Hypertension, an established independent risk factor for CHD, stroke, and CVD (1,13) is observed in approximately 60% of Japanese people aged 60 yr or older. Pharmaceutical antihypertensive therapy for elderly patients with hypertension has contributed to a dramatic reduction in cardiovascular mortality and morbidity (2,8,19,22,27). However, the fifth report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (12) pointed out that antihypertensive drug therapy should be carried out more cautiously in elderly patients. Moreover, pharmaceutical drugs cause a number of unfavorable side effects, which decrease the quality of life in such patients. For the aforementioned reasons, nonpharmacologic therapy should be applied or added as far as possible to control the blood pressure better in elderly patients.
Mild exercise training has often been proposed as a nonpharmacologic therapy for moderate essential hypertension (14-18,21,24,25,27). Recent reviews have concluded that such training decreases both the systolic and diastolic blood pressure in middle-aged hypertensive patients by approximately 10 mm Hg in systolic and 5 mm Hg in diastolic blood pressures (3,9). Moreover, well-controlled studies have also reported on the favorable effects of exercise training in elderly hypertensive patients, especially in nonpharmacologic patients (7,10). However, few studies so far have investigated the combined effect of drug therapy on such patients.
It is very important to determine whether combined drugs and exercise therapy is effective in patients in controlling blood pressure because a large number of elderly patients have already been treated by phamaceutical drug therapy. Moreover, exercise therapy alone cannot be recommended as a substitute for drug therapy to control blood pressure. In this study, we investigated the additional effectiveness of low intensity aerobic training on blood pressure in elderly hypertensive patients who were receiving drug therapy concurrently.
Subjects. Twenty-six patients (12 men and 14 women) with an average age of 75 yr (from 64 to 84) participated into this study. None had engaged in any regular exercise program before this study. Thirteen subjects volunteered to enter the training program, and we also examined 13 aged and sex-matched controls. Both groups consisted of six men and seven women. The average ages were 75.4 (SD ± 5.4) yr in the training group and 73.1 (SD ± 4.2) yr in the control group. All subjects suffered from hypertension, and 11 subjects also had complications from diabetes, four had experienced a myocardial infarction, and three had both. All subjects were receiving one or more of the following drug treatments: calcium antagonists, ACE inhibitor, diuretics, β-blocking agents, α-blocking agents, or antiangina pectoris agents such as nitrites depending on their symptoms. The class and doses of these drugs remained unchanged for the previous 1 yr and were also maintained during the training period of this study. The subjects were also asked not to change their normal lifestyle during the study including alcohol consumption, smoking, and other daily activity. Written informed consent was obtained from all subjects after the design and the potential risks of the study were explained.
Determination of exercise intensity and training method. To determine the exercise intensity, an intermittent multistage submaximal exercise test was carried out using a treadmill (Fukuda Electronic Co., MAT-2500, Japan). Exercise was started at 30 m·min−1 with a 0% gradient, and thereafter the speed increased by 10 m·min−1 at every stage. Each stage continued for 4 min with a pause of 2 min between each stage for collection of the blood lactate samples. The test was stopped if any subject experienced such symptoms as fatigue, moderate chest pain, or arrhythmia of the heart. The subjects were able to continue until the 7th stage on average. The lactate concentration was measured by a flow injection analysis using immobilized enzyme (lactic oxidase) columns with detection made by chemiluminescence (CL-760) (23). The blood lactate concentration was plotted against the exercise workload and speed for each patient. The lactate levels pass through two phases during graded exercise, and the workload at the first breaking point of lactate was used to calculate the exercise training intensity of each subject. The lactate threshold (LT) has been previously defined by the investigators. The exercise intensity for each subject in the training group was set for each subject from a determination of the LT speed. This treadmill test was reported every 3 months and the exercise intensity was readjusted in the training group. The control group was able to carry out the treadmill test. Treadmill training at this LT intensity was carried out for 30 min·d−1, three to six times per week (5.2 ± 1.4) for 9 months under the supervision of exercise physiology specialists in the training group. Training began with a 5-10 min warm-up period with light calisthenics and stretching followed by 30 min of exercise at LT using a treadmill at a steady speed. All testing and training were done at an air-conditioned outpatient clinical laboratory under the supervision of physical educators and/or doctors.
Blood pressure measurement. The blood pressure was measured indirectly using a mercury sphygmomanometer. The fifth phase of Korotkoff's sound was used for the diastolic blood pressure. The mean blood pressure was calculated as the diastolic blood pressure plus one-third pulse pressure. The blood pressure in the right arm was measured after the subject sat in a chair for 5 min. The average of duplicate measurements was used for the analysis. All measurements were performed by either the same physical educator or a physician in an air-conditioned, quiet room throughout the study. The blood pressure was measured in the morning after a 2- or 3-h fast in all subjects. The blood pressure was measured once a week during an observation period of more than 3 months. During the observation period the blood pressure at rest in both groups remained stable (blood pressure change: <20/10 mm Hg). The average blood pressure value of the last two visits of the observation period was used as a baseline value for each subject. In the control group, it was measured once a week in the study period. The average blood pressure value of the last two visits at the 3rd, 6th, and 9th month was used as the value in both the control and the training groups. The blood pressure in the training group was measured at each visit before exercise training. The blood pressure in five subjects who stopped training after 1 month were based on the average value of the last two visits.
Statistical analysis. The data were presented as the mean ± SD. The data were analyzed by repeated ANOVA while the Tukey-Kramer multiple comparison test was used to examine any changes during training. Significance between the training and control groups were analyzed using unpaired t-test. The level of significance was considered to be P < 0.05.
Table 1 shows the physical features of the subjects of both groups. No significant differences were found in any background characteristics between the training and control groups either before or after 9 months. In addition, no significant changes were observed for the body mass or BMI during the study in either the training or the control group.
Table 2 shows the changes in the blood pressure in the training and control groups throughout the experimental periods. The results showed a significant decrease from 147.2 ± 14.1 mm Hg to 132.5 ± 11.0 mm Hg in the systolic blood pressure (SBP), from 103.4 ± 8.4 mm Hg to 92.4 ± 8.7 mm Hg in the mean blood pressure (MBP), and from 81.5 ± 7.7 mm Hg to 72.5 ± 8.9 mm Hg in the diastolic blood pressure (DBP) at 3 months (P < 0.01, respectively) and thereafter remained stable throughout the rest of the study. There were significant decreases in SBP, MBP, and DBP by 17, 12, and 9 mm Hg, respectively, after the 9-month training period in the training group (P < 0.01, respectively). There was no significant change in blood pressure in the control group.
Figures 1 and 2 show comparisons of the changes in SBP and DBP between the training and control group during the 9-month training period. Compared with the control group, significant differences were shown in the changes of SBP and DBP after 3 (P < 0.01, respectively), 6 (SBP: P < 0.01, DBP: P < 0.05), 9 months (SBP: P < 0.01, DBP: P < 0.05).
A significant correlation was observed between the initial blood pressure level and the change in the blood pressure level after training for 9 months in both the SBP and DBP (SBP: r = −0.76, P < 0.01; DBP: r = −0.61, P < 0.05, respectively; Fig. 3).
Figure 4 shows the time-course changes in the blood pressures in the five subjects who stopped low intensity aerobic training after 9 months. Their blood pressure did not differ significantly after 1 month detraining compared with those at 0 month.
The LT speed significantly increased from 50.5 (SD ± 10.5) m·min−1 before training to 55.9 (± 11.6) m·min−1 after 9 months of training (P < 0.01), and the mean change rate showed a 9.8% increase in the training group.
Pharmacologic antihypertensive treatment in the elderly has been proven to reduce cardiovascular mortality and morbidity by large-scale clinical intervention studies such as SHEP (22), STOP (8), and MRC (19) studies. Consequently, a large number of elderly hypertensive patients have already been treated by pharmaceutical drug therapy. It will be even more beneficial to control the blood pressure with nonpharmacological measures such as mild aerobic training in addition to drug therapy in elderly hypertensive patients under antihypertensive medication. We tested this hypothesis in the present study and found that 9 months of mild aerobic training at the LT in elderly patients under antihypertensive medications resulted in a further reduction of blood pressure. The blood pressure stabilized after 3 months of training and remained stable throughout the rest of the study. However, the cessation of the training in five patients resulted in a return of the blood pressure to pretraining levels within 1 month.
We previously reported that training at the lactate threshold intensity (40-60% V˙O2max) decreased systolic and diastolic blood pressure at rest in middle-aged patients with moderate hypertension (14-18,21,24,25,27). Cononie et al. (7) and Hagberg et al. (10) also reported that training at 50% V˙O2max resulted in a reduction of blood pressure in elderly hypertensive patients. Our study confirmed the depressive effects of exercise at the LT in lowering blood pressure in elderly hypertensive patients in spite of antihypertensive drug therapy. Hagberg et al. (10) employed training at low and higher intensities, 53% and 73% of V˙O2max, respectively, and found that the antihypertensive effect with low-intensity exercise training was equal to or even greater than that elicited with higher-intensity training. They also concluded that only nontreated antihypertensive medication might respond favorably to exercise training, because they had only one patient under antihypertensive medication in the low-intensity group, and five of 10 patients in the higher-intensity group. In contrast, in our present study all 13 patients were receiving antihypertensive medication at the start of this study, and their blood pressures all decreased on average. Cade et al. (6) also reported that hypertensive patients equally responded to exercise regardless of whether they received antihypertensive medications. Low intensity aerobic training thus appears to have a more favorable depressive effect on the blood pressure regardless of age or the use of drug treatment.
The value of treating hypertension in elderly patients has now been established (12). Especially, concerns have been raised that lowing blood pressure too much may increase the risk of coronary disease in elderly, the so-called "J-curve" hypothesis. For this reason the goal of antihypertensive medication therapy in the elderly is to reduce the SBP levels to from 140 to 160 mm Hg, while the DBP in elderly patients are similar to those for the general population at levels of less than 90 to 80 mm Hg. In the present study, blood pressure decreased lower levels at 130 mm Hg in SBP and 78 mm Hg in DBP on an average. Although we did not observe a J-curve during the 9-month training period, it would be better to reduce or decrease the use of drugs as much as possible to control the blood pressure levels in the elderly.
Cononie et al. (7) reported that endurance training in the high blood pressure group exhibited a significant decrease in the diastolic and mean blood pressures at rest after 3 months and thereafter remained decreased throughout the 6-month study. They also exhibited a trend toward a lower systolic blood pressure after 6 months of training. However, Kiyonaga et al. (16) and Urata et al. (27) reported that the depressor effect in the systolic and diastolic pressure in middle-aged subjects reached a significantly lower level by the 5th week of the exercise period and thereafter stabilized. An early reduction in the blood pressure in elderly hypertensive patients in the present report seems to be similar to that observed in middle-aged subjects.
The magnitude of the depressor effects of mild exercise training at the lactate threshold intensity for 10 wk reportedly lowered the systolic/diastolic blood pressure by an average of 12.4/6.4 mm Hg in our eight studies of middle-aged subjects (14-18,21,24,25,27). Hagberg et al. (10) observed a slightly greater reduction in the blood pressure by 20/11 mm Hg with mild-intensity exercise for 9 months which was similar to the reduction observed in the present study. Mild exercise training might thus lower the blood pressure to an even greater extent in elderly patients than in middle-aged patients. Moreover, the magnitude of the depressive effect by the mild training in elderly patients also seems to be similar to that in nontreated patients.
The underlying antihypertensive mechanism of mild aerobic training on blood pressure has been found to be multifactorial (3,4,10). We previously reported that antihypertensive mechanisms are associated with a significant decrease in the factors involved with the pressor response, such as the plasma norepinephrine level, the serum Na·K−1 ratio, endogenous ouabain-like substances and the erythrocyte mean corpuscular volume, as well as a significant increase in the factors involved with the depressor response, such as plasma prostaglandin E, serum taurine, and urinary dopamine excretion (3,4). Although the physiological mechanisms were not directly examined in the present study, a similar mechanism seems to occur in elderly hypertensive patients under antihypertensive medications.
In this study we unexpectedly observed a significant negative correlation between the initial systolic and diastolic BP and changes in BP after training. These results suggest that mild training has an additive effect, especially in those elderly hypertensives whose blood pressure is not sufficiently controlled by antihypertensive medications, for example, one subject's initial systolic BP was 178 mm Hg before exercise training and then decreased by 48 mm Hg after 9 months. These patients might have to decrease their medication in the early period.
Cade et al. (6) previously studied the detraining effects on blood pressure and reported that lowered blood pressure by mild exercise training returned to the pretraining level within 3 months after the cessation of training. Meredith et al. (20) found that the lowered blood pressure and plasma noradrenaline levels remained for 1-2 wk, gradually increased after the cessation of training, and reached the initial sedentary levels by the third week. Similarly, the present study confirmed that the antihypertensive effects of training disappeared within 1 month even after a long period (9 months) of mild aerobic training.
In the present study, the aerobic capacity as determined by the LT increased even in elderly patients, which is consistent with previous studies (5,11). Even though we did not measure the V˙O2max, the mean walking speed equivalent to the LT did significantly increase, as in the above studies. These results thus demonstrate that training at the LT intensity could increase the aerobic capacity even in those elderly subjects who suffered from a myocardial infarction. In the present study, the magnitude of the increased aerobic capacity after training was thus not directly related to the magnitude or changes in the blood pressure reduction. This may suggest that the response for the increase in aerobic capacity is different from that involved in the reduction of blood pressure. However, it is very important to either keep or increase the aerobic capacity in elderly patients to improve their overall quality of life.
In conclusion, the increased antihypertensive effect of mild aerobic training at the LT in addition to that of antihypertensive drugs was confirmed in 13 elderly patients. However, the cessation of such training in five patients resulted in a quick return of the blood pressure within a month to the pretraining levels.
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Keywords:© Williams & Wilkins 1998. All Rights Reserved.
ELDERLY PATIENTS; LOW INTENSITY TRAINING; DRUG; BLOOD PRESSURE; HYPERTENSION