Browse evidence-based analysis of health-related claims and assertions
Even though both muscle thickness and total lean mass went up after training, they didn’t change together in a predictable way—meaning one might not be a perfect stand-in for the other.
Correlational
If you’re already experienced with weightlifting and train your legs twice a week for 8 weeks with hard sets, your muscles will grow whether you take short breaks between reps or not.
Quantitative
Even though cluster sets let you rest briefly between reps, they don’t actually let you lift more total weight over time than regular sets—if you’re pushing just as hard in both.
When people who already lift weights do either short breaks between reps (cluster sets) or long continuous sets (traditional sets), both ways make their muscles grow about the same amount if they work just as hard and do the same total number of reps.
Muscles don’t grow evenly—when you train your thigh, the top and middle parts of the front muscle grow more than the bottom, and the side muscle grows the same everywhere.
Descriptive
Even though drop sets make your thigh muscle grow more in some spots, they don’t make you stronger in a one-rep max or in a machine test than regular sets—both methods improve strength about the same.
Causal
Doing leg extensions with drop sets (going to failure, then lowering the weight and going again) makes the front part of your thigh muscle grow more than doing regular sets, but only in the upper and middle parts—not the bottom or the side muscles.
People didn’t lift more or less depending on whether they took creatine before or after their workout — they did the same amount of work in both cases.
Doing strength training with heavy weights for two months makes your muscles bigger and stronger, no matter when you take creatine.
Taking creatine before or after your workout doesn’t make a difference in how much muscle you build or how much stronger you get, as long as you take it regularly for about two months.
For women just starting weight training, how much they lift (total volume) matters a lot—but only if they also eat enough protein and calories. It’s the combo that makes a difference.
If young women who are new to weightlifting eat enough calories (35–45 per kg of body weight), they get stronger from training—but if they eat too few (15–20 kcal/kg), they might actually lose strength even while training hard.
When young women who are new to weight training do more sets and lifts, and eat at least 1.5 grams of protein per kilogram of body weight, they tend to gain more muscle than those who don’t get enough protein.
When you lift light weights until you can't go on or until you slow down, your muscles swell and your blood gets more acidic in the same way — meaning your body reacts similarly to both methods.
Using light weights until you're exhausted or slow builds your muscle stamina better than heavy weights, but doesn't make you as strong as lifting heavy weights.
Lifting light weights until you can't do another rep builds muscle just as well as lifting light weights until your speed slows down a lot, as long as you do the same total amount of work.
The untrained arm gets stronger without getting bigger—proving that the improvement comes from better nerve signals, not from muscles growing larger.
The nerves don’t become more sensitive to signals—they just fire more often and start earlier, which is how the untrained arm gets stronger without the brain sending stronger commands.
Most of the strength gain in the untrained arm happens in the first month of training—after that, it plateaus, showing that the brain and nerves adapt quickly, not the muscles.
Training one arm doesn’t just make it stronger—it also makes the muscles fire more smoothly and steadily, even in the other arm, leading to more controlled movements.
The stronger the untrained arm gets, the more consistently its motor nerves fire during effort—this tight link shows that better nerve signaling, not muscle growth, is why the arm gets stronger.
When you train one arm, the other arm’s muscles start firing more easily and more intensely during contractions—even without being exercised—making it stronger through better nerve signals, not bigger muscles.
Training one arm with heavy eccentric curls makes the other arm stronger too—even though it didn’t lift any weights—by about 10%, while the trained arm gets even stronger, by nearly 20%.
Even though both arms are just being moved by the robot, people feel like they’re working harder mentally when both arms are moving together than when only one arm is moving.