Prolonged exercise increased cerebrospinal fluid ammonia concentration, which was significantly attenuated by glucose supplementation (5.3 µM) compared to placebo (16.1 µM; P<0.05).
RCT (n=13)
Does glucose supplementation during prolonged exercise alter cerebral ammonia uptake and accumulation in humans?
Prolonged exercise increases cerebral ammonia uptake and accumulation, which is partially attenuated by glucose supplementation and correlates with perceived exertion.
Absolute Event Rate: 5.3% vs 16.1%
p-value: p=<0.05
We evaluated whether peripheral ammonia production during prolonged exercise enhances the uptake and subsequent accumulation of ammonia within the brain. Two studies determined the cerebral uptake of ammonia (arterial and jugular venous blood sampling combined with Kety-Schmidt-determined cerebral blood flow; n = 5) and the ammonia concentration in the cerebrospinal fluid (CSF; n = 8) at rest and immediately following prolonged exercise either with or without glucose supplementation. There was a net balance of ammonia across the brain at rest and at 30 min of exercise, whereas 3 h of exercise elicited an uptake of 3.7 +/- 1.3 micromol min(-1) (mean +/-s.e.m.) in the placebo trial and 2.5 +/- 1.0 micromol min(-1) in the glucose trial (P < 0.05 compared to rest, not different across trials). At rest, CSF ammonia was below the detection limit of 2 microm in all subjects, but it increased to 5.3 +/- 1.1 microm following exercise with glucose, and further to 16.1 +/- 3.3 microm after the placebo trial (P < 0.05). Correlations were established between both the cerebral uptake (r2 = 0.87; P < 0.05) and the CSF concentration (r2 = 0.72; P < 0.05) and the arterial ammonia level and, in addition, a weaker correlation (r2 = 0.37; P < 0.05) was established between perceived exertion and CSF ammonia at the end of exercise. The results let us suggest that during prolonged exercise the cerebral uptake and accumulation of ammonia may provoke fatigue, e.g. by affecting neurotransmitter metabolism.
Nybo et al. (Tue,) conducted a rct in Prolonged exercise (n=13). Glucose supplementation vs. Placebo was evaluated on Cerebrospinal fluid (CSF) ammonia concentration after exercise (p=<0.05). Prolonged exercise increased cerebrospinal fluid ammonia concentration, which was significantly attenuated by glucose supplementation (5.3 µM) compared to placebo (16.1 µM; P<0.05).