Prediction of glucose oxidation rate during exercise.
Recently, the relationship between percentage maximal heart rate vs. glucose oxidation rate has been proposed as a tool for estimating glucose oxidation rate during exercise in insulin-dependent diabetic patients. The reliability of this relationship and its applicability to long-term exercise is evaluated. Eight healthy volunteers performed a graded cycloergometric exercise (10-min steps at 30, 50, 70, 90 % of ventilatory threshold). Heart rate and glucose oxidation rate (by indirect calorimetry) were measured during the last 5 min of each step. Volunteers underwent then three 1-hour constant intensity rides at 40, 60, 80 % of ventilatory threshold. Heart rate was recorded continuously; glucose oxidation rate was determined over 15-min periods. The percentage maximal heart rate vs. glucose oxidation rate relationship obtained from the graded exercise matched that previously reported. Independently of intensity, glucose oxidation rates observed during the 1-hr rides were linearly related to the estimated ones (R(2)>0.96, p<0.001), being, however, progressively over-estimated in subsequent exercise periods. The proposed correction yields values close to the identity line (y=1.001 x x; R2=0.974, p<0.001), the difference between observed and "corrected" values amounting to 0.23+/-2.17 mg x min (-1) x kg (-1). In conclusion, glucose oxidation rate can be estimated from heart rate, once proper correction factors are applied for long duration exercises.
Francescato
M P
MP
Department of Biomedical Sciences and Technologies, University of Udine, Udine, Italy. MFrancescato@mail.dstb.uniud.it
Zanier
M
M
Gaggioli
F
F
D000328:Adult; D001642:Bicycling / Q000502:physiology*; D002151:Calorimetry; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism / Q000503:physiopathology; D015444:Exercise / Q000502:physiology*; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010865:Pilot Projects; D013997:Time Factors
D005947:Glucose