Blood glucose following training sessions in runners

The possibility that blood glucose reaches potentially dangerous concentrations following training sessions was investigated in 10 competitive runners. Blood glucose concentration was assayed in the first 60 min following a continuous run at moderate pace for 45 min, a continuous run at hard pace for 30 min, an interval training session for 15 min, and an incremental exercise test to maximum effort. Glucose concentration increased and remained high for up to 30 min following the hard-pace, interval and maximum-effort runs; maximum concentrations (mean +/- SD 6.8 +/- 1.1, 6.8 +/- 1.0, 7.8 +/- 1.1 mmol.l-1 respectively) were significantly higher (p < 0.05) than those of the moderate-pace run (4.9 +/- 0.4 mmol.l-1). A 10-min warm-down at moderate pace dramatically attenuated the surge in glucose concentration following 30 min of hard-pace running, but a pre-exercise carbohydrate snack had no effect. Level of glycation of haemoglobin in a venous blood sample (mean +/- SD 4.6 +/- 0.7 %) was normal. Thus transient elevations in blood glucose concentration following high-intensity training sessions are unlikely to damage body proteins.