Author(s): DÖSSEGGER, A., FLÜCK, M., GSPONER, T., PROTTE, C., Institution: SWISS FEDERAL INSTITUTE OF SPORT MAGGLINGEN: EIDGENOSSISCHE HOCHSCHULE FUR SPORT, Country: SWITZERLAND, Abstract-ID: 2172

INTRODUCTION:
Tactical athletes require multi-domain fitness for selection and operational readiness, combining strength, power, aerobic capacity, severe-intensity tolerance, and cognitive-motor functioning. Within Special Operations Forces (SOF), individuals must meet minimal competence across all domains but typically display distinct performance strengths. Fitness in the sense of being fit for SOF tasks may therefore be described by emergent performance phenotypes. Alpha-actinin 3 (ACTN3) R577X is a well-established genetic marker linked to fast-twitch muscle structure and power-oriented performance in sport populations. However, it remains unclear whether ACTN3 variation is reflected in power-dominant phenotype profiles within elite tactical cohorts.
METHODS:
Baseline performance data from 236 SOF candidates and operators across 10 police and military units were aggregated into five standardized domains: strength, power, severe-intensity tolerance, aerobic endurance, and reaction time. Principal component analysis was used to derive a reduced multidimensional phenotype space, followed by k-means clustering (k=3) on principal components (PC) 1–3 scores to identify performance archetypes. Bayes factors quantified whether ACTN3 genotype frequencies differed across clusters. Cluster-specific genotype proportions and uncertainty intervals were summarized using Dirichlet-multinomial posterior estimates.
RESULTS:
PC1–PC3 explained 75.4% of the variation across the five fitness domains (PC1: 31.3%, PC2: 24.5%, PC3: 19.5%). PC1 reflected a neuromuscular capacity axis dominated by strength, severe-intensity tolerance, and power, PC2 primarily captured reaction time with a secondary aerobic endurance component, and PC3 reflected aerobic endurance specialization relative to power. ACTN3 genotype frequencies differed decisively across phenotype clusters (BF10 = 505). In the power-strength cluster (C3), 78.3% of individuals carried the ACTN3 CC (sometimes called ACTN3 RR) genotype (95% credible interval 68.9–86.4%), indicating a markedly higher CC frequency than in the other clusters, whereas the endurance-oriented cluster (C1) showed a higher relative frequency of the ACTN3 TT (or XX) genotype. Pairwise contrasts confirmed maximal separation between C1 and C3 (BF10 = 3.79).
CONCLUSION:
ACTN3 CC genotype is enriched in power-dominant performance phenotypes in elite tactical athletes. This provides first evidence that ACTN3 aligns with multidomain readiness phenotypes in a mixed-demand population, without deterministic interpretation, and with relevance for elite sport contexts requiring concurrent strength, power, endurance, and rapid decision-making.