Background: Sustaining regular exercise is a major public health challenge. Self-directed, goal-oriented exercise programs may enhance autonomy and adherence compared to traditional supervised approaches. Objects: This study evaluated the effects of an 8-week individualized, goal-oriented exercise program on physical fitness and body composition in college students and assessed the durability of these effects following an 8-week washout period. Methods: In a non-randomized, fixed-sequence design, 24 healthy young adults (19 males, 5 females) completed an 8-week self-directed exercise intervention, followed by an 8-week washout and an 8-week control period. Physical fitness (vertical jump, standing long jump, handgrip strength, one-leg stance) and body composition (body mass index, skeletal muscle mass, body fat percentage) were assessed. Data were analyzed using repeated-measures ANOVA and effect size estimates. Results: Significant improvements were observed in all fitness measures post-intervention (p < 0.01). Large effect sizes were found for vertical jump (Cohen’s dav = 0.87) and standing long jump (dav = 0.99), while handgrip strength and one-leg stance showed moderate effects (dav ≈ 0.65). However, no consistent changes were detected in body composition variables. Fitness gains declined rapidly during the washout period, indicating transient adaptation. Conclusion: An 8-week goal-oriented, self-directed exercise program effectively improved physical fitness but not body composition in young adults. These findings support the utility of autonomy-supportive models, though the rapid reversal of gains highlights the critical need for sustained engagement strategies.

INTRODUCTION
MATERIALS AND METHODS
    1. Study Design and Participants
    2. Exercise Intervention
    3. Washout and Control Phases
    4. Assessment Measurements
    5. Statistical Analysis
RESULTS
    1. Exercise Program Engagement and Success
    2. Participant Characteristics
    3. Body Composition
    4. Physical Fitness
DISCUSSION
CONCLUSIONS
FUNDING
ACKNOWLEDGEMENTS
CONFLICTS OF INTEREST
AUTHOR CONTRIBUTIONS
ORCID
REFERENCES

• Myung-Jin Ko(Department of Physical Therapy, College of Biohealth)
• Ki-Song Kim(Department of Physical Therapy, College of Biohealth, Research Institute for Basic Sciences, Smart Healthcare Convergence Research Center)
• Jangwhon Yoon(Department of Physical Therapy, College of Biohealth, Research Institute for Basic Sciences, Smart Healthcare Convergence Research Center)
• In-Cheol Jeon(Department of Physical Therapy, College of Biohealth, Research Institute for Basic Sciences, Smart Healthcare Convergence Research Center)
• Young-In Hwang(Department of Physical Therapy, College of Biohealth, Research Institute for Basic Sciences, Smart Healthcare Convergence Research Center)
• Seonhong Hwang(Department of Physical Therapy, College of Biohealth, Research Institute for Basic Sciences, Smart Healthcare Convergence Research Center) Corresponding author
• Sunmin Park(Research Institute for Basic Sciences, Smart Healthcare Convergence Research Center, Department of Food and Nutrition, College of Biohealth, Hoseo University, Asan, Korea)