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Type 1 Muscle Fiber Hypertrophy after Blood Flow–restricted Training in Powerlifters

BJØRNSEN, THOMAS1; WERNBOM, MATHIAS2; KIRKETEIG, ALEXANDER3; PAULSEN, GØRAN4; SAMNØY, LARS3; BÆKKEN, LASSE5; CAMERON-SMITH, DAVID6,7,8; BERNTSEN, SVEINUNG1; RAASTAD, TRULS5

Medicine & Science in Sports & Exercise: February 2019 - Volume 51 - Issue 2 - p 288–298
doi: 10.1249/MSS.0000000000001775
APPLIED SCIENCES
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Purpose To investigate the effects of blood flow–restricted resistance exercise (BFRRE) on myofiber areas (MFA), number of myonuclei and satellite cells (SC), muscle size and strength in powerlifters.

Methods Seventeen national level powerlifters (25 ± 6 yr [mean ± SD], 15 men) were randomly assigned to either a BFRRE group (n = 9) performing two blocks (weeks 1 and 3) of five BFRRE front squat sessions within a 6.5-wk training period, or a conventional training group (Con; n = 8) performing front squats at 60%–85% of one-repetition maximum (1RM). The BFRRE consisted of four sets (first and last set to voluntary failure) at ~30% of 1RM. Muscle biopsies were obtained from m. vastus lateralis (VL) and analyzed for MFA, myonuclei, SC and capillaries. Cross-sectional areas (CSA) of VL and m. rectus femoris were measured by ultrasonography. Strength was evaluated by maximal voluntary isokinetic torque (MVIT) in knee extension and 1RM in front squat.

Results BFRRE induced selective increases in type I MFA (BFRRE: 12% vs Con: 0%, P < 0.01) and myonuclear number (BFRRE: 18% vs Con: 0%, P = 0.02). Type II MFA was unaltered in both groups. BFRRE induced greater changes in VL CSA (7.7% vs 0.5%, P = 0.04), which correlated with the increases in MFA of type I fibers (r = 0.81, P = 0.02). No group differences were observed in SC and strength changes, although MVIT increased with BFRRE (P = 0.04), whereas 1RM increased in Con (P = 0.02).

Conclusions Two blocks of low-load BFRRE in the front squat exercise resulted in increased quadriceps CSA associated with preferential hypertrophy and myonuclear addition in type 1 fibers of national level powerlifters.

1Department of Public Health, Sport and Nutrition, Faculty of Health and Sport Sciences, University of Agder, Kristiansand, NORWAY;

2Center for Health and Performance, Department of Food and Nutrition, and Sport Science, University of Gothenburg, Gothenburg, SWEDEN;

3Norwegian Powerlifting Federation, Oslo, NORWAY;

4The Norwegian Olympic Federation, Oslo, NORWAY;

5Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, NORWAY;

6Liggins Institute, University of Auckland, Auckland, NEW ZEALAND;

7Food and Bio-based Products Group, AgResearch, Palmerston North, NEW ZEALAND; and

8Riddet Institute, Palmerston North, NEW ZEALAND

Address for correspondence: Thomas Bjørnsen, M.Sc., University of Agder Faculty of Sports and Health Sciences PO. Box 422 4604 Kristiansand Norway; E-mail: thomas.bjornsen@uia.no.

Submitted for publication May 2018.

Accepted for publication August 2018.

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© 2019 American College of Sports Medicine