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Biomedical subjects

K T Francis

Publications and source records attributed to K T Francis.

At least 19 recordsLinked to original sources
PubMed1991

Physiological effects of wearing mouthguards.

Mouthguards are considered by most authorities to be an essential part of equipment for players participating in body-contact sports. Mouthguards provide excellent dental protection but not all players use them, complaining of breathing difficulties and problems with speaking. Although information exists concerning dental trauma and mouth protector use, there are no reported data that quantify the physiological effects of wearing mouthguards. The purpose of this study was to measure the ventilatory and gas exchange effects of wearing a mouthguard. Ten healthy men and seven women aged 20-36 years (mean(s.d.) 27.2(5.2) years) were used as subjects. Forced expiratory air volume at 1 s (FEV1) and peak expiratory flow rates (PEF) were measured on each subject while wearing either no mouthguard or one of three different over-the-counter mouthguards including one maxillary (mouthguard 1) and two different bimaxillary guards (mouthguards 2 and 3). To determine the effects of wearing each of the mouthguards during exercise, oxygen consumption (VO2) was measured while exercising on a cycle ergometer for 5 min at a light and heavy workload. An ANOVA of repeated measures was used to determine statistical differences. In each case, the wearing of a mouthguard significantly (P less than 0.05) reduced FEV1 and PEF in comparison with no mouthguard. FEV1 was reduced 8% with mouthguard 1, and 12% and 14% with mouthguards 2 and 3 respectively. PEF was reduced by 7, 15 and 15.8% with mouthguards 1, 2 and 3 respectively. The wearing of the different mouthguards did not significantly change VO2 while exercising at the lower work level whereas VO2 was significantly ( P < 0.05) reduced at the heavier workload. This surprising reduction in VO2 during heavy exercise may be due to a 'pursed-lip' type of breathing which has been shown to decrease CO2 tension, increase oxygenation and exercise tolerance. It can be concluded that although mouthguards may be perceptably uncomfortable and restrict forced expiratory air flow, they appear to be beneficial in prolonging exercise by improving ventilation and economy.

Adult↗
PubMed1991

Physical activity and fitness assessment.

Physical inactivity is a risk factor for the development of atherosclerosis. Members of a state chapter of the American Academy of Pediatrics were assessed about their practice behaviors and knowledge related to physical activity and fitness assessments. During health supervision evaluations 19% obtained a physical activity history and 7% measured a heart rate response to exercise. When assessing physical fitness 24% obtained an activity history which included kind, intensity, duration and frequency. 64% limited their physical fitness evaluation to an inspection of general appearance and weight, while 1% used a bicycle ergometer or treadmill, 4% used a step-test and 10% ran a child in place. Only 42% used the information to make recommendations about physical activity. 75% were not familiar with ACSM or AHA recommendations about exercise. Barriers cited to increasing physical activity and fitness assessments included lack of physician time, office space, staff time, and physician training. This survey demonstrates the need for increasing the awareness level of pediatricians about the role of exercise in preventing CHD and the need to incorporate such evaluations into their routine practice.

Alabama↗
PubMed1990

Body-composition assessment using underwater weighing techniques.

Health care professionals recommend that assessment of body composition be included as a part of an adult fitness program. Underwater weighing, based on Archimedes' principle, is the most valid technique for assessment of percentage of body fat and lean tissue in a clinical setting. This article presents a computer program written in BASIC that performs all of the decision-making calculations and provides the user with a tabular and a graphical summary of current body composition in addition to recommendations for changes in body composition that will enhance the subject's health.

Adipose Tissue↗
PubMed1990

A new single-stage step test for the clinical assessment of maximal oxygen consumption.

Assessments of cardiorespiratory fitness are important in any health-assessment program or routine involving variables that may be influenced by an individual's level of physical fitness or ability to sustain an exercise program. Recently, a new single-stage step test was introduced that uses a height-adjustable platform to normalize the height of stepping for individuals of varying stature. This computer program is designed to simplify the use of this test and to facilitate the implementation in clinical environments where equipment or time is limited, yet accuracy and validity are essential.

Adolescent↗
PubMed1989

The relationship between anaerobic threshold and heart rate linearity during cycle ergometry.

Recent studies have demonstrated there is a definitive deflection in the heart rate response to incremental velocity work that coincides with the anaerobic threshold. These studies were conducted with elite athletes who performed the specific activities in which they were trained. The purpose of this study was to determine if the same relationship in heart rate and ventilatory response to increasing velocity was evident in nine untrained healthy subjects aged 22 to 36 years performing leg ergometry under controlled laboratory conditions. All subjects began pedaling at 50 rpm with an initial power output of 100 W. Pedaling rates were increased by 5 rpm every 30 s. This increment was equivalent to a power increase of 11.1 W. The subjects cycled to the point of exhaustion or until they could no longer maintain the pedaling speed at the higher velocities. Heart rate and expiration gases were collected at 30-s intervals. The results indicated that the heart rate and ventilatory response to increasing velocity as previously reported under field conditions does not exist under laboratory conditions. While there was a definitive and statistically significant inflection in the ventilatory response to increasing velocity, heart rate remained linear. Therefore, caution should be used when determining the anaerobic threshold from the single measure of heart rate response.

Adult↗
PubMed1988

Principles of clinical decision making--an introduction to decision analysis. A special communication.

Physical therapists are becoming increasingly aware of the growing complexity of clinical decision making. The level of understanding and the sophistication necessary to diagnose, treat, and manage medical problems has increased concomitantly with the increase in new diagnostic and therapeutic procedures. The purposes of this special communication are to discuss the principles of clinical decision making and to present a hypothetical situation to illustrate a decision analysis process for choosing among alternative treatment protocols.

Cryotherapy↗
PubMed1987

An anatomical model to determine step height in step testing for estimating aerobic capacity.

Physical fitness has been reported to be inversely related to coronary heart disease and other health related problems. One of the most valid means of assessing physical fitness is the test of aerobic capacity. Aerobic capacity is the greatest rate at which the body can consume oxygen and represents the most efficient integration of the various physiological processes which make up the oxygen transport system. However, direct measurement of aerobic capacity requires sophisticated laboratory equipment, and is adversive to subjects. Step tests are widely used to estimate aerobic capacity. Because the biomechanical efficiency and work rate is determined by step height, accommodation of step height to the subject's statute height should provide a better estimation of aerobic capacity. A hip angle of 73.3 degrees, when stepping, was found to give the best relationship of recovery heart rate of a step test to direct measurement of aerobic capacity. Using 73.3 degrees, the following equations were developed for determining the stepping height when using the step test: Hf = 0.189 Ih and Hf = 0.192 Ih for females and males respectively, where hf is the step height and Ih is the statute height of the subject. A correlation coefficient (r) of 0.93 was calculated between various hip angles and calculated foot height of 182 observations of 47 females while a correlation coefficient (r) of 0.96 was calculated from 208 observations of 53 males. Using these equations to determine step height, measurement of 30 females showed a mean hip angle of 73.3 degrees +/- 2.2 and measurement of 30 males showed a mean hip angle of 73.3 degrees +/- 2.1.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1987

Fitness assessment using step tests.

The current interest in physical conditioning has resulted, to a large degree, from the desire of many individuals to improve their ability to sustain physical activity without fatigue. To safely participate in a conditioning program, an individual should first learn his initial fitness level. The step test is simple and accurate and is found in many laboratories and physicians' offices. The physical exercise should last long enough to adjust the individual's circulation and respiration to that of the level of exercise, usually three to four minutes. In addition, the work rate should be sufficiently stressful to result in a steady-state heart rate greater than 120 and less than 170 beats per minute. For most untrained adolescents and adults, this intensity of effort can be achieved using a single-stage step test of 16 in and a stepping frequency of 20 to 25 steps per minute. The single-stage step test can be used to assess more fit individuals simply by increasing stepping frequency (raising the height above 16 in is not recommended because of premature leg fatigue in heavy individuals and those of short stature). Multistage step tests are based on the same requirements as those of the single-stage test except that the multistage test provides a gradual increase in work rate and a termination level that often exceeds the exertional level experienced in a single-stage test. The multistage test can be used not only for providing reliable measurements of cardiovascular fitness but also, with the appropriate equipment, for the diagnosis of cardiovascular abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise Test↗
PubMed1979

Psychologic correlates of serum indicators of stress in man: a longitudinal study.

Correlations between serum uric acid, cortisol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol and psychometric indices of stress--namely, anxiety, hostility, and depression--were investigated in 20 students over a 2 1/2 month academic quarter. There were three peak periods of stress, with two occurring during midterm and final exams. The observed changes in serum cortisol were highly correlated with changes in anxiety and depression. Serum uric acid was significantly depressed during the first half of the quarter, but returned to control levels after midterm exams. Serum cholesterol and the LDL cholesterol subfraction were significantly elevated above control levels and remained elevated throughout the quarter after the first day of classes. Absolute levels of HDL cholesterol varied little throughout the quarter, however, the ratio of HDL cholesterol/total cholesterol was significantly depressed twice in the quarter, each time following approximately 10 days after the peak period of stress.

Adolescent↗
PubMed1979

Dantrolene inhibition of the hepatic mixed function oxidase system.

The effect of dantrolene sodium, a skeletal muscle relaxant, on the hepatic MFO system has been investigated. The dantrolene produces a dose related inhibition of the system. Single doses of 100 mg/kg and accumulative doses up to 125 mg/kg prolong pentobarbital sleeping time and decrease the rate of aminopyrine N-demethylation without altering cytochrome P450 content. However, single doses of 400 mg/kg and accumulative doses of 500 mg/kg do cause a decrease in cytochrome P450 content as part of the dantrolene induced inhibition of the hepatic MFO system.

Aminopyrine N-Demethylase↗
PubMed1979

Effect of water and electrolyte replacement during exercise in the heat on biochemical indices of stress and performance.

Eight healthy young men exercised on alternate days in a warm, humid environment (32 degrees C, 65% RH) at 50% VO2 max for 2 h while receiving a water supplement (WS), glucose-electrolyte solution (ES), or no fluid supplement (NS). The average weight loss after 2 h of exercise and NS was 2.44 kg with a resultant plasma volume decrease of 17%. This acute period of exercise with no fluid replacement elicited significant increments in serum levels of cortisol, dopamine-B-hydroxylase and uric acid. Alternatively, exercise in the heat for the same duration with water or electrolyte supplement failed to effect significant alterations in any of these physical or biochemical factors compared to preexercise levels. Heart rates under the influence of heat stress and exercise with NS averaged 18% higher at each time period studied compared with WS or ES.

Adult↗
PubMed1978

Effect of exercise in the heat on plasma renin and aldosterone with either water or a potassium-rich electrolyte solution.

Information concerning the renin-angiotension-aldosterone system during physical exercise in the heat with adequate fluid and/or electrolyte supplement is lacking. The present study was intended to describe the changes in renin activity and serum aldosterone, serum sodium, and serum potassium in subjects receiving water or a potassium-rich electrolyte solution while exercising (50% VO2 max) for 120 min in a warm environment (32 degrees C, 50% relative humidity). This study shows that, in subjects receiving the electrolyte supplement, serum potassium is elevated slightly during the exercise period whereas serum sodium is unchanged from preexercise levels without the electrolyte supplement. Plasma renin and aldosterone levels were significantly reduced in the subjects receiving the electrolyte supplement compared to subjects receiving only water. The ingestion of the electrolyte supplement replaced 42% of the sodium and 100% of the potassium lost by way of sweat and urine while exercising in the heat.

Adolescent↗
PubMed1978

The effect of dantrolene sodium on the efflux of Ca45 from rat heavy sarcoplasmic reticulum.

The effect of dantrolene on calcium (Ca2+) efflux was studied using SR vesicles isolated at 8,000 X G from rat skeletal muscle. Dantrolene concentrations of 4 to 9 X 10(-5) M suppressed the efflux of Ca45 from the isolated vesicles in a dose-related way during the first 5 minutes of incubation. The residual Ca2+ in the sarcotubular vesicles was inversely related to the dantrolene concentrations of 4, 6 and 9 X 10(-5) M. The addition of 10mM caffeine to the efflux media offset the suppressive effects of the lower concentrations of dantrolene on Ca2+ efflux. Only dantrolene concentrations of 9 X 10(-5)M resulted in significant retention of Ca2+ in the vesicles in the presence of 10mM caffeine.

Animals↗
PubMed1977

Reaction of tetrahydrofolic acid with cyanate from urea solutions: formation of an inactive folate derivative.

Liver extracts prepared in 6 M urea contain significantly less microbiologically assayable folates than extracts prepared in hot 1% ascorbate. The possibility that inactive folate derivatives are formed by reaction with the cyanate present in the urea solution was investigated. Doubly labeled 2-14C, 3',5',9(n)-3H tetrahydrofolic acid reacted under hydrogen with sodium cyanate gave a compound which, after acidification to remove excess cyanate, shows a single UV absorbing peak at 285 nm. The 14C/3H ratios of starting material and product were the same. Reaction of 14C urea with nonradioactive tetrahydrofolic acid yielded the 14C labeled derivative. The compound does not support Lactobacillus casei growth. It is postulated that folate inactivation in cyanate or thiocyanate treated patients and in uremic patients may have clinical significance.

Animals↗