Does adding extra weight only when lowering build more muscle?

Short answer

Not for muscle, if you already lift. When 28 people added 40% more barbell or machine weight only on the way down, thigh muscle grew 13% versus 11% after 10 weeks, with no difference. Among the extra-weight studies, a muscle difference showed up in two 8-week studies, one of them in 40 people just starting to train.

Does adding extra weight only when lowering build more muscle?
'Heavier lowering → more stimulus → more muscle': does this formula hold?
Muscles can control more weight on the way down than on the way up. So some say that adding extra barbell or machine weight only to the lowering part builds more muscle. We checked the evidence step by step, from the guideline to actual trials.
The guideline named 'the lowering phase'
Its evidence compared lowering-only with lifting-only training
The 2026 American College of Sports Medicine guideline, which reviewed research on more than 30,000 people, listed 10 or more sets a week and 'emphasizing the lowering phase' as ways to build muscle. The full text shows the evidence was lowering-only training building more muscle than lifting-only training. It was not a comparison of normal up-and-down lifting with extra weight added only on the way down.
What happens when the extra-weight studies are pooled?
No difference in muscle size or strength
A 2026 analysis that pooled 49 studies with 773 people compared adding extra weight only when lowering with using the same weight both ways. Combining the 3 studies that measured muscle size showed no difference, and maximum strength showed no difference either. Another 2026 analysis comparing many training techniques found no study where this method built more muscle.
What about people who already lift?
40% more for 10 weeks: 13% versus 11%
28 people with an average of 2.6 years of lifting trained their legs for 10 weeks. The outer thigh muscle grew 13% with 40% more weight on the way down and 11% with the same weight both ways, with no difference. Leg lean mass (muscle and everything except fat) rose 4.2% and 1.6%, also with no difference.
Other trials in experienced lifters matched
No difference in muscle size in arms over 9 weeks or thighs over 6 weeks
When 18 people who already lifted trained their arms for 9 weeks, arm muscle size did not grow either with extra weight on the way down or with usual training. In a 6-week trial of 25 people used to strength training, thigh muscle grew with both methods. Only the size of one type of fast muscle fiber grew with heavier lowering alone.
A muscle difference came from two 8-week studies
40 people just starting out, and 35 people with extra weight on every rep
In an 8-week study of 40 people just starting to train, only the group lowering 138% of its lifting weight gained leg lean mass. In an 8-week study of 35 people, the group with extra weight on every rep grew the front thigh muscle more. The group with extra weight on only 2 of 6 reps showed no difference from the same-weight group.
Flywheel devices did not fall behind
Instead of adding weight, you resist a spinning disc
A flywheel is a device where you resist the pull of a spinning disc, which puts more force on the lowering part. A 2017 analysis that pooled 9 studies with 276 people found more muscle than with standard machines. In an 8-week study of 16 people comparing one leg with the other, thigh muscle grew 8% and 9%, with no difference, even with fewer reps.
Summary: no muscle difference for experienced lifters
Muscle did not grow more than with the same weight both ways
When people who already lift added extra barbell or machine weight only on the way down, muscle growth did not differ from using the same weight both ways. The bigger results came from two 8-week studies, including 40 people just starting to train. Flywheel devices, where you resist a spinning disc, did not fall behind standard machines. If muscle is the goal, getting the 10 or more sets a week named by the guideline is enough.