Stretch Shortening Cycle

 

The stretch shortening cycle (SSC) is the physiological mechanism involving an eccentric muscular and tissue stretch, followed by an amplified concentric contraction. There are several physiological properties that play a role in the SSC. There is the muscle spindle (wants to speed up contraction), the Golgi Tendon (wants to slow down contraction), the muscular pre-stretch (puts muscles in better length for contraction forces and increases tension), there is an increase in neural output, neural facilitation, and many more possible unexplored physiological mechanisms (fascia, tendons, proprioception, intra-fiber proteins, intramuscular timing etc…)

Importance

The importance of the SSC in sport is evident. Nearly every movement that occurs involves some level of pre-stretch and usage of the SSC. So, naturally as a coach it is very enticing to find a way to optimize this mechanism. However, due the lack of understanding of how exactly these mechanisms work (we can’t just cut people open and look) we cannot exactly pinpoint what is best.

 

To make the SSC even more clouded, is the fact that there are two types of SSC. There is a slow SSC and a fast SSC. The differentiation between the two is determined by speed of movement and rate of neural discharges. However, as a coach, measuring such differences is not practical and may not even be that useful. Instead a coach should understand what the differences are and then apply it without instrumentation .

 

Application of increasing the SSC

 

There are lots of methods used to attempt to increase the SSC of a movement. Some of these methods range from basic jumping exercises all the way to heavily loaded eccentric to unloaded concentric jumps. There is really no definitive “best” exercise and it is probably a combination of several exercises that will elicit the optimal response (due to the complexity of the SSC). This doesn’t mean we shouldn’t try and take the time to understand what exercises my affect what aspects of the SSC.

BONUS: Explanation of muscle spindle and Golgi tendon organ

Traditional Weight Training

Traditional weight training (isoiternal exercises) includes exercises such as, but not limited to, deadlift, squats, lunges, RDLs etc… These are exercises that have been used effectively by many successful coaches to improve the aspects of the SSC. It is often theorized that such increases from traditional strength training revolve around the increases in the muscular contractile capabilities (maximal force production and rate of force production), as well as neural facilitation and inhibition (Inhibition of the Golgi tendon and increase in neural discharges). The issues with traditional weight training is that the velocity might be much too slow to bring about adaptations to most aspects of the SSC. Some consider the adaptations from traditional weight training to be  “general”, and more specific exercises might needed to better target the SSC.

 

Eccentric overloads

There are two types of eccentric overloads. One type eccentric overload involves increasing the actual load during the eccentric decent and the other involves increasing the eccentric velocity.

 

Eccentric overload (load)

Eccentric overload involving a increase in “load” can be done with many different modalities. For example, you might see an athlete perform a jump where they dip down with either a trap bar or dumbbells before jumping.  The increase in eccentric load will increase muscular activation and possibly facilitate better energy transfer from eccentric to concentric contraction. The eccentric load could possibly further decrease the inhibition of the Golgi tendon and have a greater usage of the muscle spindles than that of the traditional weight lifting exercise due to the unloaded concentric contraction.

(Active Learning) I posted something similar to this the other day and got a bunch of questions as to how the tempo should be on the eccentric and how much weight should you used. I messed around today and found that the heaviest weight I used for the day (~50% 1rm trap bar dead) for a slower eccentric (as shown in video) gave me about a ~2 inch increase in vert compared to both same weight faster eccentric and lighter weight same tempo eccentric. Not saying this is science, but I feel like the slow tempo allowed for greater eccentric tension to be built. •••••••••••••••••••••••••••••••• I will be testing supra accelerated eccentrics with band tension on Friday. Looking forward to seeing how different tensions compare. Make training a learning experience. Test it out on yourself before you test it out on your athletes.

A post shared by Max Schmarzo (ATC/CSCS/MS) (@strong_by_science) on

 

Eccentric overload (velocity)

Eccentric overload via the increase in eccentric velocity is done by increasing the eccentric velocity. Some of the methods that are used to increase eccentric velocity are banded jump squats, accelerated KB swings and depth jumps (there is a large range of intensities in this category. For example, depth jumps are much more strenuous than banded jumps or squats). Like traditional jumping methods, the increase in eccentric velocity gets closer to mimicking actual sporting movements. The higher eccentric velocity may actually put greater strain on the tissues (fascia and tendons) than that of the previous slower eccentric contraction. The high velocity may also play an important role in Golgi tendon inhibition, however with a “weaker” untrained athlete the higher velocities may put the athlete at greater risk, which is way it may not be advisable to start with such exercises.

FIRST CLIP IS ECCENTRIC LOAD SECOND IS ECCENTRIC VELOCITY

 

(Know your overloads) the video above contains clips of two different types of overloads. The first clip shows an eccentric overload using an external resistance of weighted dumbbells (mass) and the second clips uses an eccentric overload with bands (velocity). By using weights you will not increase eccentric velocity, but bands will. If you think of this in terms of momentum and changes in momentum each exercise offers a very different stimulus. The bands can mimic the stimulus of the box jumps (somewhat), but without having the ground impact stresses, while the weights mimic the eccentric overload you see in the weight room. •••••••••••••••••••••••••••••••• by understanding simple aspects of physics you can make two very similar looking movements affect the body in two very different ways.

A post shared by Max Schmarzo (ATC/CSCS/MS) (@strong_by_science) on

****There are modified versions of some of these exercises. For example, people may not always perform the concentric action ballistically. Instead, people may use banded squats (velocity emphasis) or weight releasers squats (load emphasis).

It has been shown that when doing single leg split squats you get greater muscle activation if they are done as fast as possible in a semi ballistic manner. Using a load you can handle, the fast eccentric stretch requires a greater concentric contraction to over come. This is likely due to the increase in required impulse and jerk. •••••••••••••••••••••••••••••••• The concept of the study basically implies that larger EMGS and muscle activation is either needed to overcome large impulses, induced by a greater eccentric stretch or both. Once we understand the concept of the study we can look to apply it. Scientifically, it is limited to single leg split squats, application wise the concept is not. Learn concepts not exercises. thank you for sharing @coachpyka with @repostapp ・・・ Resistance Band Split Squat ________________________________________________________Working on speed-strength with professional soccer player Cami Levin for her last phase before she heads into preseason.

A post shared by Max Schmarzo (ATC/CSCS/MS) (@strong_by_science) on

 

Band Accelerated Concentric

Band accelerated/assisted jumps are a much less studied method for improving the SSC. They can be setup by using bands hanging from either a pull up bar, rack, or some type of solid overhead support. The bands essentially counteract gravity and allow you to jump against a reduced body weight. The reduction in body weight and active resistance as you pre-load can make it a little difficult to evoke fast eccentric actions. However, if performed properly, fast eccentric actions can be evoked (typically seen in continuous jumps). The band-assisted jumps are theoretically beneficial for a couple reasons.

1) The reduced body weight allows for a faster concentric contraction and therefore a higher concentric velocity to be trained, which might be associated with higher neural firing rates.

2) The reduced body weight allows for a fast eccentric to concentric transition to occur, because the force (body weight) required to transition the movement is much less (possibly increase intra-muscular coordination).

3) The faster contraction times may actually increase the ability of a muslce to produce higher velocity (increasing their max velocity). The increase in max velocity may theoretically work in a similar fashion as the idea of a “strength reserve”.

 

****The above-mentioned benefits are not support by literature and are just theory based on other findings not specific to the band-assisted jumping methods

@strengthcoachtherapy #repost working the most ignored aspect of the strength curve (sub bw) @coach_brettb @drjmike When looking at the force velocity continuum, we typically create maximum power at very low forces. Any training done at forces higher than this (heavy squats) is only a piece of the puzzle for maximizing power. Since we know that maximum power output is obtained when a particular combination of force and velocity is demonstrated, this notion has led us to develop training strategies focusing on different areas of power development. The opposite of heavy squats might be an assisted jump, as shown above. Assisted jumps allow the athlete to develop power with lighter relative force than they are used to. Assisted jumps and overspeed training allow for extremely fast muscular contraction and neurological coordination. They are an important part of power training and are essential in the long term training picture for maximal power development. @strong_by_science . ▪️▪️▪️

A post shared by Max Schmarzo (ATC/CSCS/MS) (@strong_by_science) on

Continuous Jumps/Bounds

The most common way of improving the SSC is by using jumping variations. The issue with jumping is twofold: there is minimal variation and minimal ways to overload specific aspects of the SSC. However, this is not to say jumping is not highly effective, it is simply to point out why other mechanisms might be used. It is possible that continuous jumping and similar jumping methods may target the tissues and nervous system more so than other methods.

#Repost @vivien_streit with @repostapp This is a great example of how being strong in the right places makes all the difference. If you watch @vivien_streit land and take off you will notice the amount of knee bend is extremely minimal. Having strong ankles, tissues (fascia and tendons), hips and core allows for an extremely efficient transfer of energy and high expression of force. No matter how many squats and hang cleans one performs they will never deliver this same type of training effect. The velocities, force vectors, and time of movement cannot be mimicked with a barbell. The "strongest" athletes in the weight room do not always correlate to the strongest on the track. Thank you @vivien_streit for sharing this post ・・・ The best part of training 😁 4x110cm #hurdlejump #highjump #fun

A post shared by Max Schmarzo (ATC/CSCS/MS) (@strong_by_science) on

Conclusion

The SSC is a highly complex mechanism. There is a lot of literature written on it and a lot of insightful theories. However, it is nearly impossible to get the full understanding of how such a complex system may work. Even though such an obstacle is in the way of our accuracy, we can still give a try to be less wrong. By no means is this article a complete review of the theory and by no way does it include all possible methods. There are many useful and important concepts that were not covered.

Leave a Reply

Your email address will not be published. Required fields are marked *