The Significance of Sports Genetic Testing for Training: What ACTN3 and ACE Genes Tell You

“Was I born to climb or to sprint?” “Where is the ceiling of my potential?” These questions have long troubled cyclists who train seriously. In recent years, the proliferation of consumer genetic testing services has made “sports genes” a hot topic. But before spending money on a test, you need to understand: what genes can tell you, what they cannot tell you, and how to rationally integrate genetic information into your training plan.

The Genetic Basis of Athletic Performance

Genes vs. Environment: The Eternal Debate

Sports science research estimates that the heritability of athletic performance is approximately 30-80%, depending on the metric measured:

Metric	Heritability Estimate	Significance
Baseline VO2max	~50%	Half of your starting point comes from genes
VO2max training response	~47%	Half of your response to training comes from genes
Maximum strength	~50-60%	Strength talent has a higher genetic component
Muscle fiber type ratio	~45%	There is a genetic predisposition for fast-twitch vs. slow-twitch
Pain tolerance	~30-50%	The ability to suffer also has a genetic component
Injury risk	~20-40%	Ligament and tendon strength is partly hereditary

Key takeaway: Even for the metrics with the highest heritability, environmental factors (training, nutrition, recovery) still account for 20-50%. This means genes set the “range,” and training determines where you fall within that range.

The ACTN3 Gene: The Speed Gene

What is ACTN3?

The ACTN3 gene encodes a protein called α-actinin-3, which is found exclusively in Type II (fast-twitch) muscle fibers. Its function is to stabilize the muscle contraction structure, enabling fast-twitch muscle fibers to perform rapid, powerful contractions.

The Three Genotypes

RR Type (two normal copies):

• Produces α-actinin-3 normally
• Fast-twitch muscle fiber function is complete
• Has an advantage in short-distance, explosive-power events
• Accounts for approximately 30% of the global population

RX Type (one normal, one variant):

• Produces partial α-actinin-3
• More balanced fast-twitch and slow-twitch capabilities
• Considered the “all-rounder” gene
• Accounts for approximately 50% of the global population

XX Type (two variant copies):

• Completely unable to produce α-actinin-3
• Fast-twitch muscle fiber characteristics are altered, shifting more toward endurance traits
• May have a slight advantage in long-distance endurance events
• Accounts for approximately 20% of the global population

ACTN3 and Its Relevance to Cycling

Research findings:

• The RR type is overrepresented among track sprint cyclists (~50%)
• The XX type is slightly more prevalent among long-distance road cyclists than in the general population
• However, all three genotypes are found among elite athletes—there is no absolute exclusion effect

Implications for cyclists:

Genotype	Possible Tendency	Suggested Training Adjustments
RR	Sprint, short distance, criterium racing	Can invest more in sprint and explosive-power training
RX	Well-rounded across all disciplines	Adjust flexibly based on race goals
XX	Long distance, climbing, endurance events	May respond better to endurance base training

The ACE Gene: The Endurance Gene

What is ACE?

The ACE (Angiotensin Converting Enzyme) gene encodes angiotensin-converting enzyme, which is involved in blood pressure regulation and cardiovascular function. Its “insertion/deletion” (I/D) polymorphism is associated with athletic performance.

Genotypes and Athletic Performance

II Type (insertion/insertion):

• Lower ACE activity
• Associated with higher cardiorespiratory endurance
• More common in long-distance events
• May have higher muscle efficiency
• Better adaptation to high altitude

ID Type (insertion/deletion):

• Moderate ACE activity
• Balanced cardiorespiratory and strength characteristics
• The most common genotype

DD Type (deletion/deletion):

• Higher ACE activity
• Associated with greater muscle mass growth potential
• More common in strength and power events
• May respond better to strength training

The Combined Effect of ACE and ACTN3

The influence of genes is combinatorial. The most interesting aspect is how the two genes pair together:

The “Endurance Combo”: ACTN3-XX + ACE-II

• Theoretically most predisposed to endurance performance
• Found at higher rates among elite endurance athletes in studies
• Suitable for training focused on long distance and climbing

The “Power Combo”: ACTN3-RR + ACE-DD

• Theoretically most predisposed to explosive performance
• Found at higher rates among short-distance and track cyclists
• Suitable for training focused on sprinting and short distance

The “Balanced Combo”: ACTN3-RX + ACE-ID

• The most common combination
• No clear predisposition
• Training direction is determined by personal goals and preferences

Genes Do Not Equal Destiny

Why Genetic Testing Cannot Predict a Champion

1. Polygenic effects

Athletic performance is influenced by at least 200+ genes, and ACTN3 and ACE are merely the two most studied among them. Even if you have the “optimal” ACTN3 and ACE combination, other untested genes may tell a completely different story.

2. Plasticity of gene expression

Epigenetic research shows that training can alter gene “expression.” Long-term endurance training can upregulate the expression of genes related to slow-twitch muscle fibers, even if your genotype is predisposed toward fast-twitch fibers.

3. The enormous impact of environmental factors

• Training methods and years of experience
• Nutrition and recovery strategies
• Mental toughness and race experience
• Social support and economic conditions
• Luck and opportunity

Lessons from Real-Life Cases

Chris Froome—a four-time Tour de France champion—was reportedly considered early on as “not possessing” the talent of a top cyclist. His success came far more from extreme training, nutrition management, and tactical execution.

Many outstanding cyclists in Taiwan are the same: without knowing their genotype, they have achieved impressive results through systematic training.

How to Use Genetic Testing Results Rationally

Genetic Testing Services Available in Taiwan

1. Local Taiwanese services:

• Companies such as GeneBo provide sports gene panels
• Prices range from approximately NT$3,000-8,000
• Usually include ACTN3, ACE, and dozens of other sports-related genes

2. International services:

• Raw data from 23andMe and AncestryDNA can be analyzed using third-party tools
• Specialized sports genetic services such as DNAfit and MyFitnessPal DNA
• Prices range from NT$3,000-15,000

The Right Mindset for Interpreting Results

What You Should Do:

1. Use It as a “Fine-Tuning” Reference for Training Direction

   • If your genes favor endurance, but you love sprinting—keep sprinting!
   • But you can place more emphasis on building an endurance foundation in your auxiliary training

2. Understand Differences in Training Response

   • If you are ACTN3-XX yet training for sprinting, your progress may be slower than someone with the RR type
   • This doesn’t mean you can’t develop it; it just requires more patience

3. Optimize Recovery Strategies

   • Certain genotypes are linked to injury risk and recovery speed
   • You can adjust training volume and recovery time accordingly

What You Should NOT Do:

1. Don’t Give Up on Your Goals Because of Genetic Results

   • A genetic test is not a “pass/fail” exam
   • Even with unfavorable genes, the marginal benefits of training remain enormous

2. Don’t Over-Infer

   • Information from one or two genes is too limited to make major decisions
   • Athletic performance is the combined result of hundreds of factors

3. Don’t Spend Too Much Money

   • With the same budget (NT$5,000-10,000), purchasing a professional power test or coaching consultation might be more practically helpful

What Matters More Than Genes

The Power of Training Years

Research shows that athletes with “unfavorable genes” who train consistently for over 5 years typically surpass athletes with “favorable genes” who have only trained for 1-2 years. Long-term, consistent training is the most powerful “gene expression regulator.”

Training Smart

Understanding your power data, properly planning training cycles, and ensuring adequate recovery—the room for optimizing these “environmental factors” far exceeds genetic differences.

The Factors You Can Control

You cannot change your genes, but you have 100% control over the following factors:

✅ Consistency and continuity of training
✅ Nutrition and fueling strategies
✅ Sleep quality and duration
✅ Stress management
✅ Equipment selection and bike fitting
✅ Race tactics and mental preparation
✅ Quality of coaching guidance
✅ Training partners and environment

Conclusion: Know Yourself, But Don’t Be Defined

Genetic testing is an interesting tool for self-exploration that can help you better understand your physiological predispositions. But it is not a verdict of fate.

If you took the test and found you are an “endurance type,” and you happen to love climbing—congratulations, that’s a happy coincidence. If the test results don’t match your preferences—so what? Tadej Pogačar would attack under any genotype.

The best “gene” is the one that keeps getting you out the door to ride.

Related Reading

• Sports Genetics: The Impact of ACTN3 and ACE Genes on Endurance Performance
• Sports Genetics and Talent: How Much Does DNA Really Determine? A Triathlon Coach’s Honest Take
• The Genetics of Running: How ACTN3 and ACE Genotypes Affect Running Ability
• Genetic Influence on Cycling Training: Predicting Power and Endurance with ACTN3 Types