Investigating the Acute and Chronic Effects of Cardiovascular Exercise on Brain-Derived Neurotrophic Factor in Early Subacute Stroke.

The study enrolled only people with a first-ever ischemic stroke in the early subacute period. Many had mild stroke severity and relatively high baseline upper-limb function, so there was little room for motor improvement. The exercise group was intentionally larger than the standard care group because the randomization was weighted to study a genetic variant. Dropouts occurred for reasons unrelated to the exercise, including medical conditions, COVID-19 lockdown, falls outside training, and stroke recurrence. Two participants had no blood sample data. Blood samples could not be collected at the same clock time for every participant, although each participant's samples were taken at the same time across visits. BDNF was measured in blood, not in the brain, and the source of peripheral BDNF is uncertain, so this biomarker may not reflect central neuroplasticity. The genotype analysis had limited power, and the authors said genetic findings need cautious interpretation. There was high interindividual variability in BDNF response, and the authors said very large studies would be needed to detect effects.

The authors declared no potential conflicts of interest.

Do not conclude that exercise is unhelpful because BDNF did not change. The group receiving exercise plus standard care still improved peak oxygen uptake by 4.43 mL/kg/minute, and the null result was for blood BDNF, not for fitness or safety.