Muscle function during repetitive moderate-intensity muscle contractions in myoadenylate deaminase-deficient Dutch subjects.
We investigated whether the capacity for repetitive submaximal muscle contraction was reduced in a group of subjects (n=8) with a primary deficiency of myoadenylate deaminase (MAD). Quadriceps femoris muscle fatigue was evaluated using voluntary and electrically stimulated contractions during 20 min of repetitive voluntary isometric contractions at 40% of maximal force-generating capacity (MFGC). After 5 min of exercise, MFGC had declined significantly to 70.6+/-4.1% (mean+/-S.E.M.) and 87.2+/-1.6% of baseline values in MAD-deficient and sedentary control subjects (n=8) respectively (P=0.002 between groups). After 5 min of exercise, the half-relaxation time had increased significantly to 113.4+/-6.1% of baseline in MAD-deficient muscle, but had decreased significantly to 94.1+/-1.3% in control subjects (P=0.003 between groups). All control subjects completed the 20-min exercise test. Five of the MAD-deficient subjects had to stop exercising due to early muscle fatigue; however, three of the MAD-deficient subjects were able to complete the 20-min exercise test. In conclusion, although the capacity for repetitive submaximal isometric muscle contractions for the group of MAD-deficient subjects was significantly decreased, it remains uncertain whether MAD deficiency is the sole cause of pronounced muscle fatigue.
De Ruiter
C J
CJ
Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands. C_J_de_Ruiter@fbw.vu.nl
May
A M
AM
van Engelen
B G M
BG
Wevers
R A
RA
Steenbergen-Spanjers
G C
GC
de Haan
A
A
D000659:AMP Deaminase / Q000172:deficiency* / Q000378:metabolism; D000328:Adult; D000368:Aged; D004558:Electric Stimulation; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000502:physiology*; D013997:Time Factors
D000659:AMP Deaminase