Perhaps we need to consider the emotional background against which all competition is performed in addition to the physical stimulus. As physiological changes are clearly associated with emotional state (for example, the clearly documented negative effects of ‘stress’ on health), perhaps the physical stimulus from competition is above and beyond what would first be apparent due to the unique emotional, and thus physiological, environment in which all competitions are held?
Does the simple act of preparing for a competition both physically (warming-up) and emotionally (‘arousal’) create a rather large stimulus even if that competition is not held for whatever reason, particularly at the professional/international level where the stakes are so much higher?
Considering the frequency of soccer competitions, perhaps we underestimate the true load by looking only what happens physically during the game. What of other sports with fixed and frequent competition schedules?