Low-load resistance training to task failure with and without blood flow restriction: muscular functional and structural adaptations

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology Vol. 318; no. 2; pp. R284 - R295
• Main Authors: Pignanelli, Christopher, Petrick, Heather L., Keyvani, Fatemeh, Heigenhauser, George J. F., Quadrilatero, Joe, Holloway, Graham P., Burr, Jamie F.
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.02.2020
• Series: Physical Activity and Inactivity
• Subjects: Adaptation; Adaptation, Physiological; Adult; Blood flow; Fatigue tests; Flow resistance; Healthy Volunteers; Humans; Hypertrophy; Load resistance; Male; Mitochondria; Mitochondria, Muscle - metabolism; Muscle Contraction; Muscle Fatigue; Muscle Strength; Muscular function; Musculoskeletal system; Oxidation resistance; Performance indices; Physical Endurance; Physical training; Quadriceps Muscle - blood supply; Quadriceps Muscle - diagnostic imaging; Quadriceps Muscle - metabolism; Random Allocation; Rehabilitation; Repetition; Resistance Training; Skeletal muscle; Strength training; Structure-function relationships; Therapeutic Occlusion; Time Factors; Young Adult; high-resolution respirometry; repetition failure; BFR resistance exercise; capillary; mitochondria; low-load
• DOI: 10.1152/ajpregu.00243.2019
• ISSN: 0363-6119; 1522-1490

The application of blood flow restriction (BFR) during resistance exercise is increasingly recognized for its ability to improve rehabilitation and for its effectiveness in increasing muscle hypertrophy and strength among healthy populations. However, direct comparison of the skeletal muscle adaptations to low-load resistance exercise (LL-RE) and low-load BFR resistance exercise (LL-BFR) performed to task failure is lacking. Using a within-subject design, we examined whole muscle group and skeletal muscle adaptations to 6 wk of LL-RE and LL-BFR training to repetition failure. Muscle strength and size outcomes were similar for both types of training, despite ~33% lower total exercise volume (load × repetition) with LL-BFR than LL-RE (28,544 ± 1,771 vs. 18,949 ± 1,541 kg, P = 0.004). After training, only LL-BFR improved the average power output throughout the midportion of a voluntary muscle endurance task. Specifically, LL-BFR training sustained an 18% greater power output from baseline and resulted in a greater change from baseline than LL-RE (19 ± 3 vs. 3 ± 4 W, P = 0.008). This improvement occurred despite histological analysis revealing similar increases in capillary content of type I muscle fibers following LL-RE and LL-BFR training, which was primarily driven by increased capillary contacts (4.53 ± 0.23 before training vs. 5.33 ± 0.27 and 5.17 ± 0.25 after LL-RE and LL-BFR, respectively, both P < 0.05). Moreover, maximally supported mitochondrial respiratory capacity increased only in the LL-RE leg by 30% from baseline ( P = 0.006). Overall, low-load resistance training increased indexes of muscle oxidative capacity and strength, which were not further augmented with the application of BFR. However, performance on a muscle endurance test was improved following BFR training.