# Recurrence Quantification Analysis as a Form of Postural Control Assessment: A Systematic Review
## 4 Discussion
### Impact of Training on RQA Parameter Values  
This section includes papers where the effect of training (brisk walking program, aerobic exercises, and practice of contemporary dance) on postural responses was evaluated. [PERSON] et al. [67] indicated a lack of influence of a 6-month brisk walking program with three sessions of 60 min per week at moderate intensity on postural responses and on dynamical measures obtained by time series analysis. In subsequent studies, [PERSON] et al. [64] showed that in older sedentary women, two consecutive bouts of 6 min of aerobic exercise separated by a 20 min rest period did not alter linear postural kinematic measures but significantly increased the %DET in the ML direction. This result indicates reduced postural complexity and less adaptability in the ML direction [74]. The authors interpret it as a less adaptive behavior related to hip muscle work strategies negatively affected by walking exercise. [PERSON] et al. [43] examined the impact of contemporary dance (CD) and fall prevention (FP) programs on the postural control of older adults. The authors showed that the practice of CD in older adults reduced recurrence and mathematical stability in RQA (LMAX) as compared to the practice of FP, which tended to induce reverse patterns. Similar studies were conducted by [PERSON] et al. [62]. The authors examined whether massed CD training (4.5 h a week for one month in duration) might induce similar effects on postural control in older adults. They showed that LMAX (mathematical stability) decreased in the non-dancers (ND) group in the eyes open condition between pre- and post-test periods, whereas it remained stationary in the CD group. The authors report that such an effect may have resulted from the test-retest. Participants may have adopted a different strategy of standing upright in the post-retest assessment without intervention.  
[PERSON] et al. [20] evaluated the effect of added and removed calf vibration on balance control (without visual control) in elderly individuals who reported falling or not and in a group of young subjects. Vibrators attached bilaterally over the triceps sure muscles were activated twice for 15 s, after 15 and 75 s. CoP movement was compared in 15 s epochs before, during, and after calf vibration removal between groups. Before vibration, compared to fallers, young people had a lower %DET (were more predictable), a longer LMEAN (less sensitive to small perturbations, i.e., better balance performance), and a higher %LAM with a longer TT (were more intermittent). Compared to non-fallers, the young also had longer LMEAN and TT, but %DET and %LAM were not significantly different between young and non-fallers. In the young group, %DET and LMEAN (balance performance), %LAM, and TT (intermittent control) were higher in all epochs as compared to fallers and non-fallers. No differences were observed between fallers and non-fallers at baseline. During ankle vibration, fallers and non-fallers were not significantly different in any linear or non-linear outcome variables. In conclusion, compared to older subjects, CoP movement in the young was more predictable and less sensitive to small perturbations. Balance measurements did not differ between falling and non-falling subjects before and during vibration.