Biomedical subjects

F Bonde-Petersen

Publications and source records attributed to F Bonde-Petersen.

At least 73 records · Page 4Linked to original sources

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↗

PubMed1976

Mechano-elastic properties of human muscles at different temperatures.

The effect of changes in the muscle temperature on their ability to store elastic energy was studied by having 5 trained subjects perform maximal vertical jumps on a force platform, with and without counter movement, at muscle temperatures between about 32 degrees C and 37 degrees C. The results showed that the heights of vertical jumps were considerably reduced at lowered temperature, but the gain in height after a counter movement in the form of a jump down from a height of 0.4 m over the force platform, was significantly higher in the cold condition. T o test whether this was due to an increased stiffness of the muscles, experiments with imposed sinusoidal length variations at 14 Hz were performed. Delta force XDelta length-1 (i.e.stiffness) increased with isometric tension independent of muscle temperature. Experiments in which the rate of tension development and relaxation in voluntary maximal isometric contractions were measured at different muscle temperatures showed that maximal isometric tension changed by less than 1% per degree but the rate of tension development and relaxation by 3-5% and 5% per degree, respectively, in the temperature range studied (30 degrees to 40 degrees). These data may be explained by the hypothesis that the series elastic components of the active muscle are located in the cross-bridges between myosin and actin filaments. The storage of elastic energy would be enhanced if the rate of breaking of these bridges were decreased at lower temperatures.

Body Temperature↗

PubMed1975

The influence of varying oxygen tensions in inspired gas on 133Xenon muscle clearance and fatigue levels during sustained and dynamic conctractions.

Isometric and isotonic endurance levels of both elbow flexors and knee extensors were tested during inspired gas mixtures of ca. 10%, 21% or 100% oxygen in nitrogen. The four work loads were set a 25, 50, 60 and 70% of maximal volitional isometric strength (IS). The isotonic exercise routine was carried out using weight lifting techniques of 20 repetitions per min from 75 degrees to 105 degrees of elbow flexion and knee extensions respectively. Prior to, during, and after the endurance experiments 133Xe clearance was monitored by light weight scintillation counters. A depot of 0.1 to 0.2 ml of isotonic saline containing 50 to 150 muCi of the isotope was used as an intramuscular tracer. The exercise clearance values varied inversely to the test load during isometric exercise. Isotonic exercise for both elbow flexors and knee extensors showed increasing clearance values up to 60% IS. Above this level a decrease in total clearance was recorded. Oxygen tension had no statistical effect on the clearance values. However, the relatively large scatter of the 133Xe clearance method, and an inhomogenous perfusion of skeletal muscle may have masked any anticipated effect of the various O2 tensions. Variations due to the raised intramuscular pressure appeared to be much more dominant than the hypothezised variation due to the 3 set oxygen tensions.

Adult↗

PubMed1975

Blood flow in thigh muscle during bicycling exercise at varying work rates.

16 male subjects exercised at 25, 50, 75, 90, 100 and 120% of VO2max on a von Döbeln bicycle ergometer. The muscle mass was measured in a whole body counter. Muscle blood flow (MBF) estimated from the rate of 133Xe clearance from m. rectus femoris showed a levelling-off at about 0.5 1 of blood per min and liter of muscle tissue (equal to an irrigation coefficient of 0.5 min-1) at work rates above 50 to 60% of VO2 max. This concurs with clearance data from the literature. However, when MBF is calculated from VO2, muscle mass, and reliable values for a- vo2 differences, MBF in the present subjects would: 1. Not level off before 90 to 100% VO2max, 2. reach a value of 1.0 min-1. The underestimation of MBF calculated from 133Xe clearance and the levelling-off shown by this method may be due to a systematic error inherent in the method, the 133Xe clearance being diffusion limited at high flow rates.

Adult↗

PubMed1975

Local muscle blood flow and sustained contractions of human arm and back muscles.

The endurance during sustained contraction of elbow, flexors, elbow extensors, and back extensors was tested in 3 human subjects. The force level used was varied between ca. 15 and ca. 75% of maximal isometric strength (IS). The clearance of 133Xe from contracting muscles was registered during and after the endurance test. In this way it was possible to determine whether muscle blood flow (MBF) was increased or had stopped during the contraction. Experiments with artificial ischaemia of the upper arm together with MBF measurements showed that MBF was of no importance for continuing sustained contractions above a certain force level, which was 50,25, and 40% of IS for elbow flexors, elbow extensors and back extensors, respectively. However, the level, where longer lasting ( greater than 15 min) sustained contraction is possible is directly related to MBF. These levels were 22, 15, and 20% IS for elbow flexors, elbow extensors, and back extensors, respectively.

Adult↗

PubMed1975

A simple force platform.

The force platform consists of a sandwhich of steel, Rockwool and concrete plates about 900 X 700 mm in surface. Four steel rings were bolted to the under side of the steel plate in each corner. Each steel ring was furnished with only one strain gauge, two of which were placed on the outer- respectively on the inner side of each ring. The four strain gauges were connected to a measuring bridge. Before mounting the rings on the steel plate, the sensitivity to pressure of each ring was adjusted in such a way that they were all similar. Because of this the platform responded with a signal which was independent of where a pressure was applied within the surface of the platform. The platform showed a rectilinear response for static forces up to 500 kp with a stable zero value. In response to dynamic forces the platform showed a resononance frequency of about 50 Hz, with a damping factor of 0.15. Calibration of dynamic forces was carried out by calculation of the forces during a vertical jump compared with what would be expected from the time of flight also registered by the platform-measuring-bridge-ink-writer-set-up. The time of flight was significantly higher (11%) than exected from the time-force relations beforetake-off. This was esplained partly by the relatively low damping factor in the system, partly by the subjects not extending their knees at landing on the platform.

Body Weight↗

PubMed1975

Effects of previous exercise with arms or legs on metabolism and performance in exhaustive exercise.

The ability of additional muscles to perform after certain other muscles of the body had been exercised to exhaustion was studied in three male subjects. Exhaustive exercise was performed in two series: series L-A, a bout of leg exercise preceded a bout of arm exercise; series A-L, arm preceded leg (6-min recovery between bouts). Biopsies were taken during the course of each experiment from both the deltoideus and vastus lateralis muscles for determination of ATP, creatine phosphate, lactate, and pyruvate. Exhaustive exercise led to marked elevations in lactate and decreases in ATP and CP in exercised muscle and marked increases in blood lactate concentration. Similar changes, especially in lactate, were observed during and after the first exercise bout in nonexercised muscle. When arm or leg exercise was performed as the second bout, decreases in performance time were observed as compared to performance as the initial bout. It is suggested that the performance potential of muscle is decreased because of internal changes elicited by elevated blood lactate and/or blood H+ concentrations brought about by other muscle groups previously exercised to exhaustion.

Adenosine Triphosphate↗

PubMed1974