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Clinical Science (2003) 104, (267–273) (Printed in Great Britain)

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Short-term aerobic training and circulatory function in women: age and hormone-replacement therapy

Sonia KATYAL*, Michael FREEMAN†, Judith A. MILLER‡ and Scott G. THOMAS*§

*Graduate Department of Rehabilitation Science, University of Toronto, 256 McCaul Street, Toronto, ON, Canada M5T 1W5, †St Michael's Hospital, 30 Bond Street, Toronto, ON, Canada M5B 1W8, ‡Toronto General Hospital, 200 Elizabeth Street, Toronto, ON, Canada M5G 2C4, and §Department of Physical Therapy, Rehabilitation Sciences Building, University of Toronto, 500 University Avenue, Toronto, ON, Canada MG5 1V7

Key words: aging, blood volume, gender, hormone replacement status, stroke volume.

Abbreviations: ANCOVA, analysis of covariance; a–O₂(diff), difference between arterial and mixed venous oxygen content; BP, blood pressure; BV, blood volume; HRT, hormone-replacement therapy; PV, plasma volume; STAT, short-term aerobic training; O_2max, peak oxygen uptake.

Correspondence: Dr Scott G. Thomas, at Faculty of Physical Education and Health, 55 Harbord St, Toronto, Canada M5S 2W6 (e-mail scott.thomas@utoronto.ca).

The physiological basis of training responses in women, and particularly older women, is not well understood. Short-term aerobic training (STAT) was used to probe the effects of age and hormone-replacement therapy (HRT) on women's ability to rapidly change peak uptake (O_2max), plasma volume and cardiac function. A total of 39 females participated in the STAT programme: 15 younger (Y; aged 19–29 years), 12 postmenopausal women undergoing HRT and 12 non-medicating postmenopausal (PM) women (aged 60–75 years). Training consisted of ten sessions of cycling over a 2-week period, which progressed in duration from 20 to 60min and in intensity from 60–75% of maximum heart rate. Plasma volume (PV; as determined by Evan's Blue dye dilution), O_2max (cycle ergometry) and cardiac function (radionuclide ventriculography) were analysed using analysis of covariance or repeated measures ANOVA. All groups demonstrated similar increase in O_2max (Y, 13%; PM, 17%; HRT, 13%), but without a significant change in left-ventricular ejection fraction and diastolic function or volumes during supine exercise. PV expansion was observed among the Y group (7%; P<0.05) but not the PM group (2%; P>0.05) or women undergoing HRT (1%; P>0.05). Age and hormone-replacement status did not affect the magnitude of O_2max change. This study suggests that STAT improves O_2max, independent of central adaptations.

Received 9 July 2002/25 October 2002; accepted 29 November 2002

The Biochemical Society and the Medical Research Society © 2003