The hypothesis that endurance training increases gluconeogenesis (GNG) duri
ng rest and exercise was evaluated. We determined glucose turnover with [6,
6-H-2]glucose and lactate incorporation into glucose by use of [3-C-13]lact
ate during 1 h of cycle ergometry at two intensities [45 and 65% peak O-2 c
onsumption ((V) overdot O-2peak)] before and after training [65% pretrainin
g (V) overdot O-2peak], same absolute workload (ABT), and 65% posttraining
(V) overdot O-2peak, same relative intensity (RLT). Nine males (178.1 +/- 2
.5 cm, 81.8 +/- 3.3 kg, 27.4 +/- 2.0 yr) trained for 9 wk on a cycle ergome
ter 5 times/wk for 1 h at 75% (V) overdot O-2peak. The power output that el
icited 66.0 +/- 1.1% of (V) overdot O-2peak pretraining elicited 54.0 +/- 1
.7% posttraining. Rest and exercise arterial glucose concentrations were si
milar before and after training, regardless of exercise intensity. Arterial
lactate concentration during exercise was significantly greater than at re
st before and after training. Compared with 65% pretraining, arterial lacta
te concentration decreased at ABT (4.75 +/- 0.4 mM, 65% pretraining; 2.78 /- 0.3 mM, ABT) and RLT (3.76 +/- 0.46 mM) (P < 0.05). At rest alter traini
ng, the percentage of glucose rate of appearance (R-a) from GNG more than d
oubled(1.98 +/- 0.5% pretraining; 5.45 +/- 1.3% posttraining), as did the r
ate of GNG (0.11 +/- 0.03 mg.kg(-1).min(-1) pretraining, 0.24 +/- 0.06 mg.k
g(-1).min(-1) posttraining). During exercise after training, %glucose R-a f
rom GNG increased significantly at ABT (2.3 +/- 0.8% at 65% pre- vs. 7.6 +/
- 2.1% posttraining) and RLT (6.1 +/- 1.5%), whereas GNG increased almost t
hreefold (P < 0.05) at ABT(0.24 +/- 0.08 mg.kg(-1).min(-1) 65% pre-, and 0.
71 +/- 0.18 mg.kg(-1).min(-1) posttraining) and RLT (0.75 +/- 0.26 mg.kg(-1
).min(-1)). We conclude that endurance training increases gluconeogenesis t
wofold at rest and threefold during exercise at given absolute and relative
exercise intensities.