This analysis indicates that the current body of literature does not support a de facto decrease of in vivo muscle oxidative capacity in old age .
The heterogeneity of study results and identification of significant moderators provide clarity regarding apparent discrepancies in the literature , and indicate the importance of accounting for these variables when examining purported age-related differences in muscle oxidative capacity
Despite intensive efforts to underst and the extent to which skeletal muscle mitochondrial capacity changes in older humans , the answer to this important question remains unclear .
To determine what the preponderance of evidence from in vivo studies suggests , we conducted a systematic review and meta- analysis of the effects of age on muscle oxidative capacity as measured noninvasively by magnetic resonance spectroscopy .
A secondary aim was to examine potential moderators contributing to differences in results across studies , including muscle group , physical activity status , and sex .
Oxidative capacity and ageing in human muscle.
This study determined the decline in oxidative capacity per volume of human vastus lateralis muscle between nine adult ( mean age 38.8 years ) and 40 elderly ( mean age 68.8 years ) human subjects ( age range 25 - 80 years ) . We based our oxidative capacity estimates on the kinetics of changes in creatine phosphate content ( [ PCr ] ) during recovery from exercise as measured by (31)P magnetic resonance ( MR ) spectroscopy . A matched muscle biopsy sample permitted determination of mitochondrial volume density and the contribution of the loss of mitochondrial content to the decline in oxidative capacity with age . The maximal oxidative phosphorylation rate or oxidative capacity was estimated from the PCr recovery rate constant ( k(PCr ) ) and the [ PCr ] in accordance with a simple electrical circuit model of mitochondrial respiratory control . Oxidative capacity was 50 % lower in the elderly vs. the adult group ( 0.61 + /- 0.04 vs. 1.16 + /- 0.147 mM ATP s(-1 ) ) . Mitochondrial volume density was significantly lower in elderly compared with adult muscle ( 2.9 + /- 0.15 vs. 3.6 + /- 0.11 % ) . In addition , the oxidative capacity per mitochondrial volume ( 0.22 + /- 0.042 vs. 0.32 + /- 0.015 mM ATP ( s % ) ( -1 ) ) was reduced in elderly vs. adult subjects . This study showed that elderly subjects had nearly 50 % lower oxidative capacity per volume of muscle than adult subjects . The cellular basis of this drop was a reduction in mitochondrial content , as well as a lower oxidative capacity of the mitochondria with age
This analysis indicates that the current body of literature does not support a de facto decrease of in vivo muscle oxidative capacity in old age .
The heterogeneity of study results and identification of significant moderators provide clarity regarding apparent discrepancies in the literature , and indicate the importance of accounting for these variables when examining purported age-related differences in muscle oxidative capacity
Despite intensive efforts to underst and the extent to which skeletal muscle mitochondrial capacity changes in older humans , the answer to this important question remains unclear .
To determine what the preponderance of evidence from in vivo studies suggests , we conducted a systematic review and meta- analysis of the effects of age on muscle oxidative capacity as measured noninvasively by magnetic resonance spectroscopy .
A secondary aim was to examine potential moderators contributing to differences in results across studies , including muscle group , physical activity status , and sex .