Eccentric strengthening is something that many individuals are missing out on the vast benefits in gyms worldwide, both for performance as well as looking good in front of the mirror. In his book "Triphasic Training," Cal Dietz referred to the Eccentric phase of dynamic movement as "the deceleration or lowering portion of the movement. It is associated with muscle lengthening.
During this phase, kinetic energy is absorbed and stored in the tendons of the muscle structure to be used during the stretch reflex." Let's take a deeper look at eccentric strengthening, specifically for the hamstrings.
Newton's 3rd Law of motion states that “the acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force. In the same direction as the net force, and inversely proportional to the mass of the object.”
This says that the amount of force we can absorb (eccentric), we then have the potential to produce (concentric). The eccentric action of movement is our breaking system. We need to ask ourselves, how fast can they hit the brakes, and how quickly can they relax to hit the gas again?
The ability to produce more force in less time and absorb more force in less time. Think Barry Sanders and his ability to change direction.
In fact, “Findings from five cross-sectional studies revealed statistically significant moderate- to large-sized correlations (r = 0.45-0.89) between measures of eccentric muscle strength and change of direction speed performance in athletic populations.” (8). Barry’s ability to do what he did on a football field is eccentric strength (and poetry) in motion. So why, then, would we not be including eccentric training as an important piece (not whole) of our training with clients and athletes? Hamstrings in training are generally seen doing things such as leg curls, hip extensions (reverse hypers), step-ups, & deadlifting.
They play a significant role in stabilizing one's pelvis and taking the strain off the low back. As you eccentrically stress or strengthen the hamstrings, the ability of our "posterior chain" to absorb force to then be able to transmit it increases dramatically.
Every eccentric action in sport or competition is followed by an explosive concentric action, and this is where Flywheel eccentric training offers a great opportunity for full system development.
“Superior enhancements in power and stretch-shortening cycle (SSC) function have also been reported; there appears to be a preferential increase in the size of type II muscle fibres and the potential to exert a unique effect upon fibre type transitions. Qualitative and quantitative changes in tendon tissue that may be related to the magnitude of strain imposed have also been reported with eccentric training.” (3).
This is great news as we want to improve our ability to produce power and train and improve our SSC. Eccentrics, within reason, allows us to take the governor off of force production as it inhibits the stretch reflex produced by the Golgi Tendon Organs (GTO) that keeps us feeling safe.
This governor or stretch reflex is there for a reason, however, the body/system will choose to protect first and foremost.
Eccentric training recruits fewer total motor units compared to concentric training. (11) This, in turn, increases the amount of stress placed on each of the recruited motor units, which can lead to fatigue. In fact, according to Handford, eccentrics with >4sec of time under tension had marked increases in Blood Lactate, Growth Hormone, and testosterone.
In comparison, <2sec saw significant improvements in concentric power output (1). So, with the changing of wheels in your training, you can foster the appropriate adaptation for your goals, whether hormonal or performance-based.
With the safety of utilizing the flywheel or some traditional methods of eccentric strengthening, you can push the intensity even to higher demands. “Eccentric training performed at high intensities was shown to be more effective in promoting increases in muscle mass measured as muscle girth.
In addition, eccentric training also showed a trend towards increased muscle cross-sectional area measured with magnetic resonance imaging or computerized tomography. Subgroup analyzes suggest that the superiority of eccentric training to increase muscle strength and mass appears to be related to the higher loads developed during eccentric contractions.” (2)
Not the focus of many training programs, but something the flywheel allows us to accomplish is to establish or re-establish a rhythm with our training. Not only is the eccentric-isometric-concentric continuity of the flywheel allowing for specific adaptations, but it's also allowing for a deeper, more intrinsic response of rhythm.
“Entrainment is a broadly used term that refers to the process of alignment between systems. In the context of human behaviour and physiology, entrainment refers to the adaptive function by which we voluntarily or involuntarily synchronize our brains and bodies to the environment; entrainment to the environment is possible with any sensory modality (sound being the most precise).” (13).
The flywheel allows for this entrainment to occur and to increase our sensory awareness both intrinsically and extrinsically.
I prefer double leg or offset, as you can produce higher amounts of force, and the athlete or client can understand and become educated on what the eccentric action feels like.
I love this for various reasons, but as the flywheel pulls you back in and your arm / Lat lengthens, it is eccentrically pulling you into your front hip. A great eccentric option to work on the transfer of kinetic energy and re-pattern throwing athletes struggling with their follow-throughs.
They have been shown to be comparable to Nordic Hamstring exercises in the force and transfer seen. The majority of flywheel-hamstring research has been done on this exercise specifically. “Flywheel leg-curl involved a greater overall use of the 4 muscle bellies, more specifically in the ST and BFs”; also saw higher relaxation times.” (6). As we discussed previously, faster or higher relaxation times allow for more athlete expression.
Eccentric hamstring exercises are an important part of training for athletic performance, as well as the structural integrity of our bodies. We touched on absorbing higher rates of force. According to Dietz, "the better athletes, defined as being those with higher rates of force production, are the ones who can absorb more kinetic energy eccentrically."
We also cannot forget the important of rhythm with anything training. Rhythm and coordination are often used concurrently and thus should be observed as an essential piece of training and development. Rhythm "improves accuracies of responses to supra-threshold stimuli when target stimuli occur at an anticipated moment, compared to stimuli occurring randomly or at unanticipated times, as well as improving stimulus sensitivity.” (12).
When you can package eccentric hamstring training and rhythm together, you have a highly response exercise choice to consider in your programming.
References
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