JMIR Publications

ABSTRACT

Background:

As strength sports gain popularity, there is a growing need to explore the impact of sustained strength training on cardiac biventricular structure and function, an area that has received less attention compared to the well-established physiological cardiac adaptation to endurance training.

Objective:

Implementing a 20-week high-intensity strength training program to enhance maximal muscle strength and evaluate its impact on cardiac biventricular adaptation in healthy untrained men.

Methods:

Twenty-seven healthy and untrained young men (22.8 ± 3.2 years old) participated in a strength training program designed to increase muscle strength. The training program involved concentric, eccentric, and isometric exercise phases, conducted over a consecutive 20-week timeframe with a frequency of three weekly training sessions. Participants were evaluated before and after 12 and 20 weeks of training through body composition analysis (bioelectrical impedance), 12-lead resting electrocardiogram, 3D transthoracic echocardiography, cardiopulmonary exercise testing, and muscle isokinetic dynamometry. The progression of strength training loads was guided by 1-Repetition Maximum (RM) testing during the training program.

Results:

Of the initial cohort, 22 subjects completed the study protocol. No injuries were reported. The body mass index (69.8 ± 10.8 kg/m² vs. 72 ± 11 kg/m², P=.72) and the fat mass (15.3 ± 7.5 % vs. 16.5 ± 7 %, P=.87) remained unchanged after training. The strength training program led to significant gains in 1-RM exercise testing as early as 4 weeks into training for leg extension (69.6 ± 17.7 kg vs. 96.5 ± 31 kg, P<.001), leg curl (43.2 ± 9.7 kg vs. 52.8 ± 13.4 kg, P<.001), inclined press (174.1 ± 41.1 kg vs. 229.2 ± 50.4 kg, P<.001), butterfly (26.3 ± 6.2 kg vs. 32.5 ± 6.6 kg, P<.001), and curl biceps on desk (22.9 ± 5.2 kg vs. 29.6 ± 5.2 kg, P<.001). After 20 weeks, the 1-RM leg curl, bench press, pull-over, butterfly, leg extension, curl biceps on desk, and inclined press showed significant mean percentage gains of +40 %, +41.1 %, +50.3 %, +63.5 %, +80.1 %, +105 %, and +106 %, respectively (P<.001). Additionally, the isokinetic evaluation confirmed increases in maximal strength for the biceps (+9.2 Nm), triceps (+11.6 Nm), quadriceps (+46.8 Nm), and hamstrings (+25.3 Nm). In the present paper, only the training and muscular aspects are presented, the cardiac analysis will be addressed separately.

Conclusions:

Our study demonstrated that a short-term high-intensity strength training program was successful in achieving significant gains in muscle strength among previously untrained young men. We intend to use this protocol to gain a better understanding of the impact of high-intensity strength training on cardiac physiological remodeling, thereby providing new insights into the cardiac global response in strength athletes. Clinical Trial: ClinicalTrials.gov Identifier: NCT04187170