Low-load blood flow restriction strength training in patients with COPD: a randomised single-blind pilot study

Abstract

Objective: The objective of this study is to compare the effectiveness of lower limb low-load blood flow restriction training (LL-BFRT) with high-load strength training (HL-ST) as part of an outpatient pulmonary rehabilitation programme on leg strength in patients with chronic obstructive pulmonary disease (COPD).

Methods: Participants were randomised to LL-BFRT or HL-ST (24 sessions). LL-BFRT was done at 30% 1-repetition maximum (1-RM) with 70% arterial occlusion pressure. HL-ST was done at 70% 1-RM. Primary outcome was isometric strength of knee extensors and flexors. Secondary outcomes were 1-RM, functional exercise capacity, physical activity, symptom burden and health-related quality of life. Perceptions of dyspnoea and leg fatigue were recorded after every exercise. We compared groups with t-tests.

Results: We included 30 participants (13 women, 17 men, 64 (9) years, forced expiratory volume in 1 s 47 (18)% pred.), 24 completed the study. Isometric knee extensor strength improved to a clinically relevant degree in both legs in both groups (LL-BFRT: right leg 9 (20) Nm, left leg 10 (18) Nm; HL-ST: right leg 15 (26) Nm, left leg 16 (30) Nm, data are mean (SD)), without statistically significant or clinically relevant between-group differences (right leg mean difference= -6.4, 95% CI= -13.20 to 25.92 Nm, left leg mean difference= -5.6, 95% CI= -15.44 to 26.55 Nm). 1 min sit-to-stand test performance improved to a clinically relevant degree only in the LL-BFRT group (4 (4) vs 1 (5) repetitions). Interestingly, physical activity improved to a clinically relevant degree only in the LL-BFRT group (1506 (2441) vs -182 (1971) steps/day). LL-BFRT lowered perceived in-exercise dyspnoea and increased leg fatigue compared with HL-ST in the initial 12 trainings.

Conclusion: In patients with stable COPD undergoing outpatient pulmonary rehabilitation, LL-BFRT was not superior to HL-ST in improving leg strength. LL-BFRT led to similar strength gains as HL-ST while reducing perceptions of dyspnoea in the initial training phase.

Trial registration number: NCT04151771.

Keywords: exercise; pulmonary rehabilitation.

Figure 1

Overview of the study design and outcomes. CPET, cardiopulmonary exercise testing; FEC, functional exercise capacity (ie, 6 min walk test and 1 min sit-to-stand test).

Figure 2

Study participant flow chart. Exacerbation, experienced an acute COPD exacerbation in the last 6 weeks; thromboembolism, history of thromboembolism in the lower limb. COPD, chronic obstructive pulmonary disease; HL-ST, high-load strength training; LL-BFRT, low-load blood flow restriction training.

Figure 3

Changes in isometric leg strength stratified by group. (A) right knee extensors; (B) left knee extensors; (C) right knee flexors; (D) left knee flexors. Individual data are stratified for females (blue triangles) and males (red circles). Δ, change post–pre study intervention; HL-ST, high-load strength training; LL-BFRT, low-load blood flow restriction training; Nm, newton metres.

Figure 4

Perceived dyspnoea and leg exertion for each training session measured with the modified Borg scale. Locally estimated scatterplot smoothing (LOESS) lines are stratified by group. (A) perceived leg exertion during the leg press exercise; (B) perceived dyspnoea during the leg press exercise; (C) perceived leg exertion during the leg extension exercise; (D) perceived dyspnoea during the leg extension exercise. HL-ST, high-load strength training; LL-BFRT, low-load blood flow restriction training.