Once Again, Terrible Exercise Science Gets Praised by Mainstream Media
An important new science article has been making the rounds, with apparently every newspaper and internet news aggregator in the world repeating the message: You don't have to lift heavy weights to get stronger.
It's important because it both seems to confirm what everybody wants to believe, and because it's actually a pretty good technical study. But it is wrong, because it studies the wrong questions. Nonetheless, you now think that you don't have to lift heavier weights to get stronger.
In short, the study compared two groups of young men who had been working out in the gym for a while -- “gym bros” to us strength training professionals -- and assigned them a largely machine-based exercise program, described as “full-body Resistance Training,” to be performed four days a week.
One group performed “low reps” which the study authors considered to be 8-12 reps per set with 75-90% of their 1-rep maximum weight. The other group performed “high reps,” 20-25 reps per set with 30-50% of their 1RM. Each group did three sets to muscle failure with only a one-minute rest between sets.
This was actually not “strength training” at all. It was circuit training.
The strength and conditioning professional will immediately recognize that neither of these groups is a “low-rep” group, and neither of these groups is a “heavy-weight” group.
In other words, there was no low-rep, heavy-weight test group in a study that claims to show that there is no benefit to low-rep, heavy-weight exercise.
From the text: “The loads were adjusted in between each set to ensure that the correct repetition range was maintained,” and the loads were adjusted, either down or up, so that “failure” was achieved within the prescribed rep range for each group. In other words, if you somehow happened to get tired, they lowered the weight, because they had to.
Strength was measured by testing the change in 1-rep max on the lifts. Body composition and muscle tissue changes were assessed by the best laboratory methods available to modern science. Blood was drawn and hormones were measured, and statistical analysis was correctly performed.
The study found no significant difference in either strength or muscle size, or in growth-related hormone levels at the end of 12 weeks between the two groups.
This is not particularly surprising, since:
1.) Heavy weights were not used (you simply cannot do either 12 or 25 reps with a heavy weight, especially if you have to do three sets).
2.) To the extent that the two groups did get stronger, the group doing 8-12 reps to failure got a little stronger than the high-rep group, because they lifted heavier weights for fewer reps.
3.) The 1-Rep Max was therefore not trained. Instead, high repetitions were trained. You don't get what you don't train for.