# Higher Incidence and Longer Recovery Time from Non-Contact Muscle Injuries in ACTN3 XX Genotype Players from a Soccer Academy: A Three-Season Longitudinal Study

## TL;DR

This study found that soccer players with the ACTN3 XX genotype had longer recovery times from muscle injuries, especially in youth players, though injury rates were not significantly different.

## Contribution

The study provides new evidence that the ACTN3 XX genotype is linked to longer recovery times from non-contact muscle injuries in youth soccer players.

## Key findings

- ACTN3 XX genotype players had significantly longer return-to-play times compared to RR genotype players.
- The association between ACTN3 genotype and recovery time was most pronounced in U17 youth academy players.
- No significant differences in injury incidence were found between ACTN3 genotypes.

## Abstract

The purpose of this study was to examine whether the ACTN3 R577X polymorphism was associated with injury rate and recovery time from non-contact muscle injuries in youth academy players and professional soccer players.

The ACTN3 rs1815739 genotype was identified in 76 male soccer players (22 professional, 27 U19 and 27 U17) from a top-level French soccer club. Over three consecutive competitive seasons (2020/21 to 2022/23), the players were prospectively monitored. The club’s medical staff systematically recorded all injuries sustained during soccer exposure. Injury incidence was calculated based on total soccer exposure, and return-to-play time (RTT) for each injury was determined by the medical staff. A total of 312 injuries were documented, including 144 non-contact muscle injuries. Injury incidence rates (IRs) and rate ratios (RRs) were compared across player genotypes, both overall and within each category, using Poisson or negative binomial regression models with exposure time as an offset. RTT was analyzed by genotype using the Kruskal–Wallis test.

Overall genotype distribution was RR, 52.6%; RX, 30.3%; and XX, 17.1%. Across all players, XX carriers had the highest injury incidence (8.54 [6.54–10.39]/1000 h) followed by RX players (6.65 [5.39–7.91]/1000 h) and RR players (5.15 [4.35–5.95]/1000 h), although these differences did not reach statistical significance. The RRs for XX compared with RR players was 1.66 (95% CI: 0.85–3.23, p = 0.140), indicating a non-significant tendency toward higher incidence in XX players. However, RTT differed significantly among genotypes (p = 0.007), with median [IQR] values of 13 [10, 16] days for RR, 16 [14, 22] days for RX, and 18 [13, 19] days for XX. Subgroup analyses showed that RTT differences were significant in U17 players (p = 0.004), with XX requiring longer recovery (23 days) compared to RR players (11 days). However, these genotype-related differences in RTT were not significant among professional soccer players.

The ACTN3 R577X polymorphism was associated with recovery characteristics following non-contact muscle injuries in soccer players. Specifically, players with the XX genotype required significantly longer return-to-play times, a pattern evident in youth academy players but not in the professional group.

The distribution of the ACTN3 XX genotype was comparable between professional soccer players and those in youth academy categories (U17 and U19).When pooling all players, return-to-play time after a non-contact muscle injury was significantly longer in ACTN3 XX compared with RR players, with RX showing intermediate values.Subgroup analyses revealed that this association with longer return-to-play duration was most pronounced among youth academy players, while no statistically significant differences were observed in the professional group.

The distribution of the ACTN3 XX genotype was comparable between professional soccer players and those in youth academy categories (U17 and U19).

When pooling all players, return-to-play time after a non-contact muscle injury was significantly longer in ACTN3 XX compared with RR players, with RX showing intermediate values.

Subgroup analyses revealed that this association with longer return-to-play duration was most pronounced among youth academy players, while no statistically significant differences were observed in the professional group.