The role of muscle damage in muscle remodeling: No pain, no gain? FASEB J. 2006 20:A397 Kyle Flann, Paul C LaStayo and Stan L Lindstedt ABSTRACT Skeletal muscle is a dynamic tissue that responds adaptively to both the nature and intensity of muscle use. This study tested the hypothesis that a damaging bout of exercise is pre-requisite for muscle hypertrophy. Although this hypothesis has been widely accepted, there is surprisingly scant evidence that muscle damage, accompanied by an inflammatory response, is a necessary precursor to muscle hypertrophy. Subjects were divided into two experimental populations: (PT) pre-trained (n=7) and (NA) naïve (n=7). Muscle damage was avoided in the pre-trained group by a 3 week gradual "ramp-up" program before both groups were subjected to an 11 week high force eccentric cycle ergometry program (20min, 3x/week). Work totals throughout the 11 week session were the same for both groups. The naïve group experienced damage, whereas the pre-trained group did not, as indicated by: >5 times higher plasma CK levels and self reporting of perceived soreness, fatigue and exertion. The observed increase in mean cross sectional area (and total muscle volume) was significant for both groups (p<0.01) but not different between groups (NA=7.0% and PT=6.1%). Strength increases were also observed for all subjects in the study (PT=20% and NA=24% improvement) again, no significant difference was found between the groups. Independent of any initial muscle damage, muscle volume increases and quadriceps strength increases were found to be the same for both groups indicating that a damaging bout may not be a prerequisite to muscle hypertrophy. Arizona Technology and Research Initiative Fund.