Combined Sections Meeting of American Physical Therapy Association

Document Type

Conference Proceeding




Purpose/Hypothesis: Inclined walking is a challenging daily task in comparison with level walking. It requires specific control from central nervous system and exhibits increases in muscle activities and alternations of joint kinematics in lower extremities. However, the knowledge of the inclination effect on the inter-joint coordination is limited. Previous studies have shown the benefits of investigating the inter-joint coordination in patients with Parkinson’s disease, low back pain and hemiplegic gait. This study aimed to evaluate such coordination in healthy young adults during inclined walking.

Number of Subjects: 19 healthy young adults (13 females, 6 males; aged 22 – 29 yrs)

Materials/Methods: Subjects walked at their comfortable speeds for 2 minutes in four inclined treadmill walking conditions (0%, 5%, 10%, and 15% grade). Three-dimensional kinematics data were captured at 100 Hz by an eight-camera Qualisys motion capture system. To calculate the inter-joint coordination, the phase portraits were created by plotting the specific segment’s angular position versus its angular velocity. The trajectories of these phase portraits were converted from Cartesian coordination to polar coordination to get phase angles. These phase angles were used to calculate the continuous relative phase (CRP) dynamics during a gait cycle between two segments which contained the same joint center. A mean absolute value of the ensemble CRP curve values (MARP) was calculated by averaging the absolute values of all points of the entire ensemble curve. Low MARP indicated that two segments approached to in-phase and vice versa. A two-way repeated ANOVA with Bonferroni correction was used to determine the effect of inclination and the effect of segmental combinations (shank-thigh and foot-shank) on MARP.

Results: There was a significant interaction between the effect of inclination and the effect of segmental combinations on MARP (F(3,108) = 85.85, p < 0.001). The MARP of foot-shank combination was lower than that of shank-thigh combination when walking on 0% grade (p < 0.001, approximately 26% less) and on 5% grade (p < 0.001, approximately 28% less). However, the MARP of foot-shank combination was higher than that of shank-thigh combination when walking on 10% grade (p < 0.001, approximately 26% more) and on 15% (p < 0.001, approximately 55% more).

Conclusions: When the grade increased to a certain level, the inter-joint coordination changed to a different pattern during treadmill walking.

Clinical Relevance: Inclined treadmill walking could be used for lower extremity strengthening, gait training, and cardiopulmonary conditioning. The inclination of walking should challenge the patients properly without increased risk. Our study provided a further understanding of inclination effect on gait pattern and could be used as a reference for clinical decision making. This result suggested that the pattern of the inter-joint coordination changed when the grade was between 5% to 10%. Therefore, for population with a higher fall risk, such as older adults, below 5% grade might be recommended.