Among people who regularly lift weights, training until muscle failure for eight weeks leads to about the same increase in quadriceps muscle thickness as training with a small amount of reserve...
Mechanism
Synthesis from 1 study
When people who already lift weights train either until they can't do another rep or stop one or two reps before failure, their thighs grow the same amount because both methods end up putting about the same total stress on the muscles over the workout — even though one feels harder, the overall...
Most probable mechanism
When people who already lift weights train either until they can't do another rep or stop one or two reps before failure, their thigh muscles grow the same amount because both methods end up putting about the same total amount of stress on the muscles over the workout — even though one feels harder, the overall force applied to the muscle fibers is similar, which triggers the same growth signals (10.1080/02640414.2024.2321021).
Resistance exercises with controlled loads (8–12-RM) and full range of motion generate mechanical tension in muscle fibers during concentric and eccentric phases (10.1080/02640414.2024.2321021).
Mechanosensors such as integrins and focal adhesion kinase detect this tension and activate the PI3K/Akt/mTOR signaling pathway, which is the primary driver of muscle protein synthesis (10.1080/02640414.2024.2321021).
Training to momentary muscular failure increases acute neuromuscular fatigue and repetition loss, but training with 1–2 repetitions-in-reserve preserves the ability to maintain total repetition volume across sets, resulting in equivalent cumulative mechanical tension exposure (10.1080/02640414.2024.2321021).
The equivalent total mechanical tension exposure leads to similar activation of mTOR signaling, ribosomal biogenesis, and myofibrillar protein synthesis, resulting in comparable increases in muscle fiber cross-sectional area and quadriceps thickness (10.1080/02640414.2024.2321021).
Less supported by current evidence, but not ruled out
Because the workout starts with leg press and ends with leg extension, the order of exercises causes different parts of the quadriceps to grow slightly more depending on whether training stops before or at failure — leg press fatigues the outer thigh muscle (vastus lateralis) more when pushed to failure, while stopping short preserves energy for the leg extension, which better activates the front thigh muscle (rectus femoris) (10.1080/02640414.2024.2321021).
Leg press, a multi-joint exercise, preferentially recruits vastus lateralis and induces high fatigue in this muscle when performed to failure (10.1080/02640414.2024.2321021).
Fatigue from leg press reduces the ability to activate rectus femoris during subsequent leg extension, limiting its mechanical tension exposure in the failure group (10.1080/02640414.2024.2321021).
Training with 1–2 repetitions-in-reserve on leg press preserves neuromuscular function, allowing higher-quality leg extension sets that better activate rectus femoris due to its preferential recruitment during isolated knee extension (10.1080/02640414.2024.2321021).
This results in greater vastus lateralis hypertrophy with training to failure and greater rectus femoris hypertrophy with training at 1–2 RIR, without altering overall quadriceps thickness (10.1080/02640414.2024.2321021).
Evidence from Studies
Supporting (1)
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