How Swimming Boosts the Brain — What We Know and What We Still Don’t

Key takeaway: Regular swimming is associated with improvements in memory, attention, mood and immune response. Studies in animals and humans point to several biological mechanisms — including higher levels of brain-derived neurotrophic factor (BDNF), increased serotonin, greater dendritic spine density, angiogenesis and reduced hippocampal inflammation — but researchers have not yet determined exactly why swimming might outperform other aerobic exercises.

From a fixed brain to lifelong plasticity

Until the 1960s, scientists believed the adult brain could not make new neurons. That idea changed with clear evidence of neurogenesis — the birth of new neurons — in adult humans and animals. Today, aerobic exercise is recognized as a potent stimulus for neurogenesis and neuronal repair across species.

What the biology shows

BDNF and plasticity. One well-supported mechanism is an exercise-driven rise in brain-derived neurotrophic factor (BDNF). BDNF promotes neural plasticity — the brain’s ability to form and strengthen connections — and is strongly linked to learning and memory. Human studies associate higher BDNF levels with increased hippocampal volume and improved cognitive performance; lower BDNF is often seen in mood disorders.

Neurotransmitters and mood. Aerobic activity elevates neurotransmitters such as serotonin, which can reduce anxiety and depression and improve mood. Exercise also triggers endorphin release, contributing to the well-known post-exercise feeling of euphoria.

Structural changes. Animal research shows exercise can increase dendritic spine density — the tiny protrusions on neurons that form synapses. More spines and stronger synaptic signaling underpin better memory and cognitive function. Swimming in particular has been linked to genetic changes that boost BDNF and spine development in fish, and parallel BDNF-related spine increases have been reported in mammals.

Evidence from animal studies

Much mechanistic work uses rats because of their physiological similarities to humans. In one protocol, rats swam 60 minutes a day, five days a week. After seven days of training, rats made fewer errors in a six-arm radial water maze with a hidden platform, indicating improved short- and long-term memory. Other rat studies report that swimming activates pathways that reduce hippocampal inflammation, inhibit apoptosis (programmed cell death), support neuron survival and blunt age-related cognitive decline.

Human studies: promising but limited

Human research echoes animal findings but has constraints. An observational study of older adults found swimmers had faster mental processing and better attention than nonswimmers, though nonrandomized designs can’t exclude selection bias. A study in young adults showed 20 minutes of moderate-intensity breaststroke improved cognitive function in both swimmers and land-based athletes; immersion itself did not explain the effect. In children aged 6–12, a brief 3-minute swim before a vocabulary test led to better word retention than either coloring (a low-activity control) or a short anaerobic (CrossFit-like) routine. That study, however, did not compare swimming directly with other forms of aerobic exercise.

What remains unknown

Researchers are still trying to identify which aspects of swimming — if any — are uniquely beneficial. Possible contributors include whole-body, low-impact muscle engagement; breathing patterns and breath control; hydrostatic pressure and circulation changes from immersion; water temperature; and cardiovascular effects that promote angiogenesis (growth of new blood vessels). But definitive evidence that swimming is superior to other aerobic activities is lacking, and more randomized, controlled trials are needed to clarify dose (how long and how often), stroke type, intensity and the duration of benefits.

Practical takeaways

Existing evidence supports swimming as a highly promising, low-impact aerobic option with cognitive and mood benefits across the lifespan. Even short bouts of swimming appear to help learning in children and sharpen cognitive performance in adults. While scientists continue to probe the precise mechanisms, swimming is an accessible way to combine cardiovascular fitness with potential brain health gains.

Note: Much of the mechanistic evidence comes from animal models. Human studies show similar benefits but are often observational or small; stronger randomized trials are needed to draw firmer conclusions about how and why swimming affects the human brain.

This article is based on research summarized from peer-reviewed animal and human studies and is adapted from work by Seena Mathew (University of Mary Hardin-Baylor) originally published at The Conversation.