Effort perception and hemodynamic responses to the 3/7 vs. 3X9 methods in heart failure and in coronary artery disease patients: a randomized-cross-over study
Authors: Gillet A , Lamotte M , Forton K , Roussoulieres A , Dewachter C , Deboeck G , Van De Borne P 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: Foundation. Main funding source(s): Fonds Erasme pour la recherche médicale

Background/Introduction
The hemodynamic response to strength training depends on the intensity, the time of rest between exercise sets and the duration of the exercise (1-3). A new method (the ‘3/7 method’), which consist of 5 successive sets of exercise with an increasing number of repetitions (3 to 7) separated by brief inter-set rest intervals (15 s), achieved a greater and faster strength gain after 12 weeks of training in young healthy subjects (4-5) (Fig 1). Further characterization of the tolerability of 3/7 method, as well as rise in blood pressure (BP) and heart rate (HR) it may induce, is needed in a patient population before this methodology can be applied in cardiac rehabilitation centers (6). These parameters were compared to those induced by 3 series of 9 repetitions (‘3X9 method’) with a longer inter-set rest interval (1min), using a randomized and cross-over study design.

Purpose
This study investigated the Borg scale and hemodynamic response of the 3/7 vs. 3X9 strength training methods in heart failure patients with reduced ejection fraction (HFrEF, Left ventricular ejection fraction (LVEF) &lt; 40%) and patients with coronary artery disease (LVEF&gt; 40%, CAD).

Method
23 HFrEF (58±9 y, 13% female) and 22 CAD (64±10 y, 14% female) participated in the study. CAD underwent revascularization between 1 and 6 months prior to the study. Patients with decompensated heart failure, atrial fibrillation, major orthopedics disabilities were not included in the study. The strength training consisted in leg extension against a load of ~ 70% of 1 repetition maximal (1RM). Perceived exertion was also assessed at the end of the last set by using the modified Borg Scale (0-10). HR and BP were assessed noninvasively beat by beat (Task Force Monitor). We compared baseline and peak exercise values in each group. All participants signed an agreement form approved by the local Ethic Review Board.

Result
Baseline BP and HR and effort perception at the end of exercise did not differ between the 3/7 and 3X9 groups (Borg scale: HFrEF 3/7 method: 5,4±2,6 vs. 3X9 method: 5,8±2,5; CAD 3/7 method: 6,2±1,3 vs. 3X9 method: 6,1±1,5; p= NS) (Fig 2). HR became faster with the 3/7 method as compared to the 3X9 method in the HFrEF (85±11 vs. 83±12 bpm, p=0.014, respectively) and CAD (90±13 vs. 87±14 bpm, p=0.03, respectively) patients. In the CAD group, systolic BP increased more with the 3/7 method than with the 3X9 method (143±22 vs. 133±20 mm Hg, p&lt;0.001). Other parameters did not differ.

Conclusion
The 3/7 and 3X9 strength training protocols elicit comparable effort perception and similar hemodynamic responses in HFrEF and CAD. The 3/7 method increases transiently HR by a few more beats in both groups and raises systolic BP by 10 additional mmHg in CAD patients. Taken together, this study suggests the 3/7 method is safe in patients with HFrEF and CAD, and warrants further investigation of the usefulness of the 3/7 method in cardiac rehabilitation units.