WB-EMS is an increasingly popular exercise technology predominantly applied to address physical function, body composition and health-related outcomes. Due to its joint friendliness, time-efficiency and close supervision, WB-EMS might be a particular attractive training method for people unable or unmotivated to conduct conventional exercise programs. Although the safe application of WB-EMS is specified by (albeit non-mandatory) guidelines (Kemmler et al., 2023) and contraindications (Kemmler et al., 2019), several issues on safe WB-EMS application remain. In its predominately applied specification, WB-EMS is often considered as more of a resistance type exercise (Kemmler et al., 2022). In this context, studies on acute effects of intense resistance exercise/weightlifting on arterial blood pressure [e.g., (MacDougall et al., 1985)] revealed very pronounced peak pressures, incompatible with health-related outcomes in non-athletic cohorts. This aspect might have contributed to the decision to deem at least untreated hypertension (Kemmler et al., 2019) an absolute contraindication for commercial, non-medical WB-EMS. To our best knowledge, apart from a few studies that reported results of acute effects of WB-EMS on blood pressure (BP) as a secondary study outcome (Hoshiai et al., 2021; Cassemiliano et al., 2022; Alvarez-Barrio et al., 2023), no further study has focused on blood pressure changes related to WB-EMS. The fact that the majority of clients of the large commercial German WB-EMS facilities are middle aged to older people (EMS-Training.de, 2017), i.e., a cohort with a high prevalence of hypertension (Neuhauser et al., 2016; Neuhauser et al., 2017), illustrates the relevance of providing evidence on acute WB-EMS induced effects on BP in middle aged-older people. Of further importance, due to the limited sensitivity to endogenous electrical stimuli, the first few weeks of WB-EMS application might be particularly critical for adverse effects due to errors in intensity specification (Teschler et al., 2016). The aim of the present pilot study was thus to determine the immediate effect of WB-EMS on mean arterial pressure (MAP) by applying different stimulus intensities in hypertensive and normotensive middle aged to older novice applicants during the first 4 weeks of WB-EMS. Based on occasional assessments of acute BP in other WB-EMS studies (Kemmler et al., 2010; Kemmler et al., 2018; Kemmler and von Stengel, 2020) our primary hypothesis was that 20 min of conventional WB-EMS application would not significantly increase MAP largely independently of the stimulus intensity. Our secondary hypothesis was that both cohorts, people with and without hypertension, show comparable WB-EMS ¹ -induced MAP changes. Finally, an experimental hypothesis was that heart rate increases significantly due to standard WB-EMS combined with easy movements but quickly returns to baseline values post exercise.

The Franconian EMS and arterial blood pressure study (FrEMAP) study is a cross-sectional WB-EMS study that aimed to determine the effects of WB-EMS combined with easy movements with different stimulus intensities on MAP in novice applicants with and without hypertension. The study included men and women 40–70 years old, with overweight and osteoarthritis of the knee. The project was designed and initiated by the Institute of Radiology, University Hospital Erlangen (UKER) Germany. The University Ethics Committee approved the trial (number 359_19b). The study fully complies with the Helsinki Declaration (World Medical, 2013). After receiving detailed information, all study participants gave their written informed consent.

In summary, from our preliminary results, the acute effect of WB-EMS combined with easy movements on mean arterial blood pressure can be rated negligible to low. Indeed our finding of slight MAP increases with discreet average and individual peaks of systolic and diastolic BP values (that did not exceed 128 mmHg (MAP) or 177/110 mmHg in any case), indicates the low risk of WB-EMS triggering hypertensive effects. As hypothesized, this result is widely independent of stimulus intensity and BP status (i.e., hyper-vs. normotensive). In parallel, the physiologically less pronounced average HR increase of about 20 bpm with an individual maximum of 140 bpm and a rapid decrease towards initial HR values 2 min post-WB-EMS confirmed the low cardiovascular stress of WB-EMS application. The finding that changes in MAP were even more affected by the shift from the resting (5′pre) to the standing position compared with the change from immediately pre-to immediately post exercise, quite independently of stimulus intensity and BP status, might be the most striking evidence for applicability in cohorts with (treated) hypertension. The latter estimation was further underpinned by the finding that the discreet MAP-lowering effect of WB-EMS was more evident in participants with hypertension.

While studies that applied local NMES application were not applicable, only a few other studies addressed acute WB-EMS-induced changes of hemodynamic parameters as a study outcome [e.g., (Hoshiai et al., 2021; Cassemiliano et al., 2022)]. In summary however, no WB-EMS study reported significant changes of BP or heart rate. Closest to our WB-EMS approach, Hoshiai et al. (Hoshiai et al., 2021) applied an intermitted 20 min (20 Hz, 4–4 s) WB-EMS protocol with “the maximum tolerable intensity” in a supine passive position for his cohort of normotensive young people. HR, BP were measured every 2 minutes during and after WB-EMS. In summary, HR, BP, but also left ventricular ejection fraction and diastolic function remained unchanged during WB-EMS and up to 10 min post-WB-EMS (Hoshiai et al., 2021).

Most researchers consider WB-EMS to be a resistance (RT) type exercise, thus one may argue that a comparison of our finding with RT studies could be legitimate. However, while WB-EMS and RT share some common characteristics, i.e., training protocols with low-volume applied with moderate to high intensity and the focus on outcomes related to muscle strength, function and mass, the principles and mechanism differ fundamentally. This is particularly the case for the high mechanical intensity of dynamic RT protocols due to exercises with external loads. Reviewing pressure response after dynamic RT (one-arm overhead press to voluntary fatigue) in novice weight-trained normotensive individuals, Fleck et al. (Fleck and Dean, 1987) reported an average increase of 87 mmHg for both systolic and diastolic BP at 70% 1RM. Even the 50% 1RM protocol triggers an average pressor response to 178/142 mmHg. However, none of the reasons listed for the very pronounced rises in BP during heavy weight lifting exercises (MacDougall et al., 1985; Palatini et al., 1989) apply to WB-EMS. This is especially true for the mechanical compression of blood vessels (Hoshiai et al., 2021) and the pronounced increase in intra-thoracic and intra-abdominal pressures (Palatini et al., 1989) through the Valsalva maneuver, “unavoidable when lifting heavy loads” (i.e., >80% 1RM) (Hackett and Chow, 2013). In contrast to RT, the non-superimposed WB-EMS protocols applied by most commercial and scientific settings involve no relevant additional load and focus on low-intensity movements/exercises with short impulse phases of 4–6 s intermitted by 4 s of rest. Another contributing aspect to BP increases is the ratio of isometric vs. isotonic components with stronger blood pressure responses applying predominantly isometric contraction (Wonisch et al., 2012). Although a short phase (<1 s) of conscious isometric tension is recommended immediately before the onset of the WB-EMS impulse, this stimulus is hardly comparable to pronounced isometric RT (Coneglian et al., 2023). In parallel, the albeit not undisputed finding that involving larger muscle groups elicits greater BP responses (Coneglian et al., 2023), i.e., an aspect particularly relevant for WB-EMS, should be considered in the context of other RT-related mechanisms and might be thus of minor relevance when applying WB-EMS as such.

Our study has several particularities and limitations that prevent ultimate evidence of an absence of negative effects of WB-EMS on MAP (and HR). First, we might have failed to determine peak BP during WB-EMS due to our non-continuous, phygmomanometric BP assessment (only) immediately pre- and post-exercise. However, the rapid HR and BP decreases reported after RT [e.g., (MacDougall et al., 1985; Lassing et al., 2023)] cannot be applied to WB-EMS. Thus we think that the “afterload blood pressure” determined in the present study might widely reflect MAP values during WB-EMS.

Missing data (n = 4) were imputed by multiple imputation. We are aware that we could omit the multiple imputation and that linear-mixed effects models offer a valid approach under the missing at random (MAR) assumption. However, we are not aware of a result clearly indicating which of the two approaches performs better in practical applications. Hence, based on our experience, we decided to use the multiple imputation approach. Further, we focus on novice WB-EMS applicants unfamiliar with complying properly with the specified stimulus intensities via RPE due to limited body awareness and reference. Indeed, the reliable regulation of stimulus intensity by RPE can be considered as a weak point of WB-EMS, particular in the early stage of application. This was confirmed by the finding that WB-EMS induced severe rhabdomyolysis was predominantly reported in novice applicants [review in (Kemmler and von Stengel, 2019)]. This made it all the more important to focus on this early phase of WB-EMS application, although a longer monitoring with evaluations of stimulus intensities in the target range of non-athletic WB-EMS application [i.e., RPE 7–8 (Kemmler et al., 2023)] might have provided additional evidence for the cardiovascular burden of WB-EMS. Another aspect not intended to be addressed by the present work was untreated hypertension. Due to the low number of untreated hypertensive participants (n = 2), we are unable to reliably address differences in blood pressure kinetics in treated vs. non-treated participants. As stated, untreated hypertension is an absolute contraindication for non-medical WB-EMS applications (Kemmler et al., 2019), but the present work provides no reliable evidence for revising this categorization. Although we do not detect different results for men vs. women, the heterogeneity of the study cohort with respect to gender and age aggravates the interpretation of our results. Finally, the formula used to calculate the MAP might have slightly confounded our result due to the underrepresentation of the more pronounced systolic BP rise particularly at increased HR. However, considering the average HR (≈100 bpm, Table 2) even after the “advanced impulse intensity” session, we conclude that this aspect does not impact our finding of low BP increases after WB-EMS. Nevertheless, we feel that it is justified to widely generalize our finding to the large cohort of middle-aged to older people, be it without or with (treated) hypertension, who may consider WB-EMS at a training option. Having said this, our finding relates to the predominately-applied intermitted WB-EMS with low-intensity movements that respect current guidelines for WB-EMS application (Kemmler et al., 2023).

In summary, although ultimate evidence might not be fully provided by the present study, we conclude that treated hypertension should not be considered as a definite barrier for WB-EMS application in moderately old to older cohorts in general. This does not include superimposed WB-EMS application that relies on high (voluntary) intensity muscle activation by moderate-high mechanical loading, superimposed by additional WB-EMS application, however.