Chronic low back pain is one of the most prevalent and debilitating conditions among older adults, often compromising physical function and overall quality of life. Structured physical exercise, particularly the Pilates method, is widely recommended for managing this condition. However, existing literature primarily focuses on younger populations using mat-based group classes. This pilot study utilizes an exploratory mixed-methods design to investigate the feasibility and preliminary outcomes of a 12-week individualized, machine-based Classical Pilates program on quality of life and low back pain in active older adults (aged 55 to 75 years). Participants will complete 24 individual sessions (twice a week). The aim is to assess changes in physical domains of quality of life and perceived low back pain intensity, while gathering qualitative contextual insights on body awareness and psychosocial well-being.

The study is designed as an exploratory, quasi-experimental, single-arm pilot study. Participants presenting with moderate disability caused by low back pain (Oswestry Disability Index = 21% to 40%) will undergo a structured exercise protocol utilizing the Classical Pilates method on machines in a one-on-one setting. The intervention spans 12 weeks, consisting of two individual 50-minute sessions per week.

The pedagogical structure is divided into two distinct Classical approach components: the "Skeleton" (core base exercises on the Reformer and Mat) and the "System" (adaptations and specific exercises on auxiliary equipment like the Wunda Chair, Cadillac, and Barrels). Exercise progression is individualized based on biomechanical control, absence of pain, and ability to maintain a neutral lumbopelvic position. Resistance is modified primarily via adjustable springs on the equipment. Exercise intensity is strictly monitored using the Talk Test to ensure a light-to-moderate exertion level suitable for the geriatric demographic.

Assessments are conducted at baseline and post-intervention (12 weeks) using the WHOQOL-Bref for quality of life and the Oswestry Disability Index Version 2.0 for low back pain disability. Additionally, a qualitative focus group will be conducted post-intervention with a subsample of participants to capture contextual insights regarding mobility, psychosocial benefits, and daily habit integration.

Inclusion Criteria:

• Aged between 55 and 75 years.
• Physically active in daily routines.
• No previous experience with machine-based Pilates.
• Presenting with moderate disability (Oswestry Disability Index = 21% to 40%) caused by low back pain.

Exclusion Criteria:

• Absolute contraindications to physical exercise.
• Severe spinal pathologies (e.g., hernias requiring surgery, severe osteoporosis, idiopathic scoliosis).
• Previous or scheduled spinal surgeries.
• Severe disability (Oswestry Disability Index > 41%).
• Chronic obstructive pulmonary disease.
• Recent stroke or myocardial infarction.
• Uncontrolled hypertension.
• Active oncological treatment.
• Physical therapy treatment for low back pain within the six months prior to the study.

Data will be available on request from the corresponding author due to privacy and ethical restrictions.

Data will become available following the publication of the study results and will remain accessible for a period of 5 years.

Data will be shared with researchers who provide a methodologically sound proposal for secondary analysis. To ensure privacy and ethical compliance, requesters must obtain approval from an independent Ethics Committee. All requests should be directed to the corresponding author via email.