Beetroot juice may offer a small boost in aerobic capacity (VO₂ max), particularly for recreational exercisers. A benefit in highly trained athletes isn't clearly demonstrated. Oral bacteria convert beetroot’s nitrate into nitrite, which your body can then convert into nitric oxide. This molecule relaxes blood vessels and may help deliver more oxygen to working muscles. This biology interests me beyond fitness. Years ago, I gave my mother beet extract powder after she was diagnosed with high blood pressure. Two weeks later, her blood pressure measured normal. My mother-in-law had a similar experience! Using beetroot juice for exercise was something I started considering after interviewing @DrAndyGalpin on the podcast! I can attest to its effects after using it multiple times before a hard workout.