Muscle fiber type specific myofibrillar Ca2+ ATPase activity after spinal cord injury

Biopsies of the vastus lateralis muscle were analyzed to determine if incre ased energy demand of contraction, as indirectly reflected by myofibrillar Ca2+ adenosine triphosphate activity (qATPase), contributes to greater fati gue in affected muscle of spinal cord injured (SCI) patients. The qATPase a ctivity showed a fiber-type effect, IIax + IIx > IIa > I. Average fiber qAT Pase and fiber specific qATPase activities were not different between SCI a nd able-bodied controls, nor did they change over time. We suggest greater fatigue in SCI subjects early after injury does not reflect increased energ y demand of contraction. (C) 2000 John Wiley & Sons, Inc.