Astaxanthin is a potent antioxidant and anti-inflammatory carotenoid. Research examining whether astaxanthin (AX) could counteract exercise-induced muscle damage and improve exercise capacity reported inconsistent results.Therefore, the aim of this study was to explore the impact of 4 weeks supplementation with AX on muscle damage markers, total antioxidant status, and subjective marker of muscle pain. Twenty-four males were randomly assigned to the AX12 group (12 mg/day; n=8), AX36 group (36 mg/day; n=9), or placebo group (PLC; n=7). After 4 weeks of supplementation, blood samples were collected at rest, immediately after, and at 2, 24, 48, and 72 hours following eccentric arm exercise at 85% of predetermined one repetition maximum to assess muscle damage markers (creatine kinase and lactate dehydrogenase), total antioxidant status (malondialdehyde and uric acid), and muscle pain levels were evaluated using the Numerical Visual Pain Scale0-10.

This study followed a placebo-controlled, double-blind (participants and co-researcher administering the supplementation), and three-group parallel design to examine the effects of an AX supplement on muscle pain, muscle damage markers, and total antioxidant status (TAS).

Participants reported to the laboratory on 2 separate occasions: one initial session to measure anthropometrics and 1-repetition maximum (1RM) strength of the arm muscles and as well as to collect resting venous blood samples, prior to the four-week supplementation period. Upon arrival at the laboratory for their initial visits, each participant underwent measurements of body mass (MC 780 ST Black) and body height (Telescopic Height Meter), after which resting venous blood samples were collected from the median antecubital vein by a healthcare professional.

Following these baseline measurements, participants were assigned to one of the groups through a strict randomization process, which included selecting boxes numbered up to 24, all with the same size, color, and pattern. Participants were asked to choose one of the random numbers accompanied by an independent person other than the researchers. This process was recorded by the supervisor in paper-based surveys and digitally. Subsequently, all participants were instructed to consume their corresponding supplements (4 mg/day AX, 12 mg/day AX or 12 mg/day PLC) for 4 weeks.

After the 4 weeks of supplementation, participants reported to the laboratory for the post-supplementation measurements that included the collection of blood samples at rest, immediately after, as well as at 2, 24, 48, and 72 hours following completing eccentric arm exercises performed at 85% of predetermined 1RM.

Before obtaining blood samples (i.e., immediately after, and at 2, 24, 48, and 72 hours after exercises), participants were asked to assess their current pain levels using the Numerical Visual Pain Scale (NRS, ranging between 0-10 and 0-100) to determine any correspondence with muscle damage markers in the blood 25.

All participants were instructed to abstain from taking any medications for a minimum of 7 days prior to the study and to avoid consuming vitamins, foods, or supplements containing antioxidants, as well as analgesics, aspirin, or any other anti-inflammatory drugs throughout the duration of the study. A list of AX-rich foods, beverages and vitamins was provided to each participant prior to testing and all participants were asked to avoid these items during both 4-week supplementation periods and to maintain their regular eating habits and refrain from strenuous exercise to minimize the risk of muscle damage. A WhatsApp group was created for the purpose of monitoring the participants' supplement use.

To ascertain the extent of product usage, a survey form created using Google Forms was disseminated during the supplementation period. Participants were required to approve the form on a daily basis. At the end of each day, the data entered into the Excel file created using OneDrive was reviewed by at least one researcher.

Inclusion Criteria:

Healthy males engaging in recreational activity Aged between 20 and 30 years Non-smoker Not participating in any structured training regimen (i.e., endurance or resistance training programs)

Exclusion Criteria:

Use of any supplement or regular medications, Having hypothyroidism or hyperthyroidism.