Effect of Exercise and Magnesium on Blood Pressure and Heart Rate in Hypertensive Adults in Nairobi and Kiambu Counties, Kenya
Boit, Edwin Kiptolo
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Physical exercise and magnesium have both been shown to independently cause reductions in blood pressure (BP). The primary objective of this study was to investigate the combined effect of exercise and magnesium on blood pressure. The secondary objective was to investigate the effects on resting heart rate (RHR) over a 6 week period. Forty seven (47) hypertensive adults (25 males and 22 females) who were recruited from Kenyatta University and Thika Level 5 hospital, were randomly assigned to an exercise only group (EX; n=15), magnesium only group (MGS; n=18), and a combination of exercise and magnesium (EMG, n=14). The EX and EMG group performed moderate intensity circuit training (40≥60 VO2max) for 45 minutes, 5 times a week, with intensities being monitored using a heart rate monitor (Garmin, Olathe, Kansas, US). The EMG group also took magnesium citrate supplements (Now, Bloomingdale, IL, US) (500 mg/day) concurrently with the MGS group. This was a pretest-posttest experimental study where Brachial BP (using a Mercury Sphygmomanometer: Rudolf Reister GmbH, Bruckstr, Jungingen, Germany), RHR, and anthropometric measurements (Height, weight, hip circumference and waist circumference) were taken at baseline, mid-point and posttest. Data were analyzed using SPSS version 25 and Microsoft Excel 2013 for Windows. The significance levels were set at p<0.05. Data were tested for normal distribution using the Shapiro-Wilk test while the Levenes test were used to test for data normality, which classified all the data as parametric. A paired t-test was used to compare mean differences within the groups, while a two-way ANOVA were used to compare mean differences from baseline, mid-point and post-test between the groups. If the differences between pretest and posttest were statistically significant, the Bonferroni post-hoc test was used for pairwise comparisons. A linear regression analysis was used to determine the relationship between BP and RHR. The EMG group had the largest reduction in SBP (-7.1 ± 2.2 mmHg, p<0.001) followed by the EX group (-4.6 ± 3.1 mmHg, p<0.001) and then the MGS group (-2.3 ± 2.7 mmHg, p<0.05). At midpoint (3 week), the EMG group were the only group to have a significant (p<0.05) reduction (-3.57 ± 3.2 mmHg) in SBP. There were reductions in DBP within the EMG group (-4.9 ± 4.4 mmHg, p<0.001) and EX group (-3.4 ± 3.9 mmHg, p<0.05) however none differed significantly between the two groups (p>0.05). They were however higher than the reductions in DBP in the MGS group (- 1.0 ± 5.2 mmHg, p>0.05). The reduction in RHR were the highest in the EMG (-10.9 ± 4.0 bpm, p<0.05) followed by the EX (-6.0 ± 4.9 bpm, p<0.001), while the MGS (- 2.9 ± 6.1 bpm, p>0.05) group did not have a significant reduction. At the end of the study 19 individuals had achieved pre-hypertension status (SBP 120-139 mmHg and DBP 80-90 mmHg) (EMG; n=7, EX; n=7 and MGS; n=5) from grade 1 hypertension status. Our findings suggest that a combination of exercise and magnesium causes a larger reduction in SBP than exercise or magnesium alone. This combined method also enhances the speed with which this BP reduction occurs. This study suggests that individuals with hypertension can get an enhanced BP lowering effect by combining exercise and magnesium rather than using either one of the methods independently. Secondly, a combination of magnesium and exercise is more effective at reducing RHR than exercise alone, while magnesium supplements do not cause any significant reduction. The study recommends implementation of a combined exercise and magnesium regimen as part of the treatment plan for individuals with Grade 1 hypertension within lower and middle income countries.