Resistance exercise performed at low loads (20-30% of maximal strength) with blood flow restriction (BFR) acutely increases protein synthesis and induces hypertrophy when performed chronically. We investigated myogenic and proteolytic mRNA expression 8 hrs following an acute bout of knee extension exercise
Fifteen subjects (22.8 ± 3.7 yrs, 8 men and 7 women) were randomized to two exercise conditions: BFR or control exercise. All participants performed 4 sets of exercise (30, 15, 15 & 15 repetitions) at 20% of maximal strength. Persons in the BFR group had a cuff placed on the upper thigh inflated to 1.5 times brachial systolic blood pressure (cuff pressure range: 135-186 mmHg). Muscle biopsies from the vastus lateralis were excised 24 hrs before and 8 hrs following the exercise.
RT-PCR analysis demonstrated no change in myogenic gene expression (IGF-1, MyoD, Myogenin, Myostatin – a negative regulator) with either exercise condition (p > 0.123). However, BFR exercise downregulated mRNA expression in transcripts associated with proteolytic pathways (FOXO3A, Atrogin-1 and MuRF-1) with no change in the control exercise condition. Specifically, median mRNA expression of FOXO3A decreased by 1.92 fold (p = 0.01), Atrogin-1 by 2.10 fold (p = 0.01) and MuRF-1 by 2.44 fold (p = 0.01).
These data are consistent with the downregulation of proteolytic transcripts observed following high load resistance exercise. In summary, myogenic genes are unchanged and proteolytic genes associated with muscle remodeling are reduced 8 hours following low load BFR exercise.