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Effect of 12 weeks of moderate–intensity resistance training on arterial stiffness: a randomised controlled trial in women aged 32–59 years
  1. M Yoshizawa1,
  2. S Maeda1,2,
  3. A Miyaki1,
  4. M Misono1,
  5. Y Saito1,
  6. K Tanabe1,
  7. S Kuno1,
  8. R Ajisaka1
  1. 1
    Division of Sports Medicine, Graduate School of Comprehensive Human Sciences, Tsukuba, Japan
  2. 2
    Center for Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Japan
  1. Correspondence to Dr S Maeda, Division of Sports Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305–8577, Japan; smaeda{at}tara.tsukuba.ac.jp

Abstract

Background: Resistance training has been increasingly incorporated into the overall exercise programme because of its effect on muscle strength, functional capacity and osteoporosis. High-intensity resistance training increases arterial stiffness. However, the effect of moderate-intensity resistance training on arterial stiffness is unknown.

Objective: To determine whether 12 weeks of moderate-intensity resistance training increases arterial stiffness in middle-aged women.

Methods: 35 middle-aged women (age range 32 to 59 years) volunteered to participate. The subjects were randomly assigned to one of three groups: resistance training (RT) group, aerobic exercise training (AET) group or control group. The RT and AET groups performed 12 weeks of moderate-intensity resistance training or aerobic exercise training (two days/week).

Results: In the RT group, one-repetition maximum strength significantly increased after the intervention. Interestingly, aortic (carotid–femoral) pulse wave velocity (PWV; an index of arterial stiffness), and peripheral (femoral–ankle) PWV did not change with moderate-intensity resistance training. In contrast, in the AET group, carotid–femoral PWV significantly decreased after the intervention. Resistance training and aerobic exercise training did not affect blood pressure.

Conclusions: This study found that moderate-intensity resistance training did not increase arterial stiffness in middle-aged women, which may have great importance for health promotion with resistance training.

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Increased central arterial stiffness reduces the arterial buffering function of the pulsation of blood pressure and blood flow, which contributes to increases in systolic blood pressure (SBP) and in pulse pressure. The increased arterial stiffness is an independent predictor of adverse cardiovascular disease (CVD) and mortality,1 thus prevention and treatment of increased arterial stiffness are important.

Regular aerobic exercise and resistance training are recommended by health organisations such as the American Heart Association (AHA) and the American College of Sports Medicine (ACSM) for the prevention and treatment of CVD and frailty associated with ageing.23 It has been well established that regular aerobic (endurance) exercise inhibits the increase in central arterial stiffness that typically occurs with ageing.4567 In contrast to the beneficial effects of aerobic exercise, it has been reported that high-intensity resistance training increases arterial stiffness in young and middle-aged healthy men.891011 Few data on this issue are available for premenopausal women.12 Thus, it is likely that high-intensity resistance training has undesirable effect on arterial stiffness. On the other hand, resistance training is an effective method for maintenance of functional capacity and prevention of sarcopenia and osteoporosis.13 Resistance training is particularly important in middle-aged and older women, because the risk for osteoporosis is higher in women than in men and it increases after menopause.14 Furthermore, high-intensity resistance training is not commonly recommended for health promotion in middle-aged and elderly populations. However, the effect of moderate-intensity resistance training on arterial stiffness in middle-aged and elderly adults is unknown.

Accordingly, the major aim of the present study was to determine effect of moderate-intensity resistance training on arterial stiffness in middle-aged women. We measured aortic (carotid–femoral) pulse wave velocity (PWV; an established measure of arterial stiffness) and peripheral (femoral–ankle) PWV before and after a period of moderate-intensity resistance training. We also confirmed the effect of moderate-intensity aerobic exercise training on arterial stiffness. We hypothesised that moderate-intensity resistance training would not increase arterial stiffness in middle-aged women.

Methods

The study conformed to the principles outlined in the Helsinki Declaration. It was approved by the ethics committee of the University of Tsukuba, an all subjects gave written informed consent before participation.

Subjects

In total, 35 healthy, sedentary middle-aged women (32–59 years old) were entered into the study. Subjects were randomly assigned to one of three groups: resistance training (RT) group (n = 11), aerobic exercise training (AET) group (n = 12) or control group (n = 12). Candidates who smoked regularly or took regular medication were excluded. All subjects were free from the signs and symptoms of any overt chronic diseases. Both the RT and AET groups included two post-menopausal participants.

Exercise interventions

Subjects in the resistance training and AET groups exercised on 2 days/week for a 12-week period. The RT group performed 3 sets of 10 repetitions of the following 6 exercises using variable resistance training equipment: leg curl (hamstring), leg press (quadriceps), hip adduction (mesogluteus), hip flexion (iliopsoas), vertical press (greater pectoral muscle) and sit-ups (abdominal muscle). The intensity of resistance training was set at 60% of their one-repetition maximum (1RM). The AET group performed a 12-week aerobic exercise training programme on a cycle ergometer for 30 min/day at 60–70% of their individual VO2max. In the ACSM guidelines, moderate loading in resistance exercise is defined as 60% of 1RM1516 and moderate intensity in aerobic training is defined as 60–70% of individual VO2max.16 Therefore, we accepted the intensity of 60% of 1RM as moderate-intensity resistance training and the intensity of 60–70% of individual VO2max as moderate-intensity aerobic training.

Experimental design

All exercise training subjects completed their respective interventions. All measurements were taken after an overnight fast. The subjects abstained from alcohol, caffeine and vigorous physical activity for at least 24 hours before the experiments. Measurements after the RT or AET programmes were performed after subjects had rested for at least 2 days to exclude any acute affects from the recent bout of resistance or aerobic exercise. All measurements were performed at a constant room temperature of 25°C.

Blood biochemistry

Serum concentrations of cholesterol and insulin and plasma concentrations of glucose were determined by standard enzymatic techniques.

Arterial stiffness

PWV is the best available technique for assessing arterial stiffness.17 Carotid–femoral and femoral–ankle PWVs were measured (form PWV/ABI; Colin Medical Technology, Komaki, Japan) after a resting period of at least 20 minutes as previously described.18 Carotid–femoral PWV reflects central (aortic) arterial stiffness and femoral–ankle PWV reflects peripheral (leg) arterial stiffness. Carotid and femoral arterial pulse waves were obtained in triplicate using arterial applanation tonometry incorporating an array of 15 transducers. Carotid–femoral PWV, a measure of the speed at which the pressure wave travels, was determined by measuring the distance between the carotid and femoral pulse and dividing by the time delay between the “foot” of the carotid and femoral pressure waves. Femoral–ankle PWV was obtained by the transit time between the femoral artery site (tonometer) and ankle site. Ankle arterial pulse waves were obtained using a modified oscillometric pressure-sensor method. During the measurement of PWV, ankle blood pressure was inflated at a low pressure to obtain posterior tibial artery blood pressure waveforms. The distance travelled by the pulse waves was assessed in triplicate with a random zero-length measurement over the surface of the body with a nonelastic tape measure. Carotid–femoral and femoral–ankle PWVs were calculated as the distance divided by the transit time. We did not consider the influence of phase of menstrual cycle on measurement of PWV, because PWV is not affected by the menstrual cycle.19

Muscular strength and aerobic capacity

The 1RM strength was tested before and after the 12–week resistance training programme.

All subjects underwent an incremental cycle exercise test (after 2 minutes at 40 W, with 20 W increases every 2 minutes) until they reached exhaustion, a symptom-limited heart rate (>220 beats/min minus subject age in years), or SBP >250 mmHg

Statistical analyses

Data are expressed as mean (SE). Continuous variables were analysed by a two-way analysis of variance (ANOVA) with repeated measures before and after 12 weeks of each intervention. When a significant group-by-time interaction was seen, within-group comparisons between time points were performed using Tukey’s post hoc analysis. Measurements of strength were compared using the paired Student t test. Values of p<0.05 were accepted as significant.

Results

Table 1 shows the characteristic parameters in middle-aged women before and after each intervention. Body weight and body mass index significantly decreased after resistance training or aerobic exercise training. There were no significant differences in total, high-density lipoprotein (HDL) or low-density lipoprotein (LDL) cholesterol before and after each intervention. There were no significant differences in systolic blood pressure (SBP), diastolic blood pressure, mean blood pressure or pulse pressure at rest before and after each intervention (table 2). Resting heart rate significantly decreased after aerobic exercise training (table 2).

Table 1

Subject characteristics

Table 2

Haemodynamic characteristics.

Individual VO2max results were significantly increased after AET (table 1) and 1RM strength for all muscular exercises was significantly increased after RT (table 3).

Table 3

Changes in muscular strength with the resistance training intervention

Figure 1 shows the carotid–femoral PWV before and after 12-week intervention programmes. Carotid–femoral PWV significantly decreased after aerobic exercise training intervention programme, whereas there was no significant difference in carotid–femoral PWV before and after resistance training or sedentary lifestyle. There was no significant difference in femoral–ankle PWV in any intervention (fig 2).

Figure 1

Comparisons of carotid–femoral pulse wave velocity (PWV) before and after interventions. *p<0.05 versus before interventions.

Figure 2

Comparisons of femoral–ankle pulse wave velocity (PWV) before and after interventions.

Discussion

The major finding of the present investigation is that the arterial stiffening previously reported with high-intensity RT in young and middle-aged adults did not occur with moderate-intensity RT in middle-aged women. This result suggests that moderate-intensity RT in middle-aged women would not produce any unfavourable effects on the vasculature, which be of importance for health promotion with RT.

What is already known on this topic

  • Recent studies have reported that high-intensity RT increases arterial stiffness.

  • The effect of moderate-intensity RT on arterial stiffness in middle-aged women is unknown.

What this study adds

  • The arterial stiffening previously seen with high-intensity RT did not occur with moderate-intensity RT in middle-aged women.

  • This result suggests that moderate-intensity RT in middle-aged women would not produce any unfavourable effects on the vasculature, which may have great importance for health promotion with RT.

RT is effective for maintenance of functional capacity and prevention of sarcopenia and osteoporosis.13 Health organisations such as the AHA and the ACSM recommend RT for health promotion ;23 however, high-intensity RT has an undesirable effect on arterial stiffness, as it has been show to increase arterial stiffness in young and middle-aged healthy men.891011 Few investigations have addressed effects of RT on arterial stiffness in women. Cortez-Cooper et al12 recently reported that a high-intensity RT programme followed for 11 weeks increases aortic arterial stiffness in young healthy women. Thus, it is likely that high-intensity RT has an unfavourable effect on arterial stiffness. The results of the present study showed that moderate-intensity RT increased muscular strength and did not increase arterial stiffness in middle-aged women. These conflicting result might be due to differences in the intensity of RT. Moderate-intensity RT is recommended from the general viewpoints of health promotion and safety in the middle-aged and elderly population.13 Therefore, moderate-intensity RT in middle-aged and older adults may have clinically important effects on arterial function.

The mechanism underlying increased arterial stiffness with high-intensity RT remains unclear. Recently, we reported that higher arterial stiffness in young strength-trained men is associated with higher plasma endothelin (ET)-1, a potent vasoconstrictor peptide produced by vascular endothelial cells, concentrations.8 Thus, vascular endothelial function, especially production of endogenous ET-1, may be involved in the increase in arterial stiffness induced by high-intensity RT. Another possibility is that vigorous and frequent elevation of blood pressure during resistance exercise might engender arterial stiffening.20 In the present study, because moderate-intensity RT did not increase arterial stiffness, it is possible that these factors did not change with moderate-intensity RT in our middle-aged subjects. On the other hand, we found that AET actually decreased arterial stiffness. We previously reported that regular aerobic exercise decreased plasma ET-1 concentration.21 Therefore, in this study, the AET intervention might have caused a decrease in endogenous ET-1.

We found that 12 weeks of moderate-intensity AET decreased carotid–femoral PWV (ie, aortic PWV) but not femoral–ankle PWV (ie, leg PWV). A previous study also found that aortic PWV in middle-aged men decreased after 16 weeks of moderate-intensity AET, whereas leg PWV did not change.21 The aorta and peripheral arteries are different; the aorta is an elastic artery, whereas the peripheral (leg) arteries are muscular. Therefore, this difference in artery type may affect exercise training-induced effect on arterial stiffness.

In conclusion, we investigated the effect of moderate-intensity RT on arterial stiffness in middle-aged women. We found that 12 weeks of moderate-intensity RT did not affect arterial stiffness in middle-aged women. This suggests that the arterial stiffening previously seen with high-intensity RT does not occur with moderate-intensity resistance. We propose that moderate-intensity RT may be important for health promotion.

REFERENCES

Footnotes

  • Funding This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan (18300215, 18650186, 21970), and in part by Health and Labour Sciences Research Grants from the Ministry of Health, Labour and Welfare, Japan.

  • Competing interests none.

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