Summary of "I Spent $40,000 To Prove Them Wrong (My NEW Study)"

Summary of “I Spent $40,000 To Prove Them Wrong (My NEW Study)”

Main Ideas and Concepts

The video investigates whether emphasizing muscle stretch during training truly leads to superior muscle growth, a widely held belief in the fitness community.
The creator invested over $40,000 and a year of research to rigorously test this idea using advanced methods and custom equipment.
Despite decades of studies suggesting that training muscles in a stretched position promotes growth, there are significant gaps and limitations in existing research.
The study aimed to clarify if making an exercise hardest during the stretch phase (bottom of the movement) actually leads to more muscle growth than making it hardest during the contraction (squeeze) phase (top of the movement).

Background and Context

Early research from the 1970s showed dramatic muscle growth from loaded stretching in animals (chickens) and humans (calves, chest). Subsequent studies comparing exercises that stretch muscles more (e.g., overhead tricep extensions vs. pushdowns) demonstrated increased growth, especially in biarticular muscles—those crossing two joints like quads, calves, and triceps.

This led to a “stretch focus” trend, with many recommending exercises that emphasize stretch for faster gains. However, most studies focused on only a few muscles (biceps, quads, calves), used different exercises for comparison, or relied on ultrasound, which has limitations in measuring muscle growth evenly across the muscle.

Identified Research Gaps

Limited muscle groups studied: Most stretch studies focus on easier-to-measure muscles (biceps, quads, calves), which may not generalize to other muscles.
Exercise differences confound results: Comparing different exercises (e.g., preacher curl vs. incline curl) introduces variables like stability, not just stretch.
Measurement limitations: Ultrasound measures thickness at a single point and may miss uneven growth along the muscle length; MRI provides a more accurate 3D volume measurement but is costly.

Methodology of the New Study

Collaboration with university researchers and experts Brett Contreras and Cassm Hansen.
Tested rarely studied muscles: chest, glutes, side delts, and rear delts.
Used MRI for precise 3D muscle volume measurement (~20 hours of scanning).
Employed custom exercise machines from Prime Fitness USA capable of instantly switching resistance profiles:
- Stretch-hard resistance: hardest at the bottom (muscle stretched).
- Squeeze-hard resistance: hardest at the top (muscle contracted).
Recruited 20 participants (men and women).
Used a within-subject design: each participant trained one side of their body with stretch-focused resistance and the other side with squeeze-focused resistance, controlling for genetics, diet, and other variables.
Ensured high adherence (97%) over 10 weeks.

Key Findings

No significant difference in muscle growth between stretch-hard and squeeze-hard training for chest, side delts, rear delts, and glutes.
Muscle growth was roughly 20% on average for both conditions.
Growth was consistent along multiple points of each muscle, indicating no regional differences favoring stretch or squeeze.
These results challenge the popular notion that making the exercise hardest in the stretch phase leads to superior muscle growth for these muscles.

Interpretation and Lessons

The concept of “stretch” in training can be broken down into three distinct ideas:

Degree of stretch: Biarticular muscles (crossing two joints) like quads, calves, and triceps benefit more from stretch-focused training.
Range of motion: Training through a full range of motion (including the stretched position) is important for muscle growth.
Resistance profile: Whether the exercise is hardest in the stretch or squeeze phase does not significantly impact muscle growth, as long as tension is present through the full range.

Additional insights:

The study supports previous findings that biarticular muscles benefit from stretch emphasis but shows that for other muscles, resistance profile adjustments are less critical.
Beginners were tested, which may limit detecting subtle differences; however, most research in this field uses untrained subjects and still finds differences.
The creator experienced faster shoulder growth when switching from dumbbell lateral raises (hardest in squeeze) to cable lateral raises (hardest in stretch), possibly due to novelty or enjoyment.
Combining both stretch and squeeze-based exercises may be beneficial, but more research is needed.
This study opens the door to using a wider variety of exercises effectively, which is helpful for injury management, equipment limitations, and recovery.

Practical Recommendations

Prioritize full range of motion to include the stretch position.
Include stretch-focused exercises especially for biarticular muscles (quads, calves, triceps).
Don’t worry excessively about whether the resistance is hardest in the stretch or squeeze phase for most muscles.
Use a variety of effective exercises (e.g., hip thrusts vs. squats for glutes, reverse flies vs. cables for rear delts, chest flies vs. bench press for chest).
Consider personal preference and enjoyment to maintain consistency and effort.
Continue to follow emerging research for refined training guidance.

Additional Information

The study’s MRI data analysis was very labor-intensive (200+ hours).
The study was double-blinded: neither MRI analysts nor statisticians knew which side was which.
The creator is launching further studies, including one on back muscle growth comparing rows vs. pulldowns.
The study was funded partly by profits from the creator’s fitness app, which offers AI-based personalized coaching.
The creator encourages viewers to try the app with a free trial and Black Friday discount.

Speakers and Sources Featured

Main Speaker / Creator: Presenter and lead researcher of the study (Jeremy Ethier).
Dr. Eric Helms: Mentioned as a friend who participated in calf stretching.
Brett Contreras: Fitness expert known as “the glute guy,” collaborator and funder.
Cassm Hansen: Collaborator in study design.
Adam Jones: Head researcher who analyzed MRI data.
Jeff Nippert: Science enthusiast who commented on the results.
JJ: Friend and study participant.

This comprehensive study challenges the fitness community’s obsession with making exercises hardest in the stretched position for muscle growth, showing that for many muscles, the hardest resistance point (stretch vs. squeeze) does not significantly affect hypertrophy, provided full range of motion and tension are maintained.