## 4 Discussion  
Regarding the physiological basis for our joint angle settings, the HREs in our study were consistently performed with the knee extended (approximately 0\({}^{\circ}\) extension). This posture optimally stretches the bi-articular gastrocnemius muscles (medial and lateral heads), enabling superior force production [4; 24]. In contrast, a flexed knee, as seen in tests like those by [PERSON] et al. [52], would slacken the gastrocnemius, shifting mechanical advantage to the mono-articular soleus [25; 26]. For the ankle, we evaluated two ranges of motion: NROM and FROM. The FROM increases the length of both the gastrocnemius and soleus muscles, significantly enhancing MG activation [2] and increasing Achilles tendon mechanical loading [36]. This wider ROM also supports longitudinal muscle growth [53]. Therefore, specific joint angle and ROM choices are critical for muscle activation, force generation, and tendon loading in lower-limb biomechanics. No studies have assessed MG and LG muscle activity during weight-bearing HREs using dynamic normalization. In this study, the FROM increased EMG activity by \(\sim\)10% compared to the NROM in both bilateral and unilateral exercises. [PERSON] et al. [26] reported 4-5% differences between overground heel raises at 0\({}^{\circ}\) and 45\({}^{\circ}\) knee flexion, whereas our study observed a 12% increase between unilateral NROM and FROM conditions. Sequential knee flexion and ankle dorsiflexion may support early retraining, although differing normalization methods warrant cautious interpretation. Further studies should assess the clinical relevance of these differences. Our study showed 13.5 and 9.5% increases in MG and LG activity, respectively, consistent with prior evidence of greater MG activation during plantar flexion exercises [24; 25; 26; 28]. [PERSON] et al. [2] reported greater differences (MG: 26.7-31.2%, LG: 10.2-19.5%) across bilateral and unilateral HREs at an NROM. In contrast, [PERSON] et al. [28] and [PERSON] et al. [26] observed smaller differences (\(\sim\)2-4%) under different conditions. These findings align with the MG's larger cross-sectional area [46]. Given the importance of task-specific normalization, this study is the first to provide normative EMG data for both unilateral \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Type of** \\ **Exercise** \\ \end{tabular} } & \multirow{2}{*}{**ROM**} & \multirow{2}{*}{**Mean \(\pm\) SD**} & \multirow{2}{*}{**SE**} & \multicolumn{4}{c}{**95\% CI**} & \multirow{2}{*}{**t**} & \multirow{2}{*}{\(p\)} & \multirow{2}{*}{\(g\)} \\ \cline{5-6}  & & & & **Low** & & & & \\ \hline \multirow{2}{*}{Unilateral} & FROM & 0.19 \(\pm\) 0.42 & 0.10 & \(-\)0.01 & 0.40 & 2.04 & 0.03 * & 0.42 \\  & NROM & 0.13 \(\pm\) 0.39 & 0.09 & \(-\)0.06 & 0.31 & 1.40 & 0.09 * & 0.32 \\ \hline \multirow{2}{*}{Bilateral} & FROM & 0.06 \(\pm\) 0.45 & 0.13 & \(-\)0.21 & 0.34 & 0.49 & 0.32 & 0.10 \\  & NROM & 0.01 \(\pm\) 0.45 & 0.13 & \(-\)0.27 & 0.28 & 0.06 & 0.48 & 0.02 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Results from the paired \(t\)-test activation ratios of the MG and LG muscles of both exercises (bilateral and unilateral) performed with full and neutral ranges of motion. and bilateral HREs using dynamic normalization methods, offering a reference for future research. MG and LG EMG amplitudes during unilateral weight-bearing HREs matched those observed during sprinting [40], highlighting the high muscular demands of this exercise. The elevated MG activation supports its application in the final phase of rehabilitation. Moreover, the higher incidence of MG injuries compared to LG injuries (58-65% vs. 8-38%, respectively) in athletes [53] further supports its use in late-stage MG rehabilitation protocols. The MG and LG showed different peak EMG activity across HRE types, consistent with previously reported activation differences during dynamic tasks [7; 10; 54].