How does a short period of exercise effect toe pressures and toe-brachial indices? : a cross-sectional exploratory study

Background: Whilst post exercise ankle-brachial indices (ABI) are commonly used to help identify peripheral arterial disease (PAD), the role of post exercise toe pressures (TP) or toe-brachial indices (TBI) is unclear. The aim of this study was to determine, in a population without clinical signs of PAD, the effect that30 s of weight-bearing heel raises has on TP and TBI values. Additionally, the ability of resting TP and TBI values to predict change in post-exercise values using the heel raise method was investigated. Methods: Participants over the age of 18 with a resting TBI of ≥0.60 and ABI between 0.90 and 1.40, without diabetes, history of cardiovascular disease and not currently smoking were included. Following ten minutes of supine rest, right TP and bilateral brachial pressures were performed in a randomized order using automated devices. Participants then performed 30s of weight-bearing heel raises, immediately after which supine vascular measures were repeated. Data were assessed for normality using the Shapiro-Wilk test. For change in TP and TBI values the Wilcoxon Signed-Rank Test was performed. For correlations between resting and change in post exercise values, the Spearman Rank Order Correlations were performed, and where significant correlation identified, a linear regression undertaken. Results: Forty-eight participants were included. A statistically significant decrease was seen in the median TP from resting 103.00mmHg (IQR: 89.00 to 124.75) to post exercise 98.50mmHg (IQR: 82.00 to 119.50), z=-2.03, p=0.04. This difference of 4.50mmHg represents a 4.37% change and is considered a small effect size (r=0.21). The median TBI also demonstrated a statistically significant decrease from resting 0.79 (IQR: 0.68 to 0.94) to post exercise 0.72 (IQR: 0.60 to 0.87), z=-2.86, p=<0.01. This difference of 0.07 represents an 8.86% change and is considered a small effect size (r=0.29). Linear regression demonstrated that resting TBI predicted 22.4% of the variance in post exercise TBI, p=<0.01, coefficients beta -0.49. Conclusions: Thirty seconds of weight-bearing heel raises resulted in a similar decrease in TBI values seen in longer periods of exercise. TP values also showed a decrease post exercise; however this was contrary to previous studies.