Is physical performance (in mice) increased by Veillonella atypica or decreased by Lactobacillus bulgaricus?

• In this commentary, we discuss some controversial issues about the performance-enhancing role of the lactate-consuming bacteria Veillonella. • The relative abundance of Veillonella in human stool samples was not associated with training status or endurance performance. • In studying the effect on performance of Veillonella supplementation in mice, we found that Lactobacillus bulgaricus creates a biased control due to its interference in lactate metabolism and its influence on endurance performance. • In the absence of a vehicle-treated mouse group and ignoring the response to exercise of the native microbiota, the role of Veillonella atypica administration in maximal endurance performance in nontrained mice cannot be elucidated.