The goal of this clinical trial is to learn whether isometric exercise can improve recovery following experimentally induced delayed onset muscle soreness (DOMS) in healthy young adults.

The main questions it aims to answer are:

• Does isometric exercise reduce pain associated with delayed onset muscle soreness?
• Does isometric exercise improve pressure pain threshold, knee joint range of motion, muscle strength, and recovery following delayed onset muscle soreness?

Researchers will compare participants performing an isometric exercise program with a control group receiving no intervention to determine whether isometric exercise improves recovery after experimentally induced DOMS.

Participants will:

• Undergo a standardized exercise protocol to induce delayed onset muscle soreness.
• Be randomly assigned to either an isometric exercise group or a control group.
• Complete assessments of pain intensity, pressure pain threshold, knee range of motion, muscle strength, and thigh circumference.
• Be evaluated before exercise, immediately after exercise, and on Days 1, 3, and 5 following DOMS induction.

Delayed onset muscle soreness (DOMS) is a common consequence of unaccustomed or high-intensity physical activity, particularly exercises involving eccentric muscle contractions. DOMS is characterized by pain, tenderness, temporary reductions in muscle function, decreased range of motion, and impaired physical performance, typically peaking between 24 and 72 hours after exercise.

Various recovery strategies have been investigated to reduce the symptoms of DOMS; however, evidence regarding the effectiveness of isometric exercise in facilitating recovery remains limited. Previous studies have suggested that isometric muscle contractions may induce analgesic effects and increase pressure pain thresholds in musculoskeletal conditions. Whether these effects can improve recovery following exercise-induced muscle damage and DOMS has not been fully established.

The purpose of this randomized controlled trial was to investigate the effects of an isometric exercise program on recovery following experimentally induced DOMS in healthy adults. DOMS was induced using a standardized drop-jump protocol. Participants were randomly assigned to either an isometric exercise group or a control group. Outcome assessments were performed before DOMS induction, immediately after exercise, and during follow-up evaluations on Days 1, 3, and 5.

The findings of this study may contribute to the understanding of the role of isometric exercise as a simple, low-cost, and clinically applicable recovery strategy following exercise-induced muscle soreness.

Inclusion Criteria:

• Active athletes competing in University sports teams.
• Age between 18 and 30 years.
• Participation in organized sports training at least three times per week for the previous six months.
• No lower-extremity pain at the time of enrollment.
• Ability to safely perform the exercise protocol used to induce delayed onset muscle soreness (DOMS).
• Willingness to provide written informed consent.

Exclusion Criteria:

• History of lower-extremity musculoskeletal injury within the previous 6 months.
• Previous lower-extremity surgery.
• Current musculoskeletal pain or injury affecting sports participation.
• Neurological, rheumatological, cardiovascular, or systemic disorders affecting physical performance.
• Use of analgesic, anti-inflammatory, or muscle-relaxant medications during the study period.
• Participation in strenuous eccentric exercise within 72 hours prior to baseline testing.
• Use of recovery interventions (e.g., massage, cryotherapy, compression garments, electrical stimulation) during the study period.
• Inability to complete the exercise protocol or follow-up assessments.

De-identified individual participant data underlying the published results may be made available upon reasonable request to the corresponding author, subject to institutional approval and applicable ethical requirements.

De-identified individual participant data, study protocol, statistical analysis plan, and analytic code will be available beginning 6 months after publication of the primary study results and ending 5 years after publication.

De-identified individual participant data and supporting documents will be made available to qualified researchers upon reasonable request. Requests must include a methodologically sound research proposal and will be reviewed by the study investigators. Data will be provided after approval of the request and completion of an appropriate data-sharing agreement. Access will be limited to data necessary to achieve the approved research objectives.