Krotkiewski 1994.

Methods	Randomised controlled trial (parallel design)
Participants	Setting: laboratory; Poland n = 50 male volunteers recruited from local paper 36 to the pollen group; mean age pollen extract group 35.1 (SEM 2.62) years 14 to the placebo group; mean age placebo group 35.1 (SEM 2.62) years Inclusion/exclusion criteria Inclusion criteria were absence of hypertension, diabetes, cardiovascular disease, organic brain disease, alcohol or drug dependence and any other deviation from good health, no physical training or permanent or intensive basis and the lack of any ongoing medication
Interventions	Intervention Pollen extract; superoxide dismutase activity of approximately 30,000 units per gram/Polbax (Allegon, Sweden) Placebo Placebo not specified Duration 4 weeks
Outcomes	PRIMARY Delayed onset muscle soreness, visual analogue scale (0 to 10 cm) where 0 is "no pain and discomfort" and 10 is "intense pain and discomfort."
Exercise type	A circuit exercise test which consisted of 10 minutes on the step up test, 30 minutes cycling at 70% VO2max followed by 10 minutes on the step test. 30 minutes of cycling at 60% VO2max followed by 10 minutes on the step test repeated twice.
Sources of funding	The study was supported by the Swedish Sports Council and Askers Foundation
Notes	All the authors were contacted several times via email with no response. Maximal voluntary strength data were not reported in the manuscript either in a graph or a table and delayed onset muscle soreness data were reported as a difference between the starting values therefore data could not be extracted Authors were contacted on 3 November 2016 to request data for delayed onset muscle soreness but did not respond
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No details in manuscript 36 participants in experimental group and 14 in the placebo Authors contacted several times but did not respond
Allocation concealment (selection bias)	Unclear risk	No details in manuscript Authors contacted several times but did not respond
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Manuscript states: "tablets were given in a double blind manner"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Double‐blind
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No details in manuscript It appears as if all participants completed the study Authors contacted several times but did not respond.
Selective reporting (reporting bias)	High risk	No protocol available All data reported at all time points Adverse effects of antioxidant supplementation were not reported
Other bias	Unclear risk	Manuscript states: "All participants explicitly asked to follow their habitual style of life, particularly with regards to diet and physical activity", but no details on whether participants were asked to refrain from NSAIDs or any other supplements