Strength and conditioning isn't the field I'm the most into, but my best guess would be:
The biopsy showed he has a proportionally larger amount of type I and IIa muscle fibers, which could be reason for why he benefits from keeping a high frequency of games because:
- These types of fibers have a much better aerobic capacity, meaning they benefit from long, steady sessions, recover faster, metabolizes toxins faster and are more enduring.
- Respond better to more frequent training sessions, because they need high volumes to adapt.
- They can tolerate much higher volumes of training, so he might not be as explosive as Dembele for example, but will recover faster from the same sprinting session than Dembele will.
- Type 1 muscle fibers also atrophy faster, so again -> more frequents sessions.
So a player like Pedri would experience a relatively bigger loss in muscle strength and stamina compared to a normal player during a short break (even with a week or two), but can also recover faster and endure longer sessions with less muscle damage.
And if someone is able to recover well between games, then there's loads of general benefits that apply to keeping match rythm that reduce injury risk for all athletes:
- All our tissues in the body are incredibly specific in the way they adapt, meaning that generally the more specific you are in training in relation to your goals, the better (in general). So exposing him frequently to the exact demands of a football match will help his tissues adapt.
- He will be much better coordinated, have better neuromuscular connection and proprioception in his joints.
- Might be slight more mentally at ease during a match, which also makes a difference (Mental stress/nervousness is more often what leads to cramps than actual fatigue for example.)
- And in general many studies show even relatively short periods of relative inactivity (lack of high intensity sessions/games) increase the injury risk for athletes even if they are still in generally in good shape and keep regular excersise/training up.
This is all very general and theoretical speculating, might not be the reason at all why he is injured less now. Just as well could be because of luck or that he now sleeps more and better bc he got together with a hot chick or something. Could just be non-specific contextual effects aswell, but the above is my best guess without knowing what thes tests showed.