# Recurrence Quantification Analysis as a Form of Postural Control Assessment: A Systematic Review
## 3 Results
### Disability/Disease  
Eight publications were included in this group. A total of 501 participants were analyzed. Their mean age ranged from 24.5 \(\pm\) 0.9 [45] to 70.83 \(\pm\) 15.89 years [55]. Their mean body weight and height values ranged from 62 \(\pm\) 7.5 kg [45] to 67.1 \(\pm\) 11.2 kg [56], and from 160 \(\pm\) 14 cm [47] to 179 \(\pm\) 55 cm [46], respectively. At this point, it is worth noting that most of the authors did not provide a complete characterization of the group. In particular, height and weight were missing. In this group, Bertec platforms with a sampling rate of 100 Hz were used to evaluate fluctuations. In two papers [57; 58], [PERSON] platforms with a much lower sampling frequency of 40 Hz were used. In this group, most studies [45; 46; 47; 55; 56] evaluated CoP fluctuations in trials lasting 30 s with and without visual control. [PERSON] et al. [59] evaluated trials lasting 60 s with both legs standing on rigid and foam surfaces. [PERSON] et al. [57] and [PERSON] et al. [58] evaluated the trials lasting 51.2 s with both feet standing only with eyes closed. In this group, only [PERSON] et al. [45] stated with what tool the RQA parameters were calculated. As in the previous section, the lag time, embedding dimension, and threshold had to be determined to perform RQA. [PERSON] et al. [46; 47; 59] did not specify a lag time in any of their papers. In all the papers belonging to the disability/disease group, the embedding dimension was counted using FNN. In four papers, it was 5, and in two papers: D = 1. The radius for recurrence was considered 10% of the maximum phase space diameter using the Euclidean norm in studies by [PERSON] et al. [46; 47; 59] and [PERSON] et al. [56]. Other authors used different values: 32% and 2.5% of the mean Euclidean distance separating points in the reconstructed phase space [45; 55]. The two authors [57; 58] used a completely different approach, resulting from a more complicated methodology and purpose of the study. Table 4 includes RQA parameter values specific to the disability/disease group. Only [PERSON] et al. [57] did not provide any values. It is remarkable that in this group, almost all RQA measures were used in four papers [45; 47; 55; 56]. The least information was provided by [PERSON] and co-authors. They used only %DET in the study [59] and %DET and ENT in the paper [46]. In [47; 55], the %REC value was higher for standing with visual control than standing with eyes closed in the ML direction. [PERSON] et al. [56] obtained an inverse relationship in the AP direction while standing on a rigid surface in both study groups. In several studies [45; 47; 56], healthy subjects had higher %REC values. However, this is not a rule. %DET and ENT were reported in every paper except the one mentioned. In most of the studies, the values of both parameters were higher for healthy people. The last group of RQA parameters in Table 4 is the most variable. [PERSON] et al. [55] reported only LMAX values, showing that these values were higher in the group of Parkinson's patients. [PERSON] et al. [58] reported LMEAN values as a function of embedding dimension and time lag. They were also the only ones to report TT values. Three papers [45; 47; 56] included TREND data. In each study, the values of this parameter were negative and lower in the healthy group when standing with eyes open on a rigid surface. The one exception to this rule was the result of [PERSON] et al. [47].