SEARCH

SEARCH BY CITATION

Key points

  • • 
    The influence of normative ageing on cerebral perfusion, oxygenation and metabolism during exercise is not well known.
  • • 
    This study assessed cerebral perfusion and concentration differences for oxygen, glucose and lactate across the brain, in young and elderly individuals at rest and during incremental exercise to exhaustion.
  • • 
    We observed that during submaximal exercise (at matched relative intensities) and during maximal exercise, cerebral perfusion was reduced in older individuals compared with young individuals, while the cerebral metabolic rate for oxygen and uptake of glucose and lactate were similar.
  • • 
    The results indicate that the age-related reduction in cerebral perfusion during exercise does not affect brain uptake of lactate and glucose.

Abstract  We evaluated cerebral perfusion, oxygenation and metabolism in 11 young (22 ± 1 years) and nine older (66 ± 2 years) individuals at rest and during cycling exercise at low (25%Wmax), moderate (50%Wmax), high (75%Wmax) and exhaustive (100%Wmax) workloads. Mean middle cerebral artery blood velocity (MCA Vmean), mean arterial pressure (MAP), cardiac output (CO) and partial pressure of arterial carbon dioxide (inline image) were measured. Blood samples were obtained from the right internal jugular vein and brachial artery to determine concentration differences for oxygen (O2), glucose and lactate across the brain. The molar ratio between cerebral uptake of O2versus carbohydrate (O2–carbohydrate index; O2/[glucose +1/2 lactate]; OCI), the cerebral metabolic rate of O2 (CMRO2) and changes in mitochondrial O2 tension (inline image) were calculated. 100%Wmax was ∼33% lower in the older group. Exercise increased MAP and CO in both groups (P < 0.05 vs. rest), but at each intensity MAP was higher and CO lower in the older group (P < 0.05). MCA Vmean, inline image and cerebral vascular conductance index (MCA Vmean/MAP) were lower in the older group at each exercise intensity (P < 0.05). In contrast, young and older individuals exhibited similar increases in CMRO2 (by ∼30 μmol (100 g−1) min−1), and decreases in OCI (by ∼1.5) and inline image (by ∼10 mmHg) during exercise at ≥75%Wmax. Thus, despite the older group having reduced cerebral perfusion and maximal exercise capacity, cerebral oxygenation and uptake of lactate and glucose are similar during exercise in young and older individuals.