muscles during sprint running.

A cinematographic recording of the movements of the lower limbs together with simultaneous emg tracings from nine lower limb muscles were obtained from two male track sprinters during three phases of a 100 m sprint run. The extensor muscles of the hip joint were found to be the primary movers by acceleration of the body's center of gravity (C.G.) during the ground phase of the running cycle. The extensors of the knee joint were also important in this, but to a minor extent, while the plantar flexors of the ankle joint showed the least contribution. The biarticular muscles functioned in a way different from the monoarticular muscles in the sense that they perform eccentric work during the flight and recovery phases and concentric work during the whole ground phase (support), whereas the monoarticular muscles are restricted first to eccentric work and then to concentric work during the ground phase. Furthermore, the biarticular muscles show variation (and rate of variation) in muscle length to a larger extent than the monoarticular muscles. Paradoxical muscle actions appear to take place around the knee joint, where the hamstring muscles, m. gastrocnemius, m. vastus laterialis and m. vastus medialis act as synergists by extending the knee joint during the last part of the ground phase.

Ankle↗
PubMed1984

Lumbar curve, trunk muscles, and line of gravity with different heel heights.

The influence of different heel heights on the lumbar curve, pelvic inclination, trunk muscle activity, and the position of the line of gravity was examined in 18 healthy women. They were examined while standing on heel-supports, being 4.5 cm elevated, at the level of and 2.5 cm lower than the support of the forefoot, respectively (Figure 1). Each examination was preceeded by one-hour adaptation to a corresponding shoe type. With increasing heel height, the lumbar lordosis and the pelvis inclination were decreased. The back and abdominal muscles did not alter their activities. The position of the line of gravity kept the distance from the forefoot almost constant, but the ankle joint was shifted towards the line of gravity with increasing heel height.

Adult↗
PubMed1983

Acute effects of cigarette smoking and inhalation of carbon monoxide during maximal exercise.

The acute effect of inhaling the smoke of three cigarettes was compared to the effect of inhalation of an amount of carbon monoxide (CO), giving the same CO-saturation of the arterial blood as smoking during rest and during maximal exercise on a Krogh cycle ergometer. Sixteen male subjects were tested in the morning (1) after about 8 h without smoking (control), (2) after inhalation of the smoke of three cigarettes (smoke), and (3) after CO-inhalation (CO). It was found that the average maximal rate of O2-uptake (VO2 max) decreased during both smoke and CO by about 7%. Endurance time at VO2 max decreased 20% during smoke but only 10% during CO. A significant decrease in maximal heart rate (HR), and an increase in HR at rest, was demonstrated only during smoke. The peak lactate concentration (HLa) following maximal exercise was significantly decreased after smoke. The results suggest that the decrease in VO2 max during smoke is due to the CO-saturation of the blood, and hence to a decrease in the oxygen capacity of the blood, while the decrease in endurance time during smoke is combined effect of the CO-saturation and an increased cost of breathing caused by the smoke particles. It is further suggested that nicotine, or possibly some other components of the smoke, have an enhancing effect on the heart at rest rest, while an inhibition is seen during maximal exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1982

Central and regional circulatory adaptations to one-leg training.

Six young healthy male subjects performed submaximal and maximal exercise on bicycle ergometers with one leg and two legs before and after 8 wk of one-leg training with each of both legs. The following variables were measured during one- and two-leg exercise: oxygen uptake, heart rate, mean arterial blood pressure, cardiac output, leg blood flow, and iliac arteriovenous differences for oxygen and lactate. After training the maximal oxygen uptake during one- and two-leg exercise was increased by 19 and 11%, respectively. The corresponding cardiac outputs increased by 16 and 11%, respectively. During submaximal one-leg exercise, heart rate decreased by 11%, whereas a decrease of only 2% was seen during submaximal two-leg exercise. Mean blood pressure decreased by about 10 Torr in both types of exercise and during both submaximal and maximal exercise. Maximal leg blood flow increased only by 1.2 l/min during one-leg exercise. Leg blood flow and leg oxygen uptake were smaller during two-leg exercise than during one-leg exercise and more so after training. These findings indicate that one-leg exercise, compared with two-leg exercise, involves circulatory adaptations that respond differently to one-leg training. The findings further imply that oxygen supply to one large muscle group of exercising muscles may be limited by vasoconstriction when another large group of muscles is exercising simultaneously.

Adaptation, Physiological↗
PubMed1981

Adaptive changes in work capacity, skeletal muscle capillarization and enzyme levels during training and detraining.

Six male subjects exercised on a bicycle ergometer 30 min with left leg and 30 min with right leg 3 times a week for 8 weeks. This training resulted in a 14.6% increase in VO2 max with two-leg exercise and a 23.1% increase with one-leg exercise. A significant decrease towards pretraining VO2 max was seen during the following 8 weeks of detraining. Muscle biopsy samples were obtained at rest from m. vastus lateralis before and after training and 4 and 8 weeks after training. During training the number of capillaries per mm2 and the number of capillaries per fiber increased about 20%. The number of capillaries around each fiber type (CA) increased 20--30%. The average area of each fibre type increased only about 5%. The fibre area per CA decreased by about 10%. During 8 weeks of detraining decreases were seen in the number of capillaries per fibre, CA and in fibre area, while fibre area per CA and number of capillaries per mm2 were almost unchanged at the end of the detraining period. Pronounced increases in activities of oxidative enzymes were observed after training, while only minor increases were seen in glycolytic enzyme activities. All enzyme activities decreased towards pre-training levels during detraining. The results indicate that the training-induced improvement in oxidative capacity and in muscle capillarization expressed as capillaries per fibre and CA disappears within 8 weeks after cessation of training. However, the fibre area per CA and number of capillaries per mm2 point at a favourable long term effect on the average diffusion distance between capillaries and muscle fibres.

Adaptation, Physiological↗
PubMed1977

Central and regional circulatory effects of adding arm exercise to leg exercise.

7 young, healthy, male subjects performed exercise on bicycle ergometers in two 20 min periods with an interval of 1 h. The first 10 min of each 20 min period consisted of arm exercise (38--62% of Vo2 max for arm exercise) or leg exercise (58--78% of Vo2 max for leg exercise). During the last 10 min the subjects performed combined arm and leg exercise (71--83% of Vo2 max for this type of exercise). The following variables were measured during each type of exercise: oxygen uptake, heart rate, mean arterial blood pressure, cardiac output, leg blood flow (only during leg exercise and combined exercise), arterio-venous concentration differences for O2 and lactate at the levels of the axillary and the external iliac vessels. Superimposing a sufficiently strenuous arm exercise (oxygen uptake for arm exercise greater than 40% of oxygen uptake for combined exercise) on leg exercise caused a reduction in blood flow and oxygen uptake in the exercising legs with unchanged mean arterial blood pressure. Superimposing leg exercise on arm exercise caused a decrease in mean arterial blood pressure and an increased axillary arterio-venous oxygen difference. These findings indicate that the oxygen supply to one large group of exercising muscles may be limited by vasoconstriction or by a fall in arterial pressure, when another large group of muscles is exercising simultaneously.

Adult↗
PubMed1977

Effects of hyperoxia on leg blood flow and metabolism during exercise.

These experiments were designed to investigate the effects of O2 breathing on limb blood flow and metabolism during exercise. Six subjects took part in the study. Four subjects breathed air or 100% O2 while pedaling a Krogh bicycle at 150 W (55-70% of maximal aerobic capacity). Two subjects breathed either 60% or 100% O2 while working at a power output at or slightly in excess of their maximal aerobic capacities. The major findings of the study were 1) leg blood flow is reduced during exercise when comparing hyperoxia with normoxia; 2) VO2 of the exercising limb is not different during hyperoxia; 3) O2 delivery to the leg (the product of blood flow and arteriovenous O2 difference) is not significantly different in the two conditions; and 4) blood pressure is not markedly affected in the experiments at 150 W. Since BP was not different during hyperoxia, at a time when flow was reduced by 11%, this suggests an increased resistance to flow in the exercising limb. In general, these findings are consistent with those reported for the in situ dog muscle but are at variance with results of experiments with humans, especially the reports indicating substantial increases in O2 uptake during hypertoxic conditions.

Blood Glucose↗
PubMed1975

Pulmonary ventilation, blood gases, and blood pH after training of the arms or the legs.

In two groups of young healthy subjects who performed arm training (N = 5) and leg training (N = 5), respectively, the respiratory adaptation to submaximal exercise with trained and nontrained muscle groups was compared by measurement of the ventilatory equivalent (Ve/Vo2, pH, and blood gases (Pco2, Po2, and So2) in arterial blood and in venous blood from exercising extremities. After training Ve/Vo2 was significantly reduced during exercise with trained muscles, but unchanged during exercise with nontrained muscles. The reduction in Ve/Vo2 was closely related to a less pronounced increase in heart rate and in arterial lactate content, but showed no quantitative correlation to changes in arterial adaptations in trained muscles are mainly responsible for the reduction in Ve/Vo2. After training during exercise with trained as well as nontrained muscles a shift to the right of the blood oxygen dissociation curve occurred as extremities was lower while corresponding Po2 was higher.

Adult↗