title: Effect of fuels on exercise capacity in muscle phosphoglycerate mutase deficiency.
abstract: BACKGROUND
  Muscle phosphoglycerate mutase deficiency (PGAMD) is a rare, recessively inherited metabolic myopathy that affects one of the last steps of glycolysis. Clinically, PGAMD resembles muscle phosphorylase deficiency (McArdle disease) and phosphofructokinase deficiency (PFKD). However, it is unknown whether PGAMD is associated with a second-wind phenomenon during exercise, as in McArdle disease, and whether patients with PGAMD, like patients with PFKD and McArdle disease, benefit from supplementation with fuels that bypass the metabolic block.
  
  
  OBJECTIVE
  To investigate whether fuels that bypass the metabolic block can improve exercise capacity or whether exercise capacity improves during sustained exercise.
  
  
  METHODS
  Single-blind, placebo-controlled investigation of the effects of glucose, lactate, and intralipid on work capacity in patients with PGAMD.
  
  
  METHODS
  National University Hospital, University of Copenhagen, and Neuromuscular Center, Institute for Exercise and Environmental Medicine. Patients Two unrelated men (21 and 26 years old) with PGAMD who since their teens had experienced muscle cramps, muscle pain, and episodes of myoglobinuria provoked by brief vigorous exercise, 4 patients with McArdle disease (mean +/- SD age, 32 +/- 5 years) with 0% residual phosphorylase activity in muscle, and 6 healthy, untrained male volunteers (mean +/- SD age, 23 +/- 1 years) were studied.
  
  
  METHODS
  Using constant and variable workload protocols on a cycle ergometer, it was investigated whether a spontaneous second wind occurs during exercise in patients with PGAMD, and using a constant workload protocol followed by an incremental load to exhaustion, it was tested whether infusion of lactate, glucose, or intralipid alters the exercise tolerance in PGAMD.
  
  
  METHODS
  Whether a second wind occurs during exercise and whether fuels that bypass the metabolic block can improve exercise and oxidative capacity.
  
  
  RESULTS
  In contrast to patients with McArdle disease, with whom they share many clinical features, in patients with PGAMD, cycle exercise and oxidative capacity are virtually normal, a second wind does not occur, and lipid and lactate supplements do not improve exercise capacity.
  
  
  CONCLUSIONS
  Although the clinical manifestations of PGAMD mimic McArdle disease with respect to the presence of exertional muscle cramps, rhabdomyolysis, and myoglobinuria, this study shows that cycle exercise responses are strikingly different.
authors.affiliation: Copenhagen Muscle Research Center, National University Hospital, Denmark. vissing@rh.dk
authors.forename: John
authors.initials: J
authors.lastname: Vissing
authors.forename: Bjørn
authors.initials: B
authors.lastname: Quistorff
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Haller
mesh_terms: D000328:Adult; D015444:Exercise; D005080:Exercise Test / Q000379:methods; D005947:Glucose / Q000008:administration & dosage*; D024982:Glycogen Phosphorylase, Muscle Form / Q000172:deficiency; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D043322:Lactase / Q000008:administration & dosage*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D010736:Phosphoglycerate Mutase / Q000172:deficiency*; D016037:Single-Blind Method; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D024982:Glycogen Phosphorylase, Muscle Form; D043322:Lactase; D010736:Phosphoglycerate Mutase; D005947:Glucose