Asymmetric walking on an incline affects aspects of positive mechanical work asymmetrically

Abstract

The purpose of this study was to determine the extent to which we could use a split-belt experimental paradigm to increase limb or joint work. Split-belt treadmill walking was combined with uphill walking at 0°, 5° and 10° in young, healthy individuals to assess whether we could specifically target increased force output between and within limbs. Thirteen healthy, young adults participated in this study. Participants performed walking trials with the left belt at 1.0 m/s and the right belt at 0.5 m/s. Repeated measures ANOVAs assessed the effects of speed of the treadmill belt and incline on total and joint specific positive extensor work as well as relative work. Mechanical work varied because of the speed and incline of the treadmill belt at the level of the total limb and across joints. Positive lower extremity relative joint work varied as a result of treadmill belt speed and treadmill incline. Positive mechanical work was greater on the limb that was on the faster treadmill belt, regardless of incline. Increases in relative knee but not hip joint work increased as incline increased. The current investigation shows that the nervous system can shift mechanical work production both between and within limbs to safely walk in a novel split-belt environment. This work extends previous research by demonstrating that researchers/clinicians can also use increasing treadmill incline (or some other means to add increased resistive forces) during split-belt treadmill walking to encourage increased mechanical output at particular limbs and/or joints which may have rehabilitation implications.

Keywords: Joint work; Kinetics; Split-belt treadmill; Walking.

Fig. 1.

Summary data for all participants of mechanical work from the ankle, knee, and hip as they walked for two minutes in a split-belt treadmill environment. Group level data from the limb on the faster belt (blue, 1.0 m/s) and the slower belt (red, 0.5 m/s) is displayed along with the standard deviation (shaded area). Qualitatively, the change in mechanical output across steps is small relative to the variability in the measures.

Fig. 2.

Box and whisker plots of lower limb extensor positive work between limbs and across the different treadmill inclines is displayed. Individual data points are overlayed. Data from the limb on the faster belt (blue, 1.0 m/s) and the slower belt (red, 0.5 m/s) is displayed. The limb on the fast belt generated significantly more positive mechanical, although both the limb on the fast and slow belt produced greater mechanical work.

Fig. 3.

Box and whisker plots of lower limb extensor joint work of the hip (top) knee (middle) and ankle (bottom) between limbs across the different treadmill inclines is displayed. Individual data points are overlayed. Data from the limb on the faster belt (blue, 1.0 m/s) and the slower belt (red, 0.5 m/s) is displayed. Significant interactions were observed for the hip and knee, but not the ankle.

Fig. 4.

Relative percentage of total positive mechanical work of the lower extremities relative to the limb on the faster (1.0 m/s, Blue shades) and slower (0.5 m/s, Red Shades) treadmill belt. With incline the we observed a significant increase in knee joint work on the slower belt (p < 0.001) while the hip and the ankle generated greater relative joint work on the faster treadmill belt (p < 0.001 for both comparisons).