@joey.stax's preacher curl claims, fact-checked

What does this video actually claim?

Joey Stax argues that preacher curls with strict form, slow tempo, and full range of motion build better bicep peaks than sloppy technique. He emphasizes planting your arms, controlling the weight, and focusing on the muscle contraction.

The video promotes discipline over ego lifting. Stax positions himself as someone who "drops knowledge" about training methodology, specifically targeting bicep development through controlled movement patterns.

Does the science back up slow, controlled lifting?

Research supports Stax's emphasis on tempo and control. A 2019 study by Pereira et al. in the Journal of Human Kinetics found that slower eccentric phases (2-4 seconds) produced greater muscle hypertrophy than faster tempos over 10 weeks of training.

The full range of motion claim also holds up. Bloomquist et al. (2013) in the European Journal of Applied Physiology demonstrated that full range of motion squats produced 25% greater muscle growth than partial range versions. While this study focused on legs, the principle applies to upper body exercises.

However, the "total control" approach isn't always superior. Some research suggests explosive concentric phases can enhance power development and overall muscle activation.

Can you actually "build peaks" with specific exercises?

This is where Stax ventures into questionable territory. The bicep's peak is largely determined by genetics, specifically the length of your bicep tendon and muscle belly insertion points.

No exercise can fundamentally change your bicep's shape or create a "peak" if your genetics don't support it. Preacher curls effectively target the bicep brachii, particularly the long head, but they won't reshape your muscle architecture.

What preacher curls can do is maximize the development of whatever genetic potential you have. The exercise does provide excellent isolation and removes momentum, which can lead to better muscle activation.

What about the ego lifting criticism?

Stax gets this completely right. Research consistently shows that heavier weights with poor form don't translate to better muscle growth.

A 2014 study by Schoenfeld et al. in Sports Medicine found that moderate loads (65-85% 1RM) with proper form produced similar hypertrophy to heavier loads with compromised technique. The key factor was training to or near muscular failure.

The "squeeze like it owes you money" advice also has merit. Calatayud et al. (2016) found that consciously focusing on the target muscle during training increased EMG activity by up to 60% compared to just moving the weight.

What should you actually know?

Stax's form advice is solid, but his "peak building" claims oversell what any exercise can do. Your bicep shape is mostly genetic lottery.

The real value in his approach is maximizing muscle development through proper technique. If you're going to do preacher curls, slow tempo and full range of motion will likely produce better results than swinging heavy weight around.

But don't expect any exercise to fundamentally change your muscle's architecture. Focus on progressive overload with good form, and you'll develop whatever genetic potential you have.