Deeper Dive: Flavonoids may slightly speed up recovery from muscle-damaging exercise

Exercise, especially when it involves high-force eccentric or unaccustomed loading^[1], can produce substantial muscle fiber damage. It is thought^[2] that the initial structural damage from mechanical loading causes uncontrolled movement of calcium ions into the cytoplasm, leading to further degradation of structural proteins. While the inflammatory response that follows is aimed at clearing damaged tissue, it may result in an excessive production of reactive oxygen species, which further damage the muscle fibers. Eventually, this exercise-induced muscle damage (EIMD) manifests^[3] as muscle pain and swelling, strength and power loss, reduced range of motion (ROM), and delayed onset muscle soreness (DOMS), with these symptoms usually subsiding^[4] five to seven days after exercise.

Some research suggests that flavonoids^[5], a class of polyphenols found in high concentrations in fruits, vegetables, and other plants, may promote exercise recovery and protect against EIMD thanks to their antioxidative and anti-inflammatory properties. For example, a 2019 meta-analysis^[6] found that the consumption of whole fruits high in anthocyanins (a type of flavonoid) improved exercise-induced inflammation and oxidative stress in healthy adults. Moreover, a 2019 narrative review^[7] of randomized controlled trials suggested that supplementation with more than 1,000 mg of polyphenols for three days before and after exercise may enhance recovery from EIMD. However, a meta-analysis quantitatively analyzing the results of the available randomized controlled trials specifically looking at the effects of flavonoid polyphenols on markers of EIMD is lacking.