TY - JOUR
T1 - The relationship between creatine kinase kinetics and exercise intensity in human forearm is unchanged by age
AU - Horská, A.
AU - Fishbein, K. W.
AU - Fleg, J. L.
AU - Spencer, R. G.S.
PY - 2000
Y1 - 2000
N2 - Using 31P 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 resulted 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.
AB - Using 31P 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 resulted 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.
KW - Magnetization transfer
KW - P magnetic resonance spectroscopy
KW - Reaction rate
KW - Skeletal muscle
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U2 - 10.1152/ajpendo.2000.279.2.e333
DO - 10.1152/ajpendo.2000.279.2.e333
M3 - Article
C2 - 10913033
AN - SCOPUS:0033864226
SN - 0193-1849
VL - 279
SP - E333-E339
JO - American Journal of Physiology - Endocrinology and Metabolism
JF - American Journal of Physiology - Endocrinology and Metabolism
IS - 2 42-2
ER -