Concentric (Phase)

Definition

The concentric phase is the part of the rep where the muscle shortens while contracting, producing the force needed to lift the load against gravity. It's the "positive" half of the movement.

Examples:

• Squat: standing back up
• Bench press: pushing the bar up
• Bicep curl: bringing the weight up to the shoulder
• Pull-up: pulling yourself up to the bar

💡 The concentric phase is what most people focus on (the "effort" phase), yet the eccentric phase is just as important for hypertrophy.

What happens in the muscle?

During the concentric phase:

• Sarcomeres shorten: actin and myosin filaments slide over each other
• Cross-bridges form: actin-myosin binding generates force
• ATP is consumed: chemical energy converted into mechanical work
• The muscle shortens visibly: bicep "balls up", quad bulks

Concentric vs Eccentric

⚠️ You can lower a load 30-50% heavier than your concentric max. That's why eccentric training programs (negatives) work so well for breaking plateaus.

Optimal concentric tempo

For maximum effect:

For hypertrophy

✅ Controlled and explosive concentric (1-2 seconds). The intent of going fast = maximum motor unit recruitment, even if the actual speed remains moderate due to load.

For strength

✅ As explosive as possible: maximum bar speed, including with very heavy loads. Develops rate of force development (RFD).

For power

✅ Maximum acceleration with moderate loads (50-70% 1RM). Used in olympic lifting and ballistic exercises.

Common concentric mistakes

• ❌ Slow / passive concentric: poor motor unit recruitment
• ❌ Cheat reps: using momentum to lift, missing the targeted muscle
• ❌ Lockout neglected: stopping short of full contraction
• ❌ Bar bouncing (e.g. bench press): leveraging elastic energy
• ❌ Rushed reps with no control = lost time under tension

Specific work on the concentric phase

Some advanced techniques specifically train this phase:

• ✅ Concentric-only: a partner does the eccentric for you (specialized machines)
• ✅ Pin presses: dead start from pins, no elastic rebound
• ✅ Pause reps: pause at the bottom, then explosive concentric
• ✅ Speed work: light loads (50-70%) with maximum acceleration

Key takeaways

The concentric phase is essential but not the whole story. Train it explosively and intentionally, but don't neglect the eccentric. The full rep (concentric + eccentric) is what builds muscle and strength. Lift with intent, lower with control.