Are you still building your workout program based on tips from the old-school gym veterans? For years, certain training concepts have been gospel in the weight room. But if your goal is maximizing muscle growth (hypertrophy), science has moved on—and some of these classic ideas are actively making your program less effective.

It’s time to ditch the outdated “bro science” and embrace the most efficient, research-backed path to building muscle. Here are four common workout rules that modern exercise science has debunked.

1. Ditch the Obsession with “Time Under Tension” (TUT)

For decades, bodybuilders preached that you needed to focus on Time Under Tension (TUT)—the total amount of time your muscle is stressed during a set—to stimulate growth.

What the research shows:

The true key to muscle growth is reaching muscular failure (or getting very close to it) and performing a reasonable amount of work.

• Rep range is wide: Research has shown that sets of anywhere from 5 to 50 reps are equally effective for building muscle, provided you push that set close to failure. The rigid 8-12 rep rule is a suggestion, not a mandate. For more on how close to push each set, check out our guide on training to failure.
• Set duration is flexible: While a set that’s too short (like a 1-rep max) won’t build much muscle, there is no need to count out super-slow repetition tempos. A set duration (TUT) of 20 to 70 seconds is generally recommended for hypertrophy, and a set of 5-50 reps will almost certainly fall into this range.

Actionable takeaway:

Instead of staring at a stopwatch, focus on:

• Using a reasonable rep range (5-20 reps is a good starting point). See our article on how heavy to lift for more details on rep ranges.
• Taking at least a couple of seconds on the eccentric (lowering) phase.
• Being explosive on the concentric (lifting) phase.

2. Stop Using Muscle Activation (EMG) to Choose Exercises

You’ve seen the YouTube videos: an influencer hooks up electrodes (Surface Electromyography or EMG) to their muscle and declares that one exercise is “superior” because it produces a higher EMG reading.

What the research shows:

The assumptions that make surface EMG a good predictor of muscle growth are questionable at best. EMG measures the electrical current (neuromuscular excitation) sent to the muscle, which is not the same thing as the muscle’s growth potential.

In studies where researchers measured both EMG during an exercise (like the hip thrust vs. squat) and the actual muscle growth over time, the initial EMG readings did not correlate with the final muscle growth observed.

Actionable takeaway:

Don’t base your workout on gadget readings. Instead, use a checklist based on studies that directly measure muscle growth. Choose exercises that:

• Allow you to progress safely (add weight or reps). This ties directly into progressive overload—the foundational principle of muscle growth.
• Feel effective for you.
• Fit your body’s mechanics.

SetsApart helps here. By tracking your hard sets and progression over time, you can objectively see which exercises are actually driving results—not just which ones “feel” more active.

3. Train Muscles More Than Once Per Week

The classic 5-day “Bro Split”—Chest on Monday, Back on Tuesday, etc.—is a bodybuilding staple. The primary flaw? You are only training each muscle group once every seven days.

What the research shows:

The two latest meta-analyses on training frequency confirm that training a muscle at least twice a week is superior to training it just once a week for maximizing muscle gains. For a deeper dive into optimal training frequency, read our guide on how often to workout.

Actionable takeaway: Optimal training splits

To hit that crucial two-times-per-week frequency, structure your week based on how often you can train consistently:

• 2–3 Training Days/Week: Use a Full Body routine.
• 4–5 Training Days/Week: Use an Upper/Lower split.
• 6 Training Days/Week: Use a Push/Pull/Legs (PPL) routine.

For a complete breakdown of which split is right for you, check out our article on the best workout split.

4. Forget the 48-Hour Fixed Rest Rule

How many times have you heard, “You need 48 hours of rest between hitting the same muscle”? This rigid rule suggests that training a muscle on back-to-back days will lead to “overtraining” and kill your gains.

What the research shows:

The rest period you need is entirely dependent on context:

1. How fatiguing was the workout?
2. How good is your recovery?

For most lifters, the amount of work you do over the week (volume) matters far more than the exact way you distribute it across consecutive or non-consecutive days.

Three different studies comparing training on consecutive days (e.g., Monday, Tuesday, Wednesday) versus non-consecutive days found similar improvements in muscle strength and growth. The body is great at recovering from accumulated fatigue over the course of a week.

Actionable takeaway:

Stop letting the calendar dictate your progress. If your schedule forces you to train two days in a row, go for it. Your body is more resilient than old wisdom gives it credit for. Prioritize managing your total weekly volume and ensuring you take your sets close to failure.

This is where tracking becomes essential. SetsApart’s volume per muscle group feature shows you exactly how many hard sets you’re accumulating weekly—regardless of how you space them out. Focus on hitting your volume targets, not arbitrary rest day rules.

The Bottom Line

Modern exercise science has moved past many of the rigid rules that dominated gym culture for decades. What actually matters for muscle growth is simpler than the “bro science” suggests:

1. Train close to failure on most sets
2. Use a wide rep range (5-20 reps works great)
3. Hit each muscle at least twice per week
4. Focus on weekly volume, not daily rest rules
5. Choose exercises based on progression, not EMG readings

Stop overcomplicating your training. Track your hard sets, progressively overload over time, and let the research-backed fundamentals do the work.

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Source

This article was inspired by and summarizes key insights from the following video. Check out the video for more detail and subscribe to the channel—it’s a great resource for evidence-based training.

Watch the full video: OUTDATED: Four Workout Ideas Science Just Debunked