Overload training resulting in an overreached state is common in elite sports, and if undetected can develop into an overtraining syndrome. This risk is accentuated by the lack of reliable measures of overreaching. Coaches and scientists therefore have to use a combination of tests in the monitoring process.
Gustafsson, H., Holmberg, H., & HASSMEN, P. (2008). An elite endurance athlete's recovery from underperformance aided by a multidisciplinary sport science support team. European Journal of Sport Science, 8(5), 267-276. https://doi.org/10.1080/17461390802195652