Effects of Acute Exercise Intensity on Cerebral Blood Flow and Cognitive Function in Older Adults

With an increasingly aging population, it is paramount that we further understand the changes that occur during aging, especially those which contribute to cognitive decline. Evidence shows that cognitive function is closely linked to brain blood flow. When comparing cerebral blood flow (CBF) between old and young individuals, older adults appear to have lower baseline levels of CBF. One of the principle determinants of CBF is CO2. Since exercise results in rises in CO2 production, changes in CBF can be monitored. Older adults appear to have diminished changes in CBF compared to younger individuals during moderate intensity exercise. This then leads to the idea that older adults may need a greater exercise stimulus (i.e. HIIT) to see these changes in CBF. However, the effects of HIIT on CBF in older adults is largely unstudied.

Purpose: To analyze the acute influence of HIIT on middle cerebral artery velocity (MCAv) in older adults, and to verify the positive association between MCAv and cognitive function.

Experimental Design: Recruiting 16 healthy adults age 65 and older. The study will require each participant to report to 4 visits: a screening visit, a control, a moderate intensity exercise bout, and a high intensity exercise bout. The order of the experimental visits will be randomized to each subject, and exercise bouts will be work-matched. During the experimental visits, MCAv, end-tidal CO2, MAP, and HR will be measured continuously. Vascular measures such as pulse wave analysis and pulse wave velocity will be taken pre- and post-exercise. Additionally, blood flow through the internal carotid artery and cognitive measures (n-back test) will be measured and administered pre-exercise, and at 15 mins, 30 mins, and 45 mins post-exercise. A two-way repeated measures ANOVA will be used to determine significant differences for time (pre vs. post measures) x condition (control/moderate/HIIT).

Results: In the process of collecting data.

Implications: If the study is successful in its findings, this could change how exercise is prescribed to older adults. It could also lead to the question regarding if a greater exercise stimulus (i.e. SIT) may be even more beneficial for these individuals.

Inclusion criteria

• 65+ years of age
• Comfortable with experiencing exercise-induced fatigue
• Willingness and ability to comply with scheduled visits and study procedures
• Able to provide consent on their own behalf
• Type 2 Diabetics accepted

Exclusion criteria

• Competitive athlete (Recreationally active is okay but no more than 3 days/week of structured exercise)
• VO2max below 18 ml/kg/min in men, 15ml/kg/min in women (minimum thresholds for independent living seniors)
• Inability of study staff to acquire signal from the MCA using TCD
• Diagnosis of mild cognitive impairment, Parkinson's Disease, Alzheimer's Disease, multiple sclerosis, or psychiatric illness (unless mild depression or anxiety)
• History of brain damage/stroke/concussions
• Cardiovascular Disease, Pulmonary Disease, or dependence of supplemental O2
• Type 2 Diabetics who aren't cleared by the study physician during the first screening visit (HbA1C > 8.5%)
• Neuromuscular or musculoskeletal dysfunctions impairing one from cycling
• Changes in vasoactive medication dose or quantity, recently prior to or during the study time course, or inability to maintain regular timed ingestion of vasoactive medication
• Currently involved in Estrogen or Testosterone Replacement Therapy
• Unable to abstain from food consumption (3hrs), caffeine/alcohol consumption (12hrs), and vigorous exercise (24hrs) prior to experimental procedures