## 3 Results
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Criterion**} & \multicolumn{1}{c}{**Practical**} & \multicolumn{1}{c}{**Bias**} & \multicolumn{1}{c}{**TEE**} & \multicolumn{1}{c}{**Correlation**} & \multicolumn{1}{c}{**Correlation**} \\  & **Measure** & **Measure** & **(Standardized)** & **(Standardized)** & **Correlation** & **\(p\) Value** \\  & **(MuscleLab) (N)** & **(HandyGym) (N)** & **(HandyGym) (N)** & **(Standardized)** & **(Standardized)** & **Correlation** & **\(p\) Value** \\ \hline \multirow{5}{*}{**Load**} & **(1) Yellow** & 364.98 \(\pm\) 123.26 & 125.98 \(\pm\) 38.76 & \(-\)1.94 [1 \(-\)2.01 to \(-\)1.86] & 0.85 [0.69 \(\pm\) 1.02] & 0.76 [0.76 \(\pm\) 0.82] & \(<\)0.001 \\  & C & 462.02 \(\pm\) 86.79 & 155.25  
Figure 3 further illustrates these findings using scatter plots and Bland-Altman plots, comparing the force measured by HandyGym with the reference force from MuscleLab. High correlations (R\({}^{2}\) values ranging from 0.9316 to 0.9819) are evident across all resistance levels. However, the Bland-Altman plots reveal systematic biases that vary depending on the resistance level. With the exception of a few outliers, these biases are generally negative, indicating that HandyGym consistently underestimates force across conditions. Table 3 compares power measurements obtained using the MuscleLab system (criterion measure) and HandyGym (practical measure). The standardized bias in power ranges from \"small\" to \"very large\", with significant positive biases in the BlueWP and RedWP conditions, where HandyGym tends to overestimate power compared to the criterion measure. TEE values range from \"moderate\" to \"very large\", reflecting variability in the accuracy of the practical measure. Correlation coefficients indicate a strong relationship in most conditions, except during the eccentric phase, where the correlation is \"small\". All correlations are statistically significant (\(p<0.001\)). Figure 3: Scatterplots and Bland–Altman plots illustrating the agreement between the criterion and practical measures of force (N) across the five tested load configurations, as well as for the pooled data. The scales are consistent across all conditions. In the scatterplots, R\({}^{2}\) values and regression equations for estimating criterion measures from practical measures are provided. Regression lines are included to assess the homoscedasticity of errors. In the Bland–Altman plots, the difference between the two methods is plotted on the y-axis, with the average of the two methods on the x-axis. The solid horizontal line represents the mean bias, while the dashed horizontal lines indicate the upper and lower 95% limits of agreement. Figure 4 visually supports these results, showing that while high correlations are maintained (R\({}^{2}\) values ranging from 0.8976 to 0.9871), Bland-Altman plots reveal biases that vary by resistance level. Lower load conditions (Yellow, Blue, Red) show negative biases, indicating power underestimation, whereas higher load conditions (BlueWP, RedWP) exhibit positive biases, with overestimations increasing alongside the magnitude of power. Figure 4: _Cont._  
**Load** & \(\left[-1\to 0.83\right]\) & \(1.07\pm 109.46\) & \(-0.44\left[-0.53\ to 0.35\right]\) & \(0.83\left[1.07\ to 1.93\right]\) & \(0.78\left[0.46\ to 0.68\right]\) & \multirow{10}{*}{ \begin{tabular}{c} **\[-0.001** \\ **(moderate)** \\ \end{tabular}  } \\  & **(3) Blue** & \(\left[-1\to 0.84\right]\) & \(1.08\left[0.65\ to 0.97\right]\) & \(0.68\left[0.72\ to 0.84\right]\) & \multirow{10}{*}{ \begin{tabular}{c} **\[-0.001** \\ **(moderate)** \\ \end{tabular}  } \\  & **(4) BlueWP** & \(334.12\pm 139.25\) & \(624.05\pm 348.17\) & \((\text{very large})\) & \((\text{moderate})\) & \((\text{nearly perfect})\) & \multirow{10}{*}{\ \begin{tabular}{c} **\[-0.001** \\ **(moderate)** \\ \end{tabular}  } \\  & **(5) Blue** & \(\left[-1\to 0.84\right]\) & \(1.08\left[0.65\ to 0.97\right]\) & \(0.54\left[0.72\ to 0.84\right]\) & \multirow{10}{*}{