How Uphill and Downhill Running Interfere Posture and Muscle Activity: Descriptive Laboratory Study

Background: Downhill and uphill running alter running kinematics, force distribution, and muscle activity. While lower limb changes are well studied, research on the back and pelvis remains limited. This study examined how six gradients (-15% to 15%) affect back and pelvic posture and muscle activity. Understanding these changes is important for injury prevention and post-back injury protocols.
Methods: Twelve healthy recreational runners (6 women; age 25.0 (SD 1.6) years; body mass 61.1 (3.5) kg; height 167.8 (5.4) cm; and 6 men; age 26.3 (1.2) years; body mass 75.0 (6.9) kg; height 178.0 (8.5) cm) participated. Kinematic changes such as lumbar lordosis, hip drop, pelvic tilt, and trunk inclination were assessed using 3D motion capture. Muscle activity in the lower limbs and trunk was measured via surface electromyography.
Results: Compared to level running lumbar lordosis was increased at -15% (mean difference MD: 1.2 (4.9) degrees, Cohen’s d = 0.73) and decreased at +15% (MD: -1 (3.6) degree, d = 0.39). Total hip drop decreased at -15% (MD: 14.2 (11) mm, d = 1.93). Muscular activity of lower limb muscles was higher at steep downhill and uphill gradients. While of the abdominals only obliquus externus showed grade-specific increases, activity of erector spinae was relevantly reduced at -5% and -10%.
Discussion: Increased lumbar lordosis during downhill running may increase lumbar spine overload, especially in runners with lower back issues. For injury prevention and rehabilitation, we recommend starting with uphill running, followed by level, and then downhill. Additionally, grade-specific training is vital due to varying demands.