# Biomechanical Task-Based Gait Analysis Suggests ReWalk Gait Resembles Crutch Gait
## 3 Results  
In order to investigate changes in muscle activation patterns elicited by ReWalk, we evaluated four lower-limb muscles (RF, BF, TA, and SL) that have well-documented functions during gait. The EMG WL during natural and ReWalk gaits depict significantly different patterns, as shown in the first and second columns of Figure 2, respectively. During the initial WA phase of natural gait, the BF, RF, and TA are known to coactivate in order to facilitate the loading response and ensure stability of the ipsilateral limb [1; 36]. Furthermore, SL should be inactive to ensure proper heel striking. However, a completely altered pattern can be observed with ReWalk. The EMG signal from the RF has significantly decreased compared to the previous LA phase, and BF is activated after the WA phase has started. We also note that SL EMG signals start to increase upon FC, but TA is not activated. The differences in EMG patterns are not as drastic for the SS phase. During natural gait, a marked increase in SL and diminished BF, RF, and TA E  
Figure 2: Lower-limb EMG patterns within the gait cycle obtained during the gait sessions performed by subject 1. The gait cycle is further divided into three biomechanical task-related phases, where red, green, and blue stages represent the WA, SS, and LA phases, respectively. The red vertical line represents the ipsilateral foot’s LO position. The data are represented as mean \(\pm\) SD via black lines and grey areas, respectively. While a continuous increase of SL EMG is not observed during ReWalk gait, possibly due to early activation during the WA phase or that the body weight is partially supported via crutches, considerable levels are still observable, and the absence of TA activation suggests plantar flexion intent. Also, the other evaluated muscle sites had diminished EMG levels, which is consistent with natural gait. Lastly, other than the differences observed in the late LA phase that elicited the previously mentioned WA phase discrepancies, one notable characteristic of ReWalk gait is the significant increase in BF EMG in the early LA phase, which would result in either knee flexion or hip extension. We now examine whether the form factor, most noticeably crutches and ankle immobilization, is responsible for the changes in gait patterns by investigating EMG patterns during gait with either crutches or an AFO, shown in the third and fourth columns of Figure 2, respectively. It is clearly observable that coactivation of BF and RF is absent at the start of the WA phase during crutch gait, much like what was observed with ReWalk. Furthermore, SL is actively involved and TA is absent during the WA phase. What is interesting is that the waveforms of RF and BF EMG WL during AFO gait, despite some differences in amplitude, resemble that of natural gait. The differences found with SL and TA occur in the early WA and LA phases, respectively. However, the changes in EMG patterns observed with AFO gait were not present during ReWalk gait. Taken together, the results suggest that the changes in muscle activation patterns may have been elicited by the use of crutches. In order to identify the similarities between the ReWalk and crutch gaits, we overlay and present the EMG WL data normalized to 100% of each gait-related biomechanical phase (Figure 3) before proceeding with our qualitative analysis. We can roughly categorize each time trace within the gait-related biomechanical phase as either dormant, increasing, decreasing, leveling, peaking, or a combination of the above. During the WA gait stage, both ReWalk and crutch gait exhibit dormant, peak, dormant, and increase followed by leveling for RF, BF, TA, and SL, respectively. There are no coinciding patterns for natural gait during the WA gait stage. For the SS gait stage, BF, TA, and SL all match for ReWalk and crutch gait but the RF muscle shows different patterns, as RF is dormant for ReWalk but a peak is observed for crutch gait.