Dynamic resistance training decreases sympathetic tone in hypertensive ovariectomized rats

Abstract

The aim of this study was to investigate the effects of resistance exercise training on hemodynamics and cardiac autonomic control in ovariectomized spontaneously hypertensive rats. Female rats were divided into 4 groups: sedentary control (SC), sedentary hypertensive (SH), sedentary hypertensive ovariectomized (SHO), and resistance-trained hypertensive ovariectomized (RTHO). Resistance exercise training was performed on a vertical ladder (5 days/week, 8 weeks) at 40-60% maximal load. Direct arterial pressure was recorded. Vagal and sympathetic tones were measured by heart rate (HR) responses to methylatropine (3 mg/kg, iv) and propranolol (4 mg/kg, iv). Ovariectomy resulted in additional increases in blood pressure in hypertensive rats and was associated with decreased vagal tone. Resistance exercise trained rats had lower mean arterial pressure than untrained rats (RTHO: 159±2.2 vs SHO: 177±3.4 mmHg), as well as resting bradycardia (RTHO: 332±9.0 vs SHO: 356±5 bpm). Sympathetic tone was also lower in the trained group. Moreover, sympathetic tone was positively correlated with resting HR (r=0.7, P<0.05). The additional arterial pressure increase in hypertensive rats caused by ovarian hormone deprivation was attenuated by moderate-intensity dynamic resistance training. This benefit may be associated with resting bradycardia and reduced cardiac sympathetic tone after training, which suggests potential benefits of resistance exercise for the management of hypertension after ovarian hormone deprivation.

Resistance or aerobic training decreases blood pressure and improves cardiovascular autonomic control and oxidative stress in hypertensive menopausal rats

“…Ovarian hormones deprivation induced an additional increase in AP in ovariectomized rats (HSO group), thus confirming previously published findings (17,19,36). Postmenopausal hypertension is probably associated with estrogen loss (43).…”

“…Our group has previously reported that a reduction in mean AP was associated with increased vagal tonus in fructose-fed ovariectomized SHR after AT (35). On the other hand, it was also demonstrated that dynamic RT diminished AP in ovariectomized SHR due to a decrease in sympathetic tone (36). Therefore, in this study, we made a comparison between aerobic and RT, evidencing that both are able to induce blood pressure decrease, however, at different magnitudes and by different predominant mechanisms.…”

“…Also, RT has shown important effects in the vascular oxidative stress profile of young people, thus exhibiting its possible role in hypertension onset prevention (8). When associating menopause and hypertension, Shimojo et al (36) showed that RT in ovariectomized SHRs is able to reduce AP by sympathetic tone attenuation. However, there is yet to be a consensus regarding the beneficial hemodynamic effects of resistance exercise training in hypertensive individuals (9).…”

Uma Sessão De Exercício Resistido Dinâmico Não Induz Hipotensão Pós-Exercício Em Ratas SHR

“…Sendo assim, as adaptações periféricas responsáveis pela hipotensão no gênero feminino podem não ter sido atingidas com o exercício proposto neste estudo 24 . É interessante notar que apesar de não termos observado HPE nas ratas hipertensas no presente estudo, dados do nosso grupo demonstram que fêmeas hipertensas com prejuízo adicional da PA devido a privação de hormônios ovarianos, apresentam redução da PAM após treinamento físico resistido 25 . É importante ainda destacar que o fato de não haver agudamente aumento da PA no período pós exercício nas ratas hipertensas, sugere que o exercício físico resistido prescrito neste modelo não induziu aumento do risco cardiovascular.…”

“…Entretanto, um dado importante do presente estudo foi a redução da FC observada a partir do 15º minuto em relação aos primeiros cinco minutos da recuperação. Embora não tenha sido uma variável diretamente medida, a redução da FC observada nas fêmeas SHR pós exercício resistido dinâmico pode estar relacionada com diminuição do tônus simpático e/ou aumento do tônus parassimpático cardíaco 25 . Ao analisarmos a resposta do DP, observamos estreita semelhança com o comportamento da FC.…”