Machines or free weights
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The Method N° 04 · How muscle grows
Exercise choice
Equipment and order matter less than you think. Different exercises grow different parts of a muscle.
Every study checked against the paper, . Each section carries its grade. Run the numbers in the app.
Wobble boards add nothing
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Squatting on an unstable board grew no more muscle than a Smith machine or a free squat.3 One trial, and nothing argues the other way.
Order shapes strength, not size
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Across 11 studies, exercise order made no difference to growth, but people gained the most strength on whatever came first.4
Muscles grow unevenly
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So a second exercise earns its place
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The stretch matters
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Training a muscle where it is long tends to grow it at least as well. Seated leg curls, which stretch the hamstrings, grew them 14% against 9% for lying curls,10 and overhead triceps work grew the triceps 19.9% against 13.9%.11 Pooled across 12 studies the difference shrinks to similar, with a slight lean toward long lengths.12
Variety for its own sake does not help
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How the Vanguard app runs this
Every movement in the app's library is tagged with the one muscle it counts toward and where it loads it hardest: long, mid-range or short. A swap only ever offers movements that train the same muscle.
The research
The research
The 15 sources this chapter stands on, with what each one actually found.
Haugen, Vårvik, Larsen et al., 2023 · BMC Sports Sci Med Rehabil
Meta-analysis · 13 studies · 1,016 people
No difference in muscle growth between free weights and machines (effect −0.055), measured in 5 of the studies; strength gains followed the mode trained.
Read the paper by Haugen, Vårvik, Larsen et al., 2023 (opens in a new tab)Schwanbeck, Cornish, Barss et al., 2020 · J Strength Cond Res
Randomised trial · n = 46 · 8 weeks
Biceps and quadriceps thickness grew similarly with free weights and with machines.
Read the paper by Schwanbeck, Cornish, Barss et al., 2020 (opens in a new tab)Saeterbakken, Olsen, Behm et al., 2019 · PLoS One
Randomised trial · n = 59 men · 7 weeks
Smith machine, free-weight and wobble-board squat groups gained similar muscle thickness.
Read the paper by Saeterbakken, Olsen, Behm et al., 2019 (opens in a new tab)Nunes, Grgic, Cunha et al., 2021 · Eur J Sport Sci
Meta-analysis · 11 studies
Order made no difference to growth (effect 0.03); multi-joint strength favoured multi-joint lifts first (0.32), single-joint strength single-joint first.
Read the paper by Nunes, Grgic, Cunha et al., 2021 (opens in a new tab)Zabaleta-Korta, Fernández-Peña, Santos-Concejero, 2020 · Strength Cond J
Systematic review · 14 studies
13 of 14 studies found some regions of a muscle grew more than others.
Read the paper by Zabaleta-Korta, Fernández-Peña, Santos-Concejero, 2020 (opens in a new tab)Wakahara, Fukutani, Kawakami et al., 2013 · Med Sci Sports Exerc
Training study · n = 12 · 12 weeks
The regions of the triceps that grew most were the ones most activated in training.
Read the paper by Wakahara, Fukutani, Kawakami et al., 2013 (opens in a new tab)Zabaleta-Korta, Fernández-Peña, Torres-Unda et al., 2021 · J Sports Sci
Randomised trial
Leg extensions grew all three regions of the rectus femoris; Smith-machine squats grew only the central outer quad.
Read the paper by Zabaleta-Korta, Fernández-Peña, Torres-Unda et al., 2021 (opens in a new tab)Costa, Kassiano, Nunes et al., 2021 · Int J Sports Med
Randomised trial · n = 22 detrained men · 9 weeks
The varied-exercise group grew at every site measured; the fixed group did not grow at two of them.
Read the paper by Costa, Kassiano, Nunes et al., 2021 (opens in a new tab)Fonseca, Roschel, Tricoli et al., 2014 · J Strength Cond Res
Training study · n = 49 · 12 weeks
Varied-exercise groups grew all four heads of the quadriceps; constant-exercise groups missed some.
Read the paper by Fonseca, Roschel, Tricoli et al., 2014 (opens in a new tab)Maeo, Huang, Wu et al., 2021 · Med Sci Sports Exerc
Training study · seated against lying leg curl
Hamstrings grew 14% with the seated curl, which trains them long, against 9% with the lying curl.
Read the paper by Maeo, Huang, Wu et al., 2021 (opens in a new tab)Maeo, Wu, Huang et al., 2023 · Eur J Sport Sci
Training study · overhead against neutral-arm extensions
Whole triceps volume grew 19.9% overhead against 13.9% with the arm at the side.
Read the paper by Maeo, Wu, Huang et al., 2023 (opens in a new tab)Varovic, Wolf, Schoenfeld et al., 2025 · Int J Sports Med
Meta-analysis · 12 studies
Training at long and short muscle lengths produced similar growth, with a trivial lean toward long lengths near the far end of the muscle.
Read the paper by Varovic, Wolf, Schoenfeld et al., 2025 (opens in a new tab)Kassiano, Nunes, Costa et al., 2022 · J Strength Cond Res
Systematic review · 8 studies · 241 men
Planned variation may help regional growth; excessive random rotation may hurt it.
Read the paper by Kassiano, Nunes, Costa et al., 2022 (opens in a new tab)Kassiano, Costa, Kunevaliki et al., 2025 · Res Q Exerc Sport
Randomised trial · n = 70 women · 10 weeks
Varied and constant exercise selection grew muscle alike (7.8 to 17.7% against 7.5 to 19.3%).
Read the paper by Kassiano, Costa, Kunevaliki et al., 2025 (opens in a new tab)Baz-Valle, Schoenfeld, Torres-Unda et al., 2019 · PLoS One
n = 21 trained men · 8 weeks
Randomising exercises each session gave similar gains and raised motivation to train.
Read the paper by Baz-Valle, Schoenfeld, Torres-Unda et al., 2019 (opens in a new tab)
Research describes groups of people. Your coach will tell you how it applies to you.