Do the Norwegian 4x4 to Protect Your Hippocampus
Most people doing cardio for brain health are jogging at a comfortable pace and calling it done. That approach does produce results, but a more recent head-to-head trial shows the payoff is substantially larger if you push the intensity. In that study, older adults were split across three groups: a low-intensity group, a zone 2 treadmill group training three times per week, and a group doing the Norwegian 4x4 protocol three times per week for six months. The zone 2 group and the high-intensity group improved their cardiovascular fitness by a similar amount. But the high-intensity group had significantly better improvements in hippocampal function and better preservation of hippocampal structure on MRI. The hippocampus is the brain region most associated with memory and most vulnerable to age-related decline. That benefit held for five years after the six-month intervention ended. Wood points out that within the study, the harder people worked and the more cortisol they released during sessions, the greater the benefit. This directly contradicts the common advice to avoid high-intensity exercise because it is stressful. The stress is the mechanism. High-intensity work floods the system with lactate, which crosses the blood-brain barrier easily and stimulates BDNF production, a key driver of neuroplastic change. The protocol is not complicated. Four minutes at 85 to 95 percent of maximum heart rate, followed by a three-minute rest. Repeat that cycle four times. That is one session.