The participants completed 3 conditions, each for for 7 days:

70 grams of raw spinach daily
10 grams of a superfood supplement (which contained various vitamins and minerals and polyunsaturated fatty acids) daily
No intervention (the control)

The day after each condition, the participants performed three 30-second Wingate tests (4 minutes of rest between tests). Blood samples were collected before the intervention and 24 hours after the Wingate test. There was a 7-day washout period between the conditions.

Interleukin 6 and malondialdehyde were lower (better) and superoxide dismutase activity was higher (better) in the spinach and superfood conditions than in the control condition.

Furthermore, the interleukin 6 level was lower and superoxide dismutase activity was higher in the spinach condition than the superfood condition.

Popeye was on to something: Eating spinach might improve exercise recovery Original paper