Microdosing of Flywheel Training: Effects of Low Versus High Training Frequency on Muscle Mass, Strength, and Power

PURPOSE: This study compared the effects of low-frequency flywheel resistance training (FRT, 1 session/week) and microdosing FRT (5 sessions/week) on muscle architecture, strength, and vertical jump performance in active individuals. METHODS: Thirty participants were randomized into a microdosing group (MDG, n = 15) or a control group (CG, n = 15). Both groups completed equalized weekly training volumes (30 sets over 6 wk) using a flywheel leg press. The MDG performed one set daily, whereas the CG performed 5 sets once weekly. Vastus lateralis and rectus femoris muscle thickness, vastus lateralis fascicle length and angle, maximal voluntary isometric contraction in the half-squat exercise, countermovement and drop jump performance, rating of perceived exertion, and delayed-onset muscle soreness were assessed preintervention and postintervention. RESULTS: MDG showed significant (P < .001) increases in muscle thickness (vastus lateralis: 9.8%, 0.21 cm, effect size ES = 0.41; and rectus femoris: 7.9%, 0.18 cm, ES = 0.34), fascicle length (11.8%, 0.96 cm, ES = 0.81), and fascicle angle (14.2%, 2.29°, ES = 1.16), drop jump RSI (24.4%, ES = 0.97), and drop jump take-off velocity (5.7%, ES = 0.27) while CG showed no significant changes. Both groups showed improved maximal voluntary isometric contraction (MDG: 27.4%, ES = 0.72; CG: 18.6%; ES = 0.48), countermovement height (MDG, 7.7%, ES = 0.34; CG: 5.9%, ES = 0.17), and countermovement mRSI (MDG, 32.1%, ES = 0.98; CG: 34.0%, ES = 0.60) with no intergroup differences. However, MDG reported significantly (P < .001) lower rating of perceived exertion and delayed-onset muscle soreness scores throughout the intervention. CONCLUSIONS: FRT microdosing improved muscle architecture, while strength and power gains were similar to low-frequency FRT. Importantly, microdosing reduced fatigue and soreness, offering a practical alternative during competitive congested schedules or in rehabilitation settings.