Respiratory muscle training positively affects vasomotor response in young healthy women

Time-efficient, high-resistance inspiratory muscle strength training for cardiovascular aging

Cardiovascular diseases (CVD) remain the leading cause of death in developed and developing societies and aging is the primary risk factor for CVD. Much of the increased risk of CVD in midlife/older adults (i.e., adults aged 50 years and older) is due to increases in blood pressure, vascular endothelial dysfunction and stiffening of the large elastic arteries. Aerobic exercise training is an effective lifestyle intervention to improve CV function and decrease CVD risk with aging. However, <40% of midlife/older adults meet guidelines for aerobic exercise, due to time availability-related barriers and other obstacles to adherence. Therefore, there is a need for new lifestyle interventions that not only improve CV function with aging but also promote adherence. High-resistance inspiratory muscle strength training (IMST) is an emerging, time-efficient (5 min/day) lifestyle intervention. Early research suggests high-resistance IMST may promote adherence, lower blood pressure and potentially improve vascular endothelial function. However, additional investigation will be required to more definitively establish high-resistance IMST as a healthy lifestyle intervention for CV aging. This review will summarize the current evidence on high-resistance IMST for improving CV function with aging and will identify key research gaps and future directions.

Inspiratory muscle training improves breathing pattern and sympatho-vagal balance but not spontaneous baroreflex sensitivity in older women

Even though recent studies reported a positive inspiratory muscle training (IMT) effect on cardiovascular autonomic modulation, its underlying mechanisms as the breathing pattern remain unclear. The study aimed to investigate the IMT effects on resting heart rate variability (HRV), spontaneous baroreflex sensitivity (BRS), and spontaneous breathing pattern in older women. Fourteen healthy older women participated in this study, allocated in IMT (50 % MIP; n = 8) or Sham (5% MIP; n = 6) protocols for four weeks. Blood pressure, heart rate, and ventilatory data were continuously recorded before and after interventions. After four weeks, IMT-group increased maximal inspiratory pressure and vagal-mediated HRV, following by the reduction of sympatho-mediated HRV and the inspiratory time during the spontaneous breathing cycle compared to Sham-group, but did not change BRS. Therefore, the shorter inspiratory time suggests a putative mechanism behind improved vagal-mediated HRV post-IMT in older women.

No Evidence That Hyperpnea-Based Respiratory Muscle Training Affects Indexes of Cardiovascular Health in Young Healthy Adults

Introduction

The chronic effects of respiratory muscle training (RMT) on the cardiovascular system remain unclear. This investigation tested to which degree a single sessions of RMT with or without added vibration, which could enhance peripheral blood flow and vascular response, or a 4-week RMT program could result in changes in pulse wave velocity (PWV), blood pressure (systolic, SBP; diastolic, DBP) and other markers of cardiovascular health.

Methods

Sixteen young and healthy participants (8 m/8f) performed 15 min of either continuous normocapnic hyperpnea (RMET), sprint-interval-type hyperpnea (RMSIT) or a control session (quiet sitting). Sessions were performed once with and once without passive vibration of the lower limbs. To assess training-induced adaptations, thirty-four young and healthy participants (17 m/17f) were measured before and after 4 weeks (three weekly sessions) of RMET (n = 13, 30-min sessions of normocapnic hyperpnea), RMSIT [n = 11, 6 × 1 min (1 min break) normocapnic hyperpnea with added resistance] or placebo (n = 10).

Results

SBP was elevated from baseline at 5 min after each RMT session, but returned to baseline levels after 15 min, whereas DBP was unchanged from baseline following RMT. Carotid-femoral PWV (PWV_CF) was elevated at 5 and 15 min after RMT compared to baseline (main effect of time, P = 0.001), whereas no changes were seen for carotid-radial PWV (PWV_CR) or the PWV_CF/PWV_CR ratio. Vibration had no effects in any of the interventions. Following the 4-week training period, no differences from the placebo group were seen for SBP (P = 0.686), DBP (P = 0.233), PWV_CF (P = 0.844), PWV_CR (P = 0.815) or the PWV_CF/PWV_CR ratio (P = 0.389).

Discussion/Conclusion

Although 15 min of RMT sessions elicited transient increases in PWV_CF and SBP, no changes were detected following 4 weeks of either RMET or RMSIT. Adding passive vibration of the lower limbs during RMT sessions did not provide additional value to the session with regards to vascular responses.

Acute effects of inspiratory muscle training at different intensities in healthy young people

BACKGROUND

Understanding the acute effects of inspiratory muscle training (IMT) at different intensities on the autonomic nervous system, arterial stiffness, and blood pressure in healthy young people will be important in the constitution of appropriate IMT prescriptions.

AIMS

To investigate the acute effects of IMT at different intensities on autonomic function, arterial stiffness, and blood pressure in healthy young people METHODS: Thirty-six healthy participants were enrolled in this crossover study. All participants randomly performed IMT sessions, which consisted of diaphragmatic breathing exercise (DBE), 10%, 30%, and 60% of maximal inspiratory pressure (MIP) on consecutive days. Autonomic function and arterial stiffness were assessed by measuring heart rate variability (HRV) and aortic pulse wave velocity (AoPWV), respectively. HRV, AoPWV, and blood pressure were recorded before and immediately after each IMT session.

RESULTS

There was no significant difference in the baseline measurements between IMT sessions (p > 0.05). Heart rate (HR) significantly decreased after DBE and IMT at 10% of MIP (p < 0.05). All time domain parameters of HRV significantly improved after DBE compared with the baseline (p < 0.05). There was no difference in the frequency domain of HRV after the IMT sessions (p > 0.05). AoPWV significantly increased after IMT at 60% of MIP (p < 0.05). Mean arterial pressure significantly changed after DBE and IMT at 60% of MIP (p < 0.05).

CONCLUSIONS

A single session of DBE positively affects autonomic function and blood pressure, while IMT at 60% of MIP increases arterial stiffness. The different intensities of IMT have various impacts on autonomic function, arterial stiffness, and blood pressure.

TRIAL REGISTRATION

NCT03788356.

Evidence for improved systemic and local vascular function after long-term passive static stretching training of the musculoskeletal system

KEY POINTS

Vascular function and arterial stiffness are important markers of cardiovascular health and cardiovascular co-morbidity. Transitional phases of hypoemia and hypermia, with consequent fluctuations in shear rate, occuring during repetitive passive stretching adminstration (passive stretching training) may constitute an effective stimulus to induce an amelioration in vascular function, arterial stiffness and vascular remodelling by improving central and local blood flow control mechanisms. Vascular function, arterial stiffness and vascular remodelling were evaluated before and after 12 weeks of passive stretching training and after 6 weeks from training cessation, in the femoral, popliteal (treated with stretching), and brachial arteries (untreated) of both sides. After passive stretching training, vascular function and arterial remodelling improved, and arterial stiffness decreased in all the arteries, suggesting modifications of both central and local blood flow control mechanisms. Passive stretching-induced improvements related to central mechanisms seemed to have a short duration, as they returned to pre-training baseline within 6 weeks from training cessation, whereas those more related to a local mechanism persisted in the follow-up.

ABSTRACT

Acute passive stretching (PS) effects on blood flow ( Q ̇ ), shear rate ( Y ̇ ), and vascular function in the feeding arteries of the stretched muscle have been extensively investigated; however, few data are available on vascular adjustments induced by long-term PS training. We investigated the effects of PS training on vascular function and stiffness of the involved (femoral and popliteal) and uninvolved (brachial) arteries. Our hypothesis was that PS-induced changes in Q ̇ and Y ̇ would improve central and local mechanisms of Q ̇ control. Thirty-nine participants were randomly assigned to bilateral PS (n = 14), monolateral PS (n = 13) or no PS training (n = 12). Vascular function was measured before and after 12 weeks of knee extensor and plantar flexor muscles' PS training by single passive limb movement and flow-mediated dilatation (FMD). Central (carotid-femoral artery PWV, PWV_CF ) and peripheral (carotid-radial artery PWV, PWV_CR ) arterial stiffness was measured by pulse-wave velocity (PWV), together with systolic (SBP) and diastolic (DBP) blood pressure. After PS training, increases of 30%, 25% and 8% (P < 0.05) in femoral Δ Q ̇ , popliteal and brachial artery FMD%, respectively, occurred in both PS training groups. A decrease in PWV_CF , PWV_CR , SBP and DBP (-25%, -17%, -4% and -8%, respectively; P < 0.05) was noted. No changes occurred in controls. Vascular function improved and arterial stiffness reduced in the arteries involved and uninvolved with PS training, suggesting modifications in both central and local Q ̇ control mechanisms. PS-induced improvements had a short duration in some of vascular function parameters, as they returned to baseline within 6 weeks of PS training cessation.

Time-efficient physical training for enhancing cardiovascular function in midlife and older adults: promise and current research gaps

Cardiovascular diseases (CVD) remain the leading cause of death in developed societies, and "midlife" (50-64 yr) and older (65+) men and women bear the great majority of the burden of CVD. Much of the increased risk of CVD in this population is attributable to CV dysfunction, including adverse changes in the structure and function of the heart, increased systolic blood pressure, and arterial dysfunction. The latter is characterized by increased arterial stiffness and vascular endothelial dysfunction. Conventional aerobic exercise training, as generally recommended in public health guidelines, is an effective strategy to preserve or improve CV function with aging. However, <40% of midlife and older adults meet aerobic exercise guidelines, due in part to time availability-related barriers. As such, there is a need to develop evidence-based time-efficient exercise interventions that promote adherence and optimize CV function in these groups. Two promising interventions that may meet these criteria are interval training and inspiratory muscle strength training (IMST). Limited research suggests these modes of training may improve CV function with time commitments of ≤60 min/wk. This review will summarize the current evidence for interval training and IMST to improve CV function in midlife/older adults and identify key research gaps and future directions.

Evidence of Improved Vascular Function in the Arteries of Trained but Not Untrained Limbs After Isolated Knee-Extension Training

Vascular endothelial function is a strong marker of cardiovascular health and it refers to the ability of the body to maintain the homeostasis of vascular tone. The endothelial cells react to mechanical and chemical stimuli modulating the smooth muscle cells relaxation. The extent of the induced vasodilation depends on the magnitude of the stimulus. During exercise, the peripheral circulation is mostly controlled by the endothelial cells response that increases the peripheral blood flow in body districts involved but also not involved with exercise. However, whether vascular adaptations occur also in the brachial artery as a result of isolated leg extension muscles (KE) training is still an open question. Repetitive changes in blood flow occurring during exercise may act as vascular training for vessels supplying the active muscle bed as well as for the vessels of body districts not directly involved with exercise. This study sought to evaluate whether small muscle mass (KE) training would induce improvements in endothelial function not only in the vasculature of the lower limb (measured at the femoral artery level in the limb directly involved with training), but also in the upper limb (measured at the brachial artery level in the limb not directly involved with training) as an effect of repetitive increments in the peripheral blood flow during training sessions. Ten young healthy participants (five females, and five males; age: 23 ± 3 years; stature: 1.70 ± 0.11 m; body mass: 66 ± 11 kg; BMI: 23 ± 1 kg ⋅ m^-2) underwent an 8-week KE training study. Maximum work rate (MWR), vascular function and peripheral blood flow were assessed pre- and post-KE training by KE ergometer, flow mediated dilatation (FMD) in the brachial artery (non-trained limb), and by passive limb movement (PLM) in femoral artery (trained limb), respectively. After 8 weeks of KE training, MWR and PLM increased by 44% (p = 0.015) and 153% (p = 0.003), respectively. Despite acute increase in brachial artery blood flow during exercise occurred (+25%; p < 0.001), endothelial function did not change after training. Eight weeks of KE training improved endothelial cells response only in the lower limb (measured at the femoral artery level) directly involved with training, likely without affecting the endothelial response of the upper limb (measured at the brachial artery level) not involved with training.