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Biomedical subjects

L N Cunningham

Publications and source records attributed to L N Cunningham.

12 recordsLinked to original sources
PubMed1992

The influence of diabetes mellitus on cardiovascular function in children and adolescents.

Early manifestations of non-atherosclerotic cardiomyopathy, a recognized complication of diabetes in adults, have been suggested to contribute to depressed levels of aerobic fitness described in children and adolescents with this disease. This study measured components of aerobic fitness and cardiovascular function during maximal cycle ergometer exercise in 11 insulin-dependent diabetic boys aged 10.2-16.5 years. Mean duration of diabetes was 4.5 years. Eleven non-diabetic subjects matched for age, body size, and regular physical activity served as controls. No differences in maximal oxygen uptake or heart rate were observed between the two groups, nor were any significant differences recorded in submaximal stroke volume, cardiac output, heart rate, and pressure-rate product. This study failed to reveal any evidence of functional myocardial disease in children and young adolescents with diabetes, suggesting that manifestations of diabetic cardiomyopathy should not be expected during the pediatric years. Moreover, these findings indicating normal cardiovascular function in young diabetic subjects imply that regular levels of habitual physical activity are more likely to affect aerobic fitness in these patients rather than influences of the diabetic state itself.

Adolescent↗
PubMed1992

Oxygen uptake plateau during maximal treadmill exercise in children.

The leveling of oxygen uptake at high work loads has been utilized to define maximal VO2 during progressive exercise testing. Exercise studies in children have indicated, however, that a VO2 plateau can commonly be demonstrated in less than one half of subjects. To examine the potential contributions of subject effort, aerobic fitness, and nonaerobic performance to this variability, 15 children ages 7 to 10 years performed progressive treadmill walking to exhaustion with a ramp protocol. The VO2 plateau was defined as a change in VO2 during the final minute of exercise less than 2 SD below the mean of increases between the previous 4 to 5 submaximal minutes. Five subjects (33.3 percent) demonstrated a plateau. No significant differences in mean peak VO2, heart rate, or respiratory exchange ratio were observed between plateau and nonplateau groups. Testing results of speed (50-yard sprint) and leg power (vertical jump) were also similar. These findings suggest that following: (1) subject effort, aerobic fitness, and nonaerobic factors do not explain the presence or absence of a VO2 plateau during exercise testing of children; and (2) a VO2 plateau should not be used as a requirement for defining VO2max during treadmill testing in this age group.

Child↗
PubMed1990

Relationship of running economy, ventilatory threshold, and maximal oxygen consumption to running performance in high school females.

The purpose of the study was to relate three determinants of distance running success, (a) maximal oxygen consumption (VO2max), (b) ventilatory threshold (VT), and (c) running economy (RE), to actual running time in a 5-km race (ART). Twenty-four female runners (M age = 15.9 years) from four high school teams that competed at the Massachusetts All-State 5-km Cross Country Championship Meet and placed 1st, 7th, 19th, and 20th were tested in the laboratory. The mean VO2max of these runners was 61.7 ml.kg-1.min-1, HRmax 201 b.min-1, VEmax 100 L.min-1, and RER 1.10. The VT occurred at 79% of the VO2max, and HR of 184 b.min-1 (92% of HRmax). The velocity at VT (vVT) and velocity at VO2max (vVO2max) was correlated with ART, r(22) = .78 and .77 (p less than .001), respectively. The VO2 at VT and at maximal exercise was correlated with ART by r(22) = -.66 and -.69 (p less than .001), respectively. The VO2 at 215 m.min-1 (8 mph) was poorly related to ART, r(22) = -.05, p greater than .05. It was concluded that either of the derived variables vVT and vVO2max appear to explain significant variation in distance running performance among adolescent female cross country runners.

Adolescent↗
PubMed1990

Acute and chronic effects of exercise using an Exercycle in healthy, untrained adults.

This study examined three factors related to exercise with an Exercycle, a motordriven upper and lower body exercise machine. We examined the effects of Exercycle training on peak oxygen consumption (VO2), peak heart rate, peak minute ventilation, and peak respiratory exchange ratio. We compared the physiologic responses to graded exercise between the Exercycle and a standard lower extremity (LE) cycle ergometer. We also compared the difference in training responses between male and female subjects. A 6-week cardiorespiratory training program was completed by 20 healthy untrained adults (9 male, 11 female), aged 18 to 53 years. Pretraining and posttraining testing was completed on the Exercycle and on an LE cycle ergometer using a graded protocol. Absolute peak VO2 improved by 14% for men and by 7% for women after training based on Exercycle testing and by 6% for both men and women based on LE cycle ergometer testing. The posttraining submaximal heart rates were lower at any given absolute peak VO2 level for the Exercycle but not for the LE cycle ergometer. Exercycle testing revealed a larger peak VO2 than did LE cycle ergometer testing for both genders. The Exercycle appears to be effective for promoting cardiorespiratory fitness in healthy, untrained adults. The authors found comparable submaximal physiologic responses to graded exercise between the Exercycle and the LE cycle ergometer.

Adaptation, Physiological↗
PubMed1989

Urological manifestations of the popliteal pterygium syndrome.

We report a case of the popliteal pterygium syndrome resulting in abnormalities of the external genitalia and testicular ectopia. Management included bilateral orchiopexy and complex genitoplasty. Pterygia represent errors in development that manifest as webs across joints and can result in anomalies of the external genitalia. The genitourinary aspects of the popliteal pterygium syndrome and their management are discussed.

Abnormalities, Multiple↗
PubMed1989

Beta-endorphin activity and hypercapnic ventilatory responsiveness after marathon running.

To investigate the hypothesis that endurance exercise may lead to a decrease in ventilatory chemosensitivity as possibly mediated by an increase in endogenous beta-endorphins, we measured hypercapnic ventilatory responsiveness (HCVR) and circulating beta-endorphin immunoreactivity in six runners before and after a marathon (42.2 km) race and after administration of 10 mg iv naloxone. Similar testing was performed at identical time periods on the day before the marathon as control data. On each occasion, HCVR was measured twice 15 min apart, and the mean value was used for analysis. Six active (training distance 50-104 km/wk) and experienced (no. of marathons completed, 1-25) runners participated in the study. There were no significant changes in beta-endorphin activity or HCVR on the control day. All runners experienced a rise in beta-endorphin activity from premarathon (21.3 +/- 16.0 pg/ml) to immediate postmarathon (89.6 +/- 84.9 pg/ml) values (P less than 0.05). However, HCVR showed no significant change at any of the three testing periods on the marathon day. To investigate whether a time delay may have affected the lack of response to naloxone, additional testing was performed in five subjects, except that 10 mg iv naloxone was given within 10 min after completion of the marathon, and then HCVR was measured. Although there was a greater than fourfold increase in beta-endorphin immunoreactivity after the marathon, there was no significant change in HCVR after naloxone administration. We conclude that natural increases in endogenous beta-endorphin activity associated with marathon running do not modulate central chemosensitivity.

Adult↗
PubMed1989

Massive hemorrhage secondary to metastatic testicular carcinoma.

Massive bleeding secondary to metastatic foci of testicular carcinoma is a rare finding. Two cases of metastatic testicular carcinoma in which massive intraabdominal and gastrointestinal hemorrhage occurred are reported. The first patient, who had metastasis to the duodenum and stomach, first underwent surgery because of the concern that chemotherapy might result in rapid tumor necrosis and bowel perforation. The bleeding was controlled, postoperative chemotherapy was administered, and the patient was alive 15 months after chemotherapy. In the second case, in which metastasis was to the liver and lungs, aggressive chemotherapy was begun because of the patient's poor pulmonary status. Three days later, the patient began to hemorrhage. Operative and massive resuscitative measures failed, and the patient died shortly after surgery.

Adolescent↗
PubMed1986

Aging and exercise performance.

Diverse physiologic changes occur in the oxygen transport system during the aging process. Physical performance and VO2max decline with age, but the changes may be attenuated by exercise training. Increased ventilation is required during exercise in order to compensate for reduced efficiency of gas exchange. Cardiovascular alterations include prolonged duration of myocardial contraction, a slightly reduced left ventricular ejection fraction during exercise, decreased heart rate during both submaximal and maximal exercise, and attenuation of myocardial response to beta-adrenergic stimulation. Cardiac output during exercise can be maintained in the elderly owing to a greater dependence on ventricular filling. Appropriate exercise training leads to enhanced efficiency of the lungs, heart, and skeletal muscles. These physiologic benefits contribute to an increase in functional capacity and an enhanced sense of well-being. Exercise testing is recommended for individuals who have cardiorespiratory symptoms and for those at risk for the development of coronary artery disease. Reasonable goals for an aerobic training program are continuous activity for 30 minutes at a moderate intensity of exertion at least 3 days per week. The intensity of exercise should be based on a prescribed training heart rate. The exercise prescription should be individualized and should incorporate one or more activities for optimal enjoyment and compliance. Opportunities and facilities for indoor exercise are important during inclement weather. Regular physical exercise is important at any age!

Aged↗
PubMed1985

Validity of "generalized" equations for body composition analysis in male athletes.

Equations by Durnin and Womersley [(D-W), Br. J. Nutr. 32:77, 1974], Jackson and Pollock [(J-P), Br. J. Nutr. 40:497, 1978], and Lohman [(L), Human Biol., 53:181, 1981] for estimating body density (BD) purportedly overcome the problem of specificity by accounting for age and/or the curvilinear relationship between skinfolds (SF) and BD. Their equations were validated on 265 male athletes against percent fat measured by underwater weighing [(UWW); mean +/- SD = 9.2 +/- 4.4%]. Equations by Sloan [(S), J. Appl. Physiol. 23:311, 1967], Katch and McArdle [(K-M), Human. Biol. 45:445, 1973], and Forsyth and Sinning [(F-S), Med. Sci. Sports 5:174, 1973] were included as "linear regression models" to compare to the curvilinear models of J-P, D-W, and L. Differences between UWW and estimated mean values ranged from -1.1 to +5.9%; correlations ranged from 0.58 to 0.85; SEE ranged from +/- 2.41 to +/- 3.61% and total error (E) ranged from 2.38 to 6.97%. The seven D-W equations overestimated mean percent fat by from 3.9 to 5.9%. The K-M, S, and L equations overestimated by 1.3, 0.5, and 1.7%, respectively. The F-S equations overestimated by 2.4 to 3.8%. Of the 21 equations evaluated, only 3 by J-P gave estimates not significantly different from UWW percent fat. Regression analyses of the relationship between UWW (y) and estimated (x) percent fat values from those equations were: y = 1.037x - 0.08 +/- 2.38, E = 2.38, r = 0.84; 0.869x + 1.36 +/- 2.45, E = 2.51, r = 0.83; 1.107x - 1.14 +/- 2.51, E = 2.53, r = 0.82.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMedDate not supplied

Hormone-fuel metabolism during exercise of insulin-dependent diabetic patients treated with an artificial B-cell unit.

The effects of restoration of glucose homeostasis on hormone-fuel metabolism of diabetic individuals during exercise (40% maximal O2 consumption) were determined by monitoring fuel oxidation rates and levels of substrates and hormones in nine normal subjects and five insulin-dependent diabetic patients while on conventional insulin therapy and after 3 days on artificial B-cell directed glucose regulation. The non-protein respiratory quotient (npRQ) and carbohydrate oxidation rate of the conventionally-treated diabetic subjects (0.908 +/- 0.002 and 538 +/- 5 mg/m2.min) were lower and the lipid oxidation rate (101 +/- 2 mg/m2.min) was significantly higher than those of the normal group during the bicycle exercise (101 +/- 2 mg/m2.min) was significantly 70 +/- 4 mg/m2.min, respectively). After 3 days of artificial B-cell insulin therapy, the npRQ and carbohydrate oxidation rate of the exercising diabetics significantly increased to 0.965 +/- 0.004 and 693 +/- 13 mg/m2.min, while the lipid oxidation rate declined to 39 +/- 4 mg/m2.min (p less than 0.001). We conclude that artificial B-cell directed insulin therapy increases carbohydrate oxidation and decreases lipid oxidation in exercising insulin-dependent diabetic subjects. However, if restoration of metabolic response identical to that of exercising normals is desired, the excess in carbohydrate oxidation coincident with elevated blood lactate and pyruvate levels suggest that the artificial B-cell therapy may not have been completely optimal, probably due to the hyperinsulinization of the diabetic patients.

Adult↗