Assessment of Internal Load and External Load in Senior Football Players: Differences Between Competitive Levels

Background: Football is an intermittent sport characterized by high physical and physiological demands, which may be influenced by the competitive level. Understanding differences in match load is fundamental for optimizing training planning, fatigue management, and athlete performance and injury prevention. This study aimed to evaluate and compare external and internal load in senior football players in Portugal across five distinct competitive levels. Methods: Wimu Pro^TM (Hudl, Lincoln, NE, USA) and Garmin Heart Rate bands (Garmin International Inc., Olathe, KS, USA) were used to quantify and evaluate the external and internal load of the players. A total of 96 athletes were assessed, with ages ranging from 19 to 36 years (mean: 24.28 ± 4.72), who were divided into five competition levels (1st Division (n = 19), 2nd Division (n = 21), 3rd Division (n = 14), 4th Division (n = 20), and Regional Division (n = 22). Results: Significant differences were observed between competitive levels across several external load variables (p > 0.001). The 3rd Division and 4th Division showed higher values in variables associated with reactive and high-intensity actions (p < 0.001; effect size: 0.287), whereas the 2nd Division exhibited a more controlled load profile. Regarding internal load, significant differences were only observed in average heart rate during the second half (p = 0.043; effect size: 0.085), indicating distinct capacities to maintain physiological intensity under fatigue. Conclusions: It can be concluded that competitive level influences load profiles in football, although the differences do not follow a linear pattern. External and internal loads demonstrate greater discriminatory capacity between competitive levels than internal load.