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

Abstract

BFRRE induced selective type I fiber increases in MFA (BFRRE: 12% vs. Con: 0%, p<0.01) and myonuclear number (BFRRE: 17% 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).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 fibres of national level powerlifters.

Higher effort, rather than higher load, for resistance exercise‐induced activation of muscle fibres

“…In contrast, a group from the same study that trained with high‐loads did not exhibit significant pre‐to‐post intervention increases in the size of type I muscle fibres (Bjørnsen et al . ). Even though traditional low‐load training is not the same as low‐load blood flow restriction training (i.e.…”

“…Even though these findings might hypothetically suggest that hypertrophy of type I and type II muscle fibres would also be the same when training with low and high loads, there is still a need for future long-term studies that would directly answer this question. The need for future long-term studies is especially important to emphasize if we consider the recent evidence showing that blood flow restriction training performed with low loads (ß30% of 1RM) produces significant type I muscle fibre hypertrophy (Bjørnsen et al 2019). In contrast, a group from the same study that trained with high-loads did not exhibit significant pre-to-post intervention increases in the size of type I muscle fibres (Bjørnsen et al 2019).…”

“…The study (Bjørnsen et al . ) that reported type I muscle fibre hypertrophy with low‐load blood flow restriction training but not with high‐load utilized very short training blocks (i.e. 2 × 5 days of training).…”

“…The need for future long-term studies is especially important to emphasize if we consider the recent evidence showing that blood flow restriction training performed with low loads (ß30% of 1RM) produces significant type I muscle fibre hypertrophy (Bjørnsen et al 2019). In contrast, a group from the same study that trained with high-loads did not exhibit significant pre-to-post intervention increases in the size of type I muscle fibres (Bjørnsen et al 2019). Even though traditional low-load training is not the same as low-load blood flow restriction training (i.e.…”

“…While this idea is a speculative onebecause the data are from different cohorts -it might be that the time course of type I and type II muscle fibre hypertrophy differs with varying loads. The study (Bjørnsen et al 2019) that reported type I muscle fibre hypertrophy with low-load blood flow restriction training but not with high-load utilized very short training blocks (i.e. 2 × 5 days of training).…”