Demand is coming-Are you ready?
Today we start our story two years down the road from Part 1. We got your taste buds singing in Part 1 and now you’re hungry for more. Well you’re in luck my evidence-based epistemological friend! Here’s Part 2! Eat up!
In 2021, the Avengers reassembled and Centner and colleagues performed a study that examined the effects of 14 weeks of LL-BFR and HL training on patellar tendon adaptations in healthy male adults. Subjects performed bilateral leg press, knee extensions, and standing and sitting calf-raises using either HL or LL-BFR. The HL group trained at 70-85% 1RM with a 3x 6-12 set/rep scheme. The LL-BFR group applies 50% LOP and used 20-35% 1RM in a 30, 15, 15, 15 set/rep scheme. The load was progressed every 4 weeks for both groups after 1RM testing. The HL group started with 70% 1RM and ended the study with 85% 1RM and the LL-BFR group started the study with 20% 1RM and ended the study with 35% 1RM.
The results showed that both patellar tendon stiffness (LL-BFR: 25.2%; HL: 22.5%) as well as CSA increased following weeks of resistance training. Patellar tendon CSA changed from 95.9 ± 15.1 mm2 to 99.8 ± 13.2 mm2 in the HL group and from 94.6± 12.8 mm2 to 103.1 ± 12.8 mm2 in the LL-BFR group, respectively. The authors suggest that “strain and stress are not the only factors influencing mechanical tendon adaptations and that the number of loading cycles and/or concurrent tissue hypoxia might mediate this response.”
Both the HL and LL-BFR groups experienced similar gains in rectus femoris hypertrophy (HL: ~6%; LL-BFR: ~3%), which is to be expected from what we know about LL-BFR and muscular adaptation. Both the HL group and the LL-BFR group demonstrated increases in strength
Leg press 1RM increased in the HL group from 192.0 ± 71.0 kg to 263.9 ± 89.9 kg and in the LL-BFR group from 186.4 ± 60.7 kg to 248.9 ± 68.8 kg. Additionally, knee extension 1RM increased from 81.2 ± 17.6 kg to 112.0 ± 26.2 and from 92.5 ± 32.1 kg to 139.6 ± 33.8 kg in the HL and LL-BFR group, respectively. There was a statistically significant difference in favor of LL-BFR for knee extension strength, which is contrary to the current body of evidence. The authors postulate that the discrepancy could be a result of the two protocols not being volume-matched.
The authors concluded that, “tendinous adaptations are not merely mechanical stress and strain dependent, but also strongly rely on the metabolic environment.”
Do these studies prove that low load BFR training is a cure for tendinopathies? No. Do they allow us to think more deeply about our thinking around tendinopathies? You bet.
Centner C, Lauber B, Seynnes OR, et al. Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training. J Appl Physiol (1985). 2019;127(6):1660–7
Centner, C., Jerger, S., Lauber, B., Seynnes, O., Friedrich, T., Lolli, D., Gollhofer, A., & König, D. (2022). Low-Load Blood Flow Restriction and High-Load Resistance Training Induce Comparable Changes in Patellar Tendon Properties. Medicine and science in sports and exercise, 54(4), 582–589
****Remember, the decision to use BFR, or any treatment for that matter, should be based on the pillars of evidence-based practice.
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