# Biomechanical Analysis of Gait Compensation Strategies as a Result of Muscle Restriction
## 4 Discussion
### Compensation Strategies
#### 4.1.1 C-Restriction  
In C-restriction, the mainly restricted muscles are the GAS and TA. **Effect on the ankle motion:** \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & **Walking Speed [km/h]** & **Normal Walking** & **C-Restriction** & **CT-Restriction** \\ \hline
**Cadence** & 3.5 & 102.71 \(\pm\) 12.34 & 101.37 \(\pm\) 6.42 & 100.35 \(\pm\) 8.89 \\
**[steps/min]** & 4 & 107.97 \(\pm\) 7.70 & 104.15 \(\pm\) 7.38 & 105.46 \(\pm\) 7.79 \\ \hline
**Step Length** & 3.5 & 0.57 \(\pm\) 0.03 & 0.57 \(\pm\) 0.05 (5 *) & 0.57 \(\pm\) 0.04 ( *) \\
**[m]** & 4 & 0.60 \(\pm\) 0.03 & 0.61 \(\pm\) 0.03 (3 *) & 0.60 \(\pm\) 0.05 ( *) \\ \hline
**Single Support Phase** & 3.5 & 64.20 \(\pm\) 5.43 & 63.45 \(\pm\) 3.14 (8 *) & 64.13 \(\pm\) 3.42 (8 *) \\
**[\% stride]** & 4 & 66.36 \(\pm\) 4.25 & 63.93 \(\pm\) 4.32 (8 *) & 64.55 \(\pm\) 3.11 (9 *) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Gait timing between subjects. Median \(\pm\) IQR among subjects. The step length was normalized to the subject height. The information in parentheses indicates the number of subjects that experienced a significant reduction in the respective gait parameter. * \(p<0.05\) indicates a significant reduction in comparison with normal walking. According to [PERSON]'s simulations, when the TA and GAS muscles are weakened, their activity level reduces as the weakness increases. Additionally, when the GAS and SO muscle groups are weakened, the TA muscle activity decreases. The compensation motion observed in our study as shown in Figure 3a agrees with the decay in the TA muscle activity during the loading response and swing phases, where, in a normal gait, the TA muscle is known to have its most prominent activity in generating a dorsal-flexion moment [23]. The higher plantar flexion during the loading response phase observed in our experiment suggests that the movement of the foot toward plantar flexion after HC is not decelerated by a weak TA muscle, as it occurs in the normal gait. Thus, the ankle reaches a higher plantar flexion than normal before a sufficient dorsal-flexion moment is created at the ankle that moves the tibia forward over the articular surface of the talus (known as ankle rollover). During the swing phase, we observed that the ankle exhibited a lower dorsal flexion, resulting in a lower foot clearance. The weakness of the GAS muscle was noticeable in the majority of subjects from the mid-stance to terminal stance, when the GAS in the normal gait is most active in controlling the dorsal flexion of the ankle before TO [23]. At the end of the rollover, we observed that the ankle reached a higher dorsal-flexion angle before initiating plantar flexion to prepare for TO. This agrees with the concept of a weakened GAS muscle that could not decelerate the dorsal flexion of the ankle as normal. **Effect on the knee motion:**  
An increased knee flexion from the loading response to mid-stance was observed in the majority of subjects (see Figure 3c), that suggests a weakness in the VAS muscles. In the normal gait, these muscles prevent knee hyperflexion in the loading response phase, and extend the knee until the middle of mid-stance [23]. Moreover, the observed higher knee flexion in the terminal stance and initial swing suggests compensation from the BFS muscle as reported in the simulations of [PERSON], i.e., as a compensation for the weak GAS and SO muscles. The higher activity of the BFS muscle in a terminal stance could help prevent knee hyperextension, and the higher activity in the initial swing could compensate for the lower dorsal flexion of the ankle and ensure sufficient foot clearance. **Effect on the hip motion:**  
[PERSON]'s simulations reported increased activity in the HAM muscles as compensation for the weakness of the GAS muscle. In agreement with this compensation, we observed a higher hip extension from the loading response to the middle of the mid-stance (see Figure 3e), where in normal gait the semimembranosus and semitendinosuscles (HAM muscles) are active to extend the hip.