Background Sedentary behaviour is associated with impaired cognition, whereas exercise can acutely improve cognition.

Objective
We compared the effects of a morning bout of moderate-intensity
exercise, with and without subsequent light-intensity walking breaks
from sitting, on cognition in older adults.

Methods Sedentary overweight/obese older adults with normal cognitive function (n=67, 67±7 years, 31.2±4.1 kg/m²)
completed three conditions (6-day washout): SIT (sitting):
uninterrupted sitting (8 hours, control); EX+SIT (exercise + sitting):
sitting (1 hour), moderate-intensity walking (30 min), uninterrupted
sitting (6.5 hours); and EX+BR (exercise + breaks): sitting (1 hour),
moderate-intensity walking (30 min), sitting interrupted every 30 min
with 3 min of light-intensity walking (6.5 hours). Cognitive testing
(Cogstate) was completed at four time points assessing psychomotor
function, attention, executive function, visual learning and working
memory. Serum brain-derived neurotrophic growth factor (BDNF) was
assessed at six time points. The 8-hour net area under the curve (AUC)
was calculated for each outcome.

Results
Working memory net AUC z-score·hour (95% CI) was improved in EX+BR with
a z-score of +28 (−26 to +81), relative to SIT, −25 (−79 to +29,
p=0.04 vs EX+BR). Executive function net AUC was improved in EX+SIT, −8
(− 71 to +55), relative to SIT, −80 (−142 to −17, p=0.03 vs EX+SIT).
Serum BDNF net AUC ng/mL·hour (95% CI) was increased in both EX+SIT,
+171 (−449 to +791, p=0.03 vs SIT), and EX+BR, +139 (−481 to +759,
p=0.045 vs SIT), relative to SIT, −227 (−851 to +396).

Conclusion
A morning bout of moderate-intensity exercise improves serum BDNF and
working memory or executive function in older adults, depending on
whether or not subsequent sitting is also interrupted with intermittent
light-intensity walking.