(A–D). The relationship between changes of VO2max and changes of: LDH (A), MDA (B), and β-carotene (C), (r = −0.518, p = 0.028; r = −0.472, p = 0.036; r = −0.500, p = 0.029—respectively) as well as changes of β-carotene with changes of AOPP (D) (r = –0.500, p = 0.029). Red markers—women, blue markers—men. Changes were calculated as the difference between the absolute values after ID&BEET (implementation of dietary recommendations and beetroot juice supplementation) minus the values after ID (implementation of dietary recommendations). VO2max: Maximum rate of oxygen uptake; MDA: Malondialdehyde; LDH: Lactate dehydrogenase; AOPP: Advanced oxidation protein products.