Acute exposure to a psychological or physical stressor evokes heightened cardiovascular responses, characterized by rises in heart rate (HR) and blood pressure (BP) from a baseline or resting state, termed as cardiovascular reactivity. Over the short term, such stressor-induced cardiovascular reactivity provides hemodynamic and metabolic support to enable animals and humans to adapt to life-threatening or challenging situations (i.e., fight-or-flight response) [1]. Over the long term, however, frequent exposures to physical and/or psychological situations in day-to-day life can result in tendencies to exhibit exaggerated cardiovascular reactivity and delayed recovery, which can adversely impact homeostasis and trigger or exacerbate an array of pathophysiological changes involving the cardiovascular system [2,3]. This is so much so that individuals showing exaggerated or large magnitudes of cardiovascular reactions in response to a stressor are at greater risk for premature development of hypertension and other precursors to coronary heart disease, adverse clinical cardiovascular events and premature cardiovascular mortality [3,4]. As such, understanding how cardiovascular reactivity can be prevented or mitigated may be relevant in stress management and lowering the risk of cardiovascular disease (CVD).

The benefits of exercise on cardiovascular health are well-established. Many studies have shown that regular physical activity and exercise training are generally associated with better cardiovascular responses to acute stress, and not only does exercise attenuate the magnitude of hyperarousal associated with the stress response but also enhances cardiovascular recovery after stress exposure [2,5]. The proposed mechanisms are by lowering stress-induced cortisol responses [6,7], enhancing parasympathetic tone and reducing sympathetic nerve activity [8], leading to improved cardiac control in response to stress. Apart from exercise training, there are also reports showing that even a single or an acute bout of exercise can transiently mitigate the exaggerated cardiovascular responses to stressful conditions [9,10,11,12,13]. The evidence indicates that the beneficial effects of exercise in lowering stress-induced cardiovascular reactivity can be achieved acutely and without having to undergo extensive exercise training.

However, the evidence surrounding acute exercise and cardiovascular reactivity is still not well characterized, due to the huge variability in exercise protocols, e.g., intensity, type and duration. These huge variations in methodology have led to inconsistencies in the study findings, which limits our current understanding surrounding the role of acute exercise in minimizing cardiovascular hyperarousal related to stress response. Furthermore, with the increasing global prevalence of chronic stress especially since the coronavirus pandemic outbreak, recognizing exercise protocols that are effective to offset cardiac hyperarousal states associated with daily stress is useful to help mitigate abnormal cardiovascular responses or events in the long term, especially among those who are vulnerable to stress exposures.

In this scoping review, we specifically focused on the effects of acute or single exercise sessions of various modalities and intensities on stress-induced cardiovascular outcomes, namely BP and HR reactivity and recovery, as well as heart rate variability (HRV) in the general populations. BP reactivity was the most frequently studied outcome in these studies, followed by HR reactivity. From the total of 36 studies, we identified 17–20 articles which have reported lower BP reactivity with exercise compared to control. Overall, the majority of studies employed aerobic continuous exercise (ACE) with moderate intensity, while the high-intensity interval exercise (HIIE) modality is gaining interest in the field of exercise and stress-induced cardiovascular reactivity.

Our findings showed that there seems to be a consistent trend pointing towards lower BP reactivity with acute exercise in response to a stress exposure, in particular with ACE modality of moderate intensity. Other modalities such as HIIE and resistance exercise are also associated with reduced BP reactivity to stress to a lesser extent. Comparisons between exercise intensities or modalities are rather inconclusive; however, some of the findings seem to be suggesting that exercise of higher intensity [11,44,48] or volume [28,37] attenuates BP reactivity to a greater degree than exercise of low intensity or volume of the same modality. This may be related to a greater stimulation of endothelium-dependent vasodilation in humans through the increased production of nitric oxide, which may help to lower blood pressure responses during and post-exercise [51]. Interestingly, studies involving hypertension [9,25,51] or individuals with elevated BP [29,44,48] also showed favorable outcomes in BP reactivity with exercise, suggesting that those with an apparent cardiovascular risk factor may also benefit from the effects of acute exercise on reducing adverse BP responses from stress exposure.

Based on this review, we identified several relevant gaps that currently exist in the literature and can be avenues for further research. There is one observation that is worth noting from the review, and that is that the HIIE modality may be equally effective if not better than ACE in attenuating BP reactivity. The fact that there is growing and robust evidence that HIIE shows similar or greater efficacy compared with moderate-intensity continuous training across a range of cardiovascular outcomes [52,53,54,55] highlights the need for further research to dissect the benefits of this particular exercise in modulating BP responses to stress. Furthermore, HIIE can be performed in various ways by manipulating variables such as exercise modality, intensity, work interval, rest times and set repetitions, making it a flexible training program that can be designed to suit specific populations. In particular, it remains to be ascertained which HIIE protocol is the best in minimizing cardiovascular stress reactivity. Although the evidence in this review is limited, the findings somewhat suggest that shorter-bout protocols (<60 s) [13,29,41] may be associated with lower cardiovascular reactivity compared to longer-lasting bouts (>60 s) [21,30,46]. This is certainly an area worthy of further investigation in helping to design safer HIIE/HIIT protocols that can minimize cardiovascular stress, especially for populations with chronic stress or elevated BP.

A small number of studies in this review showed favorable outcomes on cardiovascular reactivity with acute exercise in hypertensive individuals. This has important implications for exercise as an effective therapy in combatting the deleterious impact of chronic stress and other risk factors that accelerate CVD in high-risk population. In addition, studies exploring how acute exercise can modulate molecular mediators such as muscle-derived myokines [58], and their possible cardioprotective role in mediating biological pathways involved in cardiovascular functions and stress reactivity, especially in populations with apparent cardiovascular risks, should also be considered. Finally, could it be possible that the timing of exercise and stress exposure relative to the 24 h circadian cycle has an influence on reactivity of the cardiovascular system? It is established that BP and HR exhibit diurnal variations over a 24 h period, and these changes are under the influence of behavioral, humoral and autonomic (sympathetic nervous system) factors [59,60]. Given that it is evident that the sympathetic tone is greater in the morning compared to evening [61,62], perhaps investigating the influence of timing of exercise, e.g., morning vs. evening, on cardiovascular reactivity would shed some understanding regarding timing effect and cardiovascular health.

4. Conclusion

This review intended to explore the range and variety of available studies using acute exercise as a therapeutic tool to lower stress-induced cardiovascular reactivity in the general population and to produce evidence of additional benefits of acute exercise on cardiovascular health beyond improving the traditional risk factors. We conclude that an acute bout of moderate intensity exercise is effective at preventing exaggerated blood pressure responses to a stress exposure. These findings may provide insight in understanding the therapeutic scope and effectiveness of acute exercise in managing stress responses to address the ill effects of stress on cardiovascular health.