Today’s research review will be coming from the article: “Effects of different duration isometric contractions on tendon elasticity in human quadriceps muscles”. There will be a full citation at the bottom of this article.
The purpose of this study was to compare the effect long duration and short duration isometric exercises had on tendon stiffness. Stiffness was measured in vivo.
8 male subjects were recruited for the study. There were two different training protocols used. The exercise performed was a leg extension at 80 degrees. The protocol:
- 3 sets of 50 repetitions with 1 second on and 2 seconds off with a 1 minute break in between sets.
- 4 sets of 20 seconds on and 1 minute off.
All contractions were at 70% of the subjects Maximal Voluntary Contraction (MVC). New MVC measurements were retained every 2 weeks to keep the training load up to date. Protocol #1 was performed on one leg and protocol #2 was performed on the other for each subject. They trained 4 times per week for 12 weeks.
What They Found
The researchers found that both training protocols produced an increase in the subjects MVC and muscle volume in the quadratus femoris. They also found that tendon stiffness increased significantly for the long duration exercise, but not for the short duration exercise.
It is worth noting, however, that they found that the short duration exercise did show a higher increase in elastic energy output and therefore may be more beneficial when training for exercises that utilize the Stretch Shortening Cycle.
None of these results are conclusive and much more research needs to be done before these results are confirmed.
What’s That Mean for You?
As was made clear in the article, much more research needs to be completed before any significant conclusions are drawn from this study. However, the findings they came across were definitely of interest. Here are my thoughts:
If long duration isometrics are successful in increasing tendon stiffness, and short duration/ballistic isometrics are successful in increasing the amount of elastic energy produced, why not just layer them on top of each other? In other words, perform 2-3 weeks of long duration isometrics, followed by 2-3 weeks of short duration/ballistic isometrics. We would, supposedly, be increasing tendon stiffness with the first set of exercises, and then be increasing our ability to output elastic energy with the second set of exercises. And it seems to me that by starting with increasing tendon stiffness, we would be able to maximize our use of the ballistic exercises by performing those after the longer duration iso’s due to our newfound increased tendon stiffness.
What we don’t know is how much time we need to produce these changes and the real world effect they will have on athletic performance. However, I think it’s important to note that while getting bigger and stronger is a great start, that is probably only going to get you 80-90% of your potential. At some point we need to think about structures other than muscle fibers, such as the tendons, as these other structures play a large role in high speed athletic movement, such as we see in a throw, a swing, or in running.
Moving forward, building a strength base is still priority number 1. However once that is built, training other components is probably a good idea. Unfortunately, I don’t think anyone has the magic recipe for that yet, so I can’t give you as much “practical application” in this article as I normally do, or would like to. We will be doing more research and experimentation on this moving forward, so stay tuned.
Questions or comments? Interested in remote training? I can be reached via email at brady@dacbaseball.com.
Article Citation
Kubo, K., Kanehisa, H., & Fukunaga, T. (2001). Effects of different duration isometric contractions on tendon elasticity in human quadriceps muscles. The Journal of physiology, 536(Pt 2), 649-55.