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Biomedical subjects

T G Lohman

Publications and source records attributed to T G Lohman.

At least 55 records · Page 3Linked to original sources
PubMed1990

Bone mineral content of cyclically menstruating female resistance and endurance trained athletes.

The bone mineral content (BMC) at four sites on the axial and appendicular skeleton was compared among four groups of young adult (age = 17-38 yr) cyclically menstruating athletes (N = 40) who regularly performed either weightlifting resistance exercise (body builders) or nonresistance endurance exercise (runners, swimmers) and an inactive group of females (N = 18) of about equal age. Forearm BMC was measured using single photon absorptiometry at proximal (shaft) and distal sites on the radius. Dual photon absorptiometry was used to measure BMC at the lumbar vertebrae (L2-4) and femur at the femoral neck, Ward's triangle, and greater trochanter. Fat-free body mass (FFBM) was estimated from densitometry. Body builders had greater BMC than swimmers, collegiate runners, recreational runners, and controls. Mean differences in BMC among runners, swimmers, and controls were not significant (P less than or equal to 0.05). FFBM was correlated significantly with BMC (r = 0.35-0.56) at each site in the combined group of athletes (N = 39), whereas total body weight and BMC were correlated significantly at the distal radius site (r = 0.38) only. The results suggest that weight training may provide a better stimulus for increasing BMC than run and swim training.

Adolescent↗
PubMed1990

Variation in bone mineral content and estimated body fat in young adult females.

This study was designed to determine whether variability in bone mineral content (BMC) at the lumbar vertebrae (L2-4), radius shaft (RS), femoral neck, and distal radius can significantly contribute to the variability observed in body density (Db) among 89 females (age = 25.1 +/- 5.3 yr) of varying activity levels and menstrual status. Theoretical differences in Db were calculated at +/- 1 and +/- 2 standard deviations of BMC (SDBMC) for the population as well as for the subgroups: eumenorrheic inactive controls (C), recreational runners (RR), collegiate runners (CR), body builders (BB), swimmers (S), and amenorrheic runners (AR). Multiple regression to predict Db yielded significant coefficients (b) for BMC at L2-4 (b = 0.0190, P less than 0.001) and RS (b = 0.0425, P less than 0.01) when added separately to the sum of four skinfolds (subscapula, abdomen, thigh, calf). The differences in % BFHW at +/- 1 and +/- 2 SDBMC for the sample mean for RSBMC were +/- 1.0% and +/- 2.0%, respectively. Variability in L2-4 contributed differences of +/- 1.3% and +/- 2.6% at +/- 1 and +/- 2 SDBMC. The subgroup % BFHW differences (due to L2-4 and RS combined) ranged from an average overestimation of 1.3% for the AR to an average underestimation of 1.4% for the BB. Estimated mean errors for remaining groups were less than or equal to 0.5%. Individual differences ranged from a 3.3% underestimation (BB) to a 3.0% overestimation (AR).(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1990

Estimation of minimal weight of adolescent males using multicomponent models.

The purpose of this study was to determine whether the estimation of minimal weight (the body weight at which 5% of the weight is fat) of adolescent males could be improved by accounting for differences in hydration state and bone mineral content. Improvement was defined as a larger value for minimal weight and a smaller standard deviation compared to minimal weight estimated from body density. Forty adolescent males (mean age +/- SD, 15.5 +/- 1.4 yr) were measured for height, weight, body density (hydrostatic weighing), total body water (deuterium oxide dilution), and bone mineral content (single photon absorptiometry). Twenty-two adult males (mean age +/- SD, 23.6 +/- 2.2 yr) were measured as a reference group. Percent body fat and minimal weight were calculated from the body density (MWD), body density adjusted for total body water (MWDW), and body density adjusted for body water and bone mineral content (MWDWB). Repeated-measures ANOVA was used to test for differences between the methods and for trends in the data. The results showed a slight but nonsignificant increase in minimal weight for the adolescent group when body water and bone mineral data were added. The means +/- SD for MWD, MWDW, and MWDWB values of the adolescents were 54.6 +/- 9.0 kg, 54.8 +/- 8.6 kg, and 55.4 +/- 8.4 kg, respectively. It was concluded that the multicomponent methods, which accounted for hydration and bone mineral status, did not significantly improve the estimates of minimal weight of adolescent males compared to the single component method, i.e., minimal weight from body density.

Adipose Tissue↗
PubMed1989

Validity of bioelectric impedance for body composition assessment in children.

Whole-body bioelectrical impedance analysis (BIA) was evaluated for its reliability and accuracy in estimating body composition in children. The hypothesis that the index, body height2 divided by resistance (RI), can accurately predict fat-free body mass (FFB) and percent fat (%FAT) in children was tested on 94 caucasian children 10-14 yr old. Criterion variables were FFB and %FAT estimated using multicomponent equations developed for children. BIA measurements (resistance and reactance) were found to be reliable. Prediction accuracy (standard error of the estimate, SEE) for FFB from RI alone was 2.6 kg and for %FAT from RI and body weight was 4.2%. For RI, anthropometric variables and reactance, the SEE improved to 1.9 kg FFB. For RI and anthropometric variables, the SEE was 3.3% FAT. For anthropometric variables alone, the SEE's were 2.1 kg FFB and 3.2% FAT. Adult FFB and %FAT prediction equations cross-validated with this sample resulted in SEE's similar to those for adult samples. We conclude that RI together with anthropometry is a reliable and an acceptably accurate method of estimating FFB mass and %FAT in children.

Adipose Tissue↗
PubMed1989

Impact of total body water fluctuations on estimation of body fat from body density.

The purpose was to investigate the possibility that variability in body weight in females due to water retention causes differences in body density (Db) values determined by hydrostatic weighing (HW). Determination of total body water (TBW) and Db were concurrently measured in seven females who experienced considerable fluctuations in body weight (1.5-4.5 kg) and seven males, ages 19-24. Females were measured when they felt they were at their lowest (LO) and highest (HI) body weights (BW) during a menstrual cycle. Males were randomly tested approximately 3 wk apart. Mean values of selected variables were compared in the LO vs HI testing sessions by paired t-tests. Significant mean differences were found in the females (P less than 0.01) for the following variables: BW (kg) (LO = 58.9, HI = 61.1), Db (g.cc-1) (LO = 1.0430, HI = 1.037), and percent body fat (%BF) as determined by HW alone (LO = 24.8%, HI = 27.6%). Variables significant at the P less than 0.05 level were TBW(l) (LO = 33.6, HI = 35.1) and %TBW of the fat-free body (LO = 74.5, HI = 75.9). However, changes in TBW could not entirely account for observed changes in Db. Only mean BW (kg) was significant (P less than 0.01) in the males (LO = 74.3, HI = 74.6). It is concluded that changes in TBW can in part result in significantly different Db values obtained from HW in females who did experience perceptible changes in BW during a menstrual cycle. The remaining differences may be due to changes in fat and protein content or methodological errors.

Adipose Tissue↗
PubMed1989

Age as a factor in the hemodynamic responses to isometric exercise.

This study was designed to determine the effect of isometric contractions of the finger flexors and leg extensor muscle groups on the cardiovascular responses of men 18-31 and 50-71 years of age. A 2X2X4 split-plot design was carried out with men representing two age groups, using two muscle groups and performing isometric contractions at four different intensities. Analysis of variance indicated significant differences for all main effects. The systolic and diastolic blood pressures were found to be (1) higher for the leg extension contractions compared to the finger flexion contractions, (2) higher for each increment in %MVC workload, and (3) higher for the older individuals. Heart rate responses were found to be (1) higher for the leg extension exercises, (2) higher with each increase in %MVC, and (3) higher for the younger subjects. Stroke volumes demonstrated (1) higher values for the young men at each workload, (2) lower values for leg extension exercises, and (3) a greater decline with longer contraction times. The older individuals had higher pressor responses than did the younger subjects, higher pressor and heart rate responses were observed with isometric leg extension exercises and increasing %MVC levels, and the older subjects had lower stroke volume responses compared to the younger subjects.

Adolescent↗
PubMed1988

Adolescent self-assessment of sexual maturation. Effects of fatness classification and actual sexual maturation stage.

Accuracy of self-assessed staging of sexual maturation was studied on 96 adolescents (49 boys and 47 girls) to validate previous studies and evaluate the effects of an adolescent's fatness level and actual sexual maturation stage on their ability to assess their level of sexual maturation. Correlation between the adolescents' self-assessments and physician assessments was moderately high (Kendall's tau-b = 0.65-0.82). Boys tended to overestimate, while girls underestimated their level of sexual maturation. Differences between physician and subject ratings by fatness classification or by actual sexual maturation stage was not significant. This study supports previous studies showing that adolescents can accurately assess their own stage of sexual maturation regardless of their fatness classification or actual sexual maturation stage.

Adolescent↗
PubMed1988

Effect of arm training on central and peripheral circulatory function.

The purpose of this study was to examine the effect of endurance arm training on metabolic and circulatory function during arm and leg exercise. Thirty-eight females (aged 18 to 35 yr) participated in the study, with 19 subjects in the training group and 19 in a control group. Both a specific and general training response was observed at the conclusion of the 5-wk training period. As a result of training, during peak arm exercise, significant increases (P less than 0.05) were observed for oxygen uptake (VO2), ventilation, cardiac output, stroke volume, arterial-venous oxygen difference, cumulative work, and total performance time. During peak leg exercise following arm training, significant increases (P less than 0.05) were observed for VO2, ventilation, cardiac output, cumulative work, and total performance time. Standardized partial regression coefficients were used to examine the relative influence of the metabolic and circulatory components which define VO2. Prior to training during arm work, the arterial-venous oxygen difference accounted for the largest proportion of variance in VO2; but after training, stroke volume contributed the largest portion of variance. On the other hand, during leg exercise, stroke volume accounted for the largest portion of variation in leg VO2 both before and after arm training. The data suggest that endurance arm training as prescribed in this study elicits significant circulorespiratory function adaptations to support improved performance in both arm and leg work. Further, the findings suggest both a specific and general training effect, with the more dominant effect specific to arm work.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Maximal exercise responses to acute and chronic beta-adrenergic blockade in healthy male subjects.

Conflicting data on the alterations in the maximal exercise response to beta blockade (BB) may be the result of differences in the length of time the subject has been on medication, i.e., hours vs days. The purpose of this study was to examine maximal exercise responses during acute and chronic administration of BB. Twenty-eight healthy males, 14 untrained (UT) and 14 involved in a personal training regimen (TR), performed maximal treadmill tests after 1 d and 9 d under three double-blind, randomized conditions: a placebo (PLAC), propranolol (PROP) 80 mg b.i.d., and atenolol (ATEN) 100 mg o.d. Maximal heart rate (HR), oxygen consumption (VO2), ventilation (VE), and treadmill time were significantly reduced by PROP and ATEN after an acute and chronic dose when compared to PLAC (P less than 0.05) in both groups of subjects. Maximal HR was decreased more after 1 d of BB than after 9 d of BB with both PROP and ATEN in the UT subjects and with PROP only in the TR group. VO2max, VEmax, and treadmill time were also less attenuated after 9 d of BB; however, this trend did not reach statistical significance. The nonselective beta blocker, PROP, caused greater reductions in VO2max compared to the selective beta blocker, ATEN, in both groups of subjects. These data indicate that, other than a small change in maximal HR, there is no difference in the exercise response to acute and chronic BB in normal and highly conditioned individuals.

Adrenergic beta-Antagonists↗
PubMed1987

Beta-blockade reduces tidal volume during heavy exercise in trained and untrained men.

The effects of beta-blockade on tidal volume (VT), breath cycle timing, and respiratory drive were evaluated in 14 endurance-trained [maximum O2 uptake (VO2max) approximately 65 ml X kg-1 X min-1] and 14 untrained (VO2max approximately 50 ml X kg-1 X min-1) male subjects at 45, 60, and 75% of unblocked VO2max and at VO2max. Propranolol (PROP, 80 mg twice daily), atenolol (ATEN, 100 mg once a day) and placebo (PLAC) were administered in a randomized double-blind design. In both subject groups both drugs attenuated the increases in VT associated with increasing work rate. CO2 production (VCO2) was not changed by either drug during submaximal exercise but was reduced in both subject groups by both drugs during maximal exercise. The relationship between minute ventilation (VE) and VCO2 was unaltered by either drug in both subject groups due to increases in breathing frequency. In trained subjects VT was reduced during maximal exercise from 2.58 l/breath on PLAC to 2.21 l/breath on PROP and to 2.44 l/breath on ATEN. In untrained subjects VT at maximal exercise was reduced from 2.30 l/breath on PLAC to 1.99 on PROP and 2.12 on ATEN. These observations indicate that 1) since VE vs. VCO2 was not altered by beta-adrenergic blockade, the changes in VT and f did not result from a general blunting of the ventilatory response to exercise during beta-adrenergic blockade; and 2) blockade of beta 1- and beta 2-receptors with PROP caused larger reductions in VT compared with blockade of beta 1-receptors only (ATEN), suggesting that beta 2-mediated bronchodilation plays a role in the VT response to heavy exercise.

Adrenergic beta-Antagonists↗
PubMed1986

Effects of physical training and competition on the iron status of female field hockey players.

Female collegiate field hockey players showed decreases in iron stores (as measured by serum ferritin) in each of 3 successive fall seasons studied. After the 1st season of regular play, a decrease (25-23 ng/ml was observed, but measurements after post-season tournament play for the 2nd and 3rd seasons showed significant (P less than 0.05) decreases of 37% (30-19 ng/ml) and 30% (24-17 ng/ml), respectively. The added stress of tournament play appeared to cause additional loss of reserve iron nearly as great as that experienced during early season training. After several years of play, serum ferritin levels in these athletes were frequently between 10 and 20 ng/ml, with the lowest levels occurring in 3rd- and 4th-year athletes. Those women who participated in all 3 years had progressively declining serum ferritin levels throughout their collegiate careers. Participation in collegiate field hockey jeopardizes body iron stores, and iron reserves tend to become progressively more depleted after successive seasons of competition.

Adult↗
PubMed1986

Applicability of body composition techniques and constants for children and youths.

This review has focused on the chemical immaturity of children and the implications for body composition estimates. Prepubescent and pubescent children deviate considerably in fat-free body composition from the adult reference male, and this has lead investigators to overestimate body fatness in this population using conventional body composition formulas. The use of multicomponent approaches to body composition to obtain more accurate estimates of body fatness in children has provided new information on the body composition of this population. Sex- and age-specific constants, to replace those derived from the reference male, are suggested for further testing and verification as well as for use in the clinical setting. The chemical immaturity in children has its greatest effect on estimating the extent of obesity in children 6 to 11 years of age and in estimating body fatness in the lean, athletic, prepubescent population. Previous estimates of the growth rate of fat and fat-free body are also affected by chemical immaturity. Further research is needed to study the impact of physical activity and inactivity on the composition of the fat-free body during growth, to develop constants for more accurate estimates of fatness in physically active samples of all ages and to validate the constants presented in the less active populations. Future research with multicomponent body composition systems in all populations of children and youth is essential for progress in this area. Results will have an important contribution to the estimation of childhood obesity, prediction of minimal weight in the athletic population and estimates of growth rate of fat and fat-free body mass. The development of body composition methodologies which more accurately measure the growth of muscle and bone as well as fat is a major challenge ahead.

Adipose Tissue↗
PubMed1986

Physical activity and bone mineral content in women aged 30 to 85 years.

The relationship of bone mineral content and level of physical activity was investigated in 83 Caucasian females, aged 30 to 85 yr. Bone mineral content was measured by photon absorptiometry at a site one-third the distance from the distal radius to the olecranon process. Anthropometric measurements were taken and percent fat estimated. Physical activity questionnaires were independently evaluated by five physical education professionals, and subjects were assigned to low (N = 19), moderate (N = 36), or high (N = 28) activity groups. A significant difference (P less than 0.05) was seen in bone mineral content and in bone mineral content divided by bone width between the most active group of women and the two less active groups, even with age and menstrual status as co-variates. Mean values for bone mineral content divided by bone width, when adjusted for age and menstrual status, were 0.622, 0.651, and 0.679 g . cm-2 for the low, moderate, and high activity groups, respectively. No difference was found between the moderate and low activity groups. Percent fat estimates and skinfold thicknesses showed that women in the high activity category were significantly leaner (P less than 0.05), although height, weight, and skeletal widths for the groups were equivalent. The data indicate that a high level of physical activity could be a factor in reducing age-related bone loss and in preserving lean body mass in women.

Adult↗
PubMed1984

Vitamin B6 status and static muscle function. 2 case reports.

2 young adult females, identified as vitamin B6 deficient based on xanthurenic acid excretion levels following a loading dose of tryptophan, were tested twice during each of 3 menstrual cycles for static muscle strength and endurance of the handgrip muscles. During each of the last 2 cycles either a 25-mg dose of pyridoxine hydrochloride or a placebo were administered daily in the double-blind fashion. Measurement of 24-hour xanthurenic acid and 4-pyridoxic acid excretion levels indicated correction of the biochemical indicators of vitamin B6 deficiency. Results of the tests of static muscle strength and endurance indicated no substantial improvement following vitamin B6 supplementation.

Adult↗
PubMed1984

Research progress in validation of laboratory methods of assessing body composition.

This paper presents various laboratory methods designed to estimate body composition and documents some of the progress in their validation. In addition to the well-known methods of densitometry, hydrometry, and spectrometry (40K), many other methods will be reviewed briefly for their relation to body composition. Emphasis is given to validation principles which need to be followed if new methods are to be developed. The reliance of past research on the two-component model and reference man is reviewed, and the need for multicomponent approaches to the study of body composition is emphasized. Past research using the two-component approach has until recently led to lack of research in developing new methodologies, has limited the potential usefulness of various laboratory methods in estimating body composition in different populations, and has made the relation of body composition to health, performance, and exercise an inexact science. The application of several multicomponent approaches to the characterization of both fat-free body composition and body composition of various populations will lead to the development of reference bodies so essential for the advancement of the field. The estimation of body composition changes with exercise, growth, development, and aging and the relation of body composition to health and physical performance are important areas for future research using various multicomponent approaches.

Adipose Tissue↗