期刊
JOURNAL OF PHYSIOLOGY-LONDON
卷 599, 期 12, 页码 3063-3080出版社
WILEY
DOI: 10.1113/JP281117
关键词
bioenergetics; metabolism; mitochondria; creatine kinase; glycolysis; oxidative phosphorylation; aerobic; ATP cost; ageing
资金
- ACSM Foundation Doctoral Student Research Grant from the American College of Sports Medicine Foundation
- University of Massachusetts Amherst Graduate School
- University of Massachusetts Amherst Institute for Applied Life Sciences
Muscle metabolic economy (ME) is similar in young and older adults during some isometric contractions, but age-related differences exist during dynamic contractions. Older adults have lower ME during dynamic contractions, despite similar muscle oxidative capacity and ATP flux compared to younger adults. This suggests a dissociation between cross-bridge activity and ATP utilization with age.
Key points We used 31-phosphorus magnetic resonance spectroscopy to quantify in vivo skeletal muscle metabolic economy (ME; mass-normalized torque or power produced per ATP consumed) during three 24 s maximal-effort contraction protocols: (1) sustained isometric (MVIC), (2) intermittent isokinetic (MVDCIsoK), and (3) intermittent isotonic (MVDCIsoT) in the knee extensor muscles of young and older adults. ME was not different between groups during the MVIC but was lower in older than young adults during both dynamic contraction protocols. These results are consistent with an increased energy cost of locomotion, but not postural support, with age. The effects of old age on ME were not due to age-related changes in muscle oxidative capacity or ATP flux. Specific power was lower in older than young adults, despite similar total ATP synthesis between groups. Together, this suggests a dissociation between cross-bridge activity and ATP utilization with age. Muscle metabolic economy (ME; mass-normalized torque or power produced per ATP consumed) is similar in young and older adults during some isometric contractions, but less is known about potential age-related differences in ME during dynamic contractions. We hypothesized that age-related differences in ME would exist only during dynamic contractions, due to the increased energetic demand of dynamic versus isometric contractions. Ten young (Y; 27.5 +/- 3.9 years, 6 men) and 10 older (O; 71 +/- 5 years, 5 men) healthy adults performed three 24 s bouts of maximal contractions: (1) sustained isometric (MVIC), (2) isokinetic (120 degrees center dot s(-1), MVDCIsoK; 0.5 Hz), and (3) isotonic (load = 20% MVIC, MVDCIsoT; 0.5 Hz). Phosphorus magnetic resonance spectroscopy of the vastus lateralis muscle was used to calculate ATP flux (mM ATP center dot s(-1)) through the creatine kinase reaction, glycolysis and oxidative phosphorylation. Quadriceps contractile volume (cm(3)) was measured by MRI. ME was calculated using the torque-time integral (MVIC) or power-time integral (MVDCIsoK and MVDCIsoT), total ATP synthesis and contractile volume. As hypothesized, ME was not different between Y and O during the MVIC (0.12 +/- 0.03 vs. 0.12 +/- 0.02 Nm(.)s(.)cm(-3)(.)mM ATP(-1), mean +/- SD, respectively; P = 0.847). However, during both MVDCIsoK and MVDCIsoT, ME was lower in O than Y adults (MVDCIsoK: 0.011 +/- 0.003 vs. 0.007 +/- 0.002 J(.)cm(-3)(.)mM ATP(-1); P < 0.001; MVDCIsoT: 0.011 +/- 0.002 vs. 0.008 +/- 0.002; P = 0.037, respectively), despite similar muscle oxidative capacity, oxidative and total ATP flux in both groups. The lower specific power in older than young adults, despite similar total ATP synthesis between groups, suggests there is a dissociation between cross-bridge activity and ATP utilization with age.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据