Compression Garments - The Recovery Enhancer You're not Using (Yet?) - Meta-Analysis: Gymrats May Benefit Most

Is it funny, stupid or tragic that compression garments are advertised most heavily to endurance athletes who benefit the least, while resistance trainees are supplied with useless lifting shoes and tons of questionable supplements, yet not educated on the significant recovery benefits of wearing compression garments? Maybe it's simply because we don't fully understand how they work yet.

No, I don't use them myself, but after reading the latest (and most comprehensive) meta-analysis of the use of compression garments and its effects on recovery in sports I start to believe that I may be - just like you - missing out... Let's  not move too fast, though, as the authors, Freddy Brown, Conor Gissane, Glyn Howatson, Ken van Someren, Charles Pedlar, and Jessica Hill point out, the "literature is clouded by conflicting results and uncertainty over the optimal conditions of use" (Brown 2017) - and I would add: it's full of potential bias due to sponsorships.

While the above gives us all the reason to be skeptical about the claims of immediate performance enhancement, faster removal of lactic acid (doesn't occur, btw), increased strength+power, improved endurance + muscle oxygenation, etc. the evidence that the $100 for a legging may not be the failed investment, gymgoers think it was, accumulates.
The previously cited meta-analysis by Brown et al. included only randomized controlled trials on the use of compression garments (CG) for performance recovery in healthy humans. In that, the exclusion process reduced the initial number of studies that were left after skimming titles and abstracts (N=26) to 23 studies that were eventually included in the meta-analysis, which extracted the changes from baseline scores on the most important marker of exercise recovery: the recovery of maximal physical performance following exercise. Accepted performance outcomes included the following: strength, power, and endurance.

Figure 1: Next to financial support which is no official risk of bias, the authors of the meta-analysis recorded a high risk of bias for selective reporting and problems with participant blinding - Risk of bias analysis according to Cochrane Collaboration guidelines (Brown 2017 | read up on the methodology).

The scientists differentiated between trials assessing recovery and performance, only studies that featured a temporal separation between an initial damaging intervention and subsequent performance tests were included. For example, bouts of repeated sprinting or resistance exercise that featured rests between sets met our criteria if CG were worn throughout recovery periods.

You read that, right? You got to keep those pants on, to see the benefits!

Well, ok... that's only part of the truth because pants were not the only compression equipment that was used in the methodologically diverse RCTs that were included in the meta-analysis. More specifically, the trial tested the effects of graduated tights (11 trials, 149 participants), stockings (two trials, 40 participants), knee socks/calf sleeves (two trials, 44 participants), arm sleeves (four trials, 71 participants), whole body garments (three trials, 34 participants), and a sleeved top (one trial, ten participants). Effects were tested in young (avg. age 25  ± 9 years, 74% male) individuals and with diverse performance outcomes, exercise modalities, and participant training status.

Figure 2: Forrest plots illustrating the effects of compression garments (CG) compared with control on all performance measures of recovery; effect sizes of the results for 2-8h post, 24h post (left) and >24h post workout  (right | Brown 2017).

We are thus - and this should remind you of my introductory remarks - comparing apples and oranges not in all, but in many cases. This doesn't change the fact, though, that ...

• overall, i.e. when all exercise modalities and time-points are considered, CG demonstrated small, very likely benefits [p < 0.001, ES = 0.38 (95% CI 0.25, 0.51)]
• neither pressure nor training status significantly affected these benefits (with p = 0.06, the influence of pressure was yet close to significance | training status p = 0.64)

• Figure 3: As previously pointed out, the evidence for benefits w/ resistance training is the most convincing; and yet, compression garments are marketed to and used mostly by endurance athletes.

  strength recovery was subject to greater benefits than other outcomes [p < 0.001, ES = 0.62 (95% CI 0.39, 0.84)], displaying large, very likely benefits at 2–8 h [p < 0.001, ES = 1.14 (95% CI 0.72, 1.56)] and >24 h [p < 0.001, ES = 1.03 (95% CI 0.48, 1.57) | see Figure 2]. 
• recovery from using CG was greatest following resistance exercise [p < 0.001, ES = 0.49 (95% CI 0.37, 0.61)], demonstrating the largest, very likely benefits at >24 h [p < 0.001, ES = 1.33 (95% CI 0.80, 1.85)]
• recovery from "cardio" (p = 0.01) was sign, although large, very likely benefits emerged only for cycling performance 24 h post-exercise [p = 0.01, ES = 1.05 (95% CI 0.25, 1.85)]

In other words: If you're a powerlifter who simply cannot wait to get back to the grind after each workout, you are the last person to look down upon compression garments as "pussy gadgets" and should be the first one to say: "God d*mn, what can go wrong, I'll give it a try" - for both, the upper and the lower body (in fact, Goto's 2014 study even suggests earlier benefits for the upper vs. lower body), by the way... ah, and don't forget that you got to wear those garments during and after your workouts (for ~12h, so you may need two pairs: one pre- one post-showering ;-).

Ok, fine. This sh*t works. What's the mechanism, then?

What exactly it is that triggers the benefits that have also been observed by Marqués-Jiménez, et al. in 2016, still isn't clear. Scientists speculate that compression-induced increase in venous blood flow could increase the clearance of metabolites and the supply of nutrients - this, however, should be observable if you monitor the lactate accumulation during and after workouts. Marqués-Jiménez et al. were yet not able to confirm that in their 2016 meta-analysis. In fact, "lactate is somewhat retained in the previously active muscle with compression stockings rather than being cleared more quickly without" (Marqués-Jiménez 2016) - an observation that points towards other benefits of wearing compression stockings during passive recovery: an increase in muscle glyconeogenesis, for example, as lactate is an important substrate for post-workout glycogen replenishment (Fournier 2002).

Figure 4: If you look at the results of individual studies such as Jakeman et al. (2010), you will find that some of them show quite impressive improvements of subjective and objective recovery markers.

Other (unconfirmed) candidate-mechanisms are reduced muscle damage (as non-consistently suggested by reduced CK and LDH), as well as the reduced formation of edema (by increasing lymphatic outflow and transporting the profuse fluid from the interstitium of the muscle back into the circulation) and subsequent reductions in DOMS and increases in mobility, which could at least partly explain benefits as they were observed by Brown et al. in the meta-analysis at hand.

Effects on long-term gains still in the dark

Ever since the hormesis hypothesis is gathering momentum, the one question that will always arise, when we're talking about improving recovery via a potential reduction in muscle damage is: "Will this reduce my gains?" The answer in this and 99% of the other cases is: "We don't know yet."

Without studies that investigate the long-term response to wearing compression garments, I do not want to start speculating if Kraemer et al's conclusion that the results of their 2010 study which used a very realistic resistance training protocol "appear to demonstrate the efficacy of a whole body compression garment when recovery enhancement is needed after a typical heavy resistance training workout" (Kraemer 2010) will have to be amended, with "but may impair adaptational processes in the long run"; just as it had to  be done for CWI guidelines when, in 2015, the first study showed that cold-water immersion therapy can impair the adaptational response to exercise.