Effects of Nattokinase Supplementation on Strength Recovery and Muscle Damage Biomarkers Following Exercise-Induced Muscle Injury: A Pilot Study

NCT07836634 | Active Not Recruiting

• 1 other identifier: NTSUIRB-115-102
• Study Type: interventional
• Target: 14
• Locations: 1 country
• Sites: 1

Brief Summary

This pilot study aims to investigate whether 4 weeks of nattokinase supplementation (2,000 FU/day) affects recovery following exercise-induced muscle damage in healthy adult men. Approximately 12 to 16 participants aged 18 to 40 years will receive either nattokinase or a matching placebo during the supplementation period. After supplementation, participants will complete an exercise protocol designed to induce temporary muscle damage. Recovery will be evaluated using measures of muscle strength and exercise performance, muscle soreness, blood lactate, muscle oxygenation, and blood biomarkers related to muscle damage, inflammation, and oxidative stress. Measurements will be performed before and after the exercise-induced muscle damage protocol, including follow-up assessments during the recovery period. The study is intended to provide preliminary information on the potential effects of nattokinase supplementation on muscle recovery after strenuous exercise.

Conditions

Exercise-induced Muscle Damage

Outcome Measures

Primary Outcomes (16)

• Peak Force During Isometric Mid-Thigh Pull (IMTP)

  Peak force during the isometric mid-thigh pull (IMTP) will be measured to assess maximal isometric strength. The highest value from three trials will be used for analysis.

  Day 0 baseline, pre-EIMD baseline, immediately post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Countermovement Jump (CMJ) Height

  Countermovement jump height will be measured to assess lower-limb explosive performance. The highest value from three trials will be used for analysis.

  Day 0 baseline, pre-EIMD baseline, immediately post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Blood Lactate Concentration

  Blood lactate concentration will be measured before and after the Wingate Anaerobic Test (WAnT) to assess lactate production and clearance. The WAnT will be used as a standardized high-intensity exercise stimulus.

  During the Day 0, pre-EIMD, and immediately post-EIMD WAnT assessments; blood lactate will be measured before exercise, immediately after exercise, and at 3, 5, and 10 minutes post-exercise.

• Muscle Oxygen Saturation (SmO₂)

  Muscle oxygen saturation (SmO₂) will be measured using near-infrared spectroscopy (NIRS) to assess changes in muscle oxygenation.

  Day 0 baseline, pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Total Hemoglobin (THb)

  Total hemoglobin (THb) will be measured using near-infrared spectroscopy (NIRS) to assess changes in local muscle blood volume.

  Day 0 baseline, pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD

• Subjective Muscle Soreness Using Visual Analogue Scale (VAS)

  Subjective muscle soreness will be assessed using a 100-mm visual analogue scale (VAS), ranging from no soreness to worst possible soreness.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Subjective Muscle Soreness Using Borg CR-10 Scale

  Subjective muscle soreness will also be assessed using the Borg CR-10 scale, ranging from 0 to 10.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Pressure Pain Threshold (PPT)

  Pressure pain threshold (PPT) will be measured at the vastus lateralis using a pressure algometer to objectively assess muscle soreness.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Creatine Kinase (CK) Concentration

  Blood creatine kinase (CK) concentration will be measured as a marker of exercise-induced muscle damage.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Myoglobin Concentration

  Blood myoglobin concentration will be measured as a marker of exercise-induced muscle damage.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Lactate Dehydrogenase (LDH) Concentration

  Blood lactate dehydrogenase (LDH) concentration will be measured as a marker of exercise-induced muscle damage.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• High-Sensitivity C-Reactive Protein (hs-CRP) Concentration

  Blood high-sensitivity C-reactive protein (hs-CRP) concentration will be measured to assess the inflammatory response following EIMD.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Interleukin-6 (IL-6) Concentration

  Blood interleukin-6 (IL-6) concentration will be measured to assess the inflammatory response following EIMD.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Tumor Necrosis Factor-Alpha (TNF-α) Concentration

  Blood tumor necrosis factor-alpha (TNF-α) concentration will be measured to assess the inflammatory response following EIMD.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Malondialdehyde (MDA) Concentration

  Blood malondialdehyde (MDA) concentration will be measured as a marker of oxidative stress.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

• Total Antioxidant Capacity (TAC)

  Total antioxidant capacity (TAC) will be measured to assess antioxidant capacity following EIMD.

  Pre-EIMD baseline, immediately post-EIMD, 2 hours post-EIMD, 24 hours post-EIMD, and 48 hours post-EIMD.

Secondary Outcomes (8)

• Body Weight

  Day 0 baseline and Day 28.

• Body Mass Index (BMI)

  Day 0 baseline and Day 28.

• Skeletal Muscle Mass

  Day 0 baseline and Day 28.

• Skeletal Muscle Percentage

  Day 0 baseline and Day 28.

• Body Fat Mass

  Day 0 baseline and Day 28

Study Arms (2)

Nattokinase Group

EXPERIMENTAL

Participants assigned to this arm will consume one capsule of nattokinase daily, providing 2,000 FU/day, for 28 days.

Dietary Supplement: Nattokinase

Placebo Group

PLACEBO COMPARATOR

Participants assigned to this arm will consume one matching placebo capsule daily for 28 days. The placebo is matched in appearance and flavor to the nattokinase supplement.

Dietary Supplement: Placebo

Interventions

Nattokinase DIETARY_SUPPLEMENT

Participants will consume one capsule of nattokinase orally once daily, providing 2,000 FU/day, for 28 days.

Nattokinase Group

Placebo DIETARY_SUPPLEMENT

Participants will consume one matching placebo capsule orally once daily for 28 days. The placebo is matched in appearance and flavor to the nattokinase supplement.

Placebo Group

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Male participants aged 18 to 40 years.
• Regular exercise habits, defined as exercising at least 3 times per week, including at least 1 resistance-training session per week, with a stable exercise routine maintained during the previous 3 months.
• No cardiovascular, metabolic, neurological, or musculoskeletal diseases that would prevent safe participation in the exercise testing, as assessed by the research team.
• Not currently taking medications or dietary supplements that may affect blood coagulation.
• No known allergy to natto or soy products.

You may not qualify if:

• Current use of anticoagulant or antiplatelet medications.
• History of bleeding disorders or abnormal blood coagulation.
• Major surgery within the previous 3 months.
• Known cardiovascular, renal, or other major chronic diseases.
• History of severe lower-extremity musculoskeletal injury, such as fracture, ligament injury, or meniscal injury, when judged by the research team to make exercise testing inappropriate.
• Current acute inflammation, infection, or another physical condition considered unsuitable for participation in exercise.
• Participation in high-intensity or systematic plyometric training within the previous month.
• Students currently supervised by the principal investigator or individuals with a relevant conflict of interest with the study.

Sponsors & Collaborators

• National Taiwan Sport University: lead

Study Sites (1)

Graduate Institute of Sports Science, National Taiwan Sport University

Taoyuan, Taiwan, 333325, Taiwan

Location

MeSH Terms

Interventions

nattokinase

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, INVESTIGATOR
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Study Record Dates

• First Submitted: September 14, 2026
• First Posted: September 23, 2026
• Study Start: September 3, 2026
• Primary Completion (Estimated): October 8, 2026
• Study Completion (Estimated): October 8, 2026
• Last Updated: September 23, 2026

Record last verified: 2026-09

Locations

TW (1)