Exercise-Based Strategies for Chronic Back Pain

Trunk Flexor Muscle Strength (Isokinetic Peak Torque): Trunk flexor muscle function will be assessed using an isokinetic dynamometer (Cybex NORM or HUMAC NORM system). The primary outcome will be peak torque during trunk flexion, reported in Newton-meters (N·m) (and, if applicable, normalized to body mass as N·m/kg). Higher values indicate greater trunk flexor strength.

Trunk Extensor Muscle Strength (Isokinetic Peak Torque): Trunk extensor muscle function will be assessed using an isokinetic dynamometer (Cybex NORM or HUMAC NORM system). The primary outcome will be peak torque during trunk extension, reported in N·m (and, if applicable, normalized to body mass as N·m/kg). Higher values indicate greater trunk extensor strength.

Pain intensity and pain-related characteristics will be assessed using the Short-Form McGill Pain Questionnaire (SF-MPQ). The outcome will be the SF-MPQ total score, calculated as the sum of 15 descriptor items rated on a 0-3 scale (0 = none, 1 = mild, 2 = moderate, 3 = severe). Total score ranges from 0 to 45 points, with higher scores indicating worse pain and lower scores indicating improvement.

Abdominal wall tension will be measured during the performance of standardized DNS functional tests using a wearable abdominal wall tension monitoring belt (OHMBelt). The device provides continuous, noninvasive, device-derived estimates of abdominal wall tension, which are related to changes in intra-abdominal pressure. Outcomes will include peak abdominal wall tension and mean abdominal wall tension recorded during each DNS test, reported in device-derived units (arbitrary units, a.u.) (and/or as change from baseline, as applicable). Higher values indicate greater abdominal wall tension during task performance.

Maximal oxygen uptake (VO₂max) will be assessed using a graded exercise test (GXT) on a motorized treadmill with breath-by-breath gas exchange analysis (Metalyzer metabolic cart). VO₂max will be defined as the highest 30-second averaged oxygen uptake achieved during the test and reported in mL/kg/min (and, if applicable, also in L/min). Higher VO₂max values indicate greater aerobic capacity.

Pressure pain threshold will be assessed using quantitative sensory testing with a handheld digital pressure algometer applied at standardized anatomical sites. The outcome will be reported as the pressure at pain threshold in kilopascals (kPa). Higher PPT values indicate lower mechanical pain sensitivity.

Lower-body maximal isometric force production will be assessed using an isometric mid-thigh pull (IMTP) performed on dual force plates (ForceDecks system). The primary outcome will be peak vertical ground reaction force, reported in Newtons (N) (and, if applicable, also normalized to body mass as N/kg). Higher values indicate greater maximal isometric lower-body force.

Handgrip (kg) is measured by Takei (TKK 5401, Japan).It will be measured for both hands (left and right). Three trials will be performed on each hand and the mean will be calculated. The standard for men over 40 years of age is 47 (±9.5) kg for the right hand and 45 (±9.3) kg for the left hand. The standard for women over 40 is 29 (±5.7) kg for the right hand and 28 (±5.7) kg for the left hand. Higher values are considered to be better.

Exercise motivation and self-regulation will be assessed using the Behavioral Regulation in Exercise Questionnaire-3 (BREQ-3). Items are rated on a 0-4 scale (0 = not true for me, 4 = very true for me). Outcomes will be reported as subscale mean scores (range 0-4 points). Higher scores indicate greater endorsement of the respective motivation/self-regulation construct.

Adverse events will be monitored and recorded throughout the intervention period. Events of interest include falls, injuries, musculoskeletal complaints, hypoglycemic episodes, major cardiovascular events, and any other events potentially related to study participation.

Adverse events will be captured via participant self-report at each weekly contact/session and active investigator monitoring. Each event will be documented by type, onset date, duration, severity (mild/moderate/severe), seriousness (serious vs non-serious), and relatedness to the study intervention (not related/possibly/probably/definitely related). Outcomes will be reported as the number of participants experiencing ≥1 adverse event and the total number of adverse events during the intervention.

Body mass index (BMI) will be calculated as body weight in kilograms (kg) divided by height in meters squared (m²) and reported in kg/m². Higher BMI indicates higher body mass relative to height. The World Health Organization (WHO) adult reference range for normal BMI is 18.5-24.9 kg/m².

Total body fat mass will be assessed using dual-energy X-ray absorptiometry (DEXA) and/or InBody370S and reported in kilograms (kg).

Total body lean mass will be assessed using dual-energy X-ray absorptiometry (DEXA) and/or InBody370S and reported in kilograms (kg).

Body weight will be measured using a InBody370S and reported in kilograms (kg).

Serum total cholesterol will be measured from venous blood samples using standard clinical laboratory enzymatic assays. Results will be reported in mmol/L. Laboratory-specific reference ranges will be used for clinical interpretation (e.g., 2.90-5.00 mmol/L).

Serum LDL cholesterol will be measured from venous blood samples using standard clinical laboratory assays. Results will be reported in mmol/L. Laboratory-specific reference ranges will be used for clinical interpretation (e.g., 1.20-3.00 mmol/L).

Serum HDL cholesterol will be measured from venous blood samples using standard clinical laboratory assays. Results will be reported in mmol/L. Laboratory-specific reference ranges will be used for clinical interpretation (e.g., 1.00-2.10 mmol/L).

Fasting blood glucose will be measured from venous blood samples using standard clinical laboratory assays (e.g., enzymatic methods). Results will be reported in mmol/L. Laboratory-specific reference ranges will be used for clinical interpretation (e.g., 3.30-5.59 mmol/L).

Systolic blood pressure (SBP) will be assessed in a seated resting position using a validated oscillometric device with brachial cuff-based measurement (Arteriograph). Results will be reported in millimeters of mercury (mmHg). Higher values indicate higher systolic arterial pressure. For clinical interpretation, commonly used resting thresholds include <120 mmHg (normal) and ≥140 mmHg (hypertension) (thresholds may vary by guideline and population).

Diastolic blood pressure (DBP) will be assessed in a seated resting position using a validated oscillometric device with brachial cuff-based measurement (Arteriograph). Results will be reported in mmHg. Higher values indicate higher diastolic arterial pressure. For clinical interpretation, commonly used resting thresholds include <80 mmHg (normal) and ≥90 mmHg (hypertension) (thresholds may vary by guideline and population).

Aortic pulse wave velocity (aPWV) will be assessed using oscillometric pulse wave analysis with a brachial cuff-based system (Arteriograph). Results will be reported in meters per second (m/s). Higher aPWV values indicate greater arterial stiffness. For clinical interpretation, ~10 m/s is commonly used as a threshold indicating increased arterial stiffness in adults, although reference values vary by age and blood pressure.

Resting heart rate will be assessed during seated rest using a cuff-based oscillometric measurement (Arteriograph). Results will be reported in beats per minute (bpm). Higher values indicate higher resting heart rate. In adults, a commonly cited resting reference range is approximately 60-100 bpm (may vary with fitness level, medications, and clinical status).