# Recurrence Quantification Analysis as a Form of Postural Control Assessment: A Systematic Review
## 3 Results
### Children/Young/Elderly  
Eight publications were included in this group. A total of 652 participants were analyzed. Their mean age ranged from 3 [44] to 85.7 \(\pm\) 6.7 years [37]. Their mean body weight and height values ranged from 17.35 \(\pm\) 3.16 kg [44] to 86.5 kg [42] and from 103.44 \(\pm\) 4.9 cm [44] to 194 cm [42], respectively. Two types of force platforms were used to measure CoP displacement: AMTI in five papers [20; 42; 44; 51; 54] and Medicapteurs in three [37; 50; 53]. Their sampling frequency ranged from 40 Hz [37; 50; 53] to 1000 Hz [17; 44]. In the remaining papers, the sample rate was set at 100 Hz. Only [PERSON] et al. [54] did not specify its value. Describing the conditions of the measurements, the three authors [PERSON] et al. [17], [PERSON] et al. [42], and [PERSON] et al. [54] evaluated trials lasting 30 s both leg standing with and without visual control. [PERSON] et al. [37], [PERSON] et al. [50], and [PERSON] et al. [53] evaluated 51.2 s both leg standing attempts with eyes open. [PERSON] et al. [51] evaluated trials lasting 60 s in various foot placement configurations. The shortest measurements of 15 s were made by [PERSON] et al. [44]. Three studies [17; 42; 54] additionally evaluated CoP fluctuation on the foam surface with a visual inspection. It is worth noting in three papers [17; 37; 53], the Cross Recurrence Plot Toolbox [12] was used to calculate RQA parameters. [PERSON] et al. [42] made calculations in MATLAB according to [PERSON] and [PERSON] [10]. [PERSON] et al. [44], on the other hand, used [PERSON]'s RQA toolbox [6]. The other authors did not specify which programs they used. To perform RQA analysis, time delay, embedding dimension, and threshold were used. Time lag values ranged from 1 to 30, but tau = 6 was the most common [37; 50; 53]. The embedding dimension ranged from 2 to 20, but D = 8 was the most frequent value [37; 50; 53]. The threshold was defined in three ways. (1) As a percent of mean distance; (2) as a number of data points; or (3) as a percent of recurrence rate. In the first case, values were between 20% and 35%. A number of data points were used only in one study [51], where R = 2. A percent of the recurrent rate was utilized in two publications [17; 44]. In both cases, R = 5% of the recurrent rate. [PERSON] et al. [54] did not provide information about tau, D, or R values. To improve the within-session reliability of RQA, [PERSON] et al. [17] suggest fixing the recurrence rate. Table 3 includes RQA parameter values specific to the children/young/elderly group. The authors of the two papers did not provide any values. The %REC values were provided only by [PERSON] et al. [51]. They were on the plots; therefore, it was possible to read numerically only the averages. However, it is noteworthy that the highest %REC values were for fluctuations in the AP direction. %DET was present in every paper except the two mentioned. The %DET was higher for standing with eyes open compared to trials with eyes closed [17; 44; 50]. In addition, %DET values were higher in the ML direction in four papers [37; 44; 50; 53]. ENT values were noted only in four studies [37; 50; 51; 53]. [PERSON] et al. [37] and [PERSON] et al. [53] showed that its higher values were in the ML direction. [PERSON] et al. [50] reported similarly, but only for trials with closed eyes. This trend continued in tests with visual control included, but only in the elderly group. In only two studies [17; 44], authors included %LAM, and in one--%LMAX and TT. All authors showed that %LAM remained higher while standing with eyes open compared to values in trials without visual control. [PERSON] et al. [44] showed that %LAM increases with age, but only for the AP direction when standing with eyes open and closed. Only [PERSON] et al. [17] included %LMAX and TT. Both coefficients had higher values in trials involving visual control.