Search PubMed⌕ Search

Biomedical subjects

B R Londeree

Publications and source records attributed to B R Londeree.

12 recordsLinked to original sources
PubMed1992

Bone density in postmenopausal women: high impact vs low impact exercise.

This 1 year study examined the effect of high impact and low impact activities on bone mineral density (BMD) at the lumbar vertebrae (L2-L4) in healthy, sedentary, early postmenopausal women. Fifteen subjects whose postmenopausal status was verified by the blood levels of follicle stimulating hormone (FSH) and estradiol were chosen. These subjects were tested on the following variables: BMD via dual photon absorptiometry, heart rate response to the Balke treadmill test, percent fat via skinfolds, and a 3-d dietary analysis. Subjects were matched and then assigned randomly to one of three groups: (a) a control nonexercising group, (b) a low impact exercise group, and (c) a high impact exercise group. The control nonexercising group experienced a significant linear decrease in BMD during the study (F = 12.63, P = 0.002). Both the low and high impact exercise groups maintained BMD during the study (F = 0.04, P = 0.85; F = 1.08, P = 0.31, respectively). The difference in BMD between the low impact and the high impact exercise groups was not significant (F = 0.36, P = 0.55). In conclusion, 20 min of moderate intensity low impact or high impact exercise 3 d.wk-1 for 1 yr is effective in maintaining BMD in early postmenopausal women.

Absorptiometry, Photon↗
PubMed1989

Physiological parameters related to distance running performance in female athletes.

The purpose of this study was to investigate the relationship between running pace for the 5 km, the 10 km, and the 16.09 km (10 mile) distances and the following variables: oxygen uptake and treadmill speed at predetermined lactate accumulation points (2.0 and 4.0 mmol.l-1), oxygen uptake (running economy) at three submaximal standardized treadmill speeds (196, 215, and 241 m.min-1), and maximal oxygen uptake. Thirteen moderately to highly conditioned (VO2max = 59.7 +/- 5.3 ml.kg-1.min-1; VO2 at 2.0 mmol.l-1 of plasma lactate = 46.6 +/- 4.1 ml.kg-1.min-1) female runners between the ages of 18 and 33 yr volunteered to participate. All subjects performed the laboratory tests and the 5 km, 10 km, and 16.09 km competitive time trials on an outdoor 5 km course. The correlation coefficients (r) between each race pace and maximal oxygen uptake (VO2max), speed (s) at 2.0 mmol.l-1 plasma lactate accumulation (PLA2s), and speed at 4.0 mmol.l-1 plasma lactate accumulation (PLA4s) ranged between 0.84 and 0.94. The oxygen costs of running at each of the three submaximal paces were correlated moderately with each race pace (r = -0.40 to -0.63). Hierarchal stepwise multiple regression analyses produced equations with two independent variables which explained 94 to 97% of the variability in race performance.

Adolescent↗
PubMed1979

EMG comparison of quadriceps femoris activity during knee extension and straight leg raises.

Both knee extension and straight leg raises have been used to rehabilitate atrophied quadriceps musculature following knee immobilization. A comparison of the tension developed during these two exercises was made in each of the three surface quadriceps muscles (quadriceps femoris, vastus lateralis, vastus medialis) at three different levels of activity (20%, 50%, and 80% of 1RM). Integrated EMG (m Volt-seconds) was used to measure tension developed during a seven second contraction. Tension developed was significantly greater during a seven second contraction. Tension developed was significantly greater during knee extension than during straight leg raises at each exercise intensity. For both exercises and at all three exercise levels, the vastus lateralis was the most active; the vastus medialis was the least active. The difference between knee extension and straight leg raises became greater with increasing levels of activity. Therefore, unless contraindicated by chondromalacia of lack of knee flexibility, knee extensions should be used for post-surgical knee rehabilitation. The greater tension development would lead to a more rapid return of strength, and therefore quicker rehabilitation.

Action Potentials↗
PubMed1978

Fatty acid pattern and cholesterol in skeletal muscle of men aged 22 to 73.

In order to examine the relationship between fatty acid distribution of skeletal muscle membranes and age, a needle biopsy was performed on the vastus lateralis muscle of 20 healthy, non-obese males, ranging in age from 22 to 73 years. The muscle sample was homogenized, centrifuged at 100,000 x g, and the resulting pellet was saponified and acidified. The fatty acids and cholesterol were removed by a single hexane extraction and analyzed by gas--liquid chromatography with flame ionization detection. All subjects regardless of age had no consistent differences in the fatty acid profiles and cholesterol composition in the tissue. Correlation coefficients indicated no significant relationship between the age of the individual and any of the analyzed lipids. The results of this study indicated that aging may not be reflected by gross changes in the composition of structural lipids in the cell.

Adult↗
PubMed1978

The noninvasive cardiac evaluation of long-distance runners.

Twelve long-distance runners were evaluated by physical examination, electrocardiogram, vectorcardiogram, chest x-ray film, and echocardiogram; and the results were compared to the findings in 12 normal control subjects. The athletes showed a significantly higher frequency of gallop rhythms with a third or fourth heart sound. Electrocardiographic and vectorcardiographic abnormalities consisting of right or left ventricular hypertrophy, bradycardia, and alterations in the ST-T wave were also present in the runners. Echocardiographic examination of the athletes revealed increased wall thickness, left ventricular muscular mass, diastolic volume, and ventricular function. It is essential that the physician who examines athletes be aware of the spectrum of apparently abnormal findings in this group. Echocardiographic studies should prove useful in establishing the presence or absence of some forms of cardiac disease in athletes.

Adult↗
PubMed1977

Fatty acid profile and cholesterol in skeletal muscle of trained and untrained men.

To compare the fatty acid distribution and cholesterol composition in trained and untrained isolated skeletal muscle membranes, a needle biopsy was performed on the vastus lateralis of the 10 distance runners and 10 sedentary men. The muscle sample was homogenized and centrifuged at 100,000 X g; the resulting pellet was analyzed by gas-liquid chromatography for individual fatty acids and cholesterol. The percentage of palmitic acid was significantly lower in the trained muscle tissue. Samples from the distance runners also tended to have a more frequent appearance of linolenic and eicosatrienoic acids, longer fatty acid hydrocarbon chains, and lower cholesterol concentration. It was concluded that trained muscles have an increased membrane fluidity which could beneficially affect the activity of membrane-bound enzymes and active transport. Longer chain length in the membrane lipids may be a means of producing an inner membrane cohesiveness in muscles of trained individuals.

Adult↗
PubMed1976

Trend analysis of the % VO2 max-HR regression.

The purpose of the study was to mathematically model the regression of percent of maximal oxygen consumption (% VO2 max) on relative (% of max) heart rate (HR). The 26 subjects (Ss) were classified based on activity levels into high, medium, and low-fitness. Each S performed a series of treadmill walks and runs ranging from 30 to 100% of max VO2. Percent of VO2 max and relative HR were determined during each exercise bout. The data were subjected to a trend analysis utilizing multiple regression techniques. The associated Rs were: linear 0.966, quadratic 0.971, cubic 0.971, and quartic 0.977. The second and fourth order terms statistically accounted for more of the variability than their predecessors, but these differences were not of practical significance. There were no statistically significant differences among the fitness subgroup regression slopes or intercepts for any of the sets of regression equations. The bivariate equation was Y = 1.369-X-40.99 (Y = % VO2 max and X=relative HR) with a standard error of the estimate of 5.67 % VO2 max.

Adult↗
PubMed1975

Maximal steady state versus state of conditioning.

Criteria for the identification of maximal steady state as related to state of conditioning were evaluated. 13 volunteers walker and/or ran during a series of 15 min tests on a treadmill. The speeds ranged from mild to exhaustive. Heart rate was monitored continuously; VO2 was determined from 6 min to 9 min; and venous blood was obtained at 10 min and 15 min for lactate analyses. Max VO2 was established for each subject. Subjects were classified on level of conditioning according to the quantity and quality of their activity record for the previous 6 months. The 10 min heart rate associated with a blood lactate level of 2.2 mM/L (MSSHR) was the best predictor of conditioning. The relative VO2 (% of max VO2) found with a 10 min blood lactate concentration of 2.2 mM/L (RMSSVO2) was almost as accurate as MSSHR in predicting state of conditioning. Changes in blood lactate levels between 10 min and 15 min were not significantly related to conditioning.

Adult↗