Systolic and Diastolic Left Ventricular Mechanics during and after Resistance Exercise

Effect of resistance exercise on cardiac perturbations and systolic performance: A cross-over randomized trial comparing volumes and techniques

This study investigated the magnitude and time-course of resistance exercise (RE) technique induced transient cardiac perturbations. Twenty-four participants were assigned to one of four arms: sets to failure or non-failure with 8-10 repetition maximum (RM), and sets to failure or non-failure with 15RM. Echocardiographic and blood pressure (BP) data were recorded at baseline and 30 min, 6 h and 24 h post-exercise. In all groups end-systolic circumferential wall stress (cESS), and ratio of transmitral inflow velocities (E/A) were significantly decreased while posterior wall thickness (PWT), global circumferential strain (GCS), GCS strain rate (GCSR), global longitudinal strain rate (GLSR), and stroke volume (SV) were significantly increased for up to 6 h of follow-up. In the 15RM groups, left ventricular (LV) mass and interventricular septal thickness (IVST) were significantly increased, and left atrial (LA) area was significantly decreased (p < 0.05) compared to the 8-10 RM groups. In the 15RM groups, RE decreased global longitudinal strain (GLS) and increased ejection fraction (EF) (p<0.01). After RE, transient cardiac perturbations, the reduction in LA compliance, and the improvement in LV myofibril geometry were volume dependent and influenced more by sets to failure technique. RE increased GCS and reduced the afterload, thus helping to preserve SV and EF.

Acute Left Atrial Response to Different Eccentric Resistance Exercise Loads in Patients with Heart Failure with Middle Range Ejection Fraction: A Pilot Study

In this study, we aimed to assess acute changes occurring on atrial function following single bouts of eccentric resistance exercise (ECC-RE) performed at two different loads. Twenty-five patients with chronic heart failure with middle range ejection fraction (HFmrEF) participated in three experimental sessions in a randomized order and on separate days: two sessions of ECC RE at 20% (ECC-20) of one-repetition maximum (1-RM) and 50% (ECC-50) 1-RM, and one session of control, without exercise. Each session lasted three minutes. Before and immediately after the sessions, patients underwent echocardiography and blood pressure and heart rate measurement. Peak atrial longitudinal strain (PALS) and peak atrial contractile strain (PACS) significantly increased after both ECC-20 (+16.3%) and ECC-50 (+18.1%) compared to control (between sessions p = 0.022). Peak atrial contractile strain (PACS) significantly increased after ECC-50 (+28.4%) compared to ECC-20 (+17.0%) and control (between sessions p = 0.034). The ratio of transmitral and annular velocities (E/E') increased significantly after ECC-20 (+10.4%) and ECC-50 (+19.0%) compared to control (between groups p = 0.003). EF, left ventricular longitudinal strain, and stroke volume did not change after ECC-RE sessions compared to control. Cardiac output increased significantly after ECC-20 and ECC-50 compared to control, (between groups p = 0.025). In conclusion, both ECC-RE sessions were well tolerated, and LA functional reserve was properly mobilized in response to ECC-RE in patients with HFmrEF. Cardiac output increased at the cost of an increased LV filling pressure, but no detrimental changes of LV function occurred.

Influence of breathing on variation in cardiac stroke volume at the onset of cycling

PURPOSE

During cycling, the variation in cardiac stroke volume (SVV) is similar to that at rest. However, SVV may be influenced by ventilation at the start of cycling, e.g., by a Valsalva-like maneuver used to stabilize the body. This study evaluated the influence of ventilation on SV during initiation of cycling.

METHODS

Ten healthy recreationally physical active males (mean ± SD: age 26 ± 3 years, height 184 ± 9 cm, weight 85 ± 9 kg) cycled on an ergometer for four 30 s intervals at submaximal workloads while synchronizing ventilatory and cardiovascular variables derived from gas exchange and arterial pulse contour analysis, respectively.

RESULTS

At exercise onset, cardiac output increased by an instantaneous rise in heart rate and SV (P < 0.05). In contrast, blood pressure increased only after 15 s (P < 0.05), reflected in a decline in total peripheral resistance from exercise onset (P < 0.05). SVV was similar at rest (20 ± 6%) and during exercise (21 ± 5%) except for the first 5 s of exercise when a ~ 2.5-fold elevation (47 ± 6%; P < 0.05) was correlated to variation in respiratory frequency (= 0.71, P = 0.02) and tidal volume (R = 0.66, P = 0.04) but not to variation in heart rate or blood pressure. Stepwise multiple regression analysis indicated a respiratory frequency influence on SVV at the onset of ergometer cycling.

CONCLUSION

The data provide evidence for a ventilatory influence on SVV at the onset of cycling exercise.

Cardiac Responses to Prenatal Resistance Exercise with and without the Valsalva Maneuver

PURPOSE

Exercise guidelines recommend incorporating resistance exercise (RE) into a regular aerobic training program during pregnancy. However, few women do so because of uncertainties about the safety of prenatal RE, particularly regarding the Valsalva maneuver (VM). The aim of this study was to determine the acute cardiovascular responses to prenatal RE at different intensities, with and without VM.

METHODS

Healthy pregnant (n = 15; 22.9 ± 5.9 wk of gestation) and nonpregnant women (n = 15) were recruited. Maximal strength over 10 repetitions (10RM) for semireclined leg press was determined. Women underwent standardized assessments of cardiac structure, function and mechanics (echocardiography), heart rate (ECG), and blood pressure (photoplethysmography) at baseline, during RE at 20%, 40%, and 60% 10RM while free-breathing, and at 40% 10RM with VM. Significant differences were identified between subjects at baseline (independent t-tests), between and within subjects during free-breathing RE (general linear model, baseline as a covariate), and between and within subjects for 40% 10RM free-breathing versus VM (mixed-effects model).

RESULTS

Resting cardiac output, heart rate, and stroke volume were greater in pregnant women, without differences in blood pressure, ejection fraction, or cardiac mechanics. During free-breathing RE, pregnant women had a greater ejection fraction compared with nonpregnant women; however, all other hemodynamic variables were not different between groups. Cardiac mechanics during free-breathing RE across all intensities were not different between groups, with the exception that pregnant women had a lower apical circumferential strain that did not affect global cardiac function. No differences were observed between groups during 40% 10RM RE with and without VM.

CONCLUSIONS

Pregnant women have proportionate cardiac responses to light-moderate RE, both with and without the VM. These findings reinforce the safety of RE in healthy pregnancy.

The Acute Cardiorespiratory and Cerebrovascular Response to Resistance Exercise

Resistance exercise (RE) is a popular modality for the general population and athletes alike, due to the numerous benefits of regular participation. The acute response to dynamic RE is characterised by temporary and bidirectional physiological extremes, not typically seen in continuous aerobic exercise (e.g. cycling) and headlined by phasic perturbations in blood pressure that challenge cerebral blood flow (CBF) regulation. Cerebral autoregulation has been heavily scrutinised over the last decade with new data challenging the effectiveness of this intrinsic flow regulating mechanism, particularly to abrupt changes in blood pressure over the course of seconds (i.e. dynamic cerebral autoregulation), like those observed during RE. Acutely, RE can challenge CBF regulation, resulting in adverse responses (e.g. syncope). Compared with aerobic exercise, RE is relatively understudied, particularly high-intensity dynamic RE with a concurrent Valsalva manoeuvre (VM). However, the VM alone challenges CBF regulation and generates additional complexity when trying to dissociate the mechanisms underpinning the circulatory response to RE. Given the disparate circulatory response between aerobic and RE, primarily the blood pressure profiles, regulation of CBF is ostensibly different. In this review, we summarise current literature and highlight the acute physiological responses to RE, with a focus on the cerebral circulation.

Fluctuations in cardiac stroke volume during rowing

Preload to the heart may be limited during rowing because both blood pressure and central venous pressure increase when force is applied to the oar. Considering that only the recovery phase of the rowing stroke allows for unhindered venous return, rowing may induce large fluctuations in stroke volume (SV). Thus, the purpose of this study was to evaluate SV continuously during the rowing stroke. Eight nationally competitive oarsmen (mean ± standard deviation: age 21 ± 2 years, height 190 ± 9 cm, and weight 90 ± 10 kg) rowed on an ergometer at a targeted heart rate of 130 and 160 beats per minute. SV was derived from arterial pressure waveform by pulse contour analysis, while ventilation and force on the handle were measured. Mean arterial pressure was elevated during the stroke at both work rates (to 133 ± 10 [P < .001] and 145 ± 11 mm Hg [P = .024], respectively). Also, SV fluctuated markedly during the stroke with deviations being largest at the higher work rate. Thus, SV decreased by 27 ± 10% (31 ± 11 mL) at the beginning of the stroke and increased by 25 ± 9% (28 ± 10 mL) in the recovery (P = .013), while breathing was entrained with one breath during the drive of the stroke and one prior to the next stroke. These observations indicate that during rowing cardiac output depends critically on SV surges during the recovery phase of the stroke.

Stimulus-specific functional remodeling of the left ventricle in endurance and resistance-trained men

Left ventricular (LV) structural remodeling following athletic training has been evidenced through training-specific changes in wall thickness and geometry. Whether the LV response to changes in hemodynamic load also adapts in a training-specific manner is unknown. Using echocardiography, we examined LV responses of endurance-trained (n = 15), resistance-trained (n = 14), and nonathletic men (n = 13) to 1) 20, 40, and 60% one repetition-maximum (1RM), leg-press exercise and 2) intravascular Gelofusine infusion (7 mL/kg) with passive leg raise. While resting heart rate was lower in endurance-trained participants versus controls (P = 0.001), blood pressure was similar between groups. Endurance-trained individuals had lower wall thickness but greater LV mass relative to body surface area versus controls, with no difference between resistance-trained individuals and controls. Leg press evoked a similar increase in blood pressure; however, resistance-trained participants preserved stroke volume (SV; -3 ± 8%) versus controls at 60% 1RM (-15 ± 7%, P = 0.001). While the maintenance of SV was related to the change in longitudinal strain across all groups (R = 0.537; P = 0.007), time-to-peak strain was maintained in resistance-trained but delayed in endurance-trained individuals (1 vs. 12% delay; P = 0.021). Volume infusion caused a similar increase in end-diastolic volume (EDV) and SV across groups, but leg raise further increased EDV only in endurance-trained individuals (5 ± 5 to 8 ± 5%; P = 0.018). Correlation analysis revealed a relationship between SV and longitudinal strain following infusion and leg raise (R = 0.334, P = 0.054); however, we observed no between-group differences in longitudinal myocardial mechanics. In conclusion, resistance-trained individuals better maintained SV during pressure loading, whereas endurance-trained individuals demonstrated greater EDV reserve during volume loading. These data provide novel evidence of training-specific LV functional remodeling.NEW & NOTEWORTHY Training-specific functional remodeling of the LV in response to different loading conditions has been recently suggested, but not experimentally tested in the same group of individuals. Our data provide novel evidence of a dichotomous, training-specific LV adaptive response to hemodynamic pressure or volume loading.

The effect of varying intensities of lower limb eccentric muscle contractions on left ventricular function

Purpose

The effect of eccentric (ECC) resistance exercise (RE) on myocardial mechanics is currently unknown.

Method

This study investigated ECC RE at varying intensities on left ventricular (LV) function using LV strain (ε), wall stress and haemodynamic parameters. Twenty-four healthy male volunteers completed ECC leg extensions at 20%, 50% and 80% of their ECC maximal voluntary contraction (MVC), whilst receiving echocardiograms. Global longitudinal ɛ, strain rate (SR), longitudinal tissue velocity, heart rate (HR), blood pressure (BP), mean arterial pressure (MAP), LV wall stress and rate pressure product (RPP) were assessed at baseline and during exercise.

Results

Left ventricular global ɛ, systolic SR and wall stress remained unchanged throughout. Systolic blood pressure (sBP), MAP and RPP increased at 80% and 50% intensities compared to rest (P < 0.01). Eccentric RE increased HR and peak late diastolic SR at all intensities compared to rest (P < 0.02).

Conclusion

The findings suggest acute ECC RE may not alter main parameters of LV function, supporting future potential for wider clinical use. However, future studies must investigate the impact of multiple repetitions and training on LV function.

Unaltered left ventricular mechanics and remodelling after 12 weeks of resistance exercise training – a longitudinal study in men

Previous longitudinal studies suggest that left ventricular (LV) structure is unaltered with resistance exercise training (RT) in young men. However, evidence from aerobic exercise training suggests that early changes in functional LV wall mechanics may occur prior to and independently of changes in LV size, although short-term changes in LV mechanics and structural remodelling in response to RT protocols have not been reported. Therefore, the purpose of this study was to examine the effects of RT on LV mechanics in healthy men performing 2 different time-under-tension protocols. Forty recreationally trained men (age: 23 ± 3 years) were randomized into 12 weeks of whole-body higher-repetition RT (20–25 repetitions/set to failure at ∼30%–50% 1 repetition maximum (1RM); n = 13), lower-repetition RT (8–12 repetitions/set to failure at ∼75%–90% 1RM; n = 13), or an active control period (n = 14). Speckle tracking echocardiography was performed at baseline and following the intervention period. Neither RT program altered standard measures of LV volumes (end-diastolic volume, end-systolic volume, or ejection fraction; P > 0.05) or indices of LV mechanics (total LV twist, untwisting rate, twist-to-shortening ratio, untwisting-to-twist ratio, or longitudinal strain; P > 0.05). This is the first longitudinal study to assess both LV size and mechanics after RT in healthy men, suggesting a maintenance of LV size and twist mechanics despite peripheral muscle adaptations to the training programs. These results provide no evidence for adverse LV structural or functional remodelling in response to RT in young men and support the positive role of RT in the maintenance of optimal cardiovascular function, even with strenuous RT.

Global and regional left ventricular circumferential strain during incremental cycling and isometric knee extension exercise

BACKGROUND

The objective of this study was to investigate left ventricular (LV) circumferential strain responses to incremental cycling and isometric knee extension exercises.

METHODS

Twenty-six healthy male participants (age = 30 ± 6 years) were used to study LV global (GCS) and regional circumferential strain at the apex (ACS) and base (BCS) during incremental cycling at 30% and 60% work rate maximum (W_max ) and short-duration (15 seconds contractions) isometric knee extensions at 40% and 75% maximum voluntary contraction (MVC) using two-dimensional speckle tracking echocardiography.

RESULTS

During cycling (n = 22), GCS increased progressively from rest to 60% W_max (-22.85 ± 3.26% to -29.87 ± 2.59%, P < .01). ACS increased from rest to 30% W_max (-26.29 ± 4.84% to -36.84 ± 6.94%, P < .01) and then remained unchanged to 60% W_max (-40.72 ± 4.06%, P = .068). BCS decreased from rest to 30% W_max (-19.41 ± 2.79 to -17.51 ± 4.66%, P = .05) and then remained unchanged to 60% W_max . During isometric knee extension (n = 23), GCS decreased from rest to 40% MVC (-22.63 ± 3.46 to -20.10 ± 2.78%, P < .05) and then remained unchanged to 75% MVC. Similarly, BCS decreased from rest to 40% MVC (-19.21 ± 2.58% to -13.55 ± 3.45%, P < .01) and then remained unchanged, whereas ACS did not change with exercise intensity (rest, -26.05 ± 5.34%; 40% MVC, -26.64 ± 4.53% and 75% MVC -27.22 ± 5.34%, all P > .05).

CONCLUSION

Global circumferential strain increased stepwise during incremental cycling, mediated by the apex with trivial changes at the base. In contrast, GCS decreased during the isometric knee extension to 40% MVC and then plateaued, due to decreased BCS as ACS was maintained. A novel finding is that the GCS response appears to be exercise modality dependant and is the consequence of region-specific changes.