Response of Adolescents and Young Adults with Primary Hypertension to a Sub-maximal Load and their Regime of Physical Activity

Overview

Primary hypertension is conditioned by the combined influence of genetic and external factors, in particular poor dietary habits, stress and inadequate physical activity (6, 10). Minimalization of the adverse environmental effect involves preventive measures via dietary, psychological and physical activity intervention. A very important part in the prevention of hypertension is played by physical activity (PA) (6, 10, 19). So far, however, the volume, intensity and form of PA in children and adolescents with elevated blood pressure was not defined. The objective of the investigation was to test the response of adolescents and young adults with primary hypertension to a physical load of submaximal intensity and to assess at the same time their fitness and regime of physical activity.The research project comprised 49 asymptomatic subjects - males with the primary form of hypertension aged 16 to 23 years (mean age 18.1 ± 1.9 years, body weight 81.7 ± 14.4 kg, height 180.5 ± 6.2 cm, percentage of body fat 12.8 ± 6 %, BMI 24.4 ± 5.1 kg.m2, systolic blood pressure (BPs) 133.6 ± 11.7 mm Hg, diastolic blood pressure (BPd) 80.7 ± 9.0 mm Hg). In all patients the secondary form of hypertension was ruled out. The group of normotonic subjects comprised 32 aged 16 to 23 years (mean age 19.5 ± 1.4 year, body weight 75.8 ± 6.9 kg, height 182 ± 6 cm, percentage of body fat 10.2 ± 4 %, BMI 22.7 ± 1.6 kg.m2, BPs 125.9 ± 12.1 mm Hg, BPd 75.3 ± 6.8 mm Hg). The probands of both groups were tested by walking (rate 5, 6, 7 km/h-1) and running on a treadmill (rate 9 km.h-1) with a 1.5 % gradient. In the course of the defined load the response of BP, heart rate and selected spirometric parameters (pulmonary ventilation (VE) oxygen consumption (VO2), oxygen consumption per kg body weight (VO2/kg), respiratory quotient (RQ)) were recorded.In hypertonic subjects statistically significantly higher mean values of body weight, ratio of body fat, BPs and BPd at rest, during a load and after its termination were found (p < 0.05). The differences between values of BPs and BPd during a dynamic load remain the same, the course of changes in the two groups has a similar character.The VE values in hypertonic subjects while walking at a rate of v = 5 km.h-1 are insignificantly higher as compared with values recorded in normotonic subjects. Significantly higher VE values were recorded in patients at the subsequent levels of loads (minimal difference as compared with healthy subjects 20%). The assessed VE value in normotonic subjects at the lowest load level was by 11.8% higher in hypertonic subjects as compared with normotonic ones and it increases with the increasing load to 27.8%. The differences in VO2 are most striking at a rate of v = 9 km.h-1, i.e. in patients they are by 123.5% higher (p < 0.01). The increasing respiratory quotient (RQ) of hypertonic subjects as compared with normotonic subjects is consistent with their more marked anaerobic compensation of energy. A rate of running v = 9 km.h-1 in hypertonics is close to the maximal load and therefore the investigated functional parameters are close to the maximum while the control group still has a sufficient reserve to reach the maximum. The mentioned changes in the group of hypertonic subjects indicate a lower level of aerobic fitness.According to anamnestic data the mean value of PA in the control group is 5.5 ± 4.4 hours per week, which is on average by 40 min. more (4.8 ± 3.8 hours) than in hypertonic subjects. In the submaximal zone of dynamic loads the trend of the response of hypertonic and normotonic subjects to a physical load (walking, running) is similar. After the mentioned intensity of the load the difference in BPs and BPd between the two groups remains almost independent on the intensity of the load. From the presented results ensues that a mild form of primary hypertension is no contradiction of dynamic physical loads at the submaximal intensity level. The pilot study provides also evidence on the physical fitness of hypertonic subjects, probably as the consequence of along-term low PA volume.

Key words:
juvenile hypertension, physical fitness, loading test, physical activity