For people who already train with weights, stopping sets when they have 1 to 2 reps left in the tank leads to about the same increase in quadriceps muscle size after eight weeks as pushing to...
Mechanism
Synthesis from 1 study
When people lift weights with the same total work, their thigh muscles grow the same amount whether they stop just before failing or push until they can't do another rep — because the force on the muscle fibers triggers growth, not how close they get to failure (10.1080/02640414.2024.2321021). The...
Most probable mechanism
When people lift weights with the same total number of reps and weight, whether they stop just before failing or push until they can't do another rep, their thigh muscles grow about the same because the force on the muscle fibers is what triggers growth — not how close they get to failure. The muscle fibers sense the pull from lifting, which turns on a molecular switch (mTOR) that tells the cells to build more muscle protein. Stopping short of failure helps keep fatigue low so you can still do the same total work across all sets, while pushing to failure uses up more energy and makes later sets harder — but in these studies, people still ended up doing nearly the same total work either way, so the muscle growth ended up being the same. This was shown in both protocols using leg presses and leg extensions, with muscle thickness measurements confirming the outcome (10.1080/02640414.2024.2321021).
Mechanical tension is applied to quadriceps muscle fibers during concentric and eccentric phases of resistance exercises (leg press and leg extension) using 8–12-RM loads and full range of motion, activating mechanosensors such as integrins and focal adhesion kinase (10.1080/02640414.2024.2321021).
Mechanosensor activation triggers the PI3K/Akt/mTOR signaling cascade, increasing ribosomal biogenesis and translation initiation to enhance myofibrillar protein synthesis (10.1080/02640414.2024.2321021).
Sets performed to momentary muscular failure induce greater acute neuromuscular fatigue, reducing repetition performance in subsequent sets, but total repetition volume and volume load are preserved through compensatory adjustments in set structure, matching those achieved with 1- to 2-repetitions-in-reserve training (10.1080/02640414.2024.2321021).
Net positive protein balance from sustained mechanical tension exposure leads to sarcomere addition and measurable increases in quadriceps muscle thickness, with no significant difference between failure and RIR protocols despite differing fatigue profiles (10.1080/02640414.2024.2321021).
Less supported by current evidence, but not ruled out
Because the training protocol used leg press before leg extension, the muscle fibers in the vastus lateralis grew slightly more when people trained to failure (due to higher tension during the first exercise), while the rectus femoris grew slightly more when people stopped 1–2 reps short (because they were less tired and could activate it better during the second exercise). This shows that the order of exercises can shift where growth happens within the thigh, even if total growth is the same (10.1080/02640414.2024.2321021).
Leg press (multi-joint) preferentially recruits vastus lateralis and induces high fatigue, maximizing tension and hypertrophy in this subunit when performed to failure (10.1080/02640414.2024.2321021).
Fatigue from leg press reduces rectus femoris activation during subsequent leg extension, impairing its hypertrophy in the failure protocol (10.1080/02640414.2024.2321021).
Training with 1–2 RIR preserves leg extension performance by limiting prior fatigue, allowing greater rectus femoris activation and hypertrophy due to its preferential recruitment during isolated knee extension (10.1080/02640414.2024.2321021).
Differential hypertrophy of vastus lateralis and rectus femoris occurs without altering total quadriceps muscle thickness, indicating regional adaptation driven by exercise sequence and fatigue state (10.1080/02640414.2024.2321021).
Evidence from Studies
Supporting (1)
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