Improved cardiorespiratory fitness is associated with functional changes in hippocampus during episodic memory...

Aerobic exercise that improves cardiorespiratory fitness (CRF) may induce hippocampal changes that help counteract age-related memory decline. The Umeå HIT Study, a randomized controlled trial, examined three months of controlled high-intensity interval training (HIT) and moderate-intensity training (MIT) in older adults. Here, we tested whether increases in CRF (VO₂peak), regardless of training modality, predicted changes in episodic-memory pattern completion and hippocampal structure and function (CA4/DG, CA2/3, CA1).

Forty-two older adults (66-79 years, 45% males) not engaged in regular physical exercise participated in 3 months of twice-weekly supramaximal HIT (20 min including 10 × 6-s intervals) or aerobic MIT (40 min including 3 × 8-m intervals). Before and after the exercise interventions, the participants underwent magnetic resonance imaging (MRI) of the hippocampus, including an episodic memory pattern completion task with concomitant functional MRI.

Exercise-induced change in VO₂peak (M = 1.5 mL/kg/min, 95% CI[0.8; 2.3]) after three months aerobic exercise of HIT or MIT did not predict change in pattern completion (F_(1,33) = 0.02, B = -0.061 p = .883, r² = 0.001). However, change in VO₂peak predicted BOLD signal change in the left hippocampal subfield CA4/DG (F_(1,33) = 4.56, B = 0.06 p = .04, r² = 0.12), which in turn, predicted change in pattern completion (F_(1,34) = 5.19, B = 0.026, p = .029, r² = 0.13).

Three months of high- or moderate-intensity training which improves CRF may lead to hippocampal functional changes that, in turn, are linked to enhanced episodic memory pattern completion.