Browse evidence-based analysis of health-related claims and assertions
Taking high-dose zinc lozenges every day might help adults get over colds faster—cutting how long you're sick by more than a third compared to not taking them.
Causal
Taking high-dose zinc lozenges helps adults with colds feel better, and it works the same way for everyone—no matter if they have allergies, smoke, how bad their cold is, their age, gender, or background.
Descriptive
Taking high-dose zinc lozenges can shorten how long you have a cold by about 3 days, especially for adults between 20 and 50 years old.
This is about how hard you push yourself during certain exercises. It says you might not need to go all-out to failure to build muscle in some fibers, because one study found that legs not pushed to failure kept their muscle size while legs pushed to failure actually lost a little muscle. So, how hard you try could change how your muscles react.
When people do light weight training with restricted blood flow very often (at least 5 days a week), their slow-twitch muscle fibers grow bigger faster. Some less frequent training also helps, but not as much.
Correlational
Using a special training method with lighter weights and restricted blood flow along with heavy lifting might help trained people build more muscle by growing certain muscle fibers better, but different studies have found different results.
When adults lift heavy weights, their fast-twitch muscle fibers grow much more than their slow-twitch ones, based on several studies.
When people do light weightlifting with restricted blood flow, their slow-twitch muscles can grow as much or more than their fast-twitch muscles, which is different from heavy lifting where fast-twitch muscles usually grow more.
Quantitative
It's unclear whether mixing blood flow restriction with heavy weight training helps grow more overall muscle by targeting slow-twitch fibers, as studies show mixed results.
This is about how often you do special blood flow restriction workouts. It says that training more than 5 days a week might make your slow-twitch muscle fibers grow bigger (by about 19%) compared to training less often, but scientists aren't completely sure yet because the research is mixed.
Scientists aren't sure yet if a newer type of lighter weight training works better than traditional heavy lifting for building a specific kind of muscle fiber in adults, because there haven't been enough direct comparisons and the few studies done so far have mixed results.
When adults lift heavy weights, their fast-twitch muscle fibers grow much bigger than their slow-twitch fibers - sometimes 10-15% more. But when they do lighter weights with restricted blood flow, both fiber types grow more equally or the slow-twitch ones grow more.
When adults do light weight training with restricted blood flow, their slow-twitch muscles grow as much or more than their fast-twitch muscles, which is different from heavy weight training where fast-twitch muscles usually grow more.
For top powerlifters, two types of weight training—one that restricts blood flow and one that doesn't—both leave fast-twitch muscle fibers the same size after training.
When top powerlifters do a special type of exercise that limits blood flow to their muscles, their thigh muscle size grows almost 8% bigger—way more than the tiny growth from normal workouts.
When top powerlifters do a special type of weight training that restricts blood flow, it makes their slow-twitch muscle fibers grow more cell nuclei by 18%, but normal weight training doesn't do this.
When powerlifters do squats with restricted blood flow using lighter weights, it makes their slow-twitch muscle fibers grow bigger by 12%, while regular training doesn't change muscle fiber size.
This claim says that how well people can guess how many more reps they have left in a workout doesn't depend on whether they're male or female, how long they've been training, or how strong they are at bench pressing relative to their body weight.
When trained lifters guess how many more reps they could do during bench press, their guesses are equally accurate whether they're guessing 1 rep left or 3 reps left, and this stays the same across different sets and sessions.
People who lift weights regularly are pretty good at guessing how many more reps they could do during bench press, usually only off by less than one rep, and they tend to guess a bit too low.
Whether you're new to lifting weights or have been doing it for years, you're just as good at guessing how many more reps you can do before your muscles give out.
When doing leg press exercises, men are better at guessing how many reps they can do before getting tired compared to women, but for chest press exercises, there's no difference between men and women in guessing this.
People are better at guessing how many chest press reps they can do before getting tired compared to leg press reps, with guesses being off by only about one rep for chest press but more for leg press.
When people are lifting weights and getting really tired, they're pretty good at guessing how many more reps they can do if they're almost done—only off by about one rep. But if they could do a few more, their guess is less accurate, off by more than two reps.