Karanasios et al. (2022)

Low-load resistance blood flow restriction versus sham

This trial compared low-load resistance BFR versus sham BFR in lateral elbow tendinopathy

Methodological shortcomings limit the interpretability of the findings

Conservatively speaking, the addition of BFR in rehab of lateral elbow tendinopathy may be of value, but requires rigorous confirmation from future trials

Introduction

Blood flow restriction training (BFR) is a useful option to exercise in case high-intensity training is too painful or contraindicated, let’s say in the early stages of (postoperative) rehabilitation. In knees, it has been shown to be hypoalgesic, and positive effects like improved muscle strength, growth, and tendon adaptations have been shown in healthy individuals. The current evidence supports exercise as the first-line treatment for lateral elbow tendinopathy. However, as the benefit of exercise on pain and function is mostly small, ways to improve the outcomes are welcome. The addition of BFR could be useful to improve the outcomes of exercise therapy as the evidence supporting its use (especially in the lower extremities) increases. This randomized controlled trial examined the effect of low-load resistance BFR versus sham on pain, disability, grip strength, and global rating of change.

 

Methods

The effects of low-load resistance BFR versus sham BFR was investigated in an RCT. Patients between 18 and 60 years with lateral elbow tendinopathy symptoms for more than 2 weeks were eligible candidates. The diagnosis of lateral elbow tendinopathy was made when there was pain with palpation of the lateral epicondyle, a positive Cozen’s and/or Maudsley and/or Mill’s test, and a decrease of more than 10% in grip strength with elbow extension compared to elbow flexion. It was not sure if all these criteria needed to be met.

Twelve physiotherapy sessions were conducted over a period of 6 weeks (2 sessions per week). These sessions were standardized and included soft tissue massage, supervised exercises (with BFR or sham BFR), advice, and education. Each session lasted for 30-45 minutes. A home exercise program supplemented the physical visits every second day and was delivered via an exercise booklet.

A two-stage training program was used:

  1. In the first stage, all exercises were performed with BFR or sham-BFR. Four sets (30-15-15-15 repetitions) of elbow flexion and extension exercises (concentric-eccentric) were performed at 30% of 1-RM using dumbbells. Hereafter, wrist flexion, extension, and supination-pronation exercises followed using 3 sets of 10 repetitions with the minimum free weight based on a pain-monitoring approach (acceptable pain during the exercise <2/10 NPRS). Every week, the load tolerance was assessed, and loads were increased by adding 0.5-1kg as indicated by the pain during loading. To end the treatment session, static stretching exercises (3 repetitions x 30 seconds) of the wrist extensors and flexors were performed.
  2. The second stage started at least after 2 weeks of training when patients were pain-free during or after the exercises. The second stage program continued the exercises from the first-stage training program (with BFR or sham-BFR) and hereafter exercises without BFR were performed. These included wall push-ups, wrist extension-flexion using a rubber bar, hand grip using a softball, and standing rowing exercises.

The primary outcomes included the following measures:

  • Pain intensity, measured on an NPRS scale,
  • Pain and disability were evaluated by the patient-rated tennis elbow evaluation (PRTEE) score. Scores range from 0-100 with lower scores meaning lower pain and disabilities,
  • Pain-free grip strength (PFGS)
  • Global rating of change (GROC)

 

Results

In total, 46 participants were included and randomized to the intervention or sham intervention group. They had a mean age of 45.2 years and most of them had a duration of their symptoms of 6 weeks.
The outcomes were assessed at 6 and 12 weeks and revealed that a statistically significant between-group improvement was seen in favor of the intervention group at 6 and 12 weeks for the PRTEE and GROC. At 6 weeks grip strength improved more in the intervention group, but not at 12 weeks. Pain scores improved more in the intervention group at 12 weeks.

The results revealed statistically significant improvements in the BFR group, but these differences were not clinically important between the groups for pain and pain-free grip strength! Only function, measured with the PRTEE score, exceeded the MCID.

 

Questions and thoughts

The current study shows that the addition of BFR is responsible for the improvements. Previously, BFR has been shown effective in the systematic review of Hughes in 2017. Here the authors found that low-load BFR training, compared with low-load training alone was more effective and tolerable. Therefore, the addition of BFR to low-load resistance training is recommended as a potential clinical rehabilitation tool.

Low-load resistance BFR was shown to be effective in this RCT. However, we should keep in mind that the intervention did also include soft tissue massage, advice, education, and a home exercise program. The supervision of the exercises may have likely also played a role in the positive results. So rather than assigning these results to BFR alone, one should keep in mind that the intervention consisted of much more. Furthermore, most of the participants had symptoms for 6 weeks. But the interquartile range revealed that a spectrum of acute and chronic tennis elbows was included as this ranged from 4-26 weeks. It would have been interesting to interpret the results based on the duration of symptoms, as a subanalysis. Do more chronic tennis elbow complaints respond similarly to BFR than acute ones? As the median duration of the complaints was reported to be 6 weeks, I assume we can more confidently say that these results can be expected in acute lateral elbow tendinopathy.

Interestingly, looking at the secondary outcomes you can see that the strength of the elbow flexors did increase to a statistically significant level, but the strength of the extensors did not. Why they did not include strength measurements of the wrist extensors (as the pathology originates here) is not clear.

 

Talk nerdy to me

The authors defined 4 primary outcomes and used these in the sample size calculation. According to their calculation, “A sample size of 17 in each group was estimated to be sufficient to detect an effect size of 1.0 on the PRTEE, a sample size of 21 per group to detect an effect size of 0.90 on PFGS, and a sample size of 17 per group to detect an effect size of 1.0 on pain reduction.” They accounted for a 10% loss to follow-up by increasing the minimum required sample size to 23. The method they used is not correct, though. When using multiple primary outcomes, p-values should be adjusted for multiplicity, by using for example the Bonferroni correction. This correction divides the significance level by dividing it by the number of outcomes and is best used when the outcomes are uncorrelated. Another option is to use a composite outcome, let’s say a questionnaire that covers all aspects of the disease and associated problems. A third option is to conduct a multivariate analysis of variance (MANOVA) with a subsequent analysis to assess the effect on each outcome separately. This aspect of the methodology can make or break a study as the conclusions may change drastically! A review by Vickerstaff in 2015 concluded that of the 26 studies reporting significant multiple primary outcomes, 6 would result in different conclusions with an appropriate adjustment. If the outcomes are (somewhat) correlated, as is the case here, the possibility of finding type 1 errors (false positive outcome) increases. To conclude, 23 participants were way too few and the outcomes were not corrected for the multiple primary outcomes defined.

The conclusions of this trial examining low-load resistance BFR versus sham must therefore be interpreted cautiously. They may indicate a potential benefit of BFR on function and pain that should be examined in more rigorous trials.

 

Take home messages

Low-load resistance BFR versus sham BFR was compared in this study for acute tennis elbow or lateral epicondylalgia. Very conservatively speaking, these outcomes may mean that BFR may be an interesting option to treat lateral elbow tendinopathy, especially for improving function. These results indicate that increases in function (in daily activities) and strength may be the first outcomes to improve and that improvements in pain are often delayed beyond 6 weeks. As this trial’s methodology was not 100% rigorous, these results should be viewed as very early findings, which should be explored further in methodologically correct RCTs.

 

Reference

Karanasios S, Korakakis V, Moutzouri M, Xergia SΑ, Tsepis Ε, Gioftsos G. Low-load resistance training with blood flow restriction is effective for managing lateral elbow tendinopathy: a randomized, sham-controlled trial. J Orthop Sports Phys Ther. 2022 Sep 13:1-30. doi: 10.2519/jospt.2022.11211. Epub ahead of print. PMID: 36099170. 

 

Additional reference

Hughes L, Paton B, Rosenblatt B, Gissane C, Patterson SD. Blood flow restriction training in clinical musculoskeletal rehabilitation: a systematic review and meta-analysis. Br J Sports Med. 2017 Jul;51(13):1003-1011. doi: 10.1136/bjsports-2016-097071. Epub 2017 Mar 4. PMID: 28259850.

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