Differences in the coordination of gait based on body mass index in sedentary young adults

Abstract

Purpose: Obesity is a known risk factor for knee osteoarthritis (kOA), yet there is a paucity of research investigating movement in obese individuals prior to the development of kOA. Previous studies have found very few differences in gait when comparing normal and obese young adults, yet likely differences in physical activity levels of participants have not been accounted for. Therefore, the purpose of this study was to assess knee health, gait and physical function in normal and obese sedentary young adults. Methods: Eighteen (9 normal weight (N): 21.9 ± 2.9 years, BMI 21.9 ± 1.4, 24.2 ± 4.8% body fat; and 9 obese (Ob): 24.2 ± 3.2, BMI 31.9 ± 1.2, 40.8 ± 4.8% body fat) sedentary, otherwise healthy college-aged individuals were recruited to participate in this study. Participants completed measures of physical function and knee health, including the six-minute walk test and KOOS questionnaire. Additionally, participants completed a biomechanical gait analysis at both a preferred walking velocity and a “fast” walking velocity. For this investigation, key lower extremity variables were selected for group comparison: peak external knee adduction moment (normalized to participants’ fat-free weight and height); sagittal plane knee and ankle range of motion; and sagittal plane movement coordination between the thigh and shank, and the shank and foot. A modified vector coding technique was used to assess sagittal plane movement coordination for the ankle and knee, providing a metric of segmental contribution to overall motion. Coordination was categorized into different patterns (exclusive distal segment, exclusive proximal segment, in-phase, or anti-phase motion) and the percentage of stance spent with each coordination pattern was compared across groups. A 2 × 2 (group × velocity) ANOVA statistically assessed each variable. Results: Groups were similar (P > 0.05) in preferred walking velocity (N: 1.26 m/s, Ob: 1.27 m/s), 6MW (N: 554 m, Ob: 529 m) and KOOS (N: 474.1, Ob: 478.6). There was no interaction between group and velocity, or group differences, for ankle range of motion, knee flexion excursion or peak knee adduction moment (P > 0.05, Table1). All gait variables significantly increased from preferred to fast walking (Table 1). There were no differences in sagittal plane movement coordination of the thigh and shank (P > 0.05). At the fast walking velocity, N spent a greater portion of stance with exclusive shank motion (N: 33.4%, Ob: 20.1%; P = 0.006) and significantly less time with exclusive foot motion (N: 14.8%, Ob: 33.7%; P < 0.001). Conclusions: In line with previous research, we saw an increase in range of motion at the ankle and knee joints and an increase in joint loading from preferred to fast walking velocity. Contrary to previous findings, our groups did not differ in performance on physical function tests, yet both groups were similar to obese participants in the literature. This depressed physical function is likely related to the inclusion criteria to that of sedentary individuals. Despite overall group similarities, we observed differences in the coordination of movement at the ankle, especially during fast walking. Ob walked with a greater reliance on motion of the foot to achieve ankle motion than N. This difference in coordination demonstrates that regardless of similarities in typical measures, the groups are organizing movement differently. Our findings suggest that coordination may be influenced by body mass index, not activity level. In these young healthy adults, overall movement and function do not appear to be influenced by body mass. These findings suggest a sedentary lifestyle may importantly influence research findings on kOA risk. Therefore, it is important to consider physical activity levels of participants for future studies. Furthermore, observed differences in coordination may elucidate group differences that could go unnoticed using traditional measures.Tabled 1Preferred velocityFastNormalObeseNormalObeseAnkle ROM (°)*12.18 ± 2.6211.26 ± 5.029.87 ± 3.479.19 ± 5.24Knee ROM (°)*18.63 ± 3.9219.92 ± 4.1222.30 ± 4.9024.25 ± 3.70Knee adduction moment (Nm/ffw*ht)*0.042 ± 0.0090.042 ± 0.0140.046 ± 0.0090.049 ± 0.015*There was not a significant interaction of goup and velocity, nor a significant group effect for any variable (p > 0.05). There was a significant velocity effect for each variable (p < 0.05). Open table in a new tab *There was not a significant interaction of goup and velocity, nor a significant group effect for any variable (p > 0.05). There was a significant velocity effect for each variable (p < 0.05).