- Brain-derived neurotrophic factor (BDNF), a protein member of the neurotrophin family of growth factors, has been associated with the modulation of cognition, neuroplasticity, angiogenesis, and neural connectivity. The role of BDNF in the improvement of metabolic and cardiovascular functions and in delaying the onset of neurodegenerative diseases has received increased attention. Current evidence has pointed out the influence of BDNF levels on structural and functional brain changes, including hippocampal neurogenesis, long-term potentiation, increased hippocampal volume, and survival of new born hippocampal neurons. Thus, higher BDNF levels have been associated with better cognitive performance, attention, and spatial memory. Indeed, reduced BDNF concentrations have been found in patients with dementia, mild cognitive impairment, Alzheimer’s disease, and major depression.
- A previous meta-analysis reported that aerobic exercise programs with moderate-to-vigorous intensity in adolescents did not result in a significant increase in BDNF levels. Another systematic review reported a dose response in terms of the frequency and intensity of the programmed sessions in samples including people with a variety of health conditions (i.e., healthy individuals, chronic patients). However, neither of these explored the immediate effect of exercise at different intensities on BDNF levels. Although it is known that exercise intensity is correlated with heart rate (which has been linked to BDNF levels) and that the abovementioned reviews suggest the intensity of exercise is positively related to increases in BDNF levels, there is a lack of evidence about whether or not there is a threshold of exercise intensity from which a significant increase in BDNF concentrations can be observed. This information could be relevant to guide individual exercise prescriptions aimed at improving cognitive performance.
- Therefore, the aim of the present study was to estimate the immediate changes in BDNF levels after exercise interventions at different intensities based on clinical trials in healthy young adults. Additionally, we explored whether acute changes in BDNF levels varied based on time spent on HIE (i.e., ≥30 or <30 min) or with respect to baseline cardiorespiratory fitness.
- Although brain-derived neurotrophic factor (BDNF) has been identified as a molecular biomarker of the neurophysiological effects induced by exercise, the acute effects of high-intensity exercise (HIE) on BDNF levels are inconclusive. This study aims to estimate the immediate effects of HIE on BDNF levels in healthy young adults.
- A systematic search was conducted in the MEDLINE, Embase, Cochrane CENTRAL, and SportDiscus databases up to December 2020. Randomized controlled trials (RCTs) and non-RCTs reporting pre–post changes in serum or plasma BDNF after an acute intervention of HIE compared to a control condition were included. Pooled effect sizes (p-ESs) and 95% confidence intervals (95%CIs) were calculated for RCTs using a random effects model with Stata/SE (Version 15.0; StataCorp, College Station, TX, USA). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. PROPERO registration number: CRD42020221047.
- A total of 22 studies with 552 individuals (age range: 20–31 years; 59.1% male) were included. The meta-analysis included 10 RCTs that reported valid outcome data. Higher BDNF levels were observed when HIE interventions were compared with non-exercise (p-ES = 0.55, 95%CI: 0.12–0.98; I2 = 25.7%; n = 4 studies) and light-intensity exercise (p-ES = 0.78, 95%CI: 0.15–1.40; I2 = 52.4%; n = 3 studies) but not moderate-intensity exercise (p-ES = 0.93, 95%CI: –0.16 to 2.02; I2 = 88.5%; n = 4 studies) conditions
Available online 1 September 2021