Mixed
High-intensity resistance training using a gravity-independent flywheel ergometer induces significant skeletal muscle hypertrophy (cross-sectional area increase) within 20 days, with architectural remodeling (fascicle length increase) beginning as early as 10 days.
If you are new to resistance training or returning after a break, expect your muscles to start growing structurally within the first 3 weeks, even if you don't see it in the mirror yet. Use high-intensity resistance training (like flywheel or heavy weights) 3 times a week. Focus on maximal effort during both the lifting and lowering phases to maximize the stimulus for early growth.
Significant increase in QF CSA (3.5 and 5.2% in the C and D regions, respectively) was observed after 20 days of training, along with a 2.4 +/- 0.7% increase in fascicle length from the 10th day of training.
Why this rating
Small sample size (n=7), but rigorous within-subject design with MRI and ultrasound measurements.
Source
Early skeletal muscle hypertrophy and architectural changes in response to high-intensity resistance training
Olivier Seynnes et al. · Journal of Applied Physiology · 2006
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