Fred Hatfield—better known as Dr. Squat—was an American world-champion powerlifter and one of the most influential strength coaches of all time. He famously squatted 1,014 pounds at the age of 45, which was the heaviest squat in history at the time. Beyond his lifting achievements, Hatfield earned a PhD in Sports Psychology, allowing him to uniquely combine elite physical performance with an understanding of how the body and mind respond to training stress.
Dr. Squat helped popularize a foundational principle in strength training:
athletes respond differently to training based on how their muscle fibers are best recruited and trained.
Fast-Twitch vs Slow-Twitch Muscle Fibers
In simple terms:
- Fast-twitch muscle fibers are responsible for explosive movements like sprinting, jumping, and heavy lifts.
- Slow-twitch muscle fibers are more fatigue-resistant and support longer-duration efforts.
While most athletes have a mix of both fiber types, some respond better to heavier weight and lower reps, while others tolerate lighter weight and higher reps more effectively.
This explains why one athlete may squat 80% of their max for 10 reps, while another may only manage 2–3 reps at the same percentage.
Dr. Hatfield’s 6×2 Squat Philosophy
Dr. Squat strongly believed that training fast-twitch fibers was essential for developing strength and power. This belief was reflected in his well-known 6 sets of 2 reps squat approach, which has produced results for athletes for decades and is still used today.
The goal was simple:
- Use heavier loads
- Keep reps low
- Maximize explosive intent on every rep
Fast-twitch fibers are heavily involved in actions like driving out of the bottom of a squat, exploding out of a sprint start, or jumping. Heavier weights demand higher force production, which better trains these fibers.
Why Low Reps Keep Every Rep Explosive
One of the key advantages of lower-rep sets is rep quality.
Your first rep is almost always your most explosive because fatigue hasn’t set in yet. As reps accumulate, fatigue rises, power output drops, and movement speed slows.
Instead of performing one fatiguing set of 8 reps, an athlete can perform 4 sets of 2 reps and still complete the same total number of reps—but every rep stays fast, powerful, and technically sound.
This allows athletes to:
- Maintain higher bar speed
- Produce more force on each rep
- Train explosiveness instead of grinding through fatigue
Why Heavier, Lower-Rep Training Can Be Less Stressful
Although heavier weight may seem more stressful, total stress isn’t just about load—it’s also about volume and fatigue.
For example:
- 6 sets of 2 reps at ~85% of a 470 lb max
- 12 total reps at ~400 lbs
- Total volume: ~4,800 lbs
- 12 total reps at ~400 lbs
- 6 sets of 8 reps at ~65%
- 48 total reps at ~305 lbs
- Total volume: ~14,640 lbs
- 48 total reps at ~305 lbs
Higher-rep training dramatically increases total workload, leading to greater fatigue and a higher likelihood of technique breakdown. As fatigue rises, athletes may unintentionally shift stress to joints or tissues that don’t need it.
What About Slow-Twitch–Biased Training?
Higher-rep training still has value and plays an important role in a well-rounded program.
Benefits include:
- Improved muscular endurance
- Increased work capacity
- Greater time under tension, which can support muscle growth
This approach is commonly used in bodybuilding because higher volume and longer sets increase mechanical tension and metabolic stress—two key contributors to hypertrophy.
Putting It All Together
Smart programming considers:
- The athlete’s goals
- Their sport and position
- The phase of training they’re in
Both fast-twitch and slow-twitch–biased training have a place. The key is knowing when to push explosiveness and when to build capacity.
Dr. Squat understood this long before it became mainstream—and his principles still guide effective strength and performance training today.
