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20 Sep


To maximize the effectiveness of your training, it’s critical to understand the concentric and eccentric phases of muscle contraction. This in-depth guide will delve deeper into the science behind these phases, offering evidence-based insights from experts like Brad Schoenfeld and Mike Zourdos. Additionally, we’ll explore how to implement Daily Undulating Periodization (DUP) to achieve both strength and hypertrophy.

The Underlying Science

Hypertrophy and Eccentric Mechanics

One of the most important factors in muscle growth is the eccentric phase, where the muscle lengthens under tension. When compared to concentric actions, eccentric actions are unique in their ability to impose higher levels of mechanical tension on the muscle fibers. This mechanical tension triggers a cascade of cellular events leading to muscle hypertrophy.

In a study by Brad Schoenfeld, he elaborates on the greater recruitment of Type II muscle fibers during eccentric movements (Schoenfeld, 2010). These fibers, also known as fast-twitch fibers, have a greater propensity for growth because they contain more actin and myosin contractile proteins. This makes them especially susceptible to muscle damage, another significant driver for muscle repair and growth. Moreover, it’s during the recovery period post-damage that we see a spike in muscle protein synthesis rates, which is essential for hypertrophy.

Eccentric contractions also demonstrate higher force outputs at lower levels of metabolic stress, meaning that you can lift heavier loads more efficiently during the eccentric phase. This is particularly advantageous for hypertrophy, as research indicates that lifting heavier loads while maintaining a strong mind-muscle connection can maximize muscle activation and growth. Additionally, Schoenfeld’s studies indicate that eccentric training may elevate the levels of specific growth factors, like IGF-1, within the muscle, further contributing to the hypertrophic process.

Concentric Phase and Neural Adaptations

When it comes to strength gains, the focus shifts toward the concentric phase of muscle contraction, where the muscle shortens under load. During this phase, neural adaptations play a critical role. According to research by Brad Schoenfeld, lifting heavier loads during the concentric phase initiates a set of neural responses that enable you to produce greater force in subsequent contractions (Schoenfeld, 2017).

These neural adaptations include the increased synchronization of motor units and a more efficient recruitment pattern. What this means is that your nervous system learns to activate more muscle fibers simultaneously, thereby increasing the force generated by the muscle. Enhanced neural drive also allows for quicker activation of muscle fibers, particularly Type II fibers, which are essential for explosive movements and high-force outputs. This adaptative neural behavior makes it easier to handle heavier weights, progressively increasing your strength capacities over time.

The Symbiosis of Strength and Hypertrophy

The importance of strength training in hypertrophy cannot be overstated. Strength gains have a reciprocal effect on hypertrophy, as increasing your maximal strength allows you to lift heavier weights in the hypertrophy rep range. This essentially results in greater mechanical tension on the muscles, further amplifying muscle growth. Strength phases can act as potent catalysts for hypertrophy when integrated appropriately into your training regimen.

Periodization: The Best of Both Worlds?

In bodybuilding, periodization can be invaluable for both hypertrophy and strength gains. It allows you to focus on different aspects like maximal strength or hypertrophy during specific phases.

Hypertrophy Phase Example (5-day week):

  • Monday: Chest and Triceps (8-12 reps at 65-75% 1RM)
  • Tuesday: Back and Biceps (8-12 reps at 65-75% 1RM)
  • Thursday: Legs and Shoulders (8-12 reps at 65-75% 1RM)
  • Friday: Upper Body (8-12 reps at 65-75% 1RM)
  • Saturday: Lower Body (8-12 reps at 65-75% 1RM)

Strength Phase Example (4-day week):

  • Monday: Chest and Triceps Focus (5-7 reps at 80-85% 1RM)
  • Wednesday: Back and Biceps Focus (5-7 reps at 80-85% 1RM)
  • Friday: Legs and Shoulders Focus (5-7 reps at 80-85% 1RM)
  • Sunday: Full-Body Strength (5-7 reps at 80-85% 1RM)

Daily Undulating Periodization (DUP)

Daily Undulating Periodization (DUP) by Mike Zourdos offers an integrated approach where you rotate between different rep and intensity schemes within the same week, targeting both hypertrophy and strength (Zourdos, 2016).

For example (5-day week):

  • Monday: Strength Focus, Lower Body (5-7 reps at 80-85% 1RM)
  • Tuesday: Strength Focus, Upper Body (5-7 reps at 80-85% 1RM)
  • Thursday: Hypertrophy, Chest and Triceps (8-12 reps at 65-75% 1RM)
  • Friday: Hypertrophy Focus, Legs and Shoulders (8-12 reps at 65-75% 1RM)
  • Saturday: Hypertrophy Focus, Back and Biceps (8-12 reps at 65-75% 1RM)


Bodybuilding success hinges on a nuanced understanding of the mechanics of muscle contraction, particularly the concentric and eccentric phases. By carefully integrating strength and hypertrophy training, utilizing periodization, and taking a scientific approach to exercise selection and execution, you can optimize muscle growth and performance. Daily Undulating Periodization (DUP) offers a flexible, evidence-based framework that allows you to achieve the best of both worlds, setting you on a path to becoming a more complete bodybuilder.

NOTE: Chet and Natalie are both IFBB Pros, Judges and Coaches. Interested in working with USA Physique? learn more about their Coaching Methods and visit their Coaching Plans page.


  • Schoenfeld, B. J. (2010). The mechanisms of muscle hypertrophy and their application to resistance training. Journal of Strength and Conditioning Research, 31(10), 2857-2872.
  • Schoenfeld, B. J. (2017). Strength and hypertrophy adaptations between low- vs. high-load resistance training: A systematic review and meta-analysis. Journal of Strength and Conditioning Research, 32(12), 3508-3523.
  • Zourdos, M, et al. (2016). Modified Daily Undulating Periodization Model Produces Greater Performance Than a Traditional Configuration in Powerlifters. J Strength Cond Res. 2016 Mar;30(3):784-91