Variation in weekly internal training load in professional soccer players

Quantification of weekly training load (w-TL) in professional soccer players often shows minimal variation at the team level throughout the season. The study aimed (a) to analyze respiratory and muscular weekly perceived exertion, and (b) to determine the variability during pre-season and in-season period considering each player individually. Twenty-one professional soccer players belonging to a 2nd Division soccer team were monitored over 44-weeks (i.e., 6-week of pre-season and 38-week of in-season). Internal load was assessed using differential RPE (dRPE), and statistical analysis included descriptive statistics, coefficient of variation (CV), and the Kruskal-Wallis test. Leg local-muscular in weekly training load (w-TLmus) was significantly higher (p = 0.001 & p = 0.012) than central-respiratory in weekly training load (w-TLres) during pre-season and in-season period. Moreover, larger w-TL were also greater during pre-season compared to in-season periods. Total weekly loads were also greater in pre-season than in-season. Intra-player variability was higher during pre-season (CV: from 30.4 to 75.4% and from 15.3 to 76.9%) than in-season period (CV: from 21.2 to 46.1% and from 22.1 to 44.2%), respectively. These findings suggest that players perceive and respond to training loads differently across seasonal phases, highlighting the need for individualized monitoring to optimize performance and reduce injury risk.