Association between blood pressure changes during self-paced outdoor walking and air temperature

Exaggerated elevation of systolic blood pressure (SBP) during exercise is a risk factor for future cardiovascular disease. Although there are differences between the outdoor exercise and exercise tests in the laboratory setting, there is little information regarding SBP changes during practical outdoor exercise. We investigated SBP changes during self-paced outdoor walking and the relationship to air temperature. Subjects (n=109, 47-83years) walked outdoors at their own pace wearing a blood pressure monitor on their wrist. SBP increased during walking compared to rest, but was higher at the 1km mark than both the 2 and 3km marks (rest, 124 +/- 14mmHg; 1km, 140 +/- 16mmHg; 2km, 136 +/- 18mmHg; 3km, 135 +/- 18mmHg). SBP at rest, air temperature, body mass index (BMI) and walking intensity during the first 1km were identified as predictors of SBP at the 1km mark in the stepwise regression analysis, independent of other confounders (R-2=0606). SBP at the 1km mark was higher in the lower temperature group (116-143 degrees C, 145 +/- 14mmHg) than in the intermediate (151-167 degrees C, 140 +/- 18mmHg) and higher (170-196 degrees C, 136 +/- 16mmHg) temperature groups, independent of SBP at rest, BMI and walking intensity. These results suggest that increases in SBP are higher on lower temperature days and are greater at 1km than at 2 and 3km. It is therefore recommended that measures are taken against the cold on lower temperature days to attenuate the SBP response during onset of walking.