Assessment of Central Blood Pressure and Arterial Stiffness in Practicing Long-Distance Walking Race

Methods: Central systolic (cSBP) and diastolic BP (cDBP), peripheral systolic (pSBP) and diastolic BP (pDBP), central pulse pressure (cPP), peripheral pulse pressure (pPP), amplified pulse pressure (aPP), corrected augmentation index (AIx75%) and pulse wave velocity (PWV) were measured using an oscillometric Mobil‐O‐Graph® (IEM, Stolberg, Germany) in 25 male athletes (mean age of 45.3 ± 9.1 years). A p value < 0.05 was considered a statistically‐significant difference.


Introduction
Regular moderate exercise can reduce the risk of coronary heart disease through various mechanisms, including changes in cardiovascular risk factors, 1 such as glucose, lipid metabolism and blood pressure (BP) values and weight control. The protective effects of moderate exercise on the cardiovascular system are well-established. 2 The same is not true for long-distance walking and vigorous exercise, whose effects on the cardiovascular system remain unclear. 3 A mixed walking/running race takes place every July in Original Article entire course and women approximately 50%. The race ranges between fast walking and running, the average speed being 7.6km/h. No study has evaluated the effects of this type of exercise on the cardiovascular system.
The evaluation of parameters of central BP measurement and arterial stiffness, which assess aortic and peripheral pressure, vascular resistance and pressure variations throughout the arterial tree, may help improve understanding of changes in the cardiovascular system due to exercise. 4 One parameter that should be emphasized is pulse wave velocity (PWV), which measures arterial stiffness, a factor highly predictive of cardiovascular events. In addition, arterial stiffness is associated with systolic BP (SBP) and pulse pressure (PP). 5 The lower the PWV, the more elastic and complacent the arteries. Therefore, high PWV values reflect greater arterial stiffness. 6 Age and physical activity can change the PWV. 7,8 This study studied the effects of prolonged exercise on central BP measurement in athletes during this race in Goiás.

Methods
This longitudinal study evaluated men who participated in the race in Goiás, Brazil in July 2014. The race covered 310 km and lasted 5 days. The average distance covered was 62 km/day, and the average speed was 7.6 km/h. The mean temperature of the course was 30°C (range 18-42).
The initial assessment (A0) was carried out at a specialized medical centre, and other evaluations (A2, A3 and A4) were conducted at the end of each race day in the cities where the athletes slept. Assessments included measurements of central systolic and diastolic BP (cSBP and cDBP), peripheral systolic and diastolic BP (pSBP and pDBP), central PP (cPP), peripheral PP (pPP), amplified PP (aPP), corrected augmentation index (AIx75%), PWV and total vascular resistance (TVR) using a Mobil-OGraph ® oscillometric device (IEM, Stolberg, Germany). Measurements were obtained from the right upper limb with the participant seated, arms at heart level, after resting for ≥ 5 minutes.
Measurements were carried out before dinner at the end of each day. For the initial assessment, a complete medical history was taken. Due to technical problems, no assessment was made at the end of the first day of walking. Women were excluded from the study because they had a significant difference in all BP measurements and did not cover the entire course.
The medical history included the following variables: age (in years), body mass index (kg/m 2 ), smoking (yes/no), physical activity (sufficiently active/ insufficiently active), diabetes mellitus (yes/no), dyslipidemia (yes/no) and hypertension (yes/no). Sufficiently active was defined as self-reported exercise of any type for ≥ 150 minutes weekly. 9 This study was approved by the Ethics and Research Committee of Pontifícia Universidade Católica de Goiás (number 612.800, April 09, 2014). All participants gave written informed consent.

Statistical analysis
All participants in the ecological hiking were evaluated. Descriptive statistics are presented as means, standard deviation, confidence intervals (quantitative variables with normal distribution) and absolute and relative frequencies (qualitative variables). The statistical analysis was carried out using the Statistical Package for the Social Sciences® (SPSS), version 20.0. Shapiro-Wilk test was used to determinate the distributions of the quantitative variables data. Variables related to BP measurement were compared using repeated-measures analysis of variance (ANOVA), followed by a Bonferroni post hoc test. For correlations between BP variables and age, Pearson's correlation coefficient was used. A p value <0.05 was considered a statistically significant difference.

Results
We included 25 men with a mean age of 45.3 ± 9.1 years (range 27.8-60.8). All participants engaged in physical exercise regularly, and the mean body mass index was 23.1 ± 2.6 kg/m 2 . No participant was a smoker, and three had risk for cardiovascular disease (Table 1).
In all evaluations, PWV was strongly correlated with age ( Figure 1).

Discussion
This is the first study to evaluate effects of a mixed walking/running race on parameters of central BP measurement and arterial stiffness. Values of peripheral and aortic BP in the initial assessment were within the normal range. BP decreased at the beginning of walking and returned to initial values on the last days of the race. Therefore, between the start and finish of the event, it seems that no significant changes occurred in these parameters. These findings support the vasodilation potency of this type of moderate-intensity and long-duration exercise.
Endurance athletes may present arterial remodelling, which causes an accommodation of pressure during and after exercise. The ability of the arteries of the skeletal muscle to vasodilate, promoted by training, increases the cardiac deficit without relevant repercussions in BP. This elasticity of the arterial vessels in response to physical activity suggests arterial adaptation, which is indispensable to the performance of endurance athletes. 10 Runners participating in marathons in Seoul 11 and Athens 12 showed a reduction in both DBP and SBP at the event's beginning and end. In our study, this behaviour was also identified regarding central BP measurement.
The PWV values of participants in our study were within the reference ranges for healthy individuals: 7.0 m/s for this age range. 13 We found high values compared to controls performing moderate physical exercise. 12 Therefore, because of the small amount of specific training, consisting of a few hours of training weekly, and the fact that the participants' cardiovascular parameters matched reference values, we believe that the group assessed in our study was composed of active individuals, but not professional athletes.
There was no significant change in PWV in different measurements throughout the walking event, but we observed a trend towards a reduction in the first 3 days. A study that analysed PWV in male athletes participating in a 75-km race found a reduction in PWV after 45 km; beyond that point, there was an increase until 75 km, after which values nearly returned to baseline. We found similar results. 14 Other studies have found no change in PWV before and after exercise in marathon runners, 11,12 walkers, 15 and runners with high BP. 16 In the latter two studies, the heart rate corresponded to that seen with moderate exercise.
Other studies found a significant reduction in PWV in hypertensive individuals who did running and/or walking 17 and in normotensive individuals who engaged in various types of aerobic exercise (moderate to vigorous). [18][19][20] A systematic review and meta-analysis that evaluated the effects of aerobic exercise on PWV found a reduction in PWV promoted by aerobic exercise. This reduction increased with long-duration exercises, which promote a higher oxygen consumption. 21 However, reductions in cSBP and PWV have the potential to reduce the risk of additional cardiovascular events, then reinforcing the potential benefit of regular physical activity. 5 Our study identified a strong positive correlation between PWV and age, as did studies that determined reference values, 13,22 evaluated and compared competitive athletes and active individuals, 23 and a study in men engaging in moderate exercise using a cycle ergometer. 24 Other factors may be associated with PWV, such as BP and the intensity of exercise 12 and body weight. 25 Age influences both BP and PWV − the older the age, the higher the BP and PWV. This occurs, amongst other reasons, due to changes in arterial structure. This difference in values found between central BP   However, an inversion of collagen proportion exists in relation to elastin in muscle peripheral arteries. Therefore, the aorta presents greater elasticity compared with the arteries of the limbs, which are more rigid. 26 Although this study did not evaluate the effects of inflammatory substances and endothelium adhesion, these factors must be also considered. Variations in PWV Original Article may be related to many adaptations due to moderate aerobic activity that involve increased production of a number of substances with vasodilating and anti-inflammatory properties. 27,28 A study that evaluated hypertensive and non-hypertensive ultra-marathon runners, collecting samples after 100 km, 200 km and 308 km (end of the race), identified an increase in vascular cell adhesion molecule 1 (at 100 and 200 km), E-selectin (at 100 km), and leukocytes (at 208 km), which were higher in hypertensive individuals than in normotensive individuals. In both groups, there was a gradual increase in creatine kinase and C-reactive protein. Therefore, vigorous exercise can stimulate more intense endothelial responses in hypertensive individuals, regardless of inflammatory markers. 29 Likewise, PWV depends on the arterial structure and the relationship between resistance and elasticity, properties directly related to the amount of collagen and elastin. Therefore, PWV changes are identified over time; to verify the effects of exercise on this parameter, further long-term, longitudinal studies would be needed to analyse the chronic effects of exercise. 26 Our study also did not evaluate variations in mean central BP after the end of the event. However, the acute effect was well analysed and showed that this activity is fairly safe for well-evaluated participants, even without specific training.

Conclusion
Blood pressure dropped in the first days of the race and returned to close to baseline values at the end. PWV correlates strongly with age. Ecological hiking seems to promote effects on arterial pressure and PWV similar to those seen in marathons and other long-duration and high-intensity sports. Changes promoted by this type of exercise in active and healthy individuals do not seem to pose high risks for cardiovascular health.