title: Metformin and exercise in type 2 diabetes: examining treatment modality interactions.
abstract: OBJECTIVE
  To determine the effect of metformin on the acute metabolic response to submaximal exercise, the effect of exercise on plasma metformin concentrations, and the interaction between metformin and exercise on the subsequent response to a standardized meal.
  
  
  METHODS
  Ten participants with type 2 diabetes were recruited for this randomized crossover study. Metformin or placebo was given for 28 days, followed by the alternate condition for 28 days. On the last 2 days of each condition, participants were assessed during a nonexercise and a subsequent exercise day. Exercise took place in the morning and involved a total of 35 min performed at three different submaximal intensities.
  
  
  RESULTS
  Metformin increased heart rate and plasma lactate during exercise (both P≤0.01) but lowered respiratory exchange ratio (P=0.03) without affecting total energy expenditure, which suggests increased fat oxidation. Metformin plasma concentrations were greater at several, but not all, time points on the exercise day compared with the nonexercise day. The glycemic response to a standardized meal was reduced by metformin, but the reduction was attenuated when exercise was added (metformin×exercise interaction, P=0.05). Glucagon levels were highest in the combined exercise and metformin condition.
  
  
  CONCLUSIONS
  This study reveals several ways by which metformin and exercise therapies can affect each other. By increasing heart rate, metformin could lead to the prescription of lower exercise workloads. Furthermore, under the tested conditions, exercise interfered with the glucose-lowering effect of metformin.
authors: Faculty of Physical Education and Recreation, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Canada. nboule@ualberta.ca
authors: Normand G
authors: NG
authors: Boulé
authors: Cheri
authors: C
authors: Robert
authors: Gordon J
authors: GJ
authors: Bell
authors: Steven T
authors: ST
authors: Johnson
authors: Rhonda C
authors: RC
authors: Bell
authors: Richard Z
authors: RZ
authors: Lewanczuk
authors: Raniah Q
authors: RQ
authors: Gabr
authors: Dion R
authors: DR
authors: Brocks
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