Rating of perceived exertion - a valid method for monitoring light to vigorous exercise intensity in individuals with subjective and mild cognitive impairment?

In rehabilitation settings, exercise intensity is often monitored with Borg's rating of perceived exertion (RPE). However, previous studies showed that severe cognitive impairment may limit the usability of the RPE. The aim of this study was to assess the relationship between RPE and heart rate (HR), and to establish whether a target RPE can be used to achieve exercise intensity based on an individual's HR-RPE in people with early cognitive impairment. 97 participants (74.7 ± 6 years) with early cognitive impairment completed an incremental exercise test. Of these, 54 were tested during a single, RPE guided exercise session. RPE and HR were monitored throughout. Correlations between HR and RPE were assessed using Spearman's correlation. Mean differences between measured HR and target HR were calculated and compared using a two-way ANOVA with factors cognition and exercise mode. Bland-Altman plots were constructed to analyse the agreement between target and measured HR. HR and RPE correlated moderately with each other ( < 0.001;  = 0.555) and no differences between target and measured HR were observed. Bland-Altman plots revealed a mean difference of 1.2 bpm and a 95% level of agreement was between 24.4 and -22.1 bpm. No differences in rating accuracy were observed between different cognitive impairment levels nor between different exercise modes. Bland-Altman plots revealed some variance between the participants with almost half of them missing target HR by 10bpm or more. Therefore, the RPE should only be applied with caution and, if possible, with other measurements (e.g. heart rate monitors) to ensure that target intensity is reached.