Received: 19 September 2022 Revised: 1 December 2022 Accepted: 3 December 2022 DOI: 10.1111/jch.14621 OR I G I N A L A RT I C L E Reductions in systolic blood pressure achieved by hypertensives with three isometric training sessions per week aremaintainedwith a single session per week Daniel D CohenMSc, PhD1 Gustavo Aroca-MartinezMD, PhD2 Javier Carreño-Robayo BSc,MSc1 Alvaro Castañeda-Hernández BSc,MSc1 Yaneth Herazo-Beltran BSc,MSc1 Paul A CamachoMSc,MD3 JohannaOteroMSc1 DanielMartinez-Bello PhD1 Jose P Lopez-LopezMD1 Patricio Lopez-JaramilloMD, PhD1,3 1InstitutoMASIRA. Universidad de Santander (UDES), Bucaramanga, Colombia 2Universidad Simon Bolivar, Barranquilla, Colombia 3FundaciónOftalmológica de Santander, Floridablanca, Colombia Correspondence Daniel D Cohen,MSc, PhD, InstitutoMASIRA, UDES, Lago del Cacique, Bucaramanga 680003, Santander, Colombia. Email: danielcohen1971@gmail.com Clinical trial registration: Unique Protocol ID: 129980764353 Funding information Ministerio de ciencia tecnología e innovación. Colciencias (the ColombianMinistry of Science), Grant/Award Number: 807.18 Contract number:759-18 Abstract Isometric handgrip or (wall) squat exercise performed three times per week produces reductions in systolic blood pressure (SBP) in adults with hypertension. We aimed to compare these interventions and the potential to retain benefitswith one exercise ses- sion per week. We compared blood pressure changes following handgrip and squat isometric training interventions with controls in a randomized controlled multicen- tre trial in 77 unmedicated hypertensive (SBP ≥ 130 mmHg) adults. Exercise sessions were performed in theworkplace and consisted of four repetitions—three sessions per week for the first 12 weeks (phase 1), and one session per week for the subsequent 12 weeks (phase 2). Office blood pressure (BP) was measured at baseline, post-phase 1 and post-phase 2. Post-phase 1, mean reductions in SBP were significantly greater in handgrip (–11.2 mmHg, n = 28) and squat (–12.9 mmHg, n = 27) groups than in controls (–.4 mmHg; n = 22) but changes in DBP were not. There were no signifi- cant within-group changes during phase 2 but SBP was 3.8 mmHg lower in the wall squat than the handgrip group—a small magnitude but clinically important difference. While both interventions produced significant SBP reductions, the wall squat appears to be more effective in maintaining benefits with a minimal training dose. The low time investment to achieve and retain clinically significant SBP reductions—42 and 12 min, respectively—andminimal cost, particularly of the wall squat, make it a promising intervention for delivery in public health settings. KEYWORDS exercise/hypertension, handgrip, isometric, wall squat This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and nomodifications or adaptations aremade. © 2023 The Authors. The Journal of Clinical Hypertension published byWiley Periodicals LLC. J Clin Hypertens. 2023;1–8. wileyonlinelibrary.com/journal/jch 1 https://orcid.org/0000-0002-0899-4623 https://orcid.org/0000-0002-9222-3257 https://orcid.org/0000-0001-5460-6946 https://orcid.org/0000-0001-7994-1839 https://orcid.org/0000-0003-3752-4353 https://orcid.org/0000-0002-6233-9582 https://orcid.org/0000-0002-2044-2071 https://orcid.org/0000-0003-3219-0753 https://orcid.org/0000-0001-8865-0929 https://orcid.org/0000-0002-9122-8742 mailto:danielcohen1971@gmail.com http://creativecommons.org/licenses/by-nc-nd/4.0/ https://wileyonlinelibrary.com/journal/jch http://crossmark.crossref.org/dialog/?doi=10.1111%2Fjch.14621&domain=pdf&date_stamp=2023-03-25 2 COHEN ET AL. 1 INTRODUCTION Hypertension (HTN) affects 1.39 billion individuals worldwide.1 It is one of the most significant modifiable risk factors for cardiovascu- lar diseases (e.g., coronary artery disease, stroke, and heart failure), the leading cause of death worldwide, and the third leading cause of disability-adjusted life years lost.2 Guidelines for the management of elevated BP recommend non-pharmacologic lifestyle modifications as the first line of treatment, with physical activity levels as a key component.3 As a lack of time is cited as one of the major barriers to participa- tion in physical activity/exercise,4 low time-cost exercise, effective in reducing BP is of interest from a compliance/adherence perspective. Evidence has accumulated demonstrating that low intensity isometric resistance training (IRT) involving a total time investment of up to 14 min per session, performed three times perweek can produce clinically and statistically significant reductions in systolic blood pressure (SBP) and diastolic blood pressure (DBP) in people with hypertension.5,6 These interventions, identified in a meta-analysis as being superior to aerobic exercise or dynamic resistance training in reducing BP have mainly been implemented using a handgrip dynamometer or resis- tance device,7 with three to four repetitions (reps) of 2-min isometric contractions at 30% of the individual’s maximum handgrip strength completed.6–8 While themajority of IRT interventions in people with hypertension have examined handgrip exercise, several studies have examined the effect of instead using the wall squat, a lower equipment cost, lower body, alternative.9 Remarkably, a wall squat intervention10 using the same 4 × 2 min, three session per week protocol for only 4-weeks showed BP reductions of similar magnitude as that reported follow- ing handgrip interventions of longer duration. However, the efficacy of handgrip training has not been compared with that of wall squat training within a sample of adults with hypertension. This comparison is important because on the one hand, the lower cost associated with implementing wall squat training makes it more feasible to scale and make accessible to large numbers of people with hypertension. On the other hand, the far larger body of evidence demonstrating the efficacy of handgrip exercise might favor its prescription.5,6,8,9 Another aspect of the IRT program that has yet to be examined is a change in training frequency—all wall squat and handgrip studies to date involve at least three sessions per week. If BP reductions achieved with this frequency could be maintained with a lower frequency (and therefore lower time investment), as has been demonstrated with respect to other adaptations to exercise,11 this might enhance long-term compliance. Therefore, the principal aims of this randomized controlled trial delivered within the workplace during the working day to adults with hypertension, were as follows: (1) to compare the effects of hand- grip and wall squat training on office measured BP after a 12-week 3 sessions per week training protocol (phase 1); and (2) to exam- ine BP changes following a subsequent 12-week, once per week “maintenance” protocol (phase 2). 2 METHODOLOGY 2.1 Study design The study was a parallel randomized controlled multi-centre clinical trial. Adults were recruited across seven businesses and clinics in the cities of Bucaramanga and Barranquilla, Colombia. The inclusion crite- ria for the present analysis, were as follows: aged between 35 and 65 years, individuals with a SBP of >130 mmHg (the 2017 American Col- lege of Cardiology/American Heart Association cut-point for HTN),3 but had not been prescribed medication for the condition. The sam- ple therefore included individuals who were not aware that they were hypertensive. Inclusion and exclusion criteria are shown in Figure 1. All participants were provided with, and signed informed consent and were told that they were free to withdraw at any time. Power analysis determined that with the inclusion of 144 individuals across the con- trol and two intervention groups, with a type I error (α) of 5%, power (1-β) of 90%, a mean difference of 6 mmHg (±9 mmHg) SBP between control and intervention groups. Based on the final sample size of the 77 non-medicated hypertensive participants, the study had an α of 5% and a power of 99%. 2.2 Measurements All potential participantswere interviewedat theirworkplace toobtain their medical history and sociodemographic data. Using an automatic device (OMRON HEM 705 CP, Tokyo, Japan) BP was measured fol- lowing the recommendations of the British Hypertension Society and repeated after sitting for a further 5–10 min with the mean used as day 1 BP. Day 2 BP was taken when this procedure was repeated 2 to 3 days later when body composition was also assessed, with bioimpedance analysis (Ironman, BC-554, Hawaii, USA), and waist cir- cumference. Maximal isometric handgrip strength was then assessed with a handgrip dynamometer (JAMAR, Model J00105, Lafayette Instrument Company, USA) in a seated position. For most participants, the mean of day 1 and day 2 BP measure- ments was used to determine inclusion and as the baseline value for those randomized. However, if day 1 and day 2 values differed by >10 mmHg, a third-day measure was taken (on the first day of the intervention but prior to the training session), and a mean of these 3 days was used instead. Participants with SBP values>160mmHgwere encouraged to seek a medical appointment for treatment, whereas those with between 130 and 160 mmHg SBP were directed to the 4 × 4 recommendation,12 a national strategy based on WHO guide- lines for lifestyle intervention and includes video and written material in Spanish. Wall squat performance was then evaluated with the participant in a squat position with their back against the wall, arms crossed on the chest (Figure 2A) and feet at shoulder width, 95◦ of knee flexion (measured using a goniometer at the level of the knee joint).13 17517176, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1111/jch.14621 by C ochrane C olom bia, W iley O nline L ibrary on [28/03/2023]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense COHEN ET AL. 3 F IGURE 1 Study flow diagram summarizing recruitment, inclusion/exclusion criteria, randomization, and timing of measurements. F IGURE 2 (A) Position for initial wall squat evaluation (B)Wall squat training@95◦ (C) Handgrip training. The participantwas asked to try andmaintain this position for 2min. If they could not do so the time (seconds) at which participants volun- tarily ended the testwas recorded. At endof the test, participantswere asked to provide a rating of perceived effort using the modified Borg scale. 3 INTERVENTION During phase 1, individuals in both intervention groups performed their exercise supervised by qualified physiotherapists who contacted the participants andmet them in their office (Figure 2B,C) orwork area at scheduled times. 3.1 Handgrip group (n = 28) Participants randomized to the handgrip group performed four reps of a 2-min isometric contraction with 2 min of rest between each rep. For the 2-min duration of each rep, participants produced and sus- tained a force value of 30% of handgrip strength. For the first 4 weeks this value was calculated using the maximum value they had achieved in the initial baseline measurement. After the first 4 weeks and then every 4 weeks thereafter, maximal isometric handgrip strength was re-evaluated using the protocol described above, and the 30% value used in the exercise training session adjusted if this value changed. This trainingwas performed using a digital hand dynamometer (Zhong- shan Camry Electronic Co. Ltd. Zhongshan Guangdong, China), with 17517176, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1111/jch.14621 by C ochrane C olom bia, W iley O nline L ibrary on [28/03/2023]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 4 COHEN ET AL. TABLE 1 Blood pressure at baseline, post phase 1 and post phase 2. CONTROL (n= 22) HANDGRIP (n= 28) WALL SQUAT (n= 27) Pre Post P1 p ES Post P2 p ES Pre Post P1 p ES Post P2 p ES Pre Post P1 p ES Post P2 p ES SBP 138.9 (6.4) 138.5 (12.6) .86 .04 139.4 (13.9) .69 0.06 140.0 (7.4) 128.8 (12.5) <0.001 1.09 129.3 (13.5) .74 .03 141.2 (7.4) 128.3 (10.0) <0.001 1.46 126.5 (9.2) .34 .19 DBP 86.0 (4.6) 85.1 (6.5) .52 .15 85.0 (7.6) .95 .01 86.7 (4.6) 82.7 (8.2) <0.001 .60 81.6 (8.8) .38 .12 87.0 (4.7) 82.9 (9.1) .03 0.56 80.4 (9.1) .09 .27 Note: P1, Phase 1; P2, Phase 2. p and effect size are based on within-group changes between baseline and end of P1, and P1 and between end of P1 and end of P2, respectively. Bold script indicates a significant within group change. real-time feedback of force (kg) being applied and displayed on an LCD screen allowing the physiotherapist to ensure that the target valuewas beingmaintained. 3.2 Wall squat group (n = 27) This group also performed four reps of 2 min with 2 min rest between each rep but instead, this consisted of maintaining a squat position with their back against the wall as described above for the initial wall squat test. The knee joint angle was set using a fixed goniometer fas- tened with Velcro to the thigh and leg (Figure 2A). Between each set participants were given 2min of rest while seated. We assigned wall squat group participants to one of two standard- ized program progressions based on an initial assessment of their ability to sustain the wall squat position at a knee joint angle of 95◦ for 2 min, or not. Those that were able to do so performed the exercise at 125◦ for the first 3weeksof the intervention, 115◦ forweeks4–6, 105◦ for weeks 7–9, and 95◦ for weeks 10–12. Those that were unable to do so performed the exercise at 135◦ for weeks 1–2 of the intervention, 125◦ for weeks 3–4, 115◦ for weeks 5–6, 105◦ for weeks 7–9, and 95◦ for weeks 10–12. As there is a curvilinear relationship between these joint angles and heart rate response (greater knee flexion is associated with a higherHR)13 wall squat intensity progressively increased during phase 1 for all participants. In phase 2, during the singleweekly session, all participants performed the exercise at 95◦. 3.3 Control group (C) (n = 22) The control group was involved in the same pre- and post-study 3- month BP, anthropometric, body composition, handgrip, andwall squat assessments but did not undertake any isometric training. They were however provided via e-mail with a link to the 4 × 4 recommendations for healthy lifestyles referred to above. 3.4 Statistical analysis An ANCOVA was used to evaluate potential intergroup differences in BP (adjusted for baseline values) between baseline and end of phase 1 and between baseline and the end of phase 2, respectively. Partial eta squared (η2), was used to quantify magnitude of effect size differ- ences in this analysiswith a small effect indicatedby η2= .01; amedium effect=; η2 = .06 and η2 = .14 a large effect. We also assessed the sig- nificance and magnitude of within-group changes in BP using paired samples t-tests. The magnitude of between and within group change was quantified using Cohen d’s effect size, 14 with values classified as follows: <.2 trivial, .2–.5 small, .5–.8 moderate, .8–1.2 large, >1.2 very large. 4 RESULTS The 77 non medicated people with hypertension who were recruited, randomized and assessed at baseline all completed both phases of the intervention and completed all training sessions, with no adverse events reported. The mean age of the sample was 44.9 (±9.6) and 67% were male. Anthropometric measures and lean body mass are shown in supplemental material/appendix. Mean SBP and DBP at baseline, post-phase 1 and post-phase 2 are shown in Table 1 and Figure 3. There were significant large and very large magnitude decreases in SBP between baseline and post phase 1, in the handgrip andwall squat groups respectively and significant moderate magnitude decreases in DBP in both intervention groups. Comparing BP between groups at baseline versus post phase 1 (ANCOVA adjusted for baseline values), there were significant, large magnitude differences between groups in SBP (p < .001, F = 7.9, η2 = .156) and small magnitude, non-significant differences in DBP (p = .366, F = 1.019, η2 = .024). Post hoc analysis (Table 2) revealed large magnitude, significant differences in SBP between the handgrip and control groups and very large magnitude, significant differences between the wall squat and the control. There were no significant changes within any group (Table 1) between post phase 1 and phase 2. Comparing post-phase 2 with baseline, there were significant differences between groups in SBP (p = <.001, F = 10.9, η2 = .194). Post-hoc analysis (Table 2) showed significant differences of moderate magnitude between handgrip and controls and of very large magnitude between wall squat and control groups. There was also a small magnitude, non-significant difference between handgrip and wall squat groups post phase 2. Table 2 also showsbetweengroupdifferences inDBPwereofmoderatemagnitude, 17517176, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1111/jch.14621 by C ochrane C olom bia, W iley O nline L ibrary on [28/03/2023]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense COHEN ET AL. 5 F IGURE 3 Systolic blood pressure (SBP) and diastolic blood pressure (DBP) mean and 95% confidence intervals by group at baseline, post phase 1 and post phase 2.Mean and 95% confidence intervals by group pre intervention, post phase 1 and post phase 2 for systolic blood pressure (SBP) and diastolic blood pressure (DBP). * Indicates significant difference between pre intervention and post phase one. † Indicates significant difference between pre intervention and post phase 2. TABLE 2 Between group differences in blood pressure after phase 1 and phase 2 PHASE 1 PHASE 2 SBPMean (95%CI) p/ ES DBPMean (95%CI) p/ ES SBPMean (95%CI) p/ ES DBPMean (95%CI) p/ ES CONTROL vs. HANDGRIP 10.3 (2.8 to 17.8) .004* .819 2.8 (–2.5 to 8.1) .418 .369 10.9 (3.3 to 18.5) .003* .797 3.9 (–1.7 to 9.5) .224 .466 CONTROL vs. WALL SQUAT 11.7 (4.1 to 19.3) <.001† 1.03 2.8 (–2.5 to 8.1) .427 .345 14.7 (6.8 to 22.4) <.001† 1.26 5.3 (–.32 to 11.) .068 .622 HANDGRIP vs. WALL SQUAT 1.4 (–5.7 to 8.4) .89 .119 –.01 (–5.0 to 5.0) 1 0.001 3.75 (–3.5 to 11.0) .432 .323 1.4 (–3.8 to 6.7) .795 .158 Abbreviations: SBP, systolic blood pressure;DBP, diastolic blood pressure; ES, effect size. *= p< .01; † = p< .001 for difference between groups at end of phase compared to baseline (ANCOVA adjusted for baseline values). Bold script indicates a significant within group change. but non-significant (p= .076, F=2.67, η2 =0.06)with post hoc analysis showingamoderatemagnitudedifferencebetweenwall squat andcon- trol and a small magnitude difference between handgrip and control groups. There were no significant within group changes or between group differences in body weight, BMI, waist circumference or lean body mass (Table: supplementarymaterial) 5 DISCUSSION The present study confirms previous findings demonstrating signifi- cant 11.2–12.9 mmHg reductions in SBP in adults with hypertension following three times per week isometric resistance training, changes which compare favorably with the average SBP reduction (9.1 mmHg SBP) with a single, standard dose antihypertensive drug.15,16 We also present some important novel findings. This is the first study to com- pare the BP reducing effects of isometric handgrip and wall squat exercise training. Following the initial 12-week training phase, the two modes of IRT led to similar, clinically and statistically significant reduc- tions in office-measured SBP. However, after phase 2, during which training frequency was reduced to 1 session per week, in the handgrip group SBP increased by .5 mmHg, while there was a further 1.8 mmHg decline in the wall squat group, representing a small magnitude but clinically relevant 3.8 mmHg greater SBP reduction in the wall squat group over the whole intervention–which aligns with the estimated 17517176, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1111/jch.14621 by C ochrane C olom bia, W iley O nline L ibrary on [28/03/2023]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 6 COHEN ET AL. >3 mmHg difference favoring wall squat over handgrip training in a recent meta-analysis.17 The present study is the first to examine whether reductions achieved with the standard three times per week intervention can be retained with a reduced training frequency or “maintenance dose.” While a weekly single session of wall squat exercise not only main- tains, but potentially continues to promote SBP reductions, handgrip exercise begins to show a reversal of gains and may require a higher frequency to sustain the benefits achieved. The larger muscle mass recruitedand therefore areaof vascular occlusionduring thewall squat exercise17 might explain its ability to maintain adaptations at a lower frequency of training. 5.1 Blood pressure changes-phase 1 We observed reductions in SBP of lower magnitude to that reported in medicated participants following a 12-week handgrip intervention using the same protocol,18 but higher than determined by meta- analyses which also included non-supervised and shorter intervention durations—both associated with smaller BP reductions.5,6,8 There are few wall-squat intervention studies relative to the substantial literature examining isometric handgrip training. During phase 1, reductions in SBPwere of largermagnitude (although not significantly) in the wall squat group than in the handgrip group and of similar mag- nitude as the only previous study of wall squat in unmedicated adults with hypertension.10 That study found office measured SBP and DBP reductions of 12.4 and 6.2 mmHg, respectively, after 4-weeks of three exercise sessions/week. While SBP benefits were large and robust in both IRT groups and despite significant, moderate magnitude reductions within both intervention group during phase 1, maintained during phase 2, DBP reductions were not significantly different from that of the controls at the end of either phase. However, significant DBP reductions are not a consistent finding of handgrip studies,6,18 and it is SBP control that is critical to cardiovascular health outcomes/mortality with reductions associated with reduced cardiovascular mortality.10 5.2 Blood pressure changes-Phase 2 The present study is the first to evaluate whether an IRT “maintenance dose” can be used to maintain BP reductions obtained with a three sessionsperweekprotocol. Taylor et al.10 demonstrated thatBP reduc- tions achieved during a 4-week, three session per week wall squat intervention in adults with hypertension had returned to pre inter- vention values after a 3-week “washout” (training cessation) period. We found that clinically and statistically significant SBP reductions achieved in phase 1were largely retainedwith only a single session per week, a time commitment even easier to adhere to, likely to enhance long termcompliance.Althoughour study involved supervised sessions within the workplace, and partly took place during the difficult condi- tions associatedwith the COVID-19 pandemic, no participant dropped out with 100% compliance to the 3 sessions, and then 1 session per week program. While our phase 2 findings show maintenance of adaptations, they do not indicate that significant reductions in BP could be achieved with a single weekly session of IRT. However, a single weekly session of dynamic resistance training can stimulate strength development20 and epidemiological evidence suggests that significant diabetes and cardiovascular risk reduction is achieved with participation in once-a- week training strength training.21 The only previous study examining dose-response of IRT compared 3 versus 5 handgrip training sessions per week, finding no significant difference in SBP reduction.22 Future research should examine the degree towhich lower frequency IRT (1-2 sessions per week) can promote BP reduction. The minimal equipment requirement and associated cost of wall squat training make it a more scalable and widely applicable prescrip- tion for unsupervised home and/orwork-based training IRT than hand- grip exercise. We used a relatively economic dynamometer (approx- imately $50), purchasing several devices which were shared within each workplace. While affordable to an institution, in a public health setting it may still be a prohibitively expensive to provide patients with dynamometers, particularly within the budget constraints of low- middle income country (LMIC’s). This is an important consideration as the burden of hypertension and other cardiometabolic disease is larger in LMIC than in high income countries.2 Based on our findings and other recent evidence,10,17 the wall squat appears to therefore provide the best cost-benefit in BP in hypertensives and is well tol- erated, well adhered to and with no reports of adverse events in the present or previous wall squat interventions. Indeed, no dropouts and a 77% compliance with exercise sessions was reported in a recent year-long-wall squat intervention.23 Nonetheless, handgrip exercise may be an important alternative for individuals with knee pain or pathologies. A limitation of our study is the office rather than ambulatory blood pressure measures, the latter considered the gold standard.24 How- ever, Taylor et al.10 reportedvery similar reductions in24-hambulatory and office BP measures, and of similar magnitude as observed in the present study, indirectly validating our officeBPobservations. Another potential limitation of the wall squat arm of our study was the use of a pragmatic approach to reduce the time cost of stratifying participants, whereby according to their performance in a 95◦ wall squat test, par- ticipants began the program at either of the two easiest joint angles, with intensity (angle) progressed every 2–3weeks during phase 1. This provided a crude stratification of baseline ability to perform the exer- cise. It also meant that for a number of participants, it was likely that during the earlyweeks of the intervention the intensitywas below that necessary to stimulate adaptations. In contrast, Wiles and colleagues incremental wall squat test identifies the baseline training angle asso- ciated with 95%HR peak in each participant with HRmeasured during the last 30 s of 2-min tests at progressively greater knee flexion angles, starting at 135◦.13,25 This individualized approach to identify the train- ing angle used throughout a 4-week intervention10 also ensures that each participant is physiologically challenged from the start of the program. It is also time-consuming when delivered to a large sample. 17517176, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1111/jch.14621 by C ochrane C olom bia, W iley O nline L ibrary on [28/03/2023]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense COHEN ET AL. 7 Our pragmatic stratification was conceived as a less time-consuming practical alternative that also implemented standardized progressive loading across phase 1 to compensate for the built in underloading dur- ing the initial weeks of the intervention. This early underloading may explain why Taylor et al.10 achieved a similar magnitude SBP reduc- tion in 4weeks of wall squat as we observed in 12weeks. Nonetheless, our approach, allowing participants a period of accommodation to this novel exercise before challenging them, may be beneficial from a self- efficacy and comfort perspective. Lastly, the greater attention/contact that the intervention groups receivedmay also have contributed to the beneficial trends of IRT, although a previous study which compared wall squat with a sham wall squat (inadequate intensity) only demon- strated BP reductions in the “true” intervention group suggesting that the effects are specific to the exercise itself.26 While we did not evaluate physiological parameters which might explain the SBP reductions observed, a recentmeta-analysis concluded that the principal driver of IRT induced BP reduction is reduced total peripheral resistance, potentially mediated through enhanced auto- nomic vasomotor control. Changes in cardiovascular function including significantly decreased heart rate and increased stroke volume (with stable cardiac output) are also consistently reported.17 Importantly, from an adherence perspective, IRT overcomes one of the most cited barriers to exercise participation—lack of time—and reduces barriers to implementation associated with equipment costs. It can be performed with limited space, at home or in the workplace, without even requiring a change of clothes. IRT also represents an alternative to aerobic exercise for those who are unable to adopt that form of exercise or an adjunct to it.27 The feasibility of scaling of the wall squat intervention in a public health setting has begun to be examined in the United Kingdom,28 and such scaling should also be examined in other LMIC regions with lower healthcare budgets. Finally, longitudinal studies of sufficient duration are needed to examine the ability of IRT to impact on HTA progression and cardiovascular events in people with hypertension. 6 CONCLUSION Our study is the first to compare the BP reducing effects of the two mostwell researched andpotentially applicable IRTprotocols, in adults with hypertension. The large decreases in SBPwe observed alignswith previous studies and provides further evidence to support the pre- scription of IRT to hypertensive individuals. Three sessions per week of wall squat and handgrip produce comparable SBP reductions. We also showed that SBP reductions are largelymaintained after 3months of single session per week training, but the wall squat appears to better retain benefits with this minimal dose of training—with impor- tant implications for longer term adherence. The effectiveness of this dose—12minof time investment—shouldbe confirmed in future longer duration studies and in unsupervised interventions. Future research should also determinewhether initial benefits can also be achievedwith lower frequency training interventions involving 1 or 2 sessions per week, to better define theminimum effective dose. AUTHOR CONTRIBUTIONS Daniel Dylan Cohen: Concept and design of study, preparation of manuscript. Gustavo Aroca Martinez: Leader of Barranquilla site delivery, review of manuscript. Javier Carreño-Robayo: Operational leader of Bucaramanga intervention delivery, study design, review of manuscript. Alvaro Castañeda-Hernández: Operations Bucaramanga intervention. Yaneth Herazo Beltran: Operations Barranquilla inter- vention. Paul Camacho-López: Assistancewith study design and opera- tionsBucaramanga intervention. JohannaOtero:Assistancewith study design and statistics. Daniel Martinez-Bello: Statistical expertise. Jose P. Lopez-Lopez: Review of manuscript. Patricio Lopez-Jaramillo: Study design and lab director Bucaramanga, review of manuscript. ACKNOWLEDGMENT The study was funded by the Ministerio de ciencia tecnología e inno- vación. Colciencias (theColombianMinistry of Science). Grant number: 807–18, contract number: 759–18. CONFLICT OF INTEREST The authors report no conflict of interest. PATIENT CONSENT STATEMENT All participants provided written consent. ORCID DanielDCohenMSc, PhD https://orcid.org/0000-0002-0899-4623 GustavoAroca-MartinezMD,PhD https://orcid.org/0000-0002- 9222-3257 Javier Carreño-RobayoBSc,MSc https://orcid.org/0000-0001-5460- 6946 AlvaroCastañeda-HernándezBSc,MSc https://orcid.org/0000-0001- 7994-1839 YanethHerazo-BeltranBSc,MSc https://orcid.org/0000-0003-3752- 4353 PaulACamachoMSc,MD https://orcid.org/0000-0002-6233-9582 JohannaOteroMSc https://orcid.org/0000-0002-2044-2071 DanielMartinez-Bello PhD https://orcid.org/0000-0003-3219-0753 JoseP Lopez-LopezMD https://orcid.org/0000-0001-8865-0929 Patricio Lopez-JaramilloMD, PhD https://orcid.org/0000-0002- 9122-8742 REFERENCES 1. Forouzanfar MH, Liu P, Roth GA, et al. Global burden of hypertension and systolic blood pressure of at least 110 to 115mmHg, 1990–2015. JAMA. 2017;317(2):165-182. 2. Yusuf S, Joseph P, Rangarajan S, et al. Modifiable risk factors, cardiovascular disease, and mortality in 155722 individuals from 21 high-income, middle-income, and low-income countries (PURE): a prospective cohort study. Lancet. 2019;395(10226):795–808. pii: S0140-6736(19)32008-32002. 3. Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA/AAPA/ ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: a report of the American College of Cardiology/ 17517176, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1111/jch.14621 by C ochrane C olom bia, W iley O nline L ibrary on [28/03/2023]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense https://orcid.org/0000-0002-0899-4623 https://orcid.org/0000-0002-0899-4623 https://orcid.org/0000-0002-9222-3257 https://orcid.org/0000-0002-9222-3257 https://orcid.org/0000-0002-9222-3257 https://orcid.org/0000-0001-5460-6946 https://orcid.org/0000-0001-5460-6946 https://orcid.org/0000-0001-5460-6946 https://orcid.org/0000-0001-7994-1839 https://orcid.org/0000-0001-7994-1839 https://orcid.org/0000-0001-7994-1839 https://orcid.org/0000-0003-3752-4353 https://orcid.org/0000-0003-3752-4353 https://orcid.org/0000-0003-3752-4353 https://orcid.org/0000-0002-6233-9582 https://orcid.org/0000-0002-6233-9582 https://orcid.org/0000-0002-2044-2071 https://orcid.org/0000-0002-2044-2071 https://orcid.org/0000-0003-3219-0753 https://orcid.org/0000-0003-3219-0753 https://orcid.org/0000-0001-8865-0929 https://orcid.org/0000-0001-8865-0929 https://orcid.org/0000-0002-9122-8742 https://orcid.org/0000-0002-9122-8742 https://orcid.org/0000-0002-9122-8742 8 COHEN ET AL. American Heart Association Task Force on clinical practice guidelines. J Am Coll Cardiol. 2018;71:e127-e248. 4. Gee ME, Bienek A, Campbell NR, et al. Prevalence of, and barriers to, preventive lifestyle behaviors in hypertension (from a national survey of Canadians with hypertension). Am J Cardiol. 2012;109(4):570-575. 5. Bentley DC, Nguyen CH, Thomas SG. Resting blood pressure reduc- tions following handgrip exercise training and the impact of age and sex: a systematic review and narrative synthesis. Syst Rev. 2018;7(1):229. 6. Loaiza-Betancur AF, Chulvi-Medrano I. Is low-intensity isometric handgrip exercise an efficient alternative in lifestyle blood pressure management? A systematic review. Sports Health. 2020;12(5):470- 477. 7. Cornelissen VA, Smart NA. Exercise training for blood pres- sure: a systematic review and meta-analysis. J Am Heart Assoc. 2013;2(1):e004473. 8. Smart NA, Way D, Carlson D, et al. Effects of isometric resistance training on resting blood pressure: individual participant data meta- analysis. J Hypertens. 2019;37(10):1927-1938. 9. Wiles JD, Goldring N, Coleman D. Home-based isometric exercise training induced reductions resting blood pressure. Eur J Appl Physiol. 2017;117(1):83-93. 10. TaylorKA,Wiles JD,ColemanDA, et al. Neurohumoral and ambulatory haemodynamic adaptations following isometric exercise training in unmedicated hypertensive patients. J Hypertens. 2019;37(4):827-836. 11. Rønnestad BR, Nymark BS, Raastad T. Effects of in-season strength maintenance training frequency in professional soccer players. J Strength Cond Res. 2011;25(10):2653-6015. 12. Normatividad - Ministerio de Educación Nacional de Colombia [Inter- net]. Accessed Sept 19th 2019, available: https://www.mineducacion. gov.co/1759/w3-propertyvalue-51455.html 13. Wiles JD,AllumSR,ColemanDA, Swaine IL. The relationships between exercise intensity, heart rate, and blood pressure during an incremen- tal isometric exercise test. J Sports Sci. 2008;26(2):155-162. 14. Cohen J. Statistical power analysis for the behavioral sciences. Routledge Academic; 1988. 15. Law MR, Morris JK, Wald NJ. Use of blood pressure lowering drugs in the prevention of cardiovascular disease: meta-analysis of 147 randomised trials in the context of expectations from prospective epidemiological studies. BMJ. 2009;338:b1665. 16. Zanchetti A. Randomized controlled trials of blood pressure lowering in hypertension: a critical reappraisal. Circ Res. 2015;116(6):1058- 1073. 17. Edwards JJ, Wiles J, O’Driscoll J. Mechanisms for blood pressure reduction following isometric exercise training: a systematic review andmeta-analysis. J Hypertens. 2022;40(11):2299-2306. 18. Palmeira AC, Farah BQ, Silva GOD, et al. Effects of isometric handgrip training on blood pressure among hypertensive patients seen within public primaryhealthcare: a randomized controlled trial. SaoPauloMed J. 2021;139(6):648-656. 19. Lonn EM, Bosch J, López-Jaramillo P, et al. Blood-Pressure lowering in intermediate-risk persons without cardiovascular disease. N Engl J Med. 2016;374(21):2009-2009-2010. 20. RalstonGW, Kilgore L,Wyatt FB, BuchanD, Baker JS.Weekly training frequency effects on strength gain: a meta-analysis. Sports Med Open. 2018;4(1):36. 21. Shiroma EJ, Cook NR, Manson JE, et al. Strength training and the risk of type 2 diabetes and cardiovascular disease. Med Sci Sports Exerc. 2017;49(1):40-46. 22. Badrov MB, Bartol CL, DiBartolomeo MA, et al. Effects of isometric handgrip training dose on resting blood pressure and resistance ves- sel endothelial function in normotensive women. Eur J Appl Physiol. 2013;113(8):2091-2091-2100. 23. O’Driscoll JM, Edwards JJ, Coleman DA, et al. One year of isometric exercise training for blood pressure management in men: a prospec- tive randomized controlled study. J Hypertens. 2022;40(12):2406- 2412. 24. Sega R, Facchetti R, Bombelli M, et al. Prognostic value of ambula- tory and home blood pressures compared with office blood pressure in the general population: follow-up results from the Pressioni Arte- riose Monitorate e Loro Associazioni (PAMELA) study. Circulation. 2005;111:1777-1783. 25. Wiles JD, Taylor K, Coleman D, Sharma R, O’Driscoll JM. The safety of isometric exercise: rethinking the exercise prescription paradigm for those with stage 1 hypertension. Medicine (Baltimore). 2018;97(10):e0105. 26. Decaux A, Edwards JJ, Swift HT, et al. Blood pressure and cardiac autonomic adaptations to isometric exercise training: a randomized sham-controlled study. Physiol Rep. 2022;10(2):e15112. 27. Smart NA, Gow J, Bleile B, Van der Touw T, Pearson MJ. An evidence- based analysis of managing hypertension with isometric resistance exercise-are the guidelines current? Hypertens Res. 2020;43(4):249- 254. 28. Wiles J, Rees-Roberts M, O’Driscoll JM, et al. Feasibility study to assess the delivery of a novel isometric exercise intervention for peo- ple with stage 1 hypertension in the NHS: protocol for the IsoFIT-BP study including amendments to mitigate the risk of COVID-19. Pilot Feasibility Stud. 2021;7(1):192. SUPPORTING INFORMATION Additional supporting information can be found online in the Support- ing Information section at the end of this article. How to cite this article: CohenDD, Aroca-Martinez G, Carreño-Robayo J, et al. Reductions in systolic blood pressure achieved by hypertensives with three isometric training sessions per week aremaintainedwith a single session per week. J Clin Hypertens. 2023;1-8. https://doi.org/10.1111/jch.14621 17517176, 0, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1111/jch.14621 by C ochrane C olom bia, W iley O nline L ibrary on [28/03/2023]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense https://www.mineducacion.gov.co/1759/w3-propertyvalue-51455.html https://www.mineducacion.gov.co/1759/w3-propertyvalue-51455.html https://doi.org/10.1111/jch.14621 Reductions in systolic blood pressure achieved by hypertensives with three isometric training sessions per week are maintained with a single session per week 1 | INTRODUCTION 2 | METHODOLOGY 2.1 | Study design 2.2 | Measurements 3 | INTERVENTION 3.1 | Handgrip group (n 28) 3.2 | Wall squat group (n 27) 3.3 | Control group (C) (n 22) 3.4 | Statistical analysis 4 | RESULTS 5 | DISCUSSION 5.1 | Blood pressure changes-phase 1 5.2 | Blood pressure changes-Phase 2 6 | CONCLUSION AUTHOR CONTRIBUTIONS ACKNOWLEDGMENT CONFLICT OF INTEREST PATIENT CONSENT STATEMENT ORCID REFERENCES SUPPORTING INFORMATION