Table 1.
Summary of longitudinal studies investigating the effects of LL-BFR on fiber-type-specific hypertrophy.
| Study | Sample | Design | Duration | Findings |
|---|---|---|---|---|
| Bjørnsen, Wernbom, Kirketeig et al. [25] | 17 nationally ranked powerlifters | Parallel design. Participants randomly assigned to either an HL group who performed front squats at 60–85% 1RM or an LL-BFR group who integrated 2 blocks (weeks 1 and 3) of 5 LL-BFR (~30% 1RM at a pressure of 120 mmHg) front squat sessions into the traditional training. Traditional training consisted of 6–7 sets per session whereas LL-BFR training consisted of 4 sets (first and last set to voluntary failure) with 30 s rest intervals; both groups trained 5 days/week. | 6.5 weeks | LL-BFR elicited a greater increase in type I fCSA compared to HL training (12% (ES: 0.80) vs. 0% (ES: 0.00), respectively); type II fCSA remained relatively unchanged over the study period. |
| Bjørnsen, Wernbom, Løvstad et al. [28] | 13 young, untrained men and women | One group, pre-/post-test design. Participants performed two 5-day blocks of 7 LL-BFR (20% 1RM at a pressure of 90–100 mmHg) sessions, separated by a 10-day rest period. Exercise consisted of 4 sets of unilateral knee extensions to volitional failure with 30 s rest intervals. | 3 weeks | Type I and type II fCSA decreased after the first training block (−6% and −15%, respectively). Alternatively, type I fCSA increased to a greater extent than type II fCSA after the second training block (19% (ES: 0.64) vs. 11% (ES: 0.51), respectively). |
| Bjørnsen, Wernbom, Paulsen, Berntsen et al. [30] | 17 young, untrained men | Within-subject design. Participants had their legs randomized to perform two 5-day blocks of 7 LL-BFR (20% 1RM sessions at a pressure of 90–100 mmHg), separated by a 10-day rest period, either to volitional failure or not to failure (30-15-15-15 repetitions). Exercise consisted of 4 sets of unilateral knee extensions with 30 s rest intervals. | 3 weeks | Type I fCSA decreased by 10.3% (ES: 0.70) after 10-days post-training in the failure leg while no appreciable change was observed in the nonfailure leg. Type II fCSA did not appreciably change from baseline in either condition. |
| Davids et al. [24] | 21 young, trained men and women | Parallel group design. Random assignment to either HL training (8 repetitions at 10 RM) or LL-BFR (~30% to 50% 1RM at 60% arterial occlusion pressure). Exercise consisted of combinations of the barbell back squat, leg press, Bulgarian split squat, and leg extension. Both groups performed 4 sets of 2–3 exercises 3 days/week. Intensity of effort was standardized so that both conditions trained within 1-4 repetitions from failure. | 9 weeks | Type I fCSA increased to a greater extent in LL-BFR compared to HL (10.6% (ES: 0.32) vs. 1.7% (ES: 0.07), respectively); type II hypertrophy favored HL vs. LL-BFR (17.7% (ES: 0.53) vs. 12.6% (ES: 0.36), respectively). |
| Hansen et al. [23] | 18 young men and women | Parallel group design. Random assignment to perform either HL training (70–90% 1RM) or an LL-BFR group who alternated weekly between LL-BFR (20% 1RM at a pressure of 110 mmHg) and HL Exercise consisted of the leg press and leg extension carried out 4 days/week; HL performed 2–4 sets per exercise of 3–10 repetitions with 2 min rest intervals whereas LL-BFR performed 4 sets to volitional failure with 30 s rest intervals | 6 weeks | Type I fCSA increased to a greater extent in the HL group compared to LL-BFR (12% (ES: 0.81) vs. 2.5% (ES: 0.17), respectively); type II fCSA increased similarly between groups (~16%). |
| Jakobsgaard et al. [27] | 6 healthy young untrained men and women | One group, pre-/post-test design. Subjects performed 5 sets of sit-to-stand LL-BFR (pressure of 100–180 mmHg) to volitional failure with 30 s rest intervals carried out 3 days/week. | 6 weeks | Type I fCSA increased to a greater extent than type II fCSA (8.7% (ES: 0.76) vs. 0% (ES: 0.06), respectively). |
| Nielsen et al. [22] | 18 young untrained men | Parallel group design. Participants assigned to LL training (20% 1RM) either using BFR (at a pressure of 100 mmHg) or performing exercise without occlusion. Training consisted of 4 sets of knee extension exercise carried out once or twice daily for a total of 23 sessions performed within 19 days). LL-BFR carried out sets to volitional failure, whereas LL carried out sets in a work-matched fashion. | 3 weeks | For LL-BFR, type I and type II fCSA increased similarly from baseline to 3 days post-study (35% (ES: 1.87) and 37% (ES: 1.99), respectively). Alternatively, type I and type II fCSA did not appreciably change from pre–post study in LL. |
| Pignanelli et al. [29] | 10 young, untrained men | Within-subject design. Participants had their legs randomly assigned to LL training (30% 1RM) either using BFR (at 60–70% of the lowest effective occlusive pressure) or performing exercise without occlusion. Training consisted of 4 sets of single leg squats to volitional failure with 100 s rest intervals carried out 3 days/week. | 6 weeks | Type I fCSA increased to a greater extent in LL compared to LL-BFR (15.8% (ES: 0.56) vs. 10.1% (ES: 0.38), respectively); type II fCSA increased similarly between conditions (~9% (~ES: 0.30)). |
| Sieljacks et al. [21] | 34 young, untrained men and women | Parallel group design. Random assignment to either HL training (70% 1RM) or LL-BFR (~30%/1RM at a pressure of 97 mmHg) training carried out to volitional failure. Training consisted of 4 sets of knee extension exercise carried out 3 days/week. HL performed 12 repetitions with 3 min rest intervals whereas LL-BFR performed sets to volitional failure with 30 s rest intervals | 6 weeks | Minimal pre–post study changes were observed in LL-BFR and HL conditions for both type I fCSA (−2.4% (ES: −0.20) and −2.3% (ES: −0.11), respectively) and type II fCSA (2.6% (ES: 0.15) and −2.3% (ES: −0.11), respectively). |
| Wang et al. [26] | 23 older, untrained men and women | Parallel group design. Random assignment to either LL-BFR (~30%/1RM at a pressure of 97 mmHg) training carried out to volitional failure or a nontraining control. LL-BFR training consisted of 4 sets of knee extension exercise with 30 s rest intervals carried out 3 days/week. | 6 weeks | Type I and type II fCSA increased to a similar extent (18.1% (ES: 0.62) vs. 22.2% (ES: 0.53), respectively). |
| Yasuda et al. [20] | 5 young men | Parallel group design. Participants performed either LL-BFR (20% 1RM at a pressure of 160–240 mmHg) training or LL training without occlusion. Exercise consisted of 3 sets of 15 repetitions of the squat and leg curl with 30 s rest intervals carried out twice daily for the duration of the study period. | 2 weeks | For LL-BFR, type II fCSA increased to a greater extent than type I fCSA (27.6% (ES: 0.77) vs. 5.9% (ES: 0.16), respectively). Type I and type II fCSA showed minimal pre–post study changes in LL (−2.1% (ES: −0.11) and 0.5% (ES: 0.7), respectively). |
Abbreviations: LL: low load; LL-BFR: low-load blood flow restriction; fCSA: HL: high load; fiber cross-sectional area; 1RM: 1 repetition maximum; mmHg: millimeters of mercury; ES: effect size.