You’ve probably heard it before: “Lift heavy for strength, go moderate for size, and high reps for endurance.”
But what if we told you that advice is outdated?
A groundbreaking study turned the fitness world upside down—showing that your goals might not depend on how many reps you do, but how hard you work during them.
In this post, we’ll break down the science in plain English and show you how to use it to transform your workouts whether you’re training at home, in the gym, or just starting out.
1. Strength Training: Heavy Loads Work Best (Usually)
- If you want to increase your one-rep max (1RM), training with heavy weights (like in squats or bench press) is most effective as long as you’re testing strength with the same exercise you trained.
2. Muscle Growth (Hypertrophy): Load Doesn’t Matter Much
- Whether you lift light or heavy, you can build similar amounts of muscle as long as you push yourself close to failure.
- Muscle growth works across a wide range of reps—from 3 to 30.
- There might be minor differences based on muscle fiber types (e.g., light loads may target endurance fibers slightly more), but these effects are likely small and don’t change the overall results much.
3. Muscle Endurance: Light Loads May Help, But Not Always
- Lifting lighter weights for more reps seems to help improve muscular endurance better than lifting very heavy weights.
- However, it’s not clear if doing extremely high reps (like 20+) is better than doing moderate reps (8–12).
- More research is needed to find the ideal rep range for endurance.
Key Take Away
- Use heavy weights for max strength, especially when testing with the same movement.
- Use any weight range for muscle size, just train hard and consistently.
- Go lighter for endurance, but don’t overthink the exact rep count—what matters is pushing your muscles to work.
Pro tip: there are other variables that will be crucial on planning an adequate program such as injury risk, appropriation, recovery, etc.
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