“There is simply no other exercise, and certainly no machine, that produces the level of…muscular stimulation and growth…than the correctly performed full squat.” – Mark Rippetoe

Mark Rippetoe’s quotation from Starting Strength is a timeless reminder of how to prioritize strength training. If you want to be strong, ditch the machines and pick up a barbell.

Rippetoe based this statement on his experience with countless athletes. The evidence of experience is powerful, but until now it’s all we had to support the idea that free weight exercises provide better results than machines.

An upcoming study in the Journal of Strength and Conditioning Research tackled this question. Researchers asked, “What type of exercise will elicit the most hormonal response - machines or free weights?”

They chose the leg press and back squat to duel in an epic test of which could produce the most testosterone and growth hormone.

Ten healthy men volunteered for the study, each with experience in strength training. On one day they performed six sets of ten reps of leg press, starting with 80% of 1RM.

On another day, after plenty of rest, they returned to the lab to perform the squat workout, which was also six sets of ten reps, starting with 80% of 1RM. During each of these workouts, the participants were sporting a catheter inserted into their arms so blood could be sampled quickly.

In a result that surprised no one, barbell squats produced significantly higher levels of testosterone and growth hormone. At the greatest difference, which occurred during the workout, testosterone was about 25% higher when performing full squats versus leg press. But the difference in growth hormone was incredible.

Squats produced a full 200% more growth hormone during the workout.

Even thirty minutes after the workout, participants who did squats still had 100% more growth hormone as when they performed the leg press. Double your growth hormone, double your fun?

Cortisol levels also rose more after the squat workout, further confirming the squat workout was a fundamentally different physiological experience.

So is the leg press a bad exercise? No. Any exercise that results in a positive adaptation isn’t bad. The question is one of efficiency. We all want to get the best results possible, but we have limited time and energy to devote to training.

So it makes sense to use your time and energy on exercises that provide the best bang for your buck. And is the leg press as effective as a full squat? Not a chance.