The time course of short-term hypertrophy in the absence of eccentric muscle damage.
BACKGROUND
It has been proposed that the increase in skeletal muscle mass observed during the initial weeks of initiating a resistance training program is concomitant with eccentric muscle damage and edema.


OBJECTIVE
We examined the time course of muscle hypertrophy during 4 weeks of concentric-only resistance training.


METHODS
Thirteen untrained men performed unilateral concentric-only dumbbell curls and shoulder presses twice per week for 4 weeks. Sets of 8-12 repetitions were performed to failure, and training loads were increased during each session. Subjects consumed 500 ml of whole milk during training. Assessments of soreness, lean mass, echo intensity, muscle thickness, relaxed and flexed arm circumference, and isokinetic strength were performed every 72 or 96 h.


RESULTS
Soreness, echo intensity, relaxed circumference, and peak torque data did not significantly change. Significant increases in lean mass, muscle thickness, and flexed circumference were observed within seven training sessions. Lean mass was elevated at tests #7 (+109.3 g, p = .002) and #8 (+116.1 g, p = .035), with eight different subjects showing changes above the minimal difference of 139.1 g. Muscle thickness was elevated at tests #6 (+0.23 cm, p = .004), #7 (+0.31 cm, p < .001), and #8 (+0.27 cm, p < .001), with ten subjects exceeding the minimal difference of 0.24 cm. There were no changes for the control arm.


CONCLUSIONS
In individuals beginning a resistance training program, small but detectable increases in hypertrophy may occur in the absence of eccentric muscle damage within seven training sessions.
Department of Health Professions, University of Central Florida, Health and Public Affairs Bldg I, Room 258, 4364 Scorpius Street, Orlando, FL, 32816-2205, USA. matt.stock@ucf.edu.
Matt S
MS
Stock
Department of Exercise and Sport Science, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA.
Jacob A
JA
Mota
Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, TX, USA.
Ryan N
RN
DeFranco
Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, TX, USA.
Katherine A
KA
Grue
Honors College, Texas Tech University, Lubbock, TX, USA.
A Unique
AU
Jacobo
Department of Kinesiology, Health, and Nutrition, University of Texas at San Antonio, San Antonio, TX, USA.
Eunhee
E
Chung
American Public University System,, Charles Town, WV, USA.
Jordan R
JR
Moon
Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, OK, USA.
Jason M
JM
DeFreitas
Department of Health and Exercise Science, University of Oklahoma, Norman, OK, USA.
Travis W
TW
Beck
D000328:Adult; D006801:Humans; D006984:Hypertrophy / Q000000981:diagnostic imaging; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000473:pathology / Q000502:physiology*; D063806:Myalgia / Q000000981:diagnostic imaging / Q000209:etiology*; D011930:Reaction Time; D055070:Resistance Training / Q000009:adverse effects*
Concentric; Force; Lean mass; Muscle mass; Soreness; Torque