Physiological determinants of heart rate responses and bout-to-bout stability during 2v2 and 4v4 small-sided games in football players

HRR is the sole physiological marker meaningfully associated with internal load during SSGs (and only in 4v4) while neither HRmean nor CV% in 2v2 is explained by the tested markers. More constrained formats (2v2) produce more stable cardiovascular responses. By identifying simple heart-rate-based indicators and game formats that yield more stable cardiovascular responses, these findings can inform scalable load-management strategies that help mitigate maladaptive overreaching and contribute to broader injury-prevention efforts in athletic populations, although future studies are necessary to confirm such hypothesis.