Da. Maclean et al., Muscle interstitial glucose and lactate levels during dynamic exercise in humans determined by microdialysis, J APP PHYSL, 87(4), 1999, pp. 1483-1490
The purpose of the present study was to use the microdialysis technique to
determine skeletal muscle interstitial glucose and lactate concentrations d
uring dynamic incremental exercise in humans. Microdialysis probes were ins
erted into the vastus lateralis muscle, and subjects performed knee extenso
r exercise at workloads of 10, 20, 30, 40, and 50 W. The in vivo probe reco
veries determined at rest by the internal reference method for glucose and
lactate were 28.7 +/- 2.5 and 32.0 +/- 2.7%, respectively. As exercise inte
nsity increased, probe recovery also increased, and at the highest workload
probe recovery for glucose (61.0 +/- 3.9%) and lactate (66.3 +/- 3.6%) had
more than doubled. At rest the interstitial glucose concentration (3.5 +/-
0.2 mM) was lower than both the arterial (5.6 +/- 0.2 mM) and venous (5.3
+/- 0.3 mM) plasma water glucose levels. The interstitial glucose levels re
mained lower (P < 0.05) than the arterial and venous plasma water glucose c
oncentrations during exercise at all intensities and at 10, 20, 30, and 50
W, respectively. At rest the interstitial lactate concentration (2.5 +/- 0.
2 mM) was higher (P < 0.05) than both the arterial (0.9 +/- 0.2 mM) and ven
ous (1.1 +/- 0.2 mM) plasma water lactate levels. This relationship was mai
ntained (P < 0.05) during exercise at workloads of 10, 20, and 30 W. These
data suggest that interstitial glucose delivery at rest is flow limited and
that during exercise changes in the interstitial concentrations of glucose
and lactate mirror the changes observed in the venous plasma water compart
ments. Furthermore, skeletal muscle contraction results in an increase in t
he diffusion coefficient of glucose and lactate within the interstitial spa
ce as reflected by an elevation in probe recovery during exercise.