Happy New Year everyone.
Today's podcast looks into low load BFR training and achilles tendons. This is quite an exciting paper due to the positive effects of Blood Flow Restriction training with tendon adaptation. Previously only high load strength training has shown positive responses to tendon so this is a great result for what BFR can bring to the user - i.e. we can finally use low load training to elicit a tendon response (with the addition of BFR).
The other advantage of this session was how simple it was. There was a couple of points that I feel are quite important to note. Firstly, it was a 14-week training intervention. Typically a lot of academic studies are of 4-6weeks in lengths and probably this is why previous studies may not have shown positive training responses. The other point, was an incremental loading protocol - although the loads were still low (20-35% 1RM) every 4 weeks the load was increased by 5% and the subjects' max strength was reassessed and readjusted. This highlights that the body needs a continual increase in strength, even if we are using low-load BFR training. Therefore we can start to look at bringing this type of training to an "at-home" situation providing a simple solution for everyone.
This same principle for other tendons (esp. shoulder and patella) I feel can also be applied. I've had great success with tendon issues acutely and this paper highlights that a longer (14 week) approach to tendon adaptation is needed.
The article I review today is:
Low-load blood flow restriction training induces similar morphological and mechanical Achilles tendon adaptations compared with high-load resistance training.
J Appl Physiol 2019 Dec 1;127(6):1660-1667. doi: 10.1152/japplphysiol.00602.2019. Epub 2019 Nov 14.
Low-load blood flow restriction (LL-BFR) training has gained increasing interest in the scientific community by demonstrating that increases in muscle mass and strength are comparable to conventional high-load (HL) resistance training. Although adaptations on the muscular level are well documented, there is little evidence on how LL-BFR training affects human myotendinous properties.
Therefore, the aim of the present study was to investigate morphological and mechanical Achilles tendon adaptations after 14 wk of strength training. Fifty-five male volunteers (27.9 ± 5.1 yr) were randomly allocated into the following three groups: LL-BFR [20-35% of one-repetition maximum (1RM)], HL (70-85% 1RM), or a nonexercising control (CON) group.
The LL-BFR and HL groups completed a resistance training program for 14 wk, and tendon morphology, mechanical as well as material properties, and muscle cross-sectional area (CSA) and isometric strength were assessed before and after the intervention. Both HL (+40.7%) and LL-BFR (+36.1%) training induced significant increases in tendon stiffness (P< 0.05) as well as tendon CSA (HL: +4.6%, LL-BFR: +7.8%, P< 0.001). These changes were comparable between groups without significant changes in Young's modulus.
Furthermore, gastrocnemius medialis muscle CSA and plantar flexor strength significantly increased in both training groups (P< 0.05), whereas the CON group did not show significant changes in any of the evaluated parameters.
In conclusion, the adaptive change in Achilles tendon properties following low-load resistance training with partial vascular occlusion appears comparable to that evoked by high-load resistance training.NEW &
Before you go and listen to the podcast could I ask a couple of favours:
1. If you know of someone who is suffering from achilles tendon issues please get them to listen to this podcast.
2. If you are enjoying the podcast please give it a positive rating on iTunes.
Thanks for listening.
In the methods, there was a couple of points around how Tendon properties was calculated and I mentioned that I would put it in the notes:
How did they measure Tendon Stiffness?
To assess tendon stiffness, elongation of the Achilles tendon was determined during ramped isometric contractions by B-mode US scans at 100 Hz at the gastrocnemius medialis myotendinous junction
After familiarization with the procedure and preconditioning of the tendon with five trials at 80% of MVC, participants were instructed to steadily exert torque to their individual maximum with a standardized loading rate of 50 Nm/s. This loading rate was chosen because it resulted in a ramped isometric plantar-flexion contraction lasting between 3 and 5 s for all subjects. During this process, visual online feedback of the torque signal was provided. Achilles tendon force was calculated by dividing plantar flexion torque by the tendon moment arm with a subsequent correction for ankle joint rotation by kinematic data
Tendon moment arm was calculated by measuring the perpendicular distance from the inferior tip of both medial (L1) and lateral (L2) malleolus (center of rotation) to the posterior part of the Achilles tendon. For this purpose pictures were taken from the medial and lateral sagittal planes (Sony Cyber-shot DSC-RX100 Digital Camera). In accordance with previous studies, the mean of these two measurements (L1,2) was used for further calculations. Subsequently, the intersection of L1 and L2 was indicated with a needle and the perpendicular distance (M) from the needle to the tendon’s line of action was measured (32). Tendon moment arm was then determined by subtracting M from L1,2 (for detailed descriptions see Refs. 32 and 50). All analyses were conducted with ImageJ (1.51; NIH).
Tendon stiffness was then calculated as the slope of the force-elongation curve between 50% and 80% MVC. This procedure has previously been used in the scientific literature (56). Young’s modulus was calculated as the slope of the stress-strain curve between 50% and 80% MVC.
What is Young’s Modulus?
Young's modulus is a measure of the ability of a material to withstand changes in length when under lengthwise tension or compression. Sometimes referred to as the modulus of elasticity, Young's modulus is equal to the longitudinal stress divided by the strain.