PubMed Health⌕ Search

Biomedical subjects

A R Lind

Publications and source records attributed to A R Lind.

At least 19 recordsLinked to original sources
PubMed1995

[The effect of fermented hydrolyzed whey enriched with lactates on the morphological structure of the internal organs in laboratory animals].

Results of pathomorphological investigation of rat organs fed during 1 and 3 months the diet containing 8% of protein as milk whey protein partly hydrolysed by enzymes and enriched by lactates (SGOL-1) are presented. The conducted investigation have not revealed of pathological effect of a product SGOL-1 on morphological structures of investigated internal bodies and tissues of the laboratory animals. A increase of body mass of animals and contents of RNAS in cells of practically all bodies and tissues of the animals were also marked.

Animals↗
PubMed1989

The human pressor response during and following voluntary and evoked isometric contraction with occluded local blood supply.

1. Changes in heart rate and blood pressure were observed, in nine healthy subjects, during and after voluntary and electrically evoked isometric contractions of the triceps surae under conditions of local circulatory arrest. 2. The progressive increases in heart rate and blood pressure seen during 2 min voluntary and evoked contractions at 30% of maximal voluntary contraction were not significantly different in the two conditions. On cessation of contraction but with circulatory arrest maintained, heart rate fell to control levels while blood pressure fell to a similar though still significantly elevated level in both conditions. Elevated blood pressure was maintained for 2 min until the circulatory occlusion was removed; however it was maintained at a significantly higher level for the last 60-90 s of occlusion following electrically evoked contractions compared to voluntary contraction. 3. Comparison of the responses to voluntary and involuntary electrically evoked contractions suggest that 'central command' is not necessary for the initial increases in heart rate and blood pressure to occur. In addition the removal of central command on cessation of contraction need not account for the return of heart rate to control levels or the drop in blood pressure at that time. Maintained blood pressure elevation during circulatory occlusion would seem to be due to the trapping of chemical substances within the muscle interstitium.

Adult↗
PubMed1988

Effect of different body postures on the pressures generated during an L-1 maneuver.

Changes in blood pressure, intrathoracic pressure, heart rate and the electromyographic activity of various muscle groups were determined while nine male subjects performed 15-s L-1 straining maneuvers at four spine-to-thigh angles (70, 84, 94, and 105 degrees) and two seatback angles (30 and 60 degrees). There was no significant difference between the changes in these variables due to the different body positions. At the onset of the L-1, arterial pressure immediately increased to 195 +/- 5 mm Hg, but fell progressively during the next 5 s to 160 +/- 5 mm Hg. It remained constant during the next 5 s of the maneuver and then recovered to 180 +/- mm Hg during the last 5 s of the maneuver. Esophageal pressure followed essentially the same pattern of response, but heart rate progressively increased during the entire L-1. No one muscle group was utilized more than another. Inflation of an anti-G suit to 4 PSI had no effect on the variables measured. Generation of high arterial pressures during L-1 maneuvers is transitory and not affected either positively or negatively by altering subject body position.

Adult↗
PubMed1987

The influence of straining maneuvers on the pressor response during isometric exercise.

Experiments were performed to determine to what extent increments in esophageal and abdominal pressure would have on arterial blood pressure during fatiguing isometric exercise. Arterial blood pressure was measured during handgrip and leg isometric exercise performed with both a free and occluded circulation to active muscles. Handgrip contractions were exerted at 33 and 70% MVC (maximum voluntary contraction) by 4 volunteers in a sitting position and calf muscle contractions at 50 and 70% MVC with the subjects in a kneeling position. Esophageal pressure measured at the peak of inspirations did not change during either handgrip or leg contractions but peak expiratory pressures increased progressively during both handgrip and leg contractions as fatigue occurred. These increments were independent of the tensions of the isometric contractions exerted. Intra-abdominal pressures measured at the peak of either inspiration or expiration did not change during inspiration with handgrip contractions but increased during expiration. During leg exercise, intraabdominal pressures increased during both inspiration and expiration, reaching peak levels at fatigue. The arterial blood pressure also reached peak levels at fatigue, independent of circulatory occlusion and tension exerted, averaging 18.5-20 kPa (140-150 mm Hg) for both handgrip and leg contractions. While blood pressure returned to resting levels following exercise with a free circulation, it declined by only 2.7-3.8 kPa after leg and handgrip exercise, respectively, during circulatory occlusion. These results indicate that straining maneuvers contribute 3.5 to 7.8 kPa to the change in blood pressure depending on body position.

Blood Pressure↗
PubMed1985

Sympathetic control of the forearm blood flow in man during brief isometric contractions.

Experiments were performed to assess the possible neurally mediated constriction in active skeletal muscle during isometric hand-grip contractions. Forearm blood flow was measured by venous occlusion plethysmography on 5 volunteers who exerted a series of repeated contractions of 4 s duration every 12 s at 60% of their maximum strength of fatigue. The blood flows increased initially, but then remained constant at 20-24 ml X min(-1) X 100 ml(-1) throughout the exercise even though mean arterial blood pressure reached 21-23 kPa (160-170 mm Hg). When the same exercise was performed after arterial infusion of phentolamine, forearm blood flow increased steadily to near maximal levels of 38.7 +/- 1.4 ml X min(-1) X 100 ml(-1). Venous catecholamines, principally norepinephrine, increased throughout exercise, reaching peak values of 983 +/- 258 pg X ml(-1) at fatigue. Of the vasoactive substances measured, the concentration of K+ and osmolarity in venous plasma also increased initially and reached a steady-state during the exercise but ATP increased steadily throughout the exercise. These data indicate a continually increasing alpha-adrenergic constriction to the vascular beds in active muscles in the human forearm during isometric exercise, that is only partially counteracted by vasoactive metabolites.

Adult↗
PubMed1985

Changes in isometric function following rhythmic exercise.

Seven male subjects exercised for 1, 3, 10 and 20 min on a cycle ergometer at 20, 60 and 80% VO2max, and then held to fatigue a sustained contraction of the quadriceps at 40% maximal voluntary contraction in order to determine what influence various levels of dynamic exercise would have on isometric function of the same group of muscles. Muscle temperature was measured before and within 15 s of the completion of the cycling to determine whether changes in muscle temperature might influence the subsequent isometric performance. Isometric endurance was shorter as the severity of the cycling increased beyond 20% VO2max, and as the duration of cycling increased up to 10 min. There were discrete linear relationships between muscle temperature and isometric endurance associated with cycling at 60% and 80% VO2max. There was a direct inverse relationship between quadriceps strength after cycling and muscle temperature, yet a significant reduction in strength occurred only after cycling at 80% VO2max. These results suggest that the encroachment on endurance and strength are controlled by different mechanisms. The heart rates during the isometric contractions were dependent on the preceding rhythmic exercise and decreased after exercise at 60 or 80% VO2max. In contrast, the blood pressure always increased during the isometric contractions, reaching similar values at the point of fatigue, regardless of the severity of the previous rhythmic exercise. These data provide additional evidence that separate mechanisms control changes in heart rate and blood pressure.

Blood Pressure↗
PubMed1982

Isometric fatigue induced by different levels of rhythmic exercise.

Three subjects were trained in leg extensor isometric contractions and in cycling. They then cycled for three consecutive bouts, each of 2.75 min at a constant level of VO2, from 20 to 80% VO2 max. Fifteen seconds after each bout of cycling the subjects exerted an isometric contraction of the right leg at 40% of the maximum voluntary contraction. In each experiment, the duration of the three successive isometric contractions decreased as in hand-grip contractions. There was also a linear reduction in isometric endurance as the severity of the preceding rhythmic exercise increased. In other experiments, after three bouts of rhythmic exercise at 20% VO2 max (each followed by a fatiguing contraction at 40% MVC), further bouts of cycling at increasing levels of severity up to 60% VO2 max resulted in a linear fall in isometric endurance which could be reversed by interposing a lighter level of cycling. The heart rates during these experiments showed a steady increase during the isometric exercise, to about 150 beats X min-1, as the bouts of preceding rhythmic exercise became progressively more severe. The isometric contractions had little influence on the heart rate during cycling. But the rhythmic cycling exercise markedly increased the heart rate achieved at the end of the isometric contractions while decreasing the increment in heart rate during the contraction.

Adult↗
PubMed1981

The effect of deep muscle temperature on the cardiovascular responses of man to static effort.

Eight healthy male subjects (age range 24-38 year) were asked to exert a fatiguing isometric endurance contraction with their handgrip muscles at 40% of their maximum strength after immersion of their forearms in water at various temperatures ranging from 3-40 degrees C. For each subject, isometric endurance was longest after immersion of his forearm in water at a particular characteristic bath temperature; endurance decreased markedly above or below this temperature. The increase in heart rate from the beginning to the end of the fatiguing contractions was the same irrespective of the bath temperature. In contrast, the increase in blood pressure (both systolic and diastolic) throughout the contractions was almost constant for contractions exerted after immersion of the forearm in water at 20-40 degrees C, but was reduced progressively for contractions exerted in water below 20 degrees C.

Adult↗
PubMed1981

The influence of temperature on the isometric characteristics of fast and slow muscle in the cat.

The maximum tetanic tension (initial strength) and the length of time, 20, 40 or 60%, of that initial strength could be maintained (endurance) was assessed in 2 fast twitch muscles (the plantaris and the medial gastrocnemius) and a slow twitch muscle (the soleus) of the cat at muscle temperatures ranging between 22 and 38 degrees C. The results of these experiments showed that the strength of the soleus was constant between muscle temperatures of 38 to 28 degrees C, and then gradually decreased as the muscle was cooled further. Plantaris, on the other hand, showed a reduction in strength at all muscle temperatures less than 38 degrees C; the response of the medial gastrocnemius was between these two extremes. The longest endurance for the soleus muscle was found to be at a muscle temperature of 28 degrees C, the endurance being as much as 3 times higher at this temperature than at muscle temperatures of 22 or 38 degrees C. The medial gastrocnemius showed a similar response but the endurance only doubled when comparing the endurance at a muscle temperature of 28 to 38 degrees C. In contrast, the plantaris maintained a constant endurance over the temperature range of 38 to 28 degrees C; below this muscle temperature the endurance decreased markedly. The mechanism for this response appeared to be related to the effect of temperature on the contractile characteristics of the muscles.

Animals↗
PubMed1981

Muscle fiber recruitment and blood pressure response to isometric exercise.

Blood pressure was recorded during fatiguing and nonfatiguing isometric contractions of a slow-twitch muscle (the soleus) and a mixed muscle (the medial gastrocnemius) of the cat. Four tensions were examined in each muscle; 10, 25, 40, and 70% of the muscle's initial strength (tetanic tension of the unfatigued muscle). All experiments were also repeated at two muscle temperatures, 28 and 38 degrees C. For the soleus muscle, there was no change in the blood pressure during isometric contractions. For the medial gastrocnemius muscle, both the systolic and diastolic blood pressure increased markedly when either all or just the fast-twitch motor units were stimulated; however, when only the slow-twitch motor units were stimulated, a lower pressor response was observed. Venous blood samples were drawn before, during, and after fatiguing and nonfatiguing contractions of both muscles to determine the K+ concentration in the venous blood. The mean increase in the K+ concentration during contractions was 0.6 meq/l for the slow-twitch motor units of the soleus and 5.1 meq/l for the motor units in the medial gastrocnemius.

Animals↗
PubMed1981

The blood flow through the "resting" arm during hand-grip contractions.

These experiments were designed to add information about the control of the circulation in the contralateral arm during isometric hand-grip contractions. The existing evidence came from two laboratories and was in conflict. The most recent data claimed that there is an inevitable increase in blood flow through the contralateral arm and that it is neurogenically controlled, while some degree of electromyographic activity was not associated with an increase in the blood flow. In the present experiments, the blood flow and the oxygen uptake over the arm were first "calibrated" against the electromyographic activity during isometric contractions at known low tensions. In steady state conditions, there were direct, linear relationships between all four measurements. The "calibrated" arm then became the contralateral (resting) arm, while strong isometric contractions were held by the other hand. Of 12 subjects examined, half showed no increase in blood flow or electromyographic activity. The other six subjects all showed some muscular activity (electromyogram) in the contralateral arm which was always associated with an increase in blood flow and oxygen uptake. Not all those findings fitted the "calibration" closely; the problems of this approach are discussed.

Adult↗
PubMed1981

The influence of fiber composition, recruitment order and muscle temperature on the pressor response to isometric contractions in skeletal muscle of the cat.

The blood pressure response to isometric exercise was examined in the medial gastrocnemius muscle of the cat at muscle temperatures of 28 and 38 degrees C. Contractions were sustained at tensions of between 10 and 100% of the muscle's initial strength (tetanic tension of the unfatigued muscle) with recruitment proceeding from either the fastest to the slowest or from the slowest to the fastest motor units, respectively. The results of these experiments showed that the blood pressure response throughout the duration of contractions at tensions greater than 10% of the initial strength was constant by either order of recruitment and for both muscle temperatures examined, the mean blood pressure rising linearly from an average value of 101.2 +/- 10.3 mm Hg at the onset of the contraction to 146.3 +/- 14.2 mm Hg at the point of fatigue. In contrast, during contractions at 10% of the initial strength at both muscle temperatures, the blood pressure was lower during the first 20% of the contractions when recruitment proceeded from the slowest to the fastest motor units but stayed the same throughout the remainder of the contractions. The results of these experiments indicate the importance of muscle fiber composition in determining the blood pressure response for weak isometric contractions.

Animals↗
PubMed1980

The influence of temperature on the amplitude and frequency components of the EMG during brief and sustained isometric contractions.

The influence of temperature on the amplitude and frequency components of the EMG power spectra of the surface EMG recorded over the forearm muscles was examined in five male and five female subjects during brief and fatiguing isometric contractions of their handgrip muscles. Brief (3 s) isometric contractions were exerted at tensions ranging between 10 and 100% of each subject's maximum strength while fatiguing contractions were exerted at tensions of 25, 40, and 70% of their maximum strength. The temperature of the muscles during those contractions was varied by placing the forearms of the subjects in a controlled temperature water bath at temperatures of 10, 20, 30, and 40 degrees C. The results of these experiments showed that the center frequency of the power spectra of the surface EMG was directly related to the temperature of the exercising muscles during brief isometric contractions. During fatiguing isometric contractions, the amplitude of the EMG increased while the center frequency of the EMG power spectra decreased for all tensions examined.

Adult↗
PubMed1980

The blood pressure response during isometric exercise in fast and slow twitch skeletal muscle in the cat.

The blood pressure response during fatiguing isometric contractions was examined in a slow twitch muscle (the soleus) and a mixed muscle (the medial gastrocnemius) of the cat. The results of these experiments showed that electrical stimulation of the ventral roots of the spinal cord which carried the efferent innervation to the soleus muscle failed to result in a blood pressure response during isometric exercise. Further, although stimulation of the fast twitch motor units in the medial gastrocnemius muscle was associated with a potent pressor response to isometric exercise, stimulation of the slow twitch motor units was associated with a markedly reduced response throughout the duration of the exercise. These findings infer that the pressor response to isometric exercise may be a function of the fast twitch motor units in the muscle.

Animals↗
PubMed1980

Frequency analysis of the surface electromyogram during sustained isometric contractions.

Four male and four female volunteers served as subjects in these experiments to assess the frequency components of the surface EMG during and following brief (3 s) and sustained isometric contractions of the handgrip muscles. Two types of fatiguing contractions were performed. Contractions were either maintained to fatigue at a constant tension of up to 100% of their strength or were maintained as a sustained maximal effort in the unfatigues or previously fatigued muscle. The frequency components of the surface EMG were assessed by calculating the power spectra of 1.5 s samples of the EMG from a fundamental frequency of 4 Hz through the first 128 harmonics by Fourier analysis; the centre frequencies of the resultant power spectra were then used as an index of the mean frequency of the EMG. The results of these experiments showed that the centre frequency was independent of the tension exerted by the muscle during brief isometric contractions but decreased linearly with time throughout the duration of fatiguing isometric contractions at tensions between 25 and 100% MVC. During sustained maximal effort, the frequency initially decreased linearly with time. However, once the target tension could no longer be maintained, the centre frequency remained constant throughout the remainder of the contraction. The frequency was found to recover within 1 min following exercise at all tensions examined.

Adult↗