Feasibility and effect of 3/7 strength training method in cardiac rehabilitation: preliminary results
Authors: Gillet A , Lamotte M , Forton K , Roussoulieres A , Dewachter C , Macera F M , Deboeck G , Van De Borne P 
Published: May 2023

Abstract

Funding Acknowledgements
Type of funding sources: Foundation. Main funding source(s): Erasmus Hospital.

Background
Cardiovascular rehabilitation (CR) is a type 1A intervention for cardiovascular disease. Among the various exercise modalities, resistance training (RT) is recommended for improving cardiorespiratory fitness (volume of oxygen consumption [VO2] peak). However, different modalities of RT coexist and which modalities should be preferred is still a matter of discussion. A RT method, called 3/7, allowed in healthy young subject greater strength gains with a shorter training time. However, the feasibility, the safety and its effects have never been studied in CR.

Purpose
The aim was to assess the feasibility, safety and efficiency of the 3/7 method in CR to improve VO2 peak.

Methods
In this single center randomized clinical trial, participants underwent 12 weeks of supervised training. Intervention: Group 3/7 consisting of 5 incremental sets of 3 to 7 repetitions with 15 s of inter-set intervals of RT on leg press; leg extension, leg curl, triceps press machines. Group 3X9 (usual care) of 3 sets of 9 repetitions with 1 min of inter set intervals on the same machine and at the same intensity (70% of 1RM). Patients completed 3 sessions per week; endurance training is the same in both groups. The primary outcome was a change in VO2 peak during the cardiopulmonary exercise test from baseline to 12 weeks. Secondary outcomes were isokinetic leg strength at 60°/sec and feasibility.

Results
Between 2019 and 2022 101 patients (92 male) were enrolled and randomized to 3/7 (n=49) or 3x9 RT (n=52). The mean age was 62y±8 (range 34 – 85). A total of 65 participants completed testing at 12 weeks for the primary outcome, including 32 in the 3/7 group and 33 in the 3X9 group. There were similar improvements from baseline between groups, VO2 peak by 19% in 3/7 group with 17% in the 3X9 group (mean [SD] oxygen uptake: 3/7, 3.6 [4.1] mL/kg/min; 3X9, 3.3 [4.5] mL/kg/min; P = .4). 3/7 improved quadriceps strength by 12% compared with 11% in the 3X9 group (mean [SD] isokinetic leg strength: 3/7, 23 [21] N/m; 3X9, 10 [22] N/m; P = .01). We had more dropouts in the usual care group compared to the 3/7 group (19 vs 17). 3/7 group had high feasibility scores and low rates of withdrawal due to serious adverse events (1). Most dropouts were due to other conditions (Lost of follow-up [n=11], COVID-19 [n=6], other medical problems [n=6], returns to work [n=5], withdrew [n=4]).

Conclusion(s)
In this randomized clinical trial, a 12-week RT of the 3/7 method coupled with endurance training improved VO2 peak to the same level than the usual care in cardiac rehabilitation, but more leg strength was observed. The 3/7 method may reduce the number of dropouts compared to usual RT program because the time training is reduced for the same volume of work.
Implications: These findings support inclusion of 3/7 method in cardiac rehabilitation programs as an adjunct or alternative modality to usual care.