Genetic variants associated with on-water sports performance: A systematic review

Technical Summary: Genetic Variants Associated with On-Water Sports Performance: A Systematic Review

Problem Statement
While sports performance is recognized as a complex interplay of training, technique, and genetics—with genetic factors explaining approximately 66% of the variance in athletic status—specific genetic variants associated with "on-water" sports (rowing, canoeing, kayaking, sailing, surfing, and rafting) remain largely inconclusive. Although systematic reviews exist for swimmers, endurance athletes, and combat sports, no comprehensive synthesis has previously addressed the genetic architecture of on-water sports. The authors note that despite high heritability in related phenotypes (e.g., muscle fiber composition, VO2max), the specific polymorphisms driving success in water-based disciplines are scarce and often conflicting in the literature.

Methodology
This study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines.

• Search Strategy: A systematic search was conducted in Web of Science, Scopus, and PubMed up to October 6, 2024, supplemented by a secondary search of reference lists. The search utilized PECO (Population, Exposure, Comparison, Outcome) frameworks with Boolean operators combining genetic terms (e.g., "SNP," "polymorphism") with specific on-water sports.
• Eligibility Criteria: Included studies were human-based, published in English, and examined associations between genetic variants and performance in rowing, canoeing, kayaking, sailing, surfing, or rafting. Studies had to provide detailed genotype data and meet Hardy–Weinberg equilibrium (HWE) criteria. Animal studies, reviews, editorials, and studies lacking detailed genotype data were excluded.
• Selection Process: From an initial 2,248 records, 28 articles met the inclusion criteria after duplicate removal and screening.
• Quality Assessment: The Newcastle–Ottawa Scale (NOS) was used to assess the risk of bias. Studies scoring 6 or above were considered high quality, 3–5 fair, and 0–2 poor.
• Analysis: Due to heterogeneity in genetic variants, failure of HWE in some studies, and varying risk of bias, a meta-analysis was not performed. Instead, a narrative synthesis of the findings was conducted.

Key Contributions and Results
The review analyzed 28 studies involving 29 distinct populations (primarily Russian, Polish, Spanish, Brazilian, Hungarian, Australian, Turkish, and Chinese). The studies covered 17 different genetic variants across eight genes, with the majority focusing on rowing (22 studies), followed by kayaking (4), canoeing (5), and single studies on surfing and rafting. No studies on sailing were found.

Key Genetic Findings:

• ACTN3 (R577X): The most studied variant. Evidence suggests the RR genotype is associated with better rowing performance (power/strength), while the XX genotype is linked to endurance performance in kayaking, canoeing, and windsurfing. However, conflicting results exist regarding its association with canoeing power.
• ACE (I/D): The I allele and II genotype are frequently associated with high aerobic capacity and endurance in rowers and rafters. Conversely, some studies found the II genotype less prevalent in elite lightweight rowers, and the DD genotype is generally linked to power/sprint sports.
• Other Variants:
  • Positive Associations: The G allele of GABPB1 (rs7181866) was linked to greater endurance in rowers. The PPARA GG genotype was prevalent in elite Polish rowers. Variants in UCP2 (Val allele) and UCP3 (T allele) were associated with high aerobic performance. The VEGF C allele and VEGFR2 variants were linked to endurance in rowers and kayakers. The MCT1 A allele was more common in elite rowers. The HIF1A Ser allele and Pro/Ser genotype were found in rowers.
  • Negative/Null Associations: Conflicting or null results were reported for AMPD1, CKMM, NOS3, GDF8 (myostatin), and PPARGC1A. For instance, while one study linked AMPD1 TT genotype to negative performance, another found no association. Similarly, NOS3 G/T polymorphism showed no significant association in multiple studies.
• Risk of Bias: Of the 28 included studies, 22 were rated as high quality, while 6 were identified as having a higher risk of bias due to limitations in selection, comparability, or exposure assessment.

Significance and Claims
The paper concludes that while several structural and functional genes (including ACTN3, ACE, AMPD1, GABPB1, PPARA, TFAM, VEGF, VEGFR2, UCP2, UCP3, HIF1A, and MCT1) have been identified as associated with on-water sports performance, the current evidence is insufficient to definitively determine causality or perform a meta-analysis.

The authors modestly claim that these findings can be utilized for talent identification and nurturing of water sports athletes, potentially allowing for the tailoring of training programs to maximize genetic potential. However, they emphasize that the data is currently limited by:

1. Sample Size: Many studies involved small athletic populations, particularly for niche sports like surfing and rafting.
2. Ethnic Diversity: The majority of data comes from specific European and Russian populations, limiting generalizability.
3. Single-Gene Focus: Most studies examined single polymorphisms rather than gene-gene interactions or polygenic profiles.
4. Conflicting Evidence: Discrepancies exist between studies regarding the same variants (e.g., ACTN3 and ACE).

The authors assert that future research must prioritize collaborative genome-wide association studies (GWAS), larger multi-ethnic sample sizes, and investigations into gene expression and gene-gene interactions to fully elucidate the role of these polymorphisms in enabling success in on-water sports. They also note the ethical considerations regarding the potential misuse of genetic testing in athlete selection.