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 .
The relationship between creatine kinase kinetics and exercise intensity in human forearm is unchanged by age.
Using (31)P magnetic resonance spectroscopy , creatine kinase ( CK ) reaction kinetics was assessed in the forearm flexor digitorum profundus muscle of healthy young ( n = 11 , age 34.7 + /- 5 yr ) and older ( n = 20 , age 73.5 + /- 8 yr ) subjects at rest , intermittent exercise at 20 % maximum voluntary contraction ( MVC ) , and 40 % MVC . Exercise result ed in a significant increase in the average ratio of inorganic phosphate ( P(i ) ) to phosphocreatine ( PCr ) from resting values of 0.073 + /- 0.031 ( young ) and 0.082 + /- 0.037 ( older ) to 0 . 268 + /- 0.140 ( young , P < 0.01 ) and 0.452 + /- 0.387 ( older , P < 0 . 01 ) at 40 % MVC . At 40 % MVC , intracellular pH decreased significantly , from resting values of 7.08 + /- 0.08 ( young ) and 7.08 + /- 0.11 ( older ) to 6.84 + /- 0.19 ( young , P < 0.05 ) and to 6.75 + /- 0.25 ( older , P < 0.05 ) . Average values of the pseudo-first-order reaction rate k((PCr-->ATP ) ) at rest were 0.07 + /- 0.04 s(-1 ) in the young and 0.07 + /- 0.03 s(-1 ) in the older group . At both exercise levels , the reaction rate constant increased compared with the resting value , but only the difference between the resting value and the 20 % MVC value , which showed an 86 % higher reaction rate constant in both groups , reached statistical significance ( P < 0.05 ) . No difference in the reaction rate constant between the young and older groups was observed at either exercise level . As with k((PCr-->ATP ) ) , the average phosphorus flux through the CK reaction increased during exercise at 20 % MVC ( P < 0.05 in the older group ) but decreased toward resting values at 40 % MVC in both groups . The data in our study suggest that normal aging does not significantly affect the metabolic processes associated with the CK reaction
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 .