The use of the CR-10 scale to allow self-regulation of isometric exercise intensity in pre-hypertensive and hypertensive participants.

PURPOSE: Isometric exercise (IE) has been shown to lower blood pressure (BP). Using equipment with force output displays, intensity is usually regulated at 30% maximal voluntary contraction (MVC); however, the cost of programmable equipment and their requirement for maximal contractions presents limitations. A simple, cost-effective alternative deserves investigation. The purpose of this study was (1) to explore the relationship between %MVC, change in systolic BP (ΔSBP), and perceived exertion (CR-10) and (2) to assess the validity of self-regulation of intensity during isometric hand-grip exercise. METHODS: Fourteen pre-hypertensive and hypertensive adults completed eight, 2-min isometric hand-grip exercises at randomised intensities; participants estimated their perceived exertion at 30-s intervals (estimation task). Subsequently, on three separate occasions, participants performed four 2-min contractions at an exertion level that they perceived to be equivalent to CR-10 "Level-6" (production task). RESULTS: There were significant linear relationships between the estimated exertion on the CR-10 scale, and ΔSBP (r = 0.784) and %MVC (r = 0.845). Level-6 was equivalent to an average ΔSBP of 38 mmHg (95% CI; 44, 32 mmHg) and a relative force of 33% MVC (95% CI; 36.2, 30%). During the production task, %MVC was not significantly different between the estimation task and each production trial. In at least the first two repetitions of each production trial, ΔSBP was significantly lower than that observed in the estimation task. CONCLUSION: These findings show that CR-10 "Level-6" is an appropriate method of self-regulating isometric hand-grip intensity; its use offers an affordable and accessible alternative for isometric exercise prescription aimed at reducing BP.

Reproducibility of 24-h ambulatory blood pressure and measures of autonomic function.

Determining the number of familiarization sessions required for accurate recordings of ambulatory blood pressure monitoring and autonomic function is a prerequisite for the appropriate design of intervention studies. The benefit of familiarization trials remains largely unexplored. The objective of the current investigation was to assess the reproducibility of 24-h ambulatory blood pressure, 24-h heart rate variability (HRV) and resting measurements of HRV and blood pressure variability (BPV). Eleven prehypertensive and hypertensive adults participated. Ambulatory blood pressure and HRV were measured across 24 h on four occasions. In addition, 5-min resting measures of HRV and BPV were recorded and analysed. Variability between consecutive pairs of trials was calculated. The typical error induced by ambulatory recordings of systolic blood pressure reduced over time (3.8-2.8 mmHg). The greatest effect of familiarization was observed at night. Ambulatory HRV was more reproducible than resting measures. The most reproducible markers were root mean square of successive differences [coefficient of variation (CV): 13.2-10%] and high frequency normalized units (CV: 15.2-6.4%), with the percentage of adjacent NN intervals differing by more than 50 ms showing the poorest reproducibility (CV: 23.9-20.7%). Overall BPV (SD) was more reproducible than the frequency domain low frequency component. Familiarization trials are required for the most accurate recordings of both 24-h ambulatory blood pressure monitoring and HRV. Ambulatory HRV provide superior reproducibility to resting measurements.