# Long-Term Improvement in Hippocampal-Dependent Learning Ability in Healthy, Aged Individuals Following High Intensity Interval Training

PMID: 39012673
Journal: Aging and Disease
Published: 2024 Jun 27
Authors: Blackmore DG, Schaumberg MA, Ziaei M, Belford S, To XV, O'Keeffe I, Bernard A, Mitchell J, Hume E, Rose GL, Shaw T, York A, Barth M, Cooper EJ, Skinner TL, Nasrallah F, Riek S, Bartlett PF

## Question

Does 6 months of supervised HIIT improve hippocampal-dependent learning and related brain and biomarker measures in healthy older adults?

## Summary

In healthy adults aged 65-85, a supervised 6-month treadmill HIIT program improved hippocampal-dependent paired-associate learning, with benefits reported up to 5 years after the intervention. HIIT also showed favorable hippocampal volume, connectivity, and biomarker patterns compared with low- and moderate-intensity exercise, but the study involved carefully screened older adults under close supervision.

## Population

- Healthy adults aged 65-85 without cognitive impairment who completed the exercise sessions.
- Sample size: 151
- Age: HIIT group 71.7 +/- 0.59 years at baseline
- Sex: Mixed sex
- Fitness level: Healthy older adults screened for exercise safety
- Health status: Healthy older adults without cognitive impairment and without high cardiac risk

## Methodology

- Randomized controlled exercise trial with long-term cognitive follow-up
- 6-month exercise intervention with follow-up cognitive testing up to 5 years
- University exercise clinic with supervised small-group exercise
- Randomized and controlled study design.

## Protocol

- Treadmill HIIT.
- Modality: Treadmill walking or running with speed and incline adjustment.
- Work intervals: 4 minutes.
- Recovery: 3 minutes active recovery.
- Sets or repetitions: 4 work intervals with 3 recovery intervals.
- Intensity: 85-95% HRpeak during work intervals; 60-70% HRpeak during active recoveries.
- Session duration: About 40 minutes including 10-minute warm-up and 5-minute cool-down.
- Frequency: 3 sessions per week.
- Program length: 6 months, 72 sessions.
- Progression: Exercise speed and incline were adjusted from repeated VO2peak/HRpeak assessments to maintain target heart-rate zones.
- Low-intensity and moderate-intensity exercise.
- Modality: Low-intensity stretching/balance/ROM/relaxation or continuous treadmill walking.
- Work intervals: Continuous exercise for MIT; task sequence for LIT.
- Sets or repetitions: LIT included 5-8 low-intensity tasks; MIT used 30 minutes continuous treadmill walking.
- Intensity: LIT 45-55% HRpeak; MIT 60-75% HRpeak.
- Session duration: About 45 minutes including warm-up and cool-down.
- Frequency: 3 sessions per week.
- Program length: 6 months, 72 sessions.
- Progression: Intensity targets were maintained using updated fitness testing.

## Outcomes

### Main reported result
Status: mixed
HIIT significantly improved hippocampal-dependent paired associated learning after 6 months, with retention reported up to 5 years.

### Main reported result
Status: unclear
The cognitive benefit was specific to the hippocampal learning task; other cognitive domains showed little evidence of exercise effects.

### Main reported result
Status: mixed
Right hippocampal volume was stable in HIIT but decreased in low- and moderate-intensity groups at 6 months.

### Main reported result
Status: unclear
Only HIIT showed significant increases in several resting-state connectivity pairs after 6 months.

### Main reported result
Status: mixed
Cortisol and BDNF responses predicted paired-associate-learning improvement in the HIIT group.

## Practical Insights

- For screened older adults, 4 x 4 minute HIIT can be delivered with close heart-rate monitoring and professional supervision.
- The cognitive result supports possible brain-health relevance of HIIT but should not be generalized to unscreened or cognitively impaired users.
- Long intervention duration and adherence support were central to the protocol.

## Limitations

- Participants were healthy older adults capable of completing a 6-month supervised program.
- There was no sedentary or non-exercise social control group.
- The program was highly supervised, limiting translation to unsupervised app use.
- It is unknown whether cycling, rowing, or bodyweight HIIT would produce similar outcomes.

## Safety And Adherence

- Participants were medically screened and exercise was supervised; adverse events were not highlighted in the extracted full text.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/39012673/) (pubmed)
- [DOI](https://doi.org/10.14336/AD.2024.0642) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12096939/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.