In biomechanical language: it's a type of movement training that focuses on "force dissipation" over "force generation"; or said in English, training that stops or slows the body down, rather than gets it going or speeds it up. It's highly relevant for tendon rehabilitation, injury prevention, running & jumping sports, & sports that require rapid change of direction, explosive bursts of speed or sudden stops. There's even a case to be made if you just want to feel better in your body with less aches by improving balance & shock absorption potential, which then gets into areas like "falls prevention". Eccentric training occurs whenever there's a focus on "controlling", either an external weight or the body itself, that in some way applies a "braking" force. Eccentric training predominately involves "eccentric muscle contractions", but there's more to the concept than just one type of muscle contraction.
It's well known that there are 3 types of muscle contraction, when performing any activity or exercise: concentric, isometric & eccentric. A "push up" is probably the easiest exercise to visualise all 3 in action. The concentric phase starts from the ground, when you use your chest to push the body up. The isometric phase is when you hold the body still at the top. The eccentric phase is lowering back down to the ground, again still using the chest. This eccentric or "lowering phase" can be done fast or slow, but it's an understanding that the lowering is generating a "braking" or "deceleration" force; a force that can then be redirected to apply "load" different body tissues, is how the benefits of eccentric training occur. As an "Exercise Physiologist", when I observe many people exercise, they appear to me to focus more on the concentric & isometric phases, while only giving limited, if any, focus on the eccentric phase.
In order to explain a particular movement or exercise, we might talk about each contraction type as occurring independently & separately, but that isn't entirely accurate. All 3 contractions are pretty much occurring simultaneous but in different parts of the body. It's hard to visualise but consider an AFL football analogy, where the player has jumped in the air, gained possession & is now coming back to ground. The player has to get boot-to-ball & kick it before getting tackled. In this situation concentric contractions are occurring to kick the ball, eccentric contractions are occurring on the other leg to slow the body down from the jump & isometric contractions nearly everywhere else to provide a stable platform, allowing the body to do what it does. Yer, that was an extreme example, but I use it to emphasise that all 3 contraction types are working simultaneously at some level, in different parts of the body depending on the activity. By appreciating this concept, it becomes possible to apply the basic principles of eccentric training to the entire body, which are something like: body posture/position, joint angle & the speed the movement is performed at. Once these principles are grasped, "load" can be directed purposely to different body parts & body tissues; relevant for the goal, which could be performance, rehabilitation or injury prevention!
Within sport science, adding the correct amount of "load" is the key to improving any movement parameter like: strength, size, speed, endurance, power, flexibility, balance, agility etc. Without some sort of load, there can be no improvement! There's always a catch however: not all "load" is the same & there are many variables to consider! A good first question to ask is normally, "what's the goal"? Once that's established, the "correct load" can be applied to ensure that particular goal is achieved. The concept of load is captured in the "FITT principle": Frequency, Intensity, Time & Type. In other words, "how often", "how hard", "how long", & "what type" of exercise or training.
"Chronic Adaptations to Eccentric Training: A Systematic Review". Douglas et al., (2017). Sports Med;47(5):917-941.
I recently read this journal, which prompted this blog post. These are some summary points:
The conclusions are that eccentric training is a potent stimulus for enhancements in muscle mechanical function, & muscle-tendon unit (MTU) morphological & architectural adaptations. The inclusion of eccentric loads not constrained by concentric strength appears to be superior to traditional resistance training in improving variables associated with strength, power & speed performance. Eccentric training can thus improve muscle mechanical function to a greater extent than other modalities. Novel muscle-tendon unit adaptations associated with a faster (i.e. explosive) phenotype have been reported. (This last point is one of the main reasons why eccentric training is effective in tendon rehabilitation!)
Surprisingly, it's not entirely clear what's going on with eccentric training but if we just consider the variable of "strength", the mechanisms underpinning strength improvements are thought to be a combination of factors including: neural, morphological & architectural.
Increased neural activity, or "neural drive", is observed: which basically means that you "talk better" (in a metaphorical sense) with your muscles. This translates as more "motor units" within the muscle being activated following bouts of eccentric training. The motor unit, being the basic structural unit of the nerve-muscle interface
Muscle morphology or "muscle shape" appears to be different: eccentric training tends to induce distal-muscle hypertrophy or increase in size (i.e. the part of the muscle closer to the tendon), while mid-muscle hypertrophy occurs to a greater extent following concentric training
Muscle architecture appears to be different: muscle biopsy reveals a greater increase in type II muscle fibres (i.e. fast twitch) with eccentric vs concentric or traditional training
As a runner, I've personally noticed huge gains in performing eccentric training. I've been doing it consistently for about a year, with a basic understanding of what I was trying to achieve. My understanding has developed in that time, so it has been good to write this blog, helping me articulate some things I've felt within my own practice but wasn't sure how to express directly in words. Which leads me to this point: the logic behind eccentric training is hard to articulate, but the application isn't all that complicated. Once you see it in practice, & more importantly "feel" the principles in action (as discussed above), "light bulbs" switch on & "ah-ha" moments occur!
Eccentric training represents a relatively unexplored & misunderstood practice. Future blogs will attempt to further explore the underlying basic principles of eccentric training & elucidate how those principles can work in movement practice. To get the complete picture, I think concepts like these need to be appreciated at some level:
The difference between force generation & force dissipation, which includes discussing the stretch-shorten cycle, the physics of stiffness & elastic potential energy
Various training methods that already utilise eccentric training like, plyometrics, negative reps in weight training & martial arts
The microscopic level, with a discussion on muscle fibres, muscle proteins & DOMS (delayed onset muscle soreness)
The specific application of eccentric training to achieve various goals, including how to structure workouts
Till next time...
"We cannot solve our problems with the same thinking we used when we created them."
Albert Einstein
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