Blood ammonia--heart rate relationship during graded exercise is not influenced by glycogen depletion.

The blood lactate (La) - heart rate (HR) relationship assessed during a graded maximal exercise test (GXT) is often used to provide training guidelines to athletes. Glycogen depletion is a condition that is known to influence the La response during a GXT and therefore can bias the interpretation of La curves. The purpose of our study was to determine an influence of glycogen depletion through long-term exercise (GDE) on blood La and ammonia (NH3) accumulation during a GXT. Eleven persons (5 males, 6 females; 26.3 +/- 4 yrs) performed a cycle ergometer GXT (3 min protocol) on two separate occasions with a 1-week interval. Using a randomized cross-over design, one of the two GXTs was preceded by a GDE. After GDE, blood NH3 increased more rapidly in the depleted versus control state whereas La increased less rapidly in the depleted state. The NH3 to HR relationship was not altered by glycogen depletion. We conclude, therefore, that determination of NH3 during a GXT may provide helpful additional information for training recommendations which is not available through La determination only.