Untrained Research Articles

Exercise-induced changes in the percentage of free testosterone and estradiol in trained and untrained women.

We have studied the effect of exercise on the percentage of free plasma estradiol 17-beta (E2) and testosterone (T) in 13 untrained (UT) and 8 trained (marathon runners, MR) eumenorrheic women. All women performed a standardized bicycle ergometer (UT) or treadmill (MR) test in the follicular and luteal phases of their menstrual cycles (15-min consecutive work loads of 60%, 70%, and 80% VO2 max to exhaustion). Blood was drawn through an indwelling venous catheter at 15 and 2 min before and immediately after exercise. Free E2 and T was assayed by centrifugal ultrafiltration using undiluted plasma at 37 degrees C (basal samples) and 39 degrees C (exercise samples). Statistical analysis was performed by a two-tailed paired t test. In the UT, the basal percentage of free E2 was measured to be 1.55% +/- 0.24% (mean +/- SD) in the follicular phase and 1.62% +/- 0.32% in the luteal phase (differences NS). In the MR, these values were 1.22% +/- 0.25% and 1.25% +/- 0.12% for the follicular and luteal phases, respectively. The differences between the groups were not significant. Exercise did not provoke significant changes in free E2 in either of the groups. Constrastingly, exercise induced a significant (P less than 0.02) increase in the percentage of free T from 1.56% +/- 0.27% to 2.1% +/- 0.36% and from 1.6% +/- 0.27% to 2.12% +/- 0.33% in the UT in the follicular and luteal phases, respectively. In the MR, the free percentage of T increased from 1.04% +/- 0.39% to 1.6% +/-0.16% (follicular phase) and from 1.24% +/- 0.22% to 1.67% +/- 0.18% (P less than 0.02).

Effect of ??1-receptor blockade on coronary resistance in partially trained dogs

Selective beta 1-receptor blockade with atenolol (1 mg X kg-1, i.v.) was used to determine the effect of partial exercise training on diastolic coronary resistance (DCR) during sub-maximal exercise. Seven conscious dogs were studied in the untrained (UT) and partially trained (PT) conditions. The conditioning regime consisted of treadmill running 5 d X wk-1 for 4 to 5 wk. Left circumflex coronary flow, aortic pressure, and heart rate were measured, and DCR and myocardial oxygen consumption were calculated. During sub-maximal exercise, DCR in the UT dogs decreased from a resting value of 4.08 +/- 0.18 mm Hg X ml-1 X min-1 to 1.91 +/- 0.17 mm Hg X ml-1 X min-1 at a workload of 6.4 kph (speed)/16% (grade). During exercise, DCR was significantly greater in UT than in PT dogs. Atenolol significantly increased DCR at all levels of sub-maximal workload in both UT and PT dogs. However, the percent increase in DCR with atenolol was significantly greater in the PT dogs compared to UT dogs. These findings suggest that daily exercise for 4 to 5 wk may decrease beta 2-receptor activity of the coronary vasculature during sub-maximal exercise.

Exercise acutely increases high density lipoprotein-cholesterol and lipoprotein lipase activity in trained and untrained men

We studied the effects of a single exercise session on lipid and lipoprotein concentrations and on postheparin plasma lipoprotein lipase (LPLA) and hepatic triglyceride hydrolase activities (HTGLA) in 11 trained (T) and ten untrained (UT) men. Subjects exercised on a bicycle ergometer at 80% of their maximal heart rate for one (UT) or two hours (T). Blood samples were drawn 24 hours before and at ten minutes and 24, 48, and 72 hours after exercise. Values were analyzed before and after adjustment for estimated changes in plasma volume (PV). High density lipoprotein cholesterol (HDL-C) increased 2 ± 4 mg/dL in T ( P < 0.05) and 1 ± 2 mg/dL in UT subjects beginning 48 hours after exercise. This increase was magnified by adjusting for the 5% to 8% postexercise expansion of PV. The increase in HDL in the T subjects was produced by increases in the HDL 2-C subfraction (+3 ± 4 mg/dL, P < 0.05) whereas HDL 3 increased in the UT men (+2 ± 3 mg/dL, P < 0.05). LPLA did not change in either subject group when estimated PV changes were ignored but increased 11% ( P < 0.05) at 24 hours after exercise when PV was considered. HTGLA was 11% below baseline in the UT men 24 to 72 hours after exercise ( P < 0.05) but showed no change in either subject group after adjustment for PV. These results demonstrate that exercise acutely increases HDL levels by raising the HDL 2 subfraction in T and the HDL 3 subfraction in UT men. Exercise also acutely increases LPLA, but changes in lipase activities may be obscured by concomitant changes in PV. The magnitude of acute changes in lipid, lipoprotein, and lipase values were insufficient to account for the larger differences in these parameters generally noted between T and UT subjects.

Combined use of magnetic resonance imaging (MRI) and spectroscopy (MRS) by whole body magnets in studying skeletal muscle morphology and metabolism.

As a pilot study, 31-P-spectra of the quadriceps femoris muscle (1.5T) and proton images of the right thigh (.5T) were performed in two cyclists (T) and two untrained (UT) subjects. During ischemia, while MRI did not show any change, phosphocreatine (PCr) concentration decreased and inorganic phosphate (Pi) increased. Recovery occurred within 3 minutes. Ergometric bicycle tests were performed outside the magnet. Submaximal workload (UT 150W/T 260W, 3.5 minutes) caused transient minimal changes in phosphorus metabolites. Supramaximal, partially anaerobic exercise (UT 320W/T 350W, 3.5 minutes) induced similar changes in heart rate, oxygen uptake rate, and plasma lactate in both groups. Decrease of the PCr/Pi ratio, however, was more pronounced in UT subjects and clearly lasted longer. If methodical problems can be resolved, combined MRS and MRI in whole body magnets may become a standard noninvasive modality, adding unique information on morphology (organ volume) and local metabolism to classic mechanical and global physiologic data.

Effects of cardioactive drugs on the beating activity of myocardial cell cultures isolated from offspring of trained and untrained pregnant rats.

Primary cultures of beating myocardial cells were obtained from 5-d-old offspring of trained (T) and untrained (UT), pregnant, Sprague-Dawley rats. The myocardial cells from the T and UT groups were evaluated for their beating responses to three cardioactive drugs: verapamil (V), isoproterenol (ISO), and propranolol (PRO). The myocardial cell cultures from the UT group showed complete loss of beating when the calcium (Ca++) antagonist, V, was added to the cultures for 1 h or more; the T group was able to show some beating at comparable concentrations and durations of exposure with V. The beta agonist, ISO, markedly stimulated the beating rate of both the T and UT groups, but the beating rates were higher in the UT group at comparable concentrations and durations of exposure than with the T group. When the cultures were pretreated with the beta blocker, PRO, before treatment with ISO, a concentration inhibitory effect on the beating rate was observed in both groups. However, the T cultures were more sensitive to the inhibitory effects of PRO. These results demonstrate that primary cultures of rat myocardial cells isolated from the offspring of trained and untrained pregnant rats show differential beating responses to three well-known cardioactive drugs.

Changes in diastolic coronary resistance during submaximal exercise in conditioned dogs.

Diastolic coronary resistance (DCR) was studied in 10 conscious dogs in the untrained (UT) and partially trained (PT) condition. The PT regime consisted of treadmill running 5 days/wk for 4-5 wk. Left circumflex coronary flow, aortic pressure, and heart rate were measured, and diastolic coronary resistance (DCR) was calculated. Adrenergic blockade was achieved with propranolol (1 mg/kg, iv) (beta B) and phentolamine (1 mg/kg, iv) (alpha B). During submaximal exercise in the UT condition, DCR fell from a resting value of 3.84 +/- 0.24 Torr . ml-1 . min with increasing work load to 1.57 +/- 0.12 Torr . ml-1 . min at 6.4 km/h (speed)/16% (grade). The decrease in DCR during submaximal exercise was greater in the PT than in the UT condition. DCR following alpha-adrenergic blockade was not significantly changed in the UT and PT conditions (e.g., at 6.4 km/h (speed)/16% (grade), 1.10 +/- 0.141 vs. 1.03 +/- 0.107 Torr . ml-1 . min, whereas following beta-adrenergic blockade, DCR was larger in the UT compared with the PT condition (e.g., at 6.4 km/h (speed)/16% (grade), 2.03 +/- 0.091 vs. 1.73 +/- 0.073 Torr . ml-1 X min). Myocardial oxygen consumption was not significantly different in the PT and UT conditions, indicating no difference in metabolism with partial training. The present study suggests that during submaximal exercise in the PT condition there is a change in the neurogenic control of the coronary vasculature by a reduction in sympathetic neural activity on the coronary resistance vessels.

Effect of exercise conditioning on coronary resistance.

Diastolic coronary resistance (DCR) was determined in seven conscious dogs in the untrained state and after 4-5 wk of daily exercise conditioning (partial training). The conditioning regime consisted of treadmill running 5 days/wk. The dogs were instrumented to measure aortic pressure and left circumflex coronary flow during atrial pacing with implanted electrodes. Heart rate was varied from the resting value to 240 beats/min before and after adrenergic blockade with propranolol (beta B, 1 mg/kg) or phentolamine (alpha B, 1 mg/kg); myocardial oxygen consumption (MVO2) was measured in three dogs under the same condition in both the untrained (UT) and partially trained (PT) condition. DCR decreased with increasing heart rate [from 4.75 +/- 0.56 (SE) to 2.48 +/- 0.22 Torr . ml-1 . min at 240 beats/min]; alpha B reduced DCR, whereas beta B increased DCR. In the PT condition, DCR decreased to 4.02 +/- 0.40 Torr . ml-1 . min at rest and was decreased to 1.82 +/- 0.16 Torr . ml-1 . min at 240 beats/min (P less than 0.05 compared with UT). alpha-Adrenergic and beta-adrenergic blockade in the PT condition resulted in parallel reduction in DCR compared with the UT condition. MVO2 was unaffected by either PT or adrenergic blockade but increased as heart rate increased with atrial pacing. These data suggest a change in caliber of the coronary resistance vessel because of the parallel shift in the relationship between DCR and heart rate.

Renal blood volume regulation in trained and untrained subjects during immersion.

To study the cause of the increased blood volume of endurance-trained athletes we assessed the renal blood volume regulating mechanisms in eight untrained (UT) and eight endurance-trained (TR) male subjects during a 4 h head-out immersion. In TR plasma volume remained constant whereas it decreased in UT by 2.4 ml/kg (p less than 0.025). Immersion diuresis of TR was only half as high as in UT (peak values: 3.22 ml/min in UT, 1.60 ml/min in TR). Free water clearance remained approximately constant in UT but temporarily decreased in TR (p less than 0.001). This points to poor or even absent inhibition of antidiuretic hormone secretion in the latter group. Osmolar clearance increased less in TR than in UT (p less than 0.02) which was partly due to a delayed increase of glomerular filtration rate. Plasma osmolality, creatinine, and protein concentrations as well as hematocrit values were reduced during immersion to a similar extent in both groups. The results indicate a reduced renal response of endurance-trained subjects to congestion of the low-pressure system resulting in an increase in blood volume.

Reduced aldosterone and sodium excretion in endurance-trained athletes before and during immersion

Aldosterone excretion (AE) and plasma renin activity (PRA) were measured in eight untrained (UT) and eight endurance-trained (TR) male subjects before and during 4 h head-out immersion to study the mechanism of reduced renal sodium excretion in athletes. AE was significantly lower before immersion, and decreased less during immersion, in TR than in UT. Fractional sodium excretion, too, was lower and increased less during immersion in TR than in UT. PRA decreased in the water bath in all subjects (p less than 0.001) with no significant difference between the groups. During immersion, plasma sodium concentration oscillated whereas potassium concentration showed a temporary rise in TR (p less than 0.001). The attenuated response of AE in TR may be due partly to this increase of plasma potassium concentration. The generally reduced aldosterone release in TR might be caused by a training induced adaptation of the adrenals to corticotropin. The lowered renal sodium excretion of TR in spite of the decreased AE suggests an intensified aldosterone effect in these subjects, diminishing the salt loss during exercise.

Capillary supply of skeletal muscle fibers in untrained and endurance-trained women.

Muscle fiber diameters and number of capillaries per fiber, per mm2 and around each fiber were determined in needle biopsies from the lateral part of the quadriceps muscles of 11 young women. Six subjects were untrained (UT) and five were endurance-trained athletes (ET). Average values for maximal oxygen uptake were 43.9 (UT) and 62.1 ml/kg X min (ET). Mean fiber diameter was somewhat smaller in the UT than in the ET group (39.1 and 42.7 micrometer), but the difference was not statistically significant. Fibers with the highest content of mitochondria were on the average 9 micrometer thicker than those with the lowest content. The capillary per fiber ratios were 1.11 +/- 0.07 (mean +/- S.E.) and 1.69 +/- 0.13 in the UT and ET groups, respectively. The number of capillaries around each fiber was 3.04 +/- 0.17 (UT) and 4.42 +/- 0.31 (ET). After correction for shrinkage the number of capillaries per mm2 was 301 (UT) and 404 (ET). The capillary per fiber ratio increased with increasing fiber diameter and with the content content of mitochondria.

Capillary supply of skeletal muscle fibers in untrained and endurance-trained men.

Muscle fiber diameters and numbers of capillaries per fiber, per square millimeter, and around each fiber were determined in needle biopsies from the lateral part of the quadriceps muscle of 23 young men. Twelve subjects were untrained (UT) and eleven were endurance-trained (ET) athletes. Average values for maximal oxygen uptake were 51.3 (UT) and 72.0 ml/kg-min (ET). Mean fiber diameters were not significantly different in the two groups (48.8 and 49.1 micron). The capillaries per fiber ratios were 1.77+/-0.10 and 2.49+/-0.08 (mean+/-SE) in the UT and ET groups, respectively. The numbers of capillaries around each fiber were 4.43+/-0.19 (UT) and 5.87+/-0.18 (ET). The numbers of capillaries per mm2 were 585+/-40 (UT) and 821+/-28 (ET). Fiber diameters were 28% smaller in ultrathin than in fresh-frozen sections from the same biopsies. After correction for this difference, the numbers of capillaries per mm2 were 305 and 425 in the UT and ET, respectively. The capillaries per fiber ratio increased with increasing fiber diameter, but not sufficiently to maintain the number of capillaries per mm2. Fibers containing many mitochondria are surrounded by more capillaries than fibers with few mitochondria.

Effect of physical fitness on vanillylmandelic acid excretion during immersion.

The effects of 4--6 h head-out immersion on excretion of vanillylmandelic acid (VMA), blood pressure and plasma volume were estimated in 8 endurance-trained (TR) and 8 untrained (UT) subjects. In the trained only a slight increase of VMA excretion occurred (4 h value: +2.7 +/- 10.9 ng/ml GFR), but there was a highly significant increase in the UT (+29.0 +/- 17.2 ng/ml GFR). VMA values during control experiments in supine position tended to decrease in both groups. Systolic and diastolic blood pressure fell by 20 mm Hg after beginning of immersion; in the UT plasma volume was reduced while it remained constant in TR. The results indicate that orthostatic intolerance (o.i.) after immersion is not effected by decreased sympathetic innervation of vessels; in contrast it seems to be partly compensated for by an elevated sympathetic activity at least in the UT. As a main cause for the post-immersion o.i. one might suggest a decrease in renin activity.

Red cell hemoglobin, hydrogen ion and electrolyte concentrations during exercise in trained and untrained subjects.

Red cell concentrations of hemoglobin (MCHC), H+, Na+, K+, Mg++, cl- were measured in femoral venous blood of six untrained (UT), six endurance trained (TR) and three semitrained (ST) subjects during graded increasing work (4, 8, 12, 18 and 24 mkp/s, 10-15 min on each step) on a bicycle ergometer. Before exercise no significant differences were detected for the measured variables when comparing UT and TR. During exercise MCHC, [Na+], [K+] and [Mg++] remained constant indicating lack of water shift into the erythrocytes in spite of a marked acidosis (lowest pH Blood value 7.225). This lack resulted from an elevated extracellular osmolality. [H+]Ery and [Cl-]Ery maximally increased by 2.0 X 10(-8) eq/kg H2O and 10 meq/l, respectively. The change was markedly greater in UT than in TR at equal load. However, if [H+] Ery and [Cl-] Ery were related to pH of whole blood, differences between groups, almost disappeared and the ions were distributed as predictable from in vitro experiments (Fitzsimmons and Sendroy, 1961). Behaviour of H+ and Cl- may be of importance for oxygen dissociation under in vivo conditions.