Recurrence quantification analysis of age effects on sustained sub-maximal grip contractions

Recurrence quantification analysis (RQA) was used to analyze signals of sustained sub-maximal grip contraction (SSGC) of healthy subjects across several age groups. Recurrence plots (RP) of elderly subject showed clear periodic pattern combined with disrupted features in some parts, in comparison to control subjects who displayed quasi-periodic patterns. Quantitative analysis of the RP showed significant differences between elderly subjects and the control group for RQA parameters. The results showed that the SSGC signals of the elderly and adolescents had decreased RQA parameters, which indicated more chaotic patterns. In addition the deterministic component of the signals was less complex for the elderly and adolescents than for controls. Results of this study illustrate that the RQA technique is well suited to analyze age-related effects on sustained grip-force signals.