Biomedical subjects

A D Martin

Publications and source records attributed to A D Martin.

At least 19 recordsLinked to original sources

PubMed2006

Respiratory-related evoked potential elicited in tracheostomised lung transplant patients.

The present study investigated the role of removal of upper airway and lung vagal afferents in the respiratory-related evoked potential (RREP) response to inspiratory occlusions in two patients with a tracheostomy, who had undergone double lung transplantation (DLT). The patients were 1.5 and 3 months post-DLT and surgical placement of the tracheostomy. RREP recordings in response to inspiratory occlusions were obtained under four conditions: mouth breathing ignore trial; mouth breathing attend trial; tracheostomy breathing attend trial; and tracheostomy breathing ignore trial. The RREP peak components, Nf, P1 and N1, were present in both mouth and tracheostomy ignore breathing trials. The P300 was present in both mouth and tracheostomy attend trials. RREP peak latencies were similar between conditions. The peak amplitudes were greater with mouth breathing due to greater occlusion-related inspiratory pressure. These results demonstrate that the respiratory-related evoked potential can be elicited with inspiratory occlusion in the absence of mouth, upper airway and lung vagal afferent input. This suggests that inspiratory occlusion can elicit cortical activity with activation of inspiratory pump mechanoreceptors.

Adult↗

PubMed2003

Cadaver-assessed validity of anthropometric indicators of adipose tissue distribution.

Although the waist-to-hip ratio (WHR) has emerged as the best anthropometric indicator of the body's adipose tissue distribution, it has never been directly validated. Waist and hip girths, and triceps and subscapular skinfold thickness were measured in 12 male and 13 female cadavers aged 55-94 y. Adipose tissue from the upper limbs, lower limbs, subcutaneous trunk and intra-abdominal regions was then separated by dissection and weighed. Adipose volumes were also determined by hydrostatic weighing. The following adipose tissue mass ratios (and corresponding volume ratios) were derived: trunk to sum of lower limbs, trunk to sum of upper and lower limbs, intra-abdominal to sum of lower limbs and intra-abdominal to sum of upper and lower limbs. Centrality index (CI-subscapular-to-triceps skinfold ratio) and WHR were regressed on the tissue mass and volume ratios of the 25 cadavers. WHR was significantly related to mass and volume ratios for the 12 men (R2=36.0-57.5%, P<0.05), except for intra-abdominal to sum of upper and lower limbs (R(2)=26.3%, P=0.09), but none of these relations was significant in the women. CI was significantly related to all mass and volume ratios only for men and women combined (R(2)=16.2-21.8%, P<0.05). The WHR was better related to all mass and volume ratios than the CI. These results, especially the strong association between WHR and the ratio of intra-abdominal to lower limb adipose masses (R(2)=35.4%, P=0.002), demonstrate a clear relation between the selected anthropometric variables (hip and waist girths, and subscapular and triceps skinfolds) and adipose tissue distribution, thus validating the use of WHR as an important predictor of health risk.

Abdomen↗

PubMed2002

Expiratory muscle training increases pressure support in high school band students.

An experiment to increase expiratory muscle strength for instrumentalists, using a high-intensity, low-repetition expiratory training method, was conducted with 40 healthy high school band players. Subjects trained five days per week for 2 weeks using four sets of six training breaths for a total of 24 training breaths with a spring-loaded pressure relief valve that provided an adjustable threshold. The training valve pressure was set at 75% of the subject's measured maximum expiratory pressure (up to 80 cm H2O). Results demonstrated that high-intensity, low-repetition expiratory exercises significantly increased expiratory pressure generating capacity in these subjects and the degree of the training effect was similar regardless of the instrument the band member played. The training effect occurred within 2 weeks of initiating expiratory muscle training. Thus, this simple method of expiratory-specific strength training is effective and efficient for increasing expiratory pressure support in high school band students and has possibilities of a respiratory support device for many high pressure generating purposes. The potential mechanisms of the training effect are discussed.

Adult↗

PubMed2001

Can sedentary adults accurately recall the intensity of their physical activity?

BACKGROUND: Physical activity, in particular vigorous activity (i.e., > or =6 METs), lowers mortality from chronic diseases such as cardiovascular disease (CVD). The 7-Day Physical Activity Recall (PAR), a self-administered activity log (LOG), and heart rate monitoring (HR) were used to quantify activity patterns among sedentary adults. We hypothesized that individuals in this population could accurately estimate the duration, but not the intensity, of their activity. METHODS: Sedentary adults (n = 94, 47.8 +/- 7.1 years) completed two PARs 1 week apart and underwent HR monitoring while completing a LOG for 1 day during the PAR assessment interval. RESULTS: The relationship between PARs (kcal. kg(-1). day(-1) ) was significant (r = 0.80, 95% CI 0.68-0.87) among individuals (n = 63) reporting "typical" activity patterns and among all individuals (n = 94) reporting "typical" and "not typical" activity patterns combined (r = 0.44, 95% CI 0.26-0.59). Quantity of moderate activity was greater (P = 0.0001) on PAR and LOG compared to that measured by HR. Quantity of hard (vigorous) activity was also greater (P = 0.019) on LOG compared to that measured by HR. CONCLUSIONS: Sedentary adults tend to overestimate the intensity of their activity, specifically for moderate activity. Furthermore, the aerobic capacity of our sedentary adult sample (about 7.3 METs) suggests that the definition of a threshold intensity level of activity necessary to reduce mortality from CVD should be reexamined, because a value of > or =6 METs appears to be too high in this population.

Activities of Daily Living↗

PubMed2001

The effect of maximal exercise on temporal summation of second pain (windup) in patients with fibromyalgia syndrome.

Exercise activates endogenous opioid and adrenergic systems, but attenuation of experimental pain by exercise has not been shown consistently. In this study, effects of exercise on temporal summation of late pain responses to stimulation of unmyelinated (C) nociceptors were assessed. When a preheated thermode was applied repetitively to glabrous skin of the hand in a series of brief contacts at rates of 0.2 to 0.5 Hz, the perceived intensity of late thermal sensations increased after successive contacts. This summation of pain sensations provides information regarding the status of central opioid and N-methyl-D-aspartate receptor systems. For normal subjects, temporal summation of late pain sensations was substantially attenuated when testing began 1.5 or 10 minutes after exercise. Individuals diagnosed with fibromyalgia syndrome (FMS) report generalized chronic pain that is increased after exercise. Therefore, we hypothesized that strenuous exercise would increase summation of late pain sensations in this cohort. Patients with FMS and control subjects exerted to similarly high metabolic rates, as shown by physiologic monitoring. Ratings of late pain sensations increased for patients with FMS after exercise, an effect opposite to a decrease in ratings for age/sex-matched control subjects. In contrast to this result for experimentally induced pain, clinical pain ratings were not substantially altered after strenuous exercise by patients with FMS.

Journal Article↗

PubMed2001

Temporal relationships of self-efficacy and social support as predictors of adherence in a 6-month strength-training program for older women.

The present study investigated how self-efficacy and social support predicted adherence to a strength training program for elderly women over two time periods in the initial 6 mo. of the program. Participants were 30 elderly women volunteers aged 75 to 80 who completed measures of barrier self-efficacy and general social support at baseline and 3 mo. later. Social support from the program was also measured at 3 mo. Adherence to the program was measured by attendance. Hierarchical regression equations were utilized to identify the contributions of self-efficacy and social support for adherence at 0 to 3 mo. and 4 to 6 mo. For prediction of the first 3 mo. of adherence, both self-efficacy and social support contributed significant unique variance towards the total explained variance of 36%. For the 4- to 6-mo. period, self-efficacy explained significant (12%) variance in adherence even when controlling for the previous 3-mo. adherence. Inclusion of general social support and social support from the program, however, did not account for significant variance. Researchers must continue to examine self-efficacy and social support in exercise adherence within various time periods among older adults to develop effective intervention strategies.

Aged↗

PubMed2000

Inspiratory strengthening effect on resistive load detection and magnitude estimation.

PURPOSE: This study investigated effects of inspiratory muscle training (IMT) on maximal inspiratory pressure (MIP), magnitude estimation (ME), and load detection (LD) of external resistive loads (deltaR) in healthy subjects. METHODS: Ten adult volunteers IMT trained 5 d x wk(-1) for 4 wk. A training set consisted of six inspiratory efforts at 75% of MIP; daily training trials consisted of four sets. ME was calculated by linear regression, with actual and estimated deltaR loads plotted on log-log scale. LD was calculated by determining deltaR50/Ro fraction. Dependent measures were taken pre- and post-IMT. RESULTS: MIP significantly increased from 87 to 139 cmH2O pre- to post-IMT, respectively. ME for individual loads significantly decreased post-IMT for all but the highest deltaR. There was no significant difference in LD deltaR50/Ro, post-IMT. CONCLUSIONS: The results demonstrate that inspiratory muscle strength gains were associated with decreased ME of deltaRs without changing LD deltaR50/Ro. This suggests that the mechanisms mediating the detection of deltaRs may be different than the mechanisms for estimating deltaR size.

Adult↗

PubMed2000

Effects of one year of resistance training on the relation between muscular strength and bone density in elderly women.

OBJECTIVES: There is a paucity of long term studies on exercise training in elderly women. The purpose of this study was to investigate the effects of one year of progressive resistance exercise (PRE) on dynamic muscular strength and the relations to bone mineral density (BMD) in elderly women. METHODS: Forty four healthy sedentary women (mean age 68.8 years) volunteered for this study and were randomly assigned to either an exercise group or a control group. The exercise group were involved in three one hour sessions a week for 52 weeks of supervised PRE to strengthen the large muscle groups of the body, while the control group were instructed to continue their normal lifestyle. The exercise circuit included three sets of eight repetitions at 75% of one repetition maximum focused on the large muscle groups. BMD was measured by dual energy x ray absoptiometry (Lunar DPX) at the lumbar spine and at three sites in the proximal femur. Other selected parameters of physical fitness were also measured. RESULTS: Statistical analyses (analysis of covariance) showed significant strength gains (p < 0.01) in bilateral bench press (> 29%), bilateral leg press (> 19%), and unilateral biceps curl (> 20%). No significant difference between groups was evident in body weight, grip strength, flexibility, waist to hip ratio, or the sum of eight skinfolds. Significant relations (p < 0.05) were recorded between dynamic leg strength and the BMD of the femoral neck, Ward's triangle, and the lumbar spine. CONCLUSIONS: Significant strength changes, after one year of PRE, were evident in elderly women, and the muscle increases may parallel changes in BMD; however, correlation coefficients were moderate.

Aged↗

PubMed2000

Calcium accretion in girls and boys during puberty: a longitudinal analysis.

The primary purpose of this study was to estimate the magnitude and variability of peak calcium accretion rates in the skeletons of healthy white adolescents. Total-body bone mineral content (BMC) was measured annually on six occasions by dual-energy X-ray absorptiometry (DXA; Hologic 2000, array mode), a BMC velocity curve was generated for each child by a cubic spline fit, and peak accretion rates were determined. Anthropometric measures were collected every 6 months and a 24-h dietary recall was recorded two to three times per year. Of the 113 boys and 115 girls initially enrolled in the study, 60 boys and 53 girls who had peak height velocity (PHV) and peak BMC velocity values were used in this longitudinal analysis. When the individual BMC velocity curves were aligned on the age of peak bone mineral velocity, the resulting mean peak bone mineral accrual rate was 407 g/year for boys (SD, 92 g/year; range, 226-651 g/year) and 322 g/year for girls (SD, 66 g/year; range, 194-520 g/year). Using 32.2% as the fraction of calcium in bone mineral, as determined by neutron activation analysis (Ellis et al., J Bone Miner Res 1996;11:843-848), these corresponded to peak calcium accretion rates of 359 mg/day for boys (81 mg/day; 199-574 mg/day) and 284 mg/day for girls (58 mg/day; 171-459 mg/day). These longitudinal results are 27-34% higher than our previous cross-sectional analysis in which we reported mean values of 282 mg/day for boys and 212 mg/day for girls (Martin et al., Am J Clin Nutr 1997;66:611-615). Mean age of peak calcium accretion was 14.0 years for the boys (1.0 years; 12.0-15.9 years), and 12.5 years for the girls (0.9 years; 10.5-14.6 years). Dietary calcium intake, determined as the mean of all assessments up to the age of peak accretion was 1140 mg/day (SD, 392 mg/day) for boys and 1113 mg/day (SD, 378 mg/day) for girls. We estimate that 26% of adult calcium is laid down during the 2 adolescent years of peak skeletal growth. This period of rapid growth requires high accretion rates of calcium, achieved in part by increased retention efficiency of dietary calcium.

Absorptiometry, Photon↗

PubMed2000

Detrimental effects of short-term glucocorticoid use on the rat diaphragm.

BACKGROUND AND PURPOSE: The purpose of this study was to determine the effect of short-term, high doses of glucocorticoids on both body and diaphragm weights as well as contractile characteristics of the rat diaphragm. SUBJECTS: Adult, female Sprague-Dawley rats were divided into 2 groups: a control group (n=16) and a prednisolone group (n=16). METHODS: The prednisolone group received prednisolone at a dosage of 5 mg/kg, and the control group received sham saline injections for 5 days. Animals were weighed prior to and after completion of the drug injection period. At the completion of the drug injection period, the animals were sacrificed, and the diaphragm, soleus, and extensor digitorum longus muscles were removed and weighed. A small strip of the costal diaphragm was connected to a force transducer, and the following contractile characteristics were measured: maximal specific isometric tetanic tension, peak isometric twitch specific tension, one-half relaxation time, and time to peak tension. RESULTS: Both body and diaphragm weights decreased by 15% in the prednisolone group as compared with the control group. Maximal specific isometric tetanic tension was reduced 13% in the prednisolone group as compared with the control group. There was no difference in any twitch contractile characteristics between the 2 groups. CONCLUSION AND DISCUSSION: These data support the hypothesis that glucocorticoid treatment over a 5-day period results in a decrease in specific tension as well as diaphragm and body weight. These results may have implications for the treatment of patients receiving high doses of glucocorticoids for acute medical conditions.

Animals↗

PubMed1999

Factors associated with exercise adherence among older adults. An individual perspective.

This paper reviews the literature concerning factors at the individual level associated with regular exercise among older adults. Twenty-seven cross-sectional and 14 prospective/longitudinal studies met the inclusion criteria of a mean participant age of 65 years or older. The findings are summarised by demographics, exercise experience, exercise knowledge, physiological factors, psychological factors, activity preferences and perceived social influences. In general, education and exercise history correlate positively with regular exercise, while perceived physical frailty and poor health may provide the greatest barrier to exercise adoption and adherence in the elderly. Social-cognitive theories identify several constructs that correlate with the regular exercise behaviour of older adults, such as exercise attitude, perceived behavioural control/self-efficacy, perceived social support and perceived benefits/barriers to continued activity. As well, stage modelling may provide additional information about the readiness for regular exercise behaviour among older adults. However, relatively few studies among older adults exist compared with middle-aged and younger adults. Further, the majority of current research consists of cross-sectional designs or short prospective exercise trials among motivated volunteers that may lack external validity. Future research utilising longitudinal and prospective designs with representative samples of older adults will provide a better understanding of significant causal associations between individual factors and regular exercise behaviour.

Aged↗

PubMed1997

Effects of group- versus home-based exercise in the treatment of obesity.

This study examined the effects of 2 aerobic exercise regimens on exercise participation, fitness, eating patterns, treatment adherence, and weight change in 49 obese women undergoing a year-long behavioral weight loss program. Participants were assigned randomly to weight loss treatment plus either group- or home-based exercise. All participants were instructed to complete a moderate-intensity walking program (30 min/day, 5 days/week). Group exercise participants were provided with 3 supervised group exercise sessions per week for the first 26 weeks and with 2 sessions per week thereafter. Home exercise participants were instructed to complete all exercise in their home environment. After 6 months, both conditions displayed significant improvements in exercise participation, fitness, eating patterns, and weight loss. At 12 months, the home-based program showed superior performance to the group condition in exercise participation and treatment adherence; at 15 months, participants in the home program demonstrated significantly greater weight losses than those in the group program.

Adult↗

PubMed1997

Bone mineral and calcium accretion during puberty.

We measured bone mineral content (BMC) and estimated calcium accretion in children to provide insight into dietary calcium requirements during growth. Anthropometric measurements were done semiannually and whole-body BMC was measured annually by dual-energy X-ray absorptiometry for 4 y in 228 children (471 scans in 113 boys and 507 scans in 115 girls). Mean values for BMC, skeletal area, and height were calculated for 1-y age groups from 9.5 to 19.5 y of age. Cross-sectional analysis of the pooled data gave peak height velocity and peak BMC velocity (PBMCV) and the ages at which these occurred (13.3 y in boys and 11.4 y in girls). PBMCV did not peak until 1.2 y after peak height velocity in boys and 1.6 y after peak height velocity in girls. Within 3 y on either side of PBMCV, boys had consistently higher BMC and BMC velocity compared with girls and the discrepancy increased steadily through puberty. Three years before PBMCV, BMC values in girls were 69% of those in boys; 3 y after peak height velocity this proportion fell to 51%. PBMCV was 320 g/y in boys and 240 g/y in girls. Under the assumption that bone mineral is 32.2% calcium, these values corresponded to a daily calcium retention of 282 mg in boys and 212 mg in girls. Individual values could be much greater. In one boy in a group of six subjects for whom there were enough data for individual analysis through puberty, PBMCV was 555 g Ca/y or 490 mg Ca/d. Such high skeletal demands for calcium require large dietary calcium intakes and such requirements may not be met immediately in some children.

Absorptiometry, Photon↗

PubMed1997

Exercise for the older woman: choosing the right prescription.

Many elderly women in industrially developed countries are at, or near to, functionally important strength related thresholds and so have either lost, or are in danger of losing, the ability to perform some important everyday tasks. The increased rate of healthcare expenditure due to loss of physical function is a major economic issue. Even though women make up most of the senior population, little current research on the impact of physical activity on strength and function in elderly people has included women. Elderly women typically have more barriers to participation in physical activity than do other groups and because of decreased participation, may possibly experience higher disability rates. Physical activity in old age may delay the progression of osteoporosis and is of paramount importance for maintaining the functional abilities needed to carry out daily tasks. Current research on exercise and the elderly population suggests that strength training may be the exercise mode of choice for maintenance of strength, physical function, bone integrity, and psychosocial health. This review summarises recent research on the impact of strength training on the fitness and health of elderly women and highlights considerations and potential barriers to physical activity that must be taken into account when planning exercise programmes for them.

Activities of Daily Living↗

PubMed1997

A new formula for population-based estimation of whole body muscle mass in males.

A new equation to estimate muscle mass in males was developed using parameters common to the 1981 Canada Fitness Survey and the male cadaver data of Martin et al. (1990b). The cadavers (N = 12) were randomly divided into two groups. The equation was developed on cadaver Group A and then validated on Group B. Once the equation with the most suitable variables was validated on Group B, it was redeveloped on combined data from Groups A and B. The final equation is as follows: muscle mass (gm) = Ht (0.031MUThG2 + 0.064CCG2 + 0.089CAG2) - 3,006; adjusted R2 = .96, SEE = 1,488 gm, F = 87.5, p = .0001. Variables (in cm) were Ht, height; MUThG, modified upper thigh girth; CCG, corrected calf girth; and CAG, corrected arm girth. The predictive ability of this equation was comparable to the original equation of Martin et al. (1990b) and can be a valuable tool for muscle mass estimation of male subjects in the 1981 Canada Fitness Survey.

Aged↗

PubMed1994

Calculated thermal conductivities and heat flux in man.

Using data compiled by the Brussels Cadaver Analysis Study on 13 unembalmed cadavers, this study examined the validity of assumptions often made concerning the role of the skin and adipose tissue layers in thermal insulation in vivo. Skin thickness was previously reported to vary from 0.35 to 2.55 mm, depending on the site of measurement and gender of the subject. Assuming a thermal conductivity of 0.70 x 10(-3) kcal/(cm.s-1.degree C-1) for the skin, heat flux across the skin would vary between site and gender in the order of 7.5 times, ranging from 0.16 to 1.20 kcal.min-1.degree C-1.m-2. Due to the negligible thermal gradient across the skin layer, however, this would be of little physiologic significance. Assumptions concerning the homogeneity of skin thickness across gender and measurement site when investigating thermal insulation of the peripheral tissues would not, therefore, influence the reported results significantly. However, it has recently been shown that the calculated lipid fraction of the adipose tissue layer varies according to a person's level of adiposity. Using a two-component model of adipose tissue, the predicted thermal conductivity (k) of the adipose tissue in the present sample was found to range from 0.50 to 0.97 x 10(-3) kcal/(cm.s-1.degree C-1), being significantly lower (P = 0.005) in the five most obese cadavers [6.66 +/- 0.45 x 10(-4) kcal/(cm.s-1.degree C-1)] than in the five most lean cadavers [8.22 +/- 0.93 x 10(-4) kcal/(cm.s-1.degree C-1)]. Adiposity level correlated significantly (r = 0.80; P < 0.01) with calculated k values, suggesting caution must be taken when assuming a single k for the adipose tissue layer when examining divergent populations (i.e., obese vs. thin).

Adipose Tissue↗

PubMed1994

Adipose tissue density, estimated adipose lipid fraction and whole body adiposity in male cadavers.

Lipid and water together typically make up more than 90% of the body's adipose tissue mass. Although some reports have shown that the fraction of lipid in adipose tissue is greater in obese people than in lean ones, the quantitative relationship between adipose lipid fraction and overall adiposity of the body has never been investigated. We dissected six male unembalmed cadavers and weighed all adipose tissue (range 9.7-25.7 kg), allowing the calculation of percentage adiposity as 100 x total adipose mass/body mass (range 17.8-43.9%). Adipose tissue volume was determined by hydrostatic weighing of all portions of the dissected adipose tissue. For the six cadavers, whole body adipose tissue density ranged from 0.925-0.970 g/ml. Based on a three-component model of adipose tissue (lipid, water and dry fat-free solids), an expression for lipid fraction, F, was derived. After assuming densities for adipose lipid (0.905 g/ml), water at 36 degrees C (0.997 g/ml) and the dry fat-free component (1.38 g/ml), the equation simplified to F = 6.256/D-5.912, where D is adipose tissue density (g/ml). Lipid fraction was then calculated for each of the six cadavers: the range (0.54-0.85) was in excellent agreement with published data. There was a significant correlation (r = 0.95, P < 0.005) between calculated lipid fraction and percentage adiposity. The regression equation predicting lipid fraction from percentage adiposity was y = 0.327 + 0.0124x. We conclude that the estimated fraction of lipid in human adipose tissue shows both a wide range and a strong positive linear relationship with overall body fatness.

Adipose Tissue↗

PubMed1993

Muscle mass of competitive male athletes.

The recent publication of the first validated equation for the estimation of muscle mass (MM) in men has made possible a comparison of MM in athletes from different sports. Limb girths and skinfold thicknesses were measured in 62 male athletes (aged 17-38 years) and 13 non-athletic males (aged 22-36 years). The MM (g) was calculated from the equation MM = S(0.0553 Gt2 + 0.0987 Gf2 + 0.0331 Gc2)-2445, where S is stature, Gt is the mid-thigh girth corrected for the front thigh skinfold thickness, Gc is the maximum calf girth corrected for the calf skinfold thickness and Gf is the uncorrected maximum forearm girth (all in cm). The athletes were classified as gymnasts (n = 10), basketball players (n = 10), body-builders (n = 10), track and field power athletes (n = 12), track and field long sprinters (n = 10) or distance runners (n = 10). The MM means ranged from 38.4 kg for the distance runners to 58.7 kg for the body-builders. Both body-builders and basketball players had significantly greater MM than gymnasts, long sprinters, non-athletic males and distance runners (P < 0.01). Also, MM was greater in track and field power athletes than in distance runners (P < 0.05). The MM as a percentage of body mass (%MM) ranged from 56.5% in the non-athletic group to 65.1% in the body-builders; body-builders scored higher than basketball players (P < 0.05), distance runners (P < 0.01) and the non-athletic group (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗