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Biomedical subjects

J F Nichols

Publications and source records attributed to J F Nichols.

At least 19 recordsLinked to original sources
PubMed2000

Project GRAD: two-year outcomes of a randomized controlled physical activity intervention among young adults. Graduate Ready for Activity Daily.

INTRODUCTION: Project Graduate Ready for Activity Daily evaluated a program to promote physical activity through the transition of university graduation in a randomized controlled trial. METHODS: Three hundred thirty-eight university seniors participated in either a cognitive-behavioral intervention course or a knowledge-oriented general health course during the semester before graduation. Behaviorally oriented phone and mail follow-up was delivered to the intervention group for 18 months. Physical activity outcomes and mediating variables were assessed at baseline, 1 and 2 years (93% retention rate). RESULTS: There were no significant intervention effects on physical activity outcomes at 2 years for either men or women. Experiential and behavioral processes of change were significantly improved for intervention women over 2 years. CONCLUSIONS: Despite excellent participation in a theoretically based, well-attended intervention, few long-term effects on physical activity or its mediators were found. Additional research is needed to determine optimal interventions for physical activity and to validate or alter current behavior change theory.

Adult↗
PubMed2000

Assessment of physical activity with the Computer Science and Applications, Inc., accelerometer: laboratory versus field validation.

Our purpose was to compare the validity of the Computer Science and Applications, (CSA) Inc., accelerometer in laboratory and field settings and establish CSA count ranges for light, moderate, and vigorous physical activity. Validity was determined in 60 adults during treadmill exercise, using oxygen consumption (VO2) as the criterion measure, while 30 adults walked and jogged outdoors on a 400-m track. The relationship between CSA counts and VO2 was linear (R2 = .89 SEE = 3.72 ml.kg-1.min-1), as was the relationship between velocity and counts in the field (R2 = .89, SEE = 0.89 mi.hr-1). However, significant differences were found (p < .05) between laboratory and field measures of CSA counts for light and vigorous intensity. We conclude that the CSA can be used to quantify walking and jogging outdoors on level ground; however, laboratory equations may not be appropriate for use in field settings, particularly for light and vigorous activity.

Adult↗
PubMed2000

Self-report measures and scoring protocols affect prevalence estimates of meeting physical activity guidelines.

PURPOSE: Prevalence estimates of meeting the guidelines for physical activity based on various self-report measures were compared, and the effects of various scoring protocols on the estimates were evaluated. METHOD: A sample of 575 university students aged 24.5 +/- 1.9 yr (56% women, 54% Euro-American) completed the Seven-Day Physical Activity Recall interview (PAR), Youth Risk Behavior Survey (YRBS), and National Health Interview Survey 1991 (NHIS). To determine the prevalence of meeting the ACSM (1990) fitness and the CDC/ACSM (1995) health-related guidelines, various scoring protocols were employed that closely approximated the recommendations. Protocols varied by whether frequency and duration or duration only were considered. For the health-related guidelines, scoring protocols also varied depending on the intensity of activities considered. RESULTS: Depending on the scoring protocol and instrument used, the proportion meeting the fitness guidelines ranged from 32 to 59%. The NHIS, YRBS, and PAR resulted in significantly different proportions of those meeting the health-related guideline, ranging from 4 to 70%. CONCLUSION: The type of measure as well as the scoring protocol affected prevalence estimates of meeting the physical activity guidelines. This study indicates the difficulty of comparing prevalence rates across studies using different measures.

Adult↗
PubMed2000

Retraining of a competitive master athlete following traumatic injury: a case study.

PURPOSE: The purpose of this study was to examine the physiological effects of detraining and retraining in a female master cyclist (age, 49.5 yr; wt, 54 kg) following a surgically-treated clavicular fracture complicated by brachial plexus impingement. METHODS: Variables associated with cycling performance, including VO2max, lactate threshold (LT), power output at a blood lactate concentration of 4 mM (LT(4 mM)), peak power output (PPO), muscular resistance to fatigue measured by a timed ride to exhaustion at 110% of peak power output (PPO110), and body composition (hydrostatic weight) were assessed 2 d before the injury when the subject was at the peak of her competitive season, and at days 0, 14, 28, 42, and 77 of the retraining period. Retraining gradually increased from 3 h x wk(-1) to 9-10 h x wk(-1) with an increase in intensity from approximately 70 to 95+% of HRmax. RESULTS: Detraining resulted in a 25.7% decrease in VO2max and a 16.7% and 18.9% decrease in LT and LT(4 mM), respectively, while peak power output and PPO110 declined 18.2% and 16.6%, respectively. Body fat percent increased 2.1 percentage points, while fat-free mass decreased nearly 2 kg. After 2 wk of retraining, all variables except the LT and LT(4 mM) had improved considerably; however, VO2max was still 14.8% lower and PPO and PPO110 were 12.7% and 5.7% lower than preinjury values. By the 11th week of retraining, all variables had essentially returned to their preinjury values. CONCLUSION: These data demonstrate a pattern of retraining in which aerobic power steadily improved over 6 wk, while measures of lactate threshold did not change until the fourth week of retraining when the intensity of training was markedly increased. Additional data are needed to determine whether this pattern of retraining would be consistent in other master athletes.

Bicycling↗
PubMed2000

Effect of training mode and calcium intake on bone mineral density in female master cyclist, runners, and non-athletes.

The focus of this prospective, observational study was to determine the effect of sport-specific training and calcium intake on bone mineral density (BMD) in female master cyclists, runners and non-athletes. Thirty women (12 cyclists, 9 runners, 9 controls), mean age of 49.6 +/- 7.9 years, were assessed at baseline and 18 months for calcium intake (4-day records), current exercise activity (recall questionnaire), and BMD of the lumbar spine and hip (DXA). A three (cyclists, runners, controls) by two (0 and 18 months) repeated measures ANOVA demonstrated a significant interaction effect of sport and time at the femoral neck (p <.04). Tukey post hoc analysis indicated that the BMD of the femur was maintained in cyclists and runners but declined in controls (p <.05). A significant time effect was noted in BMD at the lumbar spine (p <. 001) and the trochanter (p <.003). BMD of the lumbar spine was maintained in runners but declined in cyclists (p <.007) and in controls (p <.03), while trochanteric BMD declined in all groups (p <.01). No significant interaction effect of sport and dietary calcium intake was noted for BMD at any site.

Adult↗
PubMed1999

Evaluation of a university course to promote physical activity: project GRAD.

Project GRAD (Graduate Ready for Activity Daily) evaluates a university course to promote physical activity. In a randomized study, 338 university seniors participated in either an intervention or control course for academic credit, and posttest data were collected on 321. The control course was knowledge-oriented. The intervention course taught behavior change skills in weekly lectures and peer-led labs. Physical activity was assessed with 7-Day Physical Activity Recall interviews. The intervention had no significant effects on men. Among women, the intervention increased total physical activity during leisure, strengthening exercises, and flexibility exercise. This university course had the intended effects of promoting healthful patterns of physical activity among women, but no effects were observed on men, who were more active than women at baseline.

Adolescent↗
PubMed1999

Validity, reliability, and calibration of the Tritrac accelerometer as a measure of physical activity.

PURPOSE: The purposes of this study were to assess the validity and reliability of the Tritrac R3D accelerometer during treadmill walking and running and then to calibrate the instrument. METHODS: The Tritrac was assessed on 60 young adults (23.4 +/- 2.9 yr) during treadmill walking and running at 3.2, 6.4, and 9.7 km x h(-1). The calibration was carried out by identifying ranges of Tritrac raw data (vector magnitude) values corresponding to light (2-3.9 MET), moderate (4-7 MET), and vigorous (>7 MET) physical activity. Energy expenditure (EE), measured by indirect calorimetry, served as the criterion measure. RESULTS: Interinstrument intraclass reliability coefficients for Tritracs worn on the right and left hip ranged from 0.73-0.87, while intersession coefficients demonstrated high reliability for all speeds (R = 0.87-0.92). Paired t-tests comparing mean accelerometer counts at 6.4 km x h(-1), 0% grade (2647 +/- 456), and 6.4 km x h(-1), 5% grade (2635 +/- 435) demonstrated no significant difference (P > 0.05). Mean differences between EE measured by indirect calorimetry and that estimated by the Tritrac ranged from 0.0082 kcal x kg(-1) x min(-1) at 3.2 km x h(-1) to 0.0320 kcal x kg(-1) x min(-1) at 9.7 km x h(-1), with the Tritrac consistently overestimating EE during horizontal treadmill walking. The relationship between vector magnitude and EE across all speeds was highly linear (R2 = 0.90, SEE = 0.014 kcal x kg(-1) x min(-1)), with little overlap between light, moderate, and vigorous categories. The mean vector magnitudes at 2, 4, and 7 MET were 650, 1772, and 3455, respectively. CONCLUSIONS: These data indicate that the Tritrac is highly reliable from day to day and is sensitive to changes in speed but not grade. Furthermore, the Tritrac accurately distinguishes various intensities of walking and jogging on level ground. With limitations, these cut-points can be used to categorize light, moderate, and vigorous physical activity and to estimate EE.

Adolescent↗
PubMed1997

Relationship between blood lactate response to exercise and endurance performance in competitive female master cyclists.

The blood lactate response to graded exercise and its relationship to performance in the field was examined in highly competitive female master cyclists. Thirteen women, age 47.5+/-2.2yr (mean+/-SE), all of whom were United States Cycling Federation (USCF) competitors, underwent laboratory testing for aerobic capacity (VO2max) and lactate threshold (LT), and field testing for performance in 13.5 km and 20 km time-trials. The mean VO2max of the subjects (50.6+/-2.7 ml x kg(-1) x min[-1]) was approximately 10% higher than that previously reported for other age-matched female athletes and correlated moderately (r=-0.67) with age. Maximal heart rate was unrelated to age (r=-0.25, p>0.05). Blood lactate concentration (BLC) while time-trialing was significantly higher than that at the LT (2.86+/-0.17 mmol x l[-1]) for both the 13.5 km (7.59 mmol x l(-1), p < 0.0001), and the 20 km trials (6.99 mmol x l(-1), p<0.002). The LT occurred at a mean power output of 168+/-11.3 W and 66% of VO2max. The VO2 corresponding to a BLC of 4.0 mmol x l(-1) (LT4) was 72% of VO2max. As expected, time-trial performance was highly correlated with VO2max (r=-0.85); however, regression analysis indicated that power output at the lactate threshold was the best laboratory predictor of performance (13.5 km: r2 = 0.83; 20 km: r2 = 0.78). Relative to maximal heart rate, heart rate at LT (88% HRmax) was significantly (p<0.05) lower than time-trial heart rate (92-94% HRmax). The cyclists in this study have higher aerobic capacities and maximal heart rates than those previously reported for other age-matched female athletes and are able to cycle for extended periods at blood lactate concentrations significantly higher than those at the lactate threshold. Traditional methods of exercise prescription, particularly when using age-estimates of maximal heart rate, underestimate training intensities required to be above the LT in female master cyclists.

Adult↗
PubMed1997

Assessing perceived physical environmental variables that may influence physical activity.

The present study evaluated a measure of perceived physical environments that may influence physical activity. Forty-three self-report items were used to assess environmental variables at homes, in neighborhoods, or on frequently traveled routes. The presence of facilitators of (e.g., equipment, programs, attractive surroundings) and barriers to (e.g., high crime) physical activity was assessed. In 110 college students, test-retest reliabilities were .89 for the home equipment scale, .68 for the neighborhood scale, and .80 for the convenient facilities scale. Home equipment and convenient facilities scales were correlated with self-reported physical activity. In multiple regression analyses, the only significant association, after adjusting for neighborhood socioeconomic status, was home equipment with strength exercise. Further research is needed to identify other environmental characteristics that may influence physical activity.

Adult↗
PubMed1996

Nutritional status of patients with Alzheimer's disease: a 1-year study.

OBJECTIVE: To describe the effects of activity level and energy intake over time on the body weight of patients with Alzheimer's disease compared with cognitively normal subjects. DESIGN: Repeated measures, case-control design with measurements taken at quarterly intervals for 12 months. Subjects were grouped by gender and activity level (sedentary or active) within cognitive status. SETTING: The Alzheimer's disease Special Care Unit, The Clinical Research Center at University of California, San Diego, and the Fred Kasch Exercise Physiology Laboratories at San Diego State University. PATIENTS: Seventeen institutionalized subjects with Alzheimer's disease and 23 community-dwelling control subjects successfully completed the 1-year study. MEASUREMENTS: Before admission to the nursing home, the patients with Alzheimer's disease had a formal assessment for dementia, which showed that they met the criteria of the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association work group for probable or possible Alzheimer's disease. Control subjects were screened using the Information-Memory-Concentration Mental Status Test and were found to have no cognitive disabilities. Baseline and quarterly measurements included height, weight, bioimpedance for body composition, and activity by accelerometer counts. Dietary intake of energy and protein was determined at baseline and at 6 and 12 months. RESULTS: Patients with Alzheimer's disease had a significantly higher energy intake than patients in the control group. Both women and men with Alzheimer's disease maintained their weight. Women with Alzheimer's disease had higher percentage of fat-free mass than the control group, but there were no differences in body composition between the groups of men. CONCLUSION: Subjects with Alzheimer's disease can maintain their weight if they are given a diet with adequate energy (35 kcal/kg of body weight).

Aged↗
PubMed1993

Body composition of patients with Alzheimer's disease.

Low body weight is frequently reported in patients with Alzheimer's disease. We sought to discover why by comparing the body composition of 28 cognitively normal elders and 23 institutionalized individuals with Alzheimer's disease. Body mass index was calculated from standing height and weight. Percentages of lean body mass, body fat, and body water were derived from bioimpedance measurements of resistance and reactance. Skinfold thickness was measured at seven body sites to estimate regional fat distribution. Variables were analyzed by analysis of variance with subjects grouped by cognitive status within gender. Activity level and age were not significant covariates. Both women and men with Alzheimer's disease weighed less than control subjects. Differences in body composition were more pronounced in women with Alzheimer's disease, who had lower body mass index (22.0 +/- 3.0 vs 26.1 +/- 5.1), higher percentage of lean body mass (73.8 +/- 5.1 vs 66.9 +/- 6.5), lower percentage of body fat (26.1 +/- 5.1 vs 33.1 +/- 6.5), and higher percentage of body water (55.8 +/- 5.0 vs 49.3 +/- 6.5) compared with control women. Except for lower body weight, the body composition of men with Alzheimer's disease was not significantly different from that of control men. Patients of both sexes with Alzheimer's disease had less truncal body fat compared with controls, which gave them a youthful body habitus. These differences were not accounted for by age, diet, or activity. Our findings indicate that patients with Alzheimer's disease have lower body weight and may require higher energy intake than cognitively normal elders.

Adipose Tissue↗
PubMed1993

Efficacy of heavy-resistance training for active women over sixty: muscular strength, body composition, and program adherence.

OBJECTIVE: To determine the effects of resistance training on muscular strength, body composition (percent fat and lean tissue mass), and program adherence in active women over 60 years of age. DESIGN: This study was designed as a stratified, randomized, non-blinded trial. Subjects were stratified into rank-ordered pairs by level of physical activity according to the Blair Seven-Day Recall, then randomly assigned into either a weight-training (WT, n = 18) or control (CON, n = 18) group. PARTICIPANTS AND SETTING: Thirty-six women over the age of 60 (67.1 +/- 1.5, chi +/- SE) were recruited from the San Diego community. All subjects had to be engaging in some form of aerobic exercise at least 3 days each week for a minimum of 6 months. MEASUREMENTS AND INTERVENTION: Subjects engaged in isotonic training 3 days/week on Polaris machines at a target intensity of 80% of the 1 repetition maximum (1 RM) for three sets of seven exercises selected to train major muscle groups of the trunk and upper and lower body. The 1 RM was re-tested every 6 weeks in WT and the workload adjusted to maintain target intensity. The 1 RM was tested at 0, 12, and 24 weeks in CON. Body fatness and lean tissue mass, excluding skeletal mass, were assessed at 0 and 24 weeks by dual energy radiography using a total body scan. RESULTS: Increases in muscle strength of the weight trainers were significant for all seven exercises (5%-65%), with the greatest gains in the shoulder and trunk muscles. Percent body fat of weight trainers decreased significantly (from 38.8% to 37.9%, P < 0.05), while lean tissue mass increased by 1.5 kg (P < 0.01). No changes in body composition were observed in control subjects. Overall program adherence was 83% (15 weight trainers and 15 control women completed the study). Monthly attendance averaged 86.8 +/- 3.3%, with no incidence of injury during the training sessions. CONCLUSIONS: These data indicate that heavy-resistance weight training is safe and enjoyable for older women and that meaningful gains in muscular strength and body composition can be made even in women who are already highly active.

Aged↗
PubMed1992

A validation of a physical activity monitor for young and older adults.

The accuracy of the Caltrac accelerometer was studied in 28 young (26.1 +/- 1.1 yrs) and 28 older (64.8 +/- 1.0 yrs; M +/- SEM) men and women to determine its usefulness as an activity monitor for young and older adults. Oxygen uptake was measured by indirect calorimetry while subjects walked on a motorized treadmill at six different speeds while wearing an accelerometer on the hip and on the upper back. The test-retest reliability of the Caltrac was r = .95 and r = .98 for young and older subjects, respectively. In the young group, activity counts correlated highly to net caloric expenditure (absolute minus estimated resting expenditure) (hip vs. kcal/kg: r = .89; back vs. kcal/kg: r = .88) when averaged across speeds, but the relationship was only moderate (back: r = .51; hip: r = .46) when the influence of speed was removed. In the older group the correlations were considerably weaker (back: r = .73; hip: r = .25), and essentially zero when the influence of speed was removed. These data indicate that the Caltrac is a highly reliable accelerometer that is useful for assessing qualitative differences in the level of physical activity among groups, but it lacks accuracy in quantifying energy expenditure in individuals, especially in older adults.

Acceleration↗
PubMed1989

Short-term weight loss and exercise training effects on glucose-induced thermogenesis in obese adolescent males during hypocaloric feeding.

Our purpose was to examine the effect of short-term weight loss and exercise training on the thermic effect of a glucose load in lean and obese adolescents. Nine obese (age 14.3 +/- 0.3 years, mean +/- s.e.m.) boys were examined during the first (Ob-pre) and sixth (Ob-post) week of caloric restriction (1300-1500 kcal/day, 5441-6279 kJ/day) and aerobic exercise conditioning (walk/jog/swim/calisthenics), and compared to age-matched lean controls (Con). A 100-g oral glucose tolerance test (OGTT) was administered while simultaneously measuring energy expenditure by indirect calorimetry every 30 min for 3 h. Posttest results revealed a decrease in body weight and body fatness in obese boys, but not to the level of that in lean controls (P less than 0.01). The thermic effect of glucose, calculated as the area under the response curve for three hours in excess of resting metabolic rate, was similar in Ob-pre and Con (0.77 +/- 0.14 vs. 0.57 +/- 0.28 kcal/kg lbm/3h), but decreased in Ob-post (0.29 +/- 0.08 kcal/kg lbm/3h, P less than 0.01). The area under the response curve for glucose was elevated in Ob-pre (328.1 +/- 12.2 mg/dl/3h) compared to Con (270.4 +/- 21.4 mg/dl/3h). The insulin response was similar in Ob-pre and Con (120.4 +/- 11.3 vs 125.6 +/- 12.4 mU/ml/3h), but decreased in Ob-post (89.6 +/- 15.1 mU/ml/3h, P less than 0.05). Thus, the improvement in peripheral insulin sensitivity with short-term exercise and weight loss was unaccompanied by favorable alterations in carbohydrate-induced thermogenesis in obese adolescents.

Adolescent↗
PubMed1987

The effects of age on substrate depletion and hormonal responses during submaximal exercise in hamsters.

Senescent hamsters display a marked reduction in volume of voluntary running. The purpose of this study was to determine whether age differences exist in the pattern of fuel utilization during submaximal exercise, which may account for the reduction in voluntary running. Further, we determined the effects of age on muscle oxidative capacity to assess its relationship to endurance performance in senescent hamsters. Depletion of carbohydrate and lipid content of skeletal muscle and liver, and changes in blood concentration of various hormones and substrates during one hour of exercise at 60 percent of VO2 max served to assess age effects on utilization of metabolic substrates. Exercise produced equivalent depletion of muscle glycogen and similar rise in plasma free fatty acids in young and old hamsters. No exercise effects on skeletal muscle triglyceride concentration or on plasma glycerol, glucagon or catecholamine concentrations were noted. With palmitoyl carnitine as substrate (but not with pyruvate) State 3 respiration of cardiac and skeletal muscle homogenates was lower in old compared to young hamsters. Although old hamsters have a reduced capacity to oxidize lipids in vitro, few age differences in fuel use are evident in vivo during submaximal exercise. Thus, these minor age differences in substrate utilization do not likely account for the substantial reduction in the levels of spontaneous running in senescent hamsters.

Aging↗
PubMed1987

Physiological, metabolic and running characteristics of senescent female hamsters.

Metabolic, endocrine and biochemical variables of female hamsters were studied to define age-related alterations in their characteristics. Endurance performance, aerobic capacity and metabolic fuels and hormones were measured and compared in young-adult (2-3 months) and old (16-17 months) hamsters to determine if the storage of substrates used in endurance exercise is altered with age, and if so, its effect on performance. The results indicate that storage of metabolic fuels are not appreciably altered with age, although voluntary running is markedly reduced. Other factors are likely involved in the hypoactivity of senescent female hamsters.

Aging↗
PubMedDate not supplied

Interrelationships between physical activity and other health behaviors among university women and men.

BACKGROUND: The interrelationships among health behaviors are not well understood. The present study examines health behaviors and their relations to various types of physical activity among university seniors. METHODS: The study sample was an ethnically diverse group of 576 men and women (mean age 24.5 +/- 2 years) recruited from a large urban university. Physical activity was assessed with a modification of the Blair Seven-Day Recall by telephone interview, and health behaviors were assessed with the CDC's Youth Risk Behavior Survey, College Version. Hierarchical multiple regressions were conducted to determine whether health behaviors of men and women were associated with physical activity after adjusting for potential demographic confounders. RESULTS: Nineteen health behavior items were factor analyzed, yielding 5 factors: tobacco use, drinking and driving, unsafe sex, eating fatty foods, and eating healthy foods. Physical activity measures included leisure-time moderate and vigorous activities, flexibility, and strengthening activities. For men, a significant relation was found between three of four indices of physical activity and eating healthy foods (P < 0.05), but no association was noted with other health behaviors. For women, vigorous physical activity was related to eating healthy foods, and strengthening activities were related to eating fewer fatty foods (P < 0.05). CONCLUSIONS: Consistent with previous studies, physical activity was found to have modest associations with eating behaviors but not with other health-related behaviors.

Adolescent↗