Science about personal trainers

In a famous study at Ball State University in Indiana, researchers put two groups of 10 men through identical 12-week strength training programs.
The groups were evenly matched when they started, and they did the same combination of exercises, the same number of times, with the same
amount of rest. At the end of the experiment, one group had gained 32 percent more upper-body strength and 47 percent more lower-body strength
than the other. No performance-enhancing pills were involved—the only difference was that the more successful group had a personal trainer
watching over their workouts.
A good personal trainer—certified by an organization such as the National Strength and Conditioning Association, the American College of
Sports Medicine, or Can-Fit-Pro—will help you assess your fitness goals, design a safe and effective program to meet those goals, and motivate
you to put in the necessary work. But, as the Ball State study shows, there are other, less obvious ingredients that successful trainers provide—and
a series of recent studies offers some hints about how we can tap in to these benefits.
The crucial difference between the training of the two groups at Ball State was very simple: by the halfway point of the program, the supervised
group was choosing to lift heavier weights. Since both groups started with the same motivation level, it was the trainer’s presence leading that
group to set more ambitious targets. Other studies have consistently found that, left to their own devices, novice weightlifters tend to work out with
weights that are less than 50 percent of their one-repetition maximum, which is too low to maximize gains in strength and muscle size.
Even experienced strength trainers often fall into this trap, according to a 2008 study in the Journal of Strength and Conditioning Research.
Researchers at the College of New Jersey found that experienced women who trained on their own chose to use an average of just 42 percent of
their one-rep max for a 10-repetition set. In contrast, women who had prior experience with personal trainers chose weights averaging 51 percent
of one-rep max, even when the trainers weren’t there. “Many times, there is initial fear,” says Nicholas Ratamess, the study’s lead author. “We also
found that some women who did not have a personal trainer underestimated their own abilities because they did not routinely push themselves too
far.”
The latest attempt to address this question comes from researchers at the University of Brasilia in Brazil. They compared two groups of 100
volunteers who undertook a 12-week strength training program, supervised either by one trainer for every five athletes, or one trainer for every 25
athletes. The results display a familiar pattern: the highly supervised group improved their bench press by 16 percent, while the less supervised
group chose lighter weights and improved by only 10 percent.
In one sense, this is yet another argument for getting a personal trainer if you can afford one. But the differences here are more subtle, since
both groups had access to a trainer who could provide guidance on proper form and choosing appropriate weights. Instead, motivation and the
willingness to tackle ambitious goals seem to be the differentiating factors. As Ratamess points out, these are the kinds of benefits that an
enthusiastic training partner can also provide. For less experienced exercisers, the educational role of the personal trainer takes on greater
importance, he cautions. But beyond that, simply having someone there watching you—whether it’s a personal trainer or a workout partner—seems
to confer an additional benefit. Certainly, he says, “both have advantages compared to training independently.”