The Effect of Reducing Total Volume of Sprint Exercise in Sprint Interval Training Protocols on Circulating Levels of Brain-derived Neurotrophic Factor (BDNF)

Regular exercise is well known to be required for good physical health, but exercise can also improve mental health. Although the effects of exercise on mental health have been shown in many studies, it remains unclear how exercise improves mental health. In recent years, the potential role of a specific protein called 'brain-derived neurotrophic factor' (BDNF) has received increasing attention. Higher levels of BDNF in the blood are associated with better cognitive performance, attention, and spatial memory. Conversely, low levels of BDNF in the blood are found in patients with depression, dementia, mild cognitive impairment, and Alzheimer's disease. BDNF can be released during exercise, with greater increases after exercise performed at higher intensities. For example, classic sprint interval training (SIT), which involves four 30-second 'all-out' cycle sprints, has been shown to lead to greater increases in BDNF compared to moderate or vigorous exercise. Although these results suggest that SIT is an effective way to increase BDNF, SIT is not generally considered feasible for patients or untrained members of the general public, because it is a very tiring type of exercise. However, other more manageable protocols have been developed, such as the 'reduced-exertion, high-intensity interval training' (REHIT) protocol, which involves two 20-second 'all-out' sprints within a 10-minute low-intensity exercise session. Although it is clear that BDNF levels increase in an intensity-dependent manner in response to exercise, the effect of exercise volume remains unknown. Exercise intensity is identical for SIT and REHIT, but if BDNF levels increase to a similar extent in response to both protocols, REHIT would constitute a more feasible intervention for use in patients and the general public. The aim of the present study is to compare the effects of REHIT vs. classic SIT on levels of BDNF in the blood. For this,15 study participants will be recruited, who will each complete a SIT session, a REHIT session, and a no-exercise control session. Levels of BDNF will be measured in blood samples taken at rest, as well as directly after exercise, 30 minutes after exercise, and 90 minutes after exercise. It will be determined whether the greater amount of sprint exercise in a SIT session will be associated with a greater increase in levels of BDNF in the blood compared to the REHIT session which consists of a lower amount of sprint exercise.