Browse evidence-based analysis of health-related claims and assertions
If you train by lowering weights slowly, you get stronger at lowering them—not at pushing them up—and vice versa, even if you do the same total amount of work.
Causal
The first time you do hard eccentric exercises—like slowly lowering a heavy weight—your muscles get way more sore and damaged than if you just push the weight up.
You can get just as strong by pushing weights up as by lowering them slowly—even if lowering them doesn’t make your muscles sore or damaged.
It’s not that slow lowering of weights damages muscles—it’s that your muscles aren’t used to it. Once they get used to it, no damage happens, even if you do the same move hard.
Mechanistic
If you do hard eccentric exercises like lowering weights slowly once a week for 10 weeks, your muscles stop getting sore and damaged—even though the exercise is tough—because they get used to it.
Your chest muscles swell the same amount after a hard workout whether you use a machine, barbell, or dumbbells—so the muscle-building stress is about the same.
How much total weight you lift matters more for muscle damage than whether you use a barbell or dumbbells—even if one feels harder or heavier per rep.
Just because your triceps feel sore doesn’t mean they’re damaged or weak—sometimes they feel sore even when they’ve fully recovered, and sometimes they’re fine even when they feel fine.
Even after a super hard workout, the body’s baseline testosterone level doesn’t stay high the next day — it goes back to normal quickly.
Quantitative
After doing barbell chest presses, guys felt less ready to train again—even two days later—than after using dumbbells or a machine, meaning they needed an extra day to feel recovered.
The more the thigh swells after a workout, the more the MGF repair protein increases — suggesting MGF might be triggered by physical stretching or swelling in the muscle.
Correlational
The tools used to measure muscle size and strength were very consistent and accurate, so the results can be trusted.
In trained men, when one muscle repair protein (IGF-IEa) goes up after a workout, the other one (MGF) tends to go up too — they seem to work together.
No matter which chest press they used, the guys completed almost exactly the same number of reps in every set—showing they pushed just as hard regardless of equipment.
Even though testosterone levels go up during a heavy workout, the muscle’s testosterone receptors don’t change in number two days later in trained men.
Descriptive
When using dumbbells, guys had to use lighter weights per rep—about 18% less than with a barbell—to complete the same number of reps and total work.
After a heavy leg workout, men report their legs feeling very sore — about 3 out of 5 on a pain scale — and it lasts for at least two days.
We know muscles stretch less the second time you do a tough workout, but we don’t yet know why that happens.
Even though guys lifted less weight per rep with dumbbells, they did more reps to make up for it, so the total weight lifted ended up being about the same for everyone.
After the second tough arm workout, blood markers of muscle damage tend to be lower, but the difference isn't strong enough to be sure it's real.
After a tough leg workout, a blood marker of muscle damage (CK) spikes by more than 1.5 times and stays high for two days, showing the muscles are still healing.
After a tough chest workout, your ability to push your arm across your chest comes back fully within three days, no matter if you used a machine, barbell, or dumbbells.
The first time you stretch your biceps in each workout, it stretches the same amount—even if the second workout causes less damage overall.
After a heavy leg workout, the thigh muscles get noticeably thicker due to swelling, and this lasts for at least two days.