# Empirical Validation of a Streamlined Three-Repetition Sit-to-Stand Protocol Using MAI Motion
## 3 Results  
This study employed 3D MAI Motion capture technology to analyse key kinematic parameters, including positive and negative impulse, impulse ratio, and range of motion across critical joint movements, or categories such as knee angle, knee abduction, hip angle, hip abduction, and ankle angle, as well as left/right and core movement. These parameters were assessed during a repeated STS test performed five times (5x) by 20 participants, providing a comprehensive evaluation of dynamic joint and body motion under varying biomechanical loads [15]. The purpose of this evaluation was to determine whether 5x repeats are necessary or whether 3x repeats provide equivalent data and results. Figure 1 shows an overview of the representative data from one participant. Whilst there was considerable variation across the parameter scores within categories (for example, when comparing left and right positive and negative impulse scores for knee angle--Figure 1A) and across categories (when comparing the same parameters for knee, hip and ankle angle--Figure 1A-C), there was relatively limited variation between scores derived from 5x vs. 3x for the same parameter, with comparable means and standard deviations. Consistent with this, there were no significant differences between the means for scores derived from 5x or 3x for the same parameter. Furthermore, analysis of the coefficient of variation (CV) across the scores (Figure 1H) showed comparable CVs for 5x and 3x, which were statistically indistinguishable and typically in the range of 10 to 20%, values considered ideal to acceptable in this context [14]. Next, we analysed the difference in means (DiMs) to establish whether there were any significant differences between the results generated from an analysis of 5x or 3x repeats from all 20 participants (Figure 2). There were no significant differences between 5x or 3x, with DiMs for most parameters typically ranging between 0 and 10%, indicating good consistency between 5x and 3x repeats (as illustrated by all the mean DiMs being less than 10%). Higher values of up to 30%, were seen for some individual DiMs (which represent the DiM for that parameter for one participant), most notably for impulse ratio in knee angle, ankle angle, and hip abduction (Figure 2). Similar results were seen when mean data were grouped and analysed per participant, with no significant differences between 5x vs. 3x repeats when compared at the level of the individual participants or after combining values across participants (see Supplementary Figure S1A,B). The analysis of DiMs between 5x vs. 3x for individual participants further emphasised the consistency between the data generated by 5x and 3x repeats (see Supplementary Figure S1C). Collectively, the absence of any statistically significant differences between the DiMs for 5x and 3x and the consistency between measures suggests that an analysis of the data from 3x repeats generates results comparable to data from 5x repeats. To investigate this further, we analysed the CVs generated from the 5x or 3x repeats from all participants (Figure 3). Whilst most CV values were below 20%, in some instances higher values around 60 to 70% were evident (for example, participants 2 and 7, knee angle (red) and hip abduction (orange), Figure 3A). Importantly, where such high values were found, they were present in both the 5x and 3x repeats. Statistically significant differences were revealed when comparing the CVs between 5x vs. 3x for participants 2, 6, 7, 14, and 15. For participants 2, 7, and 15, the CVs were significantly lower in the 3x compared to 5x (14.9 \(\pm\) 10.7 vs. 18.7 \(\pm\) 12.7; 17.1 \(\pm\) 14.5 vs. 20.1 \(\pm\) 13.5; 13.0 \(\pm\) 6.94 vs. 10.9 \(\pm\) 6.3, mean \(\pm\) SD, * \(p\) < 0.025) whereas this difference was reversed for participants 6 and 14 (18.0 \(\pm\) 12.9 vs. 15.4 \(\pm\) 11.3; 15.2 \(\pm\) 7.4 vs. 16.9 \(\pm\) 10.0 mean \(\pm\) SD, * \(p\) < 0.025 or ** \(p\) < 0.002, respectively (Figure 3A).