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- November 2, 2021
By focusing your training approach, you can change your muscles and eliminate your cycling weaknesses through muscle fiber adaptations.
A sprinter or a climber be, that is the question. You may not acknowledge or identify, but it isn’t easy to deny. There are qualities inherent in you that make you better at one than the other.
You have been riding your bike alongside others long enough to know that when the terrain pitches upward, so does your ability. Or when you notice the town line sign in the distance, distance is what will be between you and the group when you arrive there.
That is not to say you haven’t tried. Climbing isn’t your thing. You’ll never be a powerful sprinter. Despite your futile attempts to the contrary, you have lost hope.
More so, you have given in to the inner revelation that you are the type of rider that you think you are. You can do nothing about it—destined to ride the terrain that your genetic pioneers mapped for you.
You put all your genetic eggs in one pannier and gravitate to the routes that suit you. Not purposefully, but you train and ride to your strengths. Neglect of your cycling weaknesses magnifies the divide and leaves no opportunity to challenge the predisposition.
Recent innovations in muscle fiber science have improved the identification of single muscle fibers. Research utilizing this technology has revealed discoveries that defy conventional muscle fiber categorization and new fiber types.
What’s more, research suggests that through focused training, those fibers can evolve and change to meet the unique demands placed on them. All hope is not lost!
A Refresher Course
In a previous post entitled Muscle Fiber Types and other Basic Essentials for the Virtual Cyclist, the basics of muscle make-up and the cycling-specific implications were outlined. Here is a review, just in case.
Human muscle is composed of fibers and when they contract it causes our joints to move. The fibers are generally classified by the characteristics of their components and their function. There are three main types.
Type I, or slow-twitch fibers, contract slowly and are relatively fatigue resistant. Type I fibers are seen in high abundance in endurance athletes.
Type IIa fibers, or fast oxidative glycolytic, contract at a higher speed and are less fatigue resistant than type I fibers.
Type IIb, or fast glycolytic fibers, have the fastest speeds but are highly fatigable.
Type II fibers are found in greater proportion in the muscles of power athletes. With that out of the way, let’s move on to the interesting new science.
Innovations in Identification Techniques Have Unlocked Secrets
The classification of muscle fiber types in the way described above is considered crude by many researchers. Limiting the description of muscle fiber characteristics and function to three broad categories lacks the nuance required to answer many physiological and performance questions.
Fiber type identification techniques have evolved as we ask more questions. The advent of Single Fiber Analysis has proven to be more effective at examining the detailed make-up of muscle fibers. For a deep dive into single fiber analysis, click here.
Hybrid fibers were discovered through the measurement of the distribution of fibers by single fiber analysis. Mixed hybrid fibers share a combination of the characteristic types, like I/IIa, IIa/IIb, I/IIa/IIb, etc. A significant proportion of our muscles consist of hybrid fibers.
Through this more appropriate and sophisticated identification technique, researchers may finally address a mystery of muscle adaptation.
Do muscle fibers have the ability to shift between slow and fast, or hybrid and pure?
Harnessing this technique opens the possibility of unique discoveries into how training affects muscle fiber type.
Do Muscle Fiber Types Have the Ability to Change?
The ability of muscle fiber types to change from slow to fast and vice versa has undergone extensive investigation. The chicken and egg scenario has been an ongoing topic of contention among researchers.
An athlete’s muscle composition is predictive of performance. Athletes with a more significant proportion of type I fibers excel in slower, more extended, endurance-oriented events. Athletes with success in short-duration events requiring rapid bursts of power have more type II fibers.
What came first? Does a sprinter win crit races because he was born with more type II fibers? Did she develop more fast-twitch fibers by training for and competing in events that required them to be successful?
Therein lies the question that recent innovations in muscle fiber identification and research strive to answer.
Can a Climber Become a Sprinter?
The current literature based on single fiber analysis says you can, but it depends upon how you go about it.
Resistance training at high loads (>70% of one-repetition maximum) performed at slow speeds causes a shift from IIb and IIb/IIa hybrids to pure IIa, and away from type I slow fibers [Adams et al., Carroll, et al.]
The results are much different when a strength training program utilizes more explosive fast motion and plyometric movements. In a recent study, researchers investigated the effect of traditional strength training on a combination involving rapid movements and plyometrics.
In short, the authors reported that the group that completed six weeks of strength training alone experienced a shift to more IIa fibers (49.4% to 66.7%) from IIb (33.4% to 19.5%), with no change in type I fiber proportion.
However, the combination training group did not display a significant loss of IIb fibers but instead experienced an increase in type IIa fibers (47.7 to 62.7%) and a loss in type I fibers (18.2% to 9.2%).
Key Takeaway
The performance of strength training utilizing fast, explosive movements in combination with plyometrics causes a significant shift from slow-twitch to fast-twitch fibers.
Can a Sprinter Become a Climber?
The totality of the evidence suggests you can and that endurance training generally induces a fiber type shift to more slow-twitch oxidative type I fibers.
A recent study investigated the effects of 13 weeks of marathon training, followed by a 3-week taper on fiber type shifts in novice runners. The investigators biopsied the recreational runners’ vastus lateralis (outer quadricep) muscles and used single fiber isolation techniques to determine the fiber composition.
The Vastus lateralis type I fiber composition increased (42.6% to 48.6%), I/IIa increased (5.1% to 8.2%), IIa decreased (40.1% to 35.8%), IIa/IIx decreased (11.9% to 6.4%), and IIb increased (0% to 1%).
Would the transition have occurred if the study was on elite athletes? The predominance of variables makes the evidence somewhat less clear. If such exists in science, another interesting recent study provides a more “apples to apples” comparison.
Study of Identical Twins Gives Interesting Insight
In this study, the authors examined a set of identical 52-year-old twins. One twin was an avid recreational endurance athlete and had been for decades. The other was largely sedentary throughout the majority of his life.
Single fiber type analysis showed the trained twin had a vastus lateralis composition that mainly was slow-twitch (95% type I), amounting to 55% more type I fibers than the untrained twin. Moreover, the untrained twin possessed many more type IIa and hybrid fibers than the trained twin.
Based upon the presumption that the brothers shared identical muscle fiber composition at birth,
this study provides strong evidence that a shift toward one fiber type occurs with long-term training.
Key Takeaway
Long-term endurance training results in a shift from fast-twitch to more fatigue resistant slow-twitch fibers.
Conclusion
Are you convinced that you can become a different rider than you think you are? Reinvent your cycling self? Likely not. To be frank, neither am I.
Based on recent research and scientific innovations, I am also not convinced that genetic predisposition toward a particular muscle fiber composition prevents me from improving my weaknesses. An athlete’s muscle fibers can change to meet training stress through focused training on identified deficiencies.
I will never be a sprinter. I can, however, train to be better at sprinting and maximize my potential. With the right approach to training, you can change the relative proportion of muscle fiber types in your body.
All hope is not lost!
Citation: Plotkin, D.L.; Roberts, M.D.; Haun, C.T.; Schoenfeld, B.J. Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives. Sports 2021, 9, 127. https://doi.org/10.3390/sports9090127
Your thoughts?
Do you ever wish you could be a different type of rider than you think you are? Will you try knowing that all hope is not lost? Comment below! Your fellow virtual cyclists want to know.
If you found this article interesting, check out this recent post entitled Two New Studies Will Change the Way You Look at Strength Training and Cycling Performance.
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Semi-retired as owner and director of his private Orthopedic Physical Therapy practice after over 20 years, Chris is blessed with the freedom to pursue his passion for virtual cycling and writing. On a continual quest to give back to his bike for all the rewarding experiences and relationships it has provided him, he created a non-profit. Chris is committed to helping others with his bike through its work and the pages of his site.
In the summer of 2022, he rode 3,900 miles from San Francisco to New York to support the charity he founded, TheDIRTDadFund. His “Gain Cave” resides on the North Fork of Long Island, where he lives with his beautiful wife and is proud of his two independent children.
You will read him promoting his passion on the pages of Cycling Weekly, Cycling News, road.cc, Zwift Insider, Endurance.biz, and Bicycling. Chris is co-host of The Virtual Velo Podcast, too!
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