QUOTE(Heavy_Lifter85 @ Feb 1 2008, 08:14 AM) [snapback]453630[/snapback]
Kimbo has an excellent point, but isn't that effect only seen in novices? Maybe calorie restriction (also, IF) is increasing BDNF, allowing for greater neurological adaptations than would normally be observed.
At a certain point you have to increase muscle fiber cross-section in order to continue making gains in strength, but you can get pretty far with inter/intramuscular coordination too. There's also other things to consider, like increased connective tissue strength, golgi tendon organ disinhibition, etc., all of which can contribute to strength gains without muscle gains. There's even the ratio of sarcomere:sarcoplasm in the muscle to consider - if contractile tissue increases as much as sarcoplasm decreases then the muscle will be the same size, it'll just be capable of moving more weight.
As Mitosis suggested, this is something you see a lot in strength sports with weight classes (anything under superheavy that is). Many of these guys are pretty lean (about as lean as you can get without it impacting strength levels) and are more or less maxed out on muscle for their size, but they can continue to make gains in their lifts, albeit small gains. You see this a lot with elite level Oly lifters.
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I've had some incredible jumps in deadlifting PR's without adding mass on an IF routine. Come to think of it, most IF logs report very consistent strength gains at the same BW.
Was this possibly due to recomp?