Biomedical subjects

Thomas Rowland

Publications and source records attributed to Thomas Rowland.

9 recordsLinked to original sources

PubMed2006

Cardiovascular responses to static exercise in boys: insights from tissue Doppler imaging.

Ventricular functional changes and mechanisms of the cardiovascular responses during static exercise have not been well delineated in children. In this study, Doppler echocardiographic techniques were utilized to assess cardiovascular adaptations to bilateral isometric leg extension at 30% maximal voluntary contraction for three minutes in a group of 14 healthy boys (mean age 10.2 +/- 1.5 years). Mean heart rate rose from 77 +/- 9 to 106 +/- 11 bpm, stroke volume fell from 59 +/- 9 to 52 +/- 7 ml, and cardiac output increased from 4.58 +/- 0.58 to 5.62 +/- 0.81 l min(-1) (P < 0.05). Mean arterial pressure rose from 86 +/- 7 to 109 +/- 9 mm Hg, with no significant change in peripheral vascular resistance. By tissue Doppler imaging markers, inotropic function improved by 59%, while lusitropic function increased 38%. These findings suggest that (1) cardiovascular responses to static leg extension in boys are similar to those in adult men, and (2) isometric leg extension triggers modest increases in both systolic and diastolic function.

Blood Pressure↗

PubMed2006

Tissue Doppler assessment of ventricular function during cycling in 7- to 12-yr-old boys.

PURPOSE: Studies utilizing submaximal supine exercise have indicated that tissue Doppler imaging (TDI) may be useful for assessing ventricular systolic and diastolic function during exercise and might offer a means of detecting patients with early myocardial dysfunction. This investigation of 14 healthy boys ages 7-12 yr was designed to assess measures of inotropic and lusitropic function during maximal upright cycle exercise. METHODS: Color tissue Doppler imaging (S and E' waves, indicative of systolic and diastolic function, respectively), stroke volume, and mitral peak inflow velocity (E wave) were recorded at rest and during a progressive upright cycle test to exhaustion. RESULTS: Values of TDI-S and TDI-E' were obtained at exhaustive exercise in all but one subject. Mean value of S rose 163% (3.8+/-1.2 to 10.0+/-2.5 cm.s), and average E' increased by 92% (-6.3+/-2.2 to -12.1+/-3.2 cm.s). No significant changes were observed in the ratio of E' to mitral peak flow velocity (E), suggesting that left ventricular end-diastolic pressure remained stable. CONCLUSIONS: These data indicate that measurement of TDI is feasible during maximal upright exercise, and velocities obtained may provide insights into ventricular systolic and diastolic functional capacity.

Bicycling↗

PubMed2005

Effect of pectus excavatum deformity on cardiorespiratory fitness in adolescent boys.

OBJECTIVE: To determine the magnitude of the effects of pectus excavatum deformity on endurance fitness and cardiorespiratory functional reserve in adolescent boys. DESIGN: Cross-sectional comparison of cardiac and ventilatory variables at rest and during a maximal cycle exercise test. SETTING: Pediatric exercise-testing laboratory. PARTICIPANTS: Twelve boys (mean +/- SD age, 14.1 +/- 1.8 years; age range, 11.8-18.0 years) with moderate-to-severe pectus excavatum deformity (mean +/- SD Haller index, 3.95 +/- 0.88) and 20 control boys (mean +/- SD age, 12.5 +/- 0.4 years; age range, 12.1-13.5 years) without musculoskeletal deformity. MAIN OUTCOME MEASURES: Endurance fitness (physical work capacity); respiratory rate, tidal volume, and minute ventilation; and cardiac output and stroke volume by Doppler echocardiography. RESULTS: Patients with pectus deformity had significantly lower endurance fitness than controls (mean +/- SD physical work capacity, 2.60 +/- 0.28 W . kg(-1) vs 3.11 +/- 0.45 W . kg(-1)) and reduced mean +/- SD values for maximal cardiac index (10.6 +/- 1.6 L . min(-1) vs 12.0 +/- 2.2 L . min(-1)) and peak tidal volume (3.02 +/- 0.27 mL . kg(-1) . 10(-2) vs 3.46 +/- 0.30 mL . kg(-1) . 10(-2)). However, considerable overlap was observed in these values between the 2 groups. CONCLUSIONS: As a group, boys with pectus excavatum deformity have lower endurance fitness than controls, and this is associated with reduced cardiac output and tidal volume responses to exercise. However, the wide variability of these measures makes it difficult to assign pectus deformity as a cause of exercise intolerance in individual patients.

Adolescent↗

PubMed2005

Evidence based physical activity for school-age youth.

OBJECTIVES: To review the effects of physical activity on health and behavior outcomes and develop evidence-based recommendations for physical activity in youth. STUDY DESIGN: A systematic literature review identified 850 articles; additional papers were identified by the expert panelists. Articles in the identified outcome areas were reviewed, evaluated and summarized by an expert panelist. The strength of the evidence, conclusions, key issues, and gaps in the evidence were abstracted in a standardized format and presented and discussed by panelists and organizational representatives. RESULTS: Most intervention studies used supervised programs of moderate to vigorous physical activity of 30 to 45 minutes duration 3 to 5 days per week. The panel believed that a greater amount of physical activity would be necessary to achieve similar beneficial effects on health and behavioral outcomes in ordinary daily circumstances (typically intermittent and unsupervised activity). CONCLUSION: School-age youth should participate daily in 60 minutes or more of moderate to vigorous physical activity that is developmentally appropriate, enjoyable, and involves a variety of activities.

Achievement↗

PubMed2004

Scaling or normalising maximum oxygen uptake to predict 1-mile run time in boys.

There is still considerable debate and some confusion as to the most appropriate method of scaling or normalizing maximum oxygen uptake (VO2max) for differences in body mass (m) in both adults and children. Previous studies on adult populations have demonstrated that although the traditional ratio standard VO2max (ml kg(-1) min(-1)) fails to render VO2max independent of body mass, the ratio standard is still the best predictor of running performance. However, no such evidence exists in children. Hence, the purpose of the present study was to investigate whether the ratio standard is still the most appropriate method of normalising VO2max to predict 1-mile run speed in a group of 12-year-old children (n=36). Using a power function model and log-linear regression, the best predictor of 1-mile run speed was given by: speed (m s(-1))=55.1 VO2max(0.986) m(-0.96). With both the VO2max and body mass exponents being close to unity but with opposite signs, the model suggest the best predictor of 1-mile run speed is almost exactly the traditional ratio standard recorded in the units (ml kg(-1) min(-1)). Clearly, reporting the traditional ratio standard VO2max, recorded in the units (ml kg(-1) min(-1)), still has an important place in publishing the results of studies investigating cardiovascular fitness of both children and adults.

Algorithms↗

PubMed2003

Cardiac response to progressive cycle exercise in moderately obese adolescent females.

PURPOSE: To assess cardiac responses to exercise and cardiac functional capacity in moderately obese adolescent females. METHODS: Thirteen healthy females (mean age 13.6 +/- 1.5 years) with a body mass index from 30 to 43 kg per m(2) underwent maximal cycle testing. Cardiac responses were measured by Doppler echocardiogram, and gas exchange variables were determined with open circuit spirometry. Data were analyzed by independent Student's t-tests. RESULTS: Peak oxygen uptake relative to height(3.0) was significantly greater in the obese (570 +/- 90 ml m(-3)) compared to the nonobese controls (485 +/- 60 ml m(-3)). This difference was explained by a higher peak cardiac output (4.50 +/- 1.06 L m(-3) vs. 3.81 +/- 58 L m(-3)) and stroke volume (24 +/- 5 ml m(-3) vs. 19 +/- 3 ml m(-3)) in the obese. Maximal cardiac index was similar in the two groups. There was no evidence of myocardial dysfunction during exercise in either group. CONCLUSIONS: Low aerobic fitness in obese adolescents as indicated by depressed peak VO(2) per kg body mass and limited endurance performance does not reflect decreased cardiac functional capacity.

Adolescent↗

PubMed2002

Left ventricular response to dynamic exercise in young cyclists.

PURPOSE: The purpose of this study was to compare cardiac physiological and dimensional responses to exercise in highly trained young male cyclists (mean age 13.7 +/- 1.0 yr) with those of nontrained boys. METHODS: Ventricular systolic and diastolic dimensions were measured by two-dimensional echocardiography, and stroke volume was estimated by Doppler echocardiography during a progressive maximal upright cycle test. RESULTS: At rest, the cyclists demonstrated larger left ventricular dimensions relative to body size than the nonathletes. Maximal stroke index and cardiac index were significantly greater in the cyclists. The pattern of stroke volume response to exercise was similar in the two groups, with an early rise and then plateau to exhaustion. Left ventricular diastolic dimension increased slightly at onset of exercise and then gradually declined as workload increased in both groups. CONCLUSION: Factors responsible for the greater maximal stroke volume in young endurance athletes involve those variables that contribute to resting left ventricular diastolic filling (preload).

Adolescent↗

PubMed2002

Doppler echocardiography for the estimation of cardiac output with exercise.

Insights into both normal and pathological cardiac responses to exercise have been hampered by lack of a safe, accurate, feasible means of estimating cardiac output (Q) during high-intensity and maximal exercise. Doppler ultrasound noninvasively measures blood velocity as it exits the heart and can be performed during exhaustive exercise without interference of the subject or need for steady state. From the product of aortic blood velocity and cross-sectional area of the aorta, stroke volume (SV) can be calculated. Despite these advantages of the Doppler technique, a number of potential sources of error have raised concern regarding the accuracy of this method. These include transducer angulation, change in aortic cross-sectional area during exercise, turbulence and alteration of a flat velocity profile in the aorta with increased Q, and uncertainties regarding the proper location for measurement of aortic outflow area. The magnitude of the influence of these potentially confounding variables on the accuracy of SV measurements determined by the Doppler technique is unknown. Estimates of both construct and concurrent validity suggest that the overall error may be small. Test-retest studies have indicated a high level of reliability with this technique.

Aorta↗

PubMed2000

Cardiac dynamics during upright cycle exercise in boys.

Insight into the cardiac responses to exercise necessitates an understanding of both physiological data and cardiac dimensional changes. This study was designed to assess cardiovascular alterations during progressive upright cycle exercise in ten healthy 10-12-year-old boys. Doppler echocardiography was used to estimate stroke volume, and 2-dimensional echocardiography was used to evaluate changes in left ventricular systolic and diastolic dimensions. Test-retest reproducibility was high for both techniques. Mean peak stroke index and cardiac index values were 62 +/- 12 ml m(-2) and 11.79 + 2.62 L min(-1) m(-2), respectively. Stroke volume rose by 40% over resting values with early exercise (50 watt work load), but beyond moderate intensities (approximately 50% VO(2)max) little change was seen. The left ventricular diastolic dimension rose slightly at the onset of exercise and then declined slowly. A progressive and more precipitous decline was observed in systolic dimension, resulting in an increase in shortening fraction from 29% to 47%. This was accompanied by a dramatic fall in peripheral vascular resistance from 13.9 to 8.0 units at the onset of exercise. These findings suggest a close matching of increases in heart rate and systemic venous return and imply a significant role of peripheral pump function in the circulatory responses to exercise in children. The cardiac dynamics observed in this study mimic those previously described in adult subjects. Am. J. Hum. Biol. 12:749-757, 2000. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗