Objective Small muscle mass training localized to the quadriceps femoris muscle group has been proposed as an intervention to reverse heart failure-related skeletal muscle impairments. Although this training paradigm has demonstrated efficacy in heart failure, it remains to be evaluated in a conventional clinical context. Hence, the aim of this proposed study is to determine the effects of integrating high-intensity small muscle mass training (HISMT) isolated to the knee extensor muscles within a standard heart failure rehabilitation program.

Methods This single-blind, randomized controlled trial will aim to recruit 70 participants with heart failure. Participants will be randomized to either (i) standard training: combination of upper and lower extremity cardiovascular and resistance-based exercises, or (ii) high-intensity small muscle mass training plus modified standard training: bilateral knee extensor high-intensity small muscle mass training and a modified version of the standard training, so that the total volume of work will be similar to standard training alone. The training interventions will be undertaken twice weekly for 12 weeks in an outpatient clinical setting. Outcome measurements will be performed at baseline and after the 12-week intervention period. The primary outcome will be exercise capacity (6-Minute Walk Test), with secondary outcomes being physical performance measures, muscle strength, and health-related quality of life. Data will be analyzed using the intention-to-treat principle.

Impact This study will address a gap in the literature regarding the efficacy of small muscle training under routine clinical conditions for individuals with heart failure. The findings will also provide insight into the effects of high-intensity small muscle mass training within a heart failure rehabilitation program, thus enabling the optimization of exercise prescription for this patient population.