Acute low-load resistance exercise with and without blood flow restriction increased protein signalling and number of satellite cells in human skeletal muscle.
OBJECTIVE
To investigate hypertrophic signalling after a single bout of low-load resistance exercise with and without blood flow restriction (BFR).


METHODS
Seven subjects performed unilateral knee extensions at 30 % of their one repetition maximum. The subjects performed five sets to failure with BFR on one leg, and then repeated the same amount of work with the other leg without BFR. Biopsies were obtained from m. vastus lateralis before and 1, 24 and 48 h after exercise.


RESULTS
At 1-h post-exercise, phosphorylation of p70S6KThr389 and p38MAPKThr180/Tyr182 was elevated in the BFR leg, but not in the free-flow leg. Phospho-p70S6KThr389 was elevated three- to fourfold in both legs at 24-h post-exercise, but back to baseline at 48 h. The number of visible satellite cells (SCs) per muscle fibre was increased for all post-exercise time points and in both legs (33–53 %). The proportion of SCs with cytoplasmic extensions was elevated at 1-h post in the BFR leg and the number of SCs positive for myogenin and/or MyoD was increased at 1- and 24-h post-exercise for both legs combined.


CONCLUSIONS
Acute low-load resistance exercise with BFR resulted in early (1 h) and late (24 h) enhancement of phospho-p70S6KThr389, an early response of p38MAPK, and an increased number of SCs per muscle fibre. Enhanced phospho-p70S6KThr389 at 24-h post-exercise and increases in SC numbers were seen also in the free-flow leg. Implications of these findings for the hypertrophic effects of fatiguing low-load resistance exercise with and without BFR are discussed.
Mathias
M
Wernbom
William
W
Apro
Gøran
G
Paulsen
Tormod S
TS
Nilsen
Eva
E
Blomstrand
Truls
T
Raastad
D000328:Adult; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D017570:MyoD Protein / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D012039:Regional Blood Flow; D055070:Resistance Training; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology* / Q000378:metabolism; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
D017570:MyoD Protein; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D048051:p38 Mitogen-Activated Protein Kinases