PubMed Health⌕ Search

Biomedical subjects

C O Dotson

Publications and source records attributed to C O Dotson.

17 recordsLinked to original sources
PubMed1996

Peak oxygen consumption and lactate threshold in full mask versus mouth mask conditions during incremental exercise.

Respirator masks vary in inhalation and exhalation resistance, and in dead volume. It is believed that these factors may contribute significantly to an early anaerobic threshold in mask wearers during maximal exercise. Very little is known concerning the effect of respirator masks on maximal oxygen consumption (VO2max) and the lactate threshold (LT). The purpose of the present study was to assess peak VO2 (VO2peak), LT and the ventilatory threshold (VT) of 14 experienced cyclists performing two maximal cycle exercise protocols while wearing a full respirator mask (FM) (M17 type) and a mouth mask (MM). VO2peak was 10% lower under FM conditions. Peak values for ventilation (VEpeak), respiratory rate (fbpeak) and tidal volume (VTpeak) were all significantly lower under with FM versus MM conditions. Performance time and maximal heart rate (fcpeak) were not different between mask conditions. The LT and VT when expressed in %VO2peak, and the lactate concentration (mmol.l-1) at LT and VT were not significantly different across mask conditions. Bland-Altman plots demonstrated longer inhalation times, decreased Fr values and greater oxygen extraction under FM conditions. Thus, perhaps due to the increased inhalation resistance of the FM condition, subjects were unable to attain their "normal" VO2 despite similar performance times and maximal fc. Furthermore, despite a diminished VO2peak with FM, LT and VT appeared to be the same as with a MM.

Adolescent↗
PubMed1996

Effects of chromium and resistive training on muscle strength and body composition.

Sixteen untrained males (23 +/- 4 yr), were studied to determine the effects of chromium (Cr) supplementation (200 micrograms.d-1) and a 12-wk resistive exercise training program on muscle strength, body composition, and Cr excretion. The subjects trained 3 times per week with two sets of 8-10 repetitions at 90% of 1 repetition maximum using Keiser variable resistance machines. Food records were used to estimate Cr intake (approximately 36 micrograms.d-1), energy intake, and the percent kJ from protein. The resistive training program resulted in significant increases in total body muscular strength in both the Cr and placebo groups (24% and 33%; P < 0.05). Body weight, percent body fat, lean body mass, and skinfold thicknesses were unchanged in either group after resistive training. Cr excretion increased in the Cr group after 6 wk of Cr supplementation (0.15 +/- 0.08 vs 1.52 +/- 1.26 micrograms.d-1; P < 0.01) and remained higher at 12 wk of training (2.03 +/- 1.73). These results indicate that Cr supplementation, in conjunction with a progressive, resistive exercise training program, does not promote a significant increase in strength and lean body mass, or a significant decrease in percent body fat. Cr supplementation results in a significant increase in Cr excretion that is not altered by resistive training.

Adult↗
PubMed1995

Miles run per week and high-density lipoprotein cholesterol levels in healthy, middle-aged men. A dose-response relationship.

OBJECTIVE: To examine the association between miles run per week and high-density lipoprotein cholesterol levels in healthy middle-aged men. BACKGROUND: Regular exercise increases levels of high-density lipoprotein cholesterol. However, the exercise requirements for such increases are not well defined. METHODS: Healthy, nonsmoking men (n = 2906; age, 43 +/- 4 years) completed a questionnaire on health habits and physical activities and a symptom-limited exercise test. They were then stratified on the basis of the number of miles run per week. Six groups, with mileages of 0, 5, 9, 12, 17, and 31 per week, were established. RESULTS: A gradual increase in high-density lipoprotein cholesterol level was observed with increased miles (0.008-mmol/L [0.308-mg/dL] increase in high-density lipoprotein cholesterol level per mile). Most of the changes were associated with distances of 7 to 14 miles per week. Levels of low-density lipoprotein cholesterol, triglycerides, and the ratio of total cholesterol to high-density lipoprotein cholesterol also improved with weekly mileage. The high-density lipoprotein cholesterol level correlated significantly with all exercise components, anthropometric measures, and alcohol consumption. Group comparisons disclosed significant differences (P < .05) in exercise time to exhaustion, miles run per week, body fat, body weight, and body mass index. Age and alcohol consumption were similar across groups. CONCLUSIONS: These results indicate a dose-response relationship between miles run per week, high-density lipoprotein cholesterol level, and other lipoprotein-lipid levels. Most changes were noted in those who ran 7 to 14 miles per week at mild to moderate intensities. A mile-age threshold for changes in high-density lipoprotein cholesterol level was not observed. However, when compared with those of the nonexercising group, high-density lipoprotein cholesterol levels attained statistical significance at 7 or more miles per week.

Cholesterol, HDL↗
PubMed1995

Cardiorespiratory fitness and coronary heart disease risk factor association in women.

OBJECTIVES: The purpose of this study was to examine the association between cardiorespiratory fitness and coronary risk factors in healthy, nonsmoking adult women. BACKGROUND: A sedentary life-style is recognized as an independent risk factor for coronary heart disease, and increasing physical activity is strongly recommended to reduce this risk. However, studies examining the effects of increased physical activity on coronary heart disease risk factors in women are relatively few, and the findings have been equivocal. METHODS: Subjects provided written informed consent, completed a questionnaire on medical history and performed an exercise tolerance test. Blood chemistry and lipid levels were determined from fasting blood samples. Three fitness categories were established on the basis of treadmill time to exhaustion and were adjusted for age. RESULTS: The women in the lowest fitness category had less favorable lipid profiles, blood glucose levels, blood pressures and anthropometric indexes than those in the moderate and high fitness categories. CONCLUSIONS: Moderate fitness (equivalent to 10 metabolic equivalents [METs]) is required to improve the coronary risk profile in women.

Adult↗
PubMed1995

Respirator mask effects on exercise metabolic measures.

To test effects of respirator masks on maximum oxygen uptake, ventilation threshold, and lactate threshold, 14 subjects underwent incremental bicycle exercise with and without masks. There was a statistically significant difference in final oxygen consumption between the two conditions, but other results suggest that the physiological measure of maximum oxygen uptake was not reached at termination for the full-mask condition. Lactate and ventilation thresholds were not affected by mask condition. Hypoventilation while wearing masks caused higher amounts of blood lactate accumulation. The resulting higher mask CO2 levels and lower O2 levels, normally attributed to mask dead volume, may instead be due to mask resistance.

Adult↗
PubMed1992

Muscular strength and endurance as a function of age and activity level.

Muscular strength, endurance, and rate of fatigue were studied in populations of various ages actively engaged in strength and endurance training, as compared with those not engaged in such activities. The strength and fatigability of the elbow flexor muscles were studied for 62 subjects at the ages of 20 (n = 11 active, 10 inactive), 35 (n = 11 active, 10 inactive), and 50 (n = 10 active, 10 inactive) years, tested within 2 years of the appropriate age. They performed a 6-min bout of maximal rhythmic contractions of the dominant arm at a rate of 30 contractions per min. Force applied to the transducer was converted into electrical activity and transmitted to a recorder, where differences in mean values for initial strength, final strength, absolute endurance, and relative endurance were examined for significance. Rates of fatigue and the fatigue curves were also obtained for each group. Results revealed significantly less muscular strength, absolute endurance, and relative endurance as the age of the subjects increased, but no significant difference for age was found in final strength at the conclusion of the exercise bout. Significant differences were found between active and inactive subjects in initial strength, final strength, and absolute endurance in favor of the active subjects. No significant interaction between activity level and age was found for any of the dependent variables. The rates of fatigue were similar for all ages except for the inactive 20-year-old subjects, whose rate of fatigue was markedly slower than that found for all other groups of subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Job performance testing: an alternative to age discrimination.

The Age Discrimination in Employment Act has raised the issue of Bona Fide Occupational Qualifications for employment in the public safety sector. Complicating the issue is the number of lawsuits filed for violation of the Age Discrimination in Employment Act. Physical performance testing as an alternative to arbitrary age limitations is considered for physically demanding tasks in fire fighting, law enforcement, and the military. Tests with criterion-related validity are presented that are useful for screening new applicants and for periodic re-evaluation of incumbents. Extensive testing in our laboratory, in concert with the literature review, support the observation that age is a poor predictor of performance across the full range of employment years. It is concluded that individuals who are otherwise healthy, with proper attention to their lifestyles, can develop and maintain the necessary physiological profile to successfully execute the duties of physically demanding jobs well into their advancing years.

Adult↗
PubMed1986

In vivo opioid receptor occupation in the rat brain following exercise.

The effects of prolonged swim-stress (2 h and 1 h) upon brain opioid receptor binding of tritiated [3H]diprenorphine were investigated in male Sprague-Dawley rats. This was accomplished by injecting the label intravenously immediately following the swim, then allowing 20 min for tracer washout from non-specific binding sites, sacrificing the animal, dissecting the brain into several discrete areas (medulla-pons, mid-brain, mesolimbic, caudate, thalamus, and hypothalamus), and subsequently preparing homogenates from each brain area. Data were obtained from scintillation counting of the homogenates. A separate support experiment measured circulating beta-endorphin endorphin like immunoreactivity immediately following 2 h of swim-stress. Blood-borne beta-endorphin levels were significantly enhanced by the swim. Additionally, [3H]diprenorphine binding was insignificantly elevated following the 1-h swim and significantly greater in 5 of 6 brain areas examined subsequent to the 2-h swim. Greater availability of opioid receptors to allow enhanced binding of [3H]diprenorphine may have been caused by decreased competition for available receptors from endogenously produced peptides or possibly by alterations in receptor-binding characteristics. These proposed explanations await further investigation. As a result of these studies, we conclude: exercise-induced enhancement of peripheral beta-endorphin probably does not have a supraspinal action; and prolonged swim-stress apparently alters opioid receptor occupancy in the rat brain, and this effect may be dependent upon exercise duration.

Animals↗
PubMed1984

Maximal oxygen intake estimated from submaximal heart rate.

This study investigated the predictability of maximal oxygen intake from three different submaximal heart rates assessed during an initial and follow-up ride on a cycle ergometer. Twenty-four healthy male subjects performed workloads of 600, 750, and 900 kpm's for six minutes on each of two visits to the laboratory. Analysis of variance for a randomised complete blocks design, with subjects constituting blocks, was used to analyse heart rate, estimated maximal oxygen intake, and residual estimated maximal oxygen intake variations among the experimental conditions. Relationships between the actual and estimated maximal oxygen intakes were determined using the Pearson Product-Moment formula of correlation. The average estimated maximal oxygen intake was significantly increased from the first testing occasion to the second. Although errors of estimation decreased significantly (450 ml to 366 ml) in favour of the second testing condition, the decrease was neither consistent with workloads nor subjects. The correlation coefficients were consistently low at 600 kpm for both testing occasions (0.68 and 0.73, respectively), consistently high at 750 kpm (0.82 and 0.84, respectively), and quite variable at 900 kpm (0.71 and 0.84, respectively), indicated that the validity of the nomogram was not consistent with all workloads or testing occasions. Despite these inconsistencies, the nomogram is, for practical purposes, a valid predictor of maximal oxygen consumption.

Adolescent↗
PubMed1984

Endurance training effects on plasma hormonal responsiveness and sex hormone excretion.

A prospective study of the hormonal effects of a moderate exercise training program (4-wk control, 8-wk training) was conducted in seven young women. Sixty-minutes continuous bicycle ergometer tests of fixed relative intensity were performed at the beginning, middle, and end of the training period. The capacity of these acute bouts of exercise to affect circulating levels of stress markers, reproductive hormones, and hormones with possible antireproductive potential was measured. In addition, the urinary excretion of reproductive hormones was monitored continuously via serial overnight urine collections. Within testing sessions, plasma concentrations of all stress markers and antireproductive hormones rose significantly. Across testing sessions, only beta-endorphin + beta-lipotropin and cortisol exhibited an increment in peak responses as training progressed. Plasma reproductive hormone levels showed insignificant acute changes, and cyclic menstruation and preovulatory gonadotropin surges continued in all subjects. However, ovarian function was disturbed in four subjects as evidenced by a decreased excretion of estriol, free progesterone, or both. Transient infertility is a known clinical accompaniment of hormonal changes of comparable subtlety.

Adolescent↗
PubMed1982

Relationship between simulated fire fighting tasks and physical performance measures.

Twenty-six physical performance variables were assessed on 100 professional fire fighters and correlated against timed measures of five sequentially performed fire fighting tasks and against fractionated heart rates collected during performance of the fire fighting tasks via Holter monitoring of the ECG. Canonical correlation analysis revealed that two factors, physical work capacity and resistance to fatigue, accounted for the fractionated time and heart rate data. The first factor, influenced heavily by the average intra-task heart rate (L = 0.94) and by the approximately equal weights for the five simulated tasks (-0.53 less than L less than -0.36), reflected the fact that relatively high muscular strength and endurance, coupled with a near maximal aerobic capacity effort, were required to complete the simulated tasks. The battery of physical performance variables best predicting the first factor (R2 = 0.63) included maximal heart rate, sit-ups, grip strength, age, and submaximal oxygen pulse. The second factor (R2 = 0.39), most heavily loaded by the simulated rescue (L = 0.70) and chopping tasks (L = 0.42), appeared to represent an ability to complete all tasks quickly by exhibiting a resistance to fatigue brought on by the demands of the earlier tasks. The battery of physical performance variables best predicting the second factor included lean body weight, maximal heart rate, final treadmill grade, age, and percent fat. This study demonstrated that physiological factors related to the performance of occupational tasks can be identified and measured.

Adult↗
PubMed1973

Analysis of change.

Explore the source record for details and available documents.

Analysis of Variance↗