Eccentric vs Concentric: How much stronger are we?
When physical therapists, athletic trainers, and strength & conditioning coaches design eccentric exercise, how should they determine the overload? In preparing an eccentric exercise clinical practice guide, I took a deep dive into the questions of minimal effective dose, optimal dose, and eccentric capacity.
Our field appears to prescribe a wide range of relative loads for eccentric training and rehabilitation — i.e., 100 to 190% of individuals’ 1RM.
These prescriptions are all based on the understanding that we are stronger eccentrically than we are concentrically. But how much stronger exactly — and what are the factors that influence it?
The answer is 130-150% stronger.
Nuzzo et al., recently put out a pre-print that comprehensively evaluates this topic for most body joints, various ages, and velocities. Overall, humans appear to be 140% stronger during eccentric contractions than concentric contraction.
Since we focus mainly on the knee joint in this blog series, I pulled the data for knee flexors and extensors below. These results, which include over 500 studies, demonstrate a fairly wide distribution for both muscle groups.
The quadriceps are 1.47x stronger eccentrically than concentrically — i.e., so a concentric 1-RM of 100 pounds could mean an eccentric 1-RM of 147 pounds!
The hamstrings and other knee flexors are 1.38x stronger eccentrically than concentrically.
Prescribing Eccentric Exercise In Rehabilitation
How can you use this information in exercise prescription and rehabilitation? Simple. Accentuated eccentric exercise and eccentric specific reps can be dialed up by 130-150% of the typical concentric load.
Here are some examples:
Normally prescribe 5 sets of 5 for concentric strength at 85% 1-RM? Go with 128% 1-RM for your eccentric exercise blocks.
Using flywheel training? Target a peak overload of 30-50% of concentric force. This can be achieved by adjusting the inertia and coaching your client on how to absorb and reverse the load.
Accentuated Eccentric Training (e.g., “Two-Up, One-Down” Training)? This is commonly used in ACL rehabilitation during leg extensions and leg presses. Select a load that is >100% of the individuals concentric 1-RM. Have clients lift concentrically with both limbs and ask them to control the eccentric phase with just the involved/injured limb. Customize load, velocity, and level of assistance provided by the uninvolved limb to ensure safety.
Velocity and other factors that influence eccentric strength.
This topic is a bit more nuanced that these recommendations may let on. For example, we know from the force-velocity curve, that concentric strength declines rapidly with increasing velocity, whereas eccentric strength increases. If we plot these data by the velocities used in data collection, we can see this is clearly the case:
Nuzzo et al., discusses this in the pre-print. Check it out to dive deeper.
All data visualized are made available by the authors on Open Science Framework.
