“…This confirms conclusions from stable isotope studies reporting that ϳ50% of total fat oxidation is accounted for by plasma FFA oxidation, suggesting that other substrate sources like IMTG play a substantial role in energy provision during exercise (22,38,45,55). However, as noted in the introduction, the importance of IMTG stores as a substrate source has been disputed as some (4,11,13,17,20,25,42,56), but certainly not all, studies (3,21,30,31,44,49,50,58) using the biochemical triglyceride extraction method on muscle samples collected before and after exercise have been able to show a significant decline in IMTG content after prolonged endurance exercise. The apparent controversy, elegantly described by Watt et al (57), can be explained partly by the marked between-biopsy variability (ϳ24%) that has been reported when this technique (58) is used.…”