Impaired skeletal muscle efficiency potentially contributes to the age-related decline in exercise capacity and may explain the altered haemodynamic response to exercise in the elderly. Thus we examined whether (i) the ATP cost of contraction increases with age, and (ii) this results in altered convective O2 delivery to maintain microvascular oxygenation in the calf muscle. To this aim, we used an integrative experimental approach combining 31P-MRS (magnetic resonance spectroscopy), Doppler ultrasound imaging and NIRS (near-IR spectroscopy) during dynamic plantar flexion exercise at 40% of WRmax (maximal power output) in 20 healthy young and 20 older subjects matched for physical activity. The ATP cost of contraction was significantly higher in the old (7.2±4.1 mM/min per W) compared with the young (2.4±1.9 mM/min per W; P<0.05) and this was only significantly correlated with the plantar flexion WRmax value in the old subjects (r=−0.52; P<0.05). Even when differences in power output were taken into account, end-exercise blood flow (old, 259±168 ml/min per W and young, 134±40 ml/min per W; P<0.05) and convective O2 delivery (old, 0.048±0.031 l/min per W and young, 0.026±0.008 l/min per W; P<0.05) were greater in the old in comparison with the young subjects. In contrast, the NIRS oxyhaemoglobin, deoxyhaemoglobin and microvascular oxygenation indices were not significantly different between the groups (P>0.05). Therefore the present study reveals that, although the peripheral haemodynamic responses to plantar flexion exercise appear to be appropriate, the elevated energy cost of contraction and associated reduction in the WRmax value in this muscle group may play a role in limiting exercise capacity with age.
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Research Article|
December 08 2013
In vivo evidence of an age-related increase in ATP cost of contraction in the plantar flexor muscles
Gwenael Layec;
*Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT, U.S.A.
†Geriatric Research, Education and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, U.S.A.
Correspondence: Dr Gwenael Layec (email gwenael.layec@utah.edu).
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Joel D. Trinity;
Joel D. Trinity
*Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT, U.S.A.
†Geriatric Research, Education and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, U.S.A.
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Corey R. Hart;
Corey R. Hart
†Geriatric Research, Education and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, U.S.A.
‡Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, U.S.A.
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Seong-Eun Kim;
Seong-Eun Kim
§Department of Radiology and Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, U.S.A.
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Henderik Jonathan Groot;
Henderik Jonathan Groot
†Geriatric Research, Education and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, U.S.A.
‡Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, U.S.A.
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Yann Le Fur;
Yann Le Fur
¶Centre de Resonance Magnetique Biologique et Medicale, UMR CNRS 7339, Faculté de Médecine de Marseille, Marseille, France
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Jacob R. Sorensen;
Jacob R. Sorensen
†Geriatric Research, Education and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, U.S.A.
‡Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, U.S.A.
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Eun-Kee Jeong;
Eun-Kee Jeong
§Department of Radiology and Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, U.S.A.
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Russell S. Richardson
Russell S. Richardson
*Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT, U.S.A.
†Geriatric Research, Education and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT, U.S.A.
‡Department of Exercise and Sport Science, University of Utah, Salt Lake City, UT, U.S.A.
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Clin Sci (Lond) (2014) 126 (8): 581–592.
Article history
Received:
July 30 2013
Revision Received:
November 08 2013
Accepted:
November 14 2013
Accepted Manuscript online:
November 14 2013
Citation
Gwenael Layec, Joel D. Trinity, Corey R. Hart, Seong-Eun Kim, Henderik Jonathan Groot, Yann Le Fur, Jacob R. Sorensen, Eun-Kee Jeong, Russell S. Richardson; In vivo evidence of an age-related increase in ATP cost of contraction in the plantar flexor muscles. Clin Sci (Lond) 1 April 2014; 126 (8): 581–592. doi: https://doi.org/10.1042/CS20130442
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