The following is the abstract of the article discussed in the subsequent letter:

Friedlander, Anne L., Gretchen A. Casazza, Michael A. Horning, Melvin J. Huie, and George A. Brooks. Training-induced alterations of glucose flux in men. J. Appl. Physiol. 82(4): 1360-1369, 1997.We examined the hypothesis that glucose flux was directly related to relative exercise intensity both before and after a 10-wk cycle ergometer training program in 19 healthy male subjects. Two pretraining trials [45 and 65% of peak O₂ consumption (O_{2 peak})] and two post- training trials (same absolute and relative intensities as 65% pretraining) were performed for 90 min of rest and 1 h of cycling exercise. After training, subjects increased O_{2 peak} by 9.4 ± 1.4%. Pretraining, the intensity effect on glucose kinetics was evident with rates of appearance (R_a; 5.84 ± 0.23 vs. 4.73 ± 0.19 mg · kg¹ · min¹), disappearance (R_d; 5.78 ± 0.19 vs. 4.73 ± 0.19 mg · kg¹ · min¹), oxidation (R_ox; 5.36 ± 0.15 vs. 3.41 ± 0.23 mg · kg¹ · min¹), and metabolic clearance (7.03 ± 0.56 vs. 5.20 ± 0.28 ml · kg¹ · min¹) of glucose being significantly greater (P  0.05) in the 65% than the 45% O_{2 peak} trial. When R_d was expressed as a percentage of total energy expended per minute (R_{d E}), there was no difference between the 45 and 65% intensities. Training did reduce R_a(4.63 ± 0.25), R_d(4.65 ± 0.24), R_ox(3.77 ± 0.43), and R_{d E} (15.30 ± 0.40 to 12.85 ± 0.81) when subjects were tested at the same absolute workload (P  0.05). However, when they were tested at the same relative workload, R_a, R_d, and R_{d E} were not different, although R_ox was lower posttraining (5.36 ± 0.15 vs. 4.41 ± 0.42, P  0.05). These results show 1) glucose use is directly related to exercise intensity; 2) training decreases glucose flux for a given power output; 3) when expressed as relative exercise intensity, training does not affect the magnitude of blood glucose use during exercise; 4) training alters the pathways of glucose disposal.