(13-11-12) Skeletal Muscle Mitochondrial Energetics Are Associated With Maximal Aerobic Capacity and Walking Speed in Older Adults.

Coen PM, Jubrias SA, Distefano G, Amati F, Mackey DC, Glynn NW, Manini TM, Wohlgemuth SE, Leeuwenburgh C, Cummings SR, Newman AB, Ferrucci L, Toledo FG, Shankland E, Conley KE, Goodpaster BH.
Source
Department of Health and Physical Activity, University of Pittsburgh, Trees Hall Rm 134D, Allequippa St. and Darragh St., Pittsburgh, PA 15260. [email protected].
Abstract
BACKGROUND:
Lower ambulatory performance with aging may be related to a reduced oxidative capacity within skeletal muscle. This study examined the associations between skeletal muscle mitochondrial capacity and efficiency with walking performance of the elderly participants.
METHODS:
Thirty-seven older adults (mean age 78 years; 21 men and 16 women) completed an aerobic capacity (VO(2) peak) test and measurement of preferred walking speed more than 400 m. Maximal coupled (State 3; St3) mitochondrial respiration was determined by high-resolution respirometry in saponin-permeabilized myofibers obtained from percutanous biopsies of vastus lateralis (n = 22). Maximal phosphorylation capacity (ATP(max)) of vastus lateralis was determined in vivo by (31)P magnetic resonance spectroscopy (n = 30). Quadriceps contractile volume was determined by magnetic resonance imaging. Mitochondrial efficiency (max ATP production/max O(2) consumption) was characterized using ATP(max) per St3 respiration (ATP(max)/St3).
RESULTS:
In vitro St3 respiration was significantly correlated with in vivo ATP(max) (r(2) = .47, p = .004). Total oxidative capacity of the quadriceps (St3*quadriceps contractile volume) was a determinant of VO(2) peak (r(2) = .33, p = .006). ATP(max) (r(2) = .158, p = .03) and VO(2) peak (r(2) = .475, p < .0001) were correlated with preferred walking speed. Inclusion of both ATP(max)/St3 and VO(2) peak in a multiple linear regression improved the prediction of preferred walking speed (r(2) = .647, p < .0001), suggesting that mitochondrial efficiency is an important determinant for preferred walking speed.
CONCLUSIONS:
Lower mitochondrial capacity and efficiency were both associated with slower walking speed within a group of older participants with a wide range of function. In addition to aerobic capacity, lower mitochondrial capacity and efficiency likely play roles in slowing gait speed with age.

Source: J Gerontol A Biol Sci Med Sci. 2012 Oct 9.

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