Carbohydrate oxidation and glucose utilisation under hyperglycaemia in aged and young males during exercise at the...

The purpose of the present study was to investigate the age-related carbohydrate oxidation and glucose utilisation rate response during exercise at the same relative intensity under hyperglycaemia in aged and young males.

16 endurance-trained aged (n = 8; 69.1 ± 5.2 year) and young (n = 8; 22.4 ± 2.9 year) males were studied during 40 min of cycling exercise (60% [Formula: see text]) under both hyperglycaemic and euglycaemic (control) conditions. Venous blood samples were collected at baseline, post-infusion, mid- and post-exercise. Carbohydrate and fat oxidation rates were determined at both 15 and 35 min during exercise, and glucose utilisation rates were calculated.

The aged group displayed significantly lower rates of carbohydrate oxidation during exercise during maintained hyperglycemia (15 min = 2.3 ± 0.4 vs. 1.6 ± 0.5 g min^-1; 35 min = 2.3 ± 0.5 vs. 1.5 ± 0.5 g min^-1) and control (15 min = 2.2 ± 0.4 vs. 1.6 ± 0.7 g min^-1; 35 min = 1.9 ± 0.7 vs. 1.3 ± 0.7 g min^-1) conditions (P = 0.01). The rate of glucose utilisation during exercise was also significantly reduced (85.76 ± 23.95 vs. 56.67 ± 15.09 μM kg^-1 min^-1). There were no differences between age groups for anthropometric measures, fat oxidation, insulin, glucose, NEFA, glycerol and lactate (P > 0.05) although hyperglycemia resulted in elevated glucose and insulin, and attenuated fat metabolite levels.

Our findings highlight that ageing results in a reduction in carbohydrate oxidation and utilisation rates during exercise at the same relative exercise intensity.