Estimation of joint and muscle forces during exercise in various postures

Area of Science:

• Biomechanics
• Musculoskeletal Disorders
• Exercise Physiology

Background:

• Accurate assessment of joint and muscle forces is vital for effective exercise prescription in patients with musculoskeletal disorders.
• Previous research has primarily focused on standing exercises, with less emphasis on forces generated during sitting or supine postures.

Purpose of the Study:

• To quantify and compare joint and muscle forces during various standing, sitting, and supine exercises.
• To identify exercises that may pose a higher risk for individuals with low back pain.

Main Methods:

• Musculoskeletal modeling and motion capture were used to estimate joint and muscle forces in ten healthy males.
• Exercises included gait, squat, forward lunge (standing), knee extension, straight leg raise, and bridging (sitting/supine).
• Optimization algorithms estimated external forces from the chair or floor during sitting/supine exercises.

Main Results:

• Standing exercises (gait, squat, lunge) generally produced greater hip, tibiofemoral, and lower extremity muscle forces (VL, GMAX, GAS).
• Bridging exercise showed comparable L4-L5 joint forces to gait and squat, and higher erector spinae (ES) and multifidus (MF) muscle forces than gait.
• Sitting/supine exercises, particularly bridging, induced significant L4-L5 joint and hip loading, and greater trunk extensor muscle activation.

Conclusions:

• While standing exercises often yield higher overall joint and muscle forces, specific supine exercises like bridging can impose substantial loads on the lumbar spine and hip.
• Physical therapists should exercise caution when prescribing supine exercises, such as bridging, for patients experiencing low back pain.
• The findings highlight the importance of considering exercise posture when evaluating joint and muscle loading for rehabilitation.