Neuromuscular responses and inter-limb asymmetry in relation to external load across two sequential pre-season training camp contexts in soccer players.

Introduction: Different pre-season training camp contexts may be accompanied by distinct neuromuscular responses, including changes in fatigue and inter-limb asymmetry, in soccer players. However, limited research has examined how players' neuromuscular responses differ across sequential conditioning-focused and game-based camp contexts and how these responses relate to external load. Methods: Fourteen male national-level soccer players were assessed before and after a 10-day conditioning camp and an 11-day game-based camp separated by 14 days. Neuromuscular performance was evaluated using countermovement jump (CMJ) and Nordic hamstring strength (Nordic Curl), while external load was monitored using GPS-derived metrics, including total distance, high-speed running (HSR), and sprint distance. Percentage changes and correlations between neuromuscular variables and accumulated external load were analyzed using an exploratory descriptive approach. Results: Following the conditioning-focused camp context, players showed greater neuromuscular changes, including increased CMJ performance (Δ = 3.82%), reduced hamstring strength (Δ = -3.43% and -0.62% for the left and right limbs, respectively), and increased inter-limb asymmetry, whereas only trivial changes were observed following the game-based camp context. Accumulated external load differed between the two camp contexts, with higher total distance and high-speed running during the conditioning-focused camp context and slightly higher sprint distance during the game-based camp context. Relationships between external load and neuromuscular changes differed between camps. During the conditioning camp, higher external load was associated with a smaller increase in asymmetry, whereas during the game-based camp, external load was related to reductions in CMJ performance and increases in hamstring strength. Conclusion: Players showed different neuromuscular responses across the two sequential camp contexts, and load-response relationships appeared to be context dependent and individual. Given the small sample and exploratory design, these findings should be interpreted cautiously. Integrating external load monitoring with neuromuscular assessments may improve training and recovery strategies in team sports.