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Impact of Exercise in Type 2 Diabetes Patients

Rise in cerebral blood flow studied as cause of fatigue during physical activity…

The development of fatigue is still a complication among type 2 diabetics. During exercise, a person with diabetes will experience a loss of muscle generating capacity. Currently, the mechanism of action of reduced exercise tolerance is still uncertain. It is known that cerebral blood flow is vital in maintaining oxygen and substrate source to the brain. The brain is stimulated during exercise and increases cerebral blood flow and oxygen. This mechanism is inhibiting in type 2 diabetic patients due to several explanations that can justify the lack of rise in cerebral blood flow and cerebral oxygenation in type 2 diabetic patients.

The purpose of this study was to evaluate the idea that the rise in cerebral blood flow may be diminished in patients with type 2 diabetes. The study consisted of 8 physically active male type 2 patients and 7 age- and sex-matched healthy participants. Physically active was defined as engagement of >2.5 hours of cycling exercise per week for >10 years. Cerebral blood flow, cerebral oxygenation parameters, and cerebral uptake of glucose and lactose from arterial-to-venous was measured during exercise among the participants. Patient blood pressure was also observed during physical activities among the two groups.

The results showed that the partial pressure of arterial carbon dioxide was reduced at higher workloads in type 2 diabetic patients. Also, it showed that type 2 diabetics had an increase in work capacity and increase in cardiac output of only 80% in comparison to the control group.

Cerebral blood flow and cerebral oxygenation were decreased during exercise in type 2 diabetic patients (P < 0.05). Type 2 diabetic patients experienced an increased rate of perceived exertion (P < 0.05). The control group had an increase of cerebral blood flow (~20%) during exercise. The brain uptake of lactate and glucose was comparable in the both groups.

To conclude, the results from this study suggest that lack of increased cerebral blood flow during exercise is due to a lack of increase in cardiac output in patients with type 2 diabetes.

Practice Pearls:

  • There is an association between the lack an increased cardiac output and a lack of cerebral blood flow during exercise.
  • Type 2 diabetic patients experience a reduction of vasodilatory capacity with increase in fatigue while exercising.
  • The decrease in cardiac output during exercise by type 2 patients could be a factor in a higher perceived exertion.

Kim YS, Seifert T, Brassard P, et al. Impaired cerebral blood flow and oxygenation during exercise in type 2 diabetic patients. Physiol Rep. 2015;3(6).