Wednesday, October 25, 2017

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.
BFR and Hypoxia Training are different from training w/ compression garments

BFR, Cortisol & GH Responses

BFR - Where are we now?

BFR as Add-On to Classic Lifts

BFR for Injured Athletes

BFR B4 Workouts = WIN!?

BFR + Cardio = GainZ?
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.
Illustration of the compression garment with adhesive silicone stripes on the anterior and posterior leg as it was used in Born 2014 | In Hill 2017 a high pressure (ca. 15 mmHg) medical grade stockings beat sport-specific ones with lower pressures (ca. 8 mmHg); the problem: Ali 2011 shows opposing results, so what's best ain't clear.
Bottom line: No, I haven't ordered my pair of extra-skinny compression pants,... yet ;-) But I am as tempted as I am afraid to spend money on a product that doesn't even work. While the meta-analysis at hand reports no effect of pressure and thus the only garment-specific variable that was investigated, the reason that the effects were only borderline significant (p = 0.06) is probably a lack of studies. Being based on the comparison of only 8 studies (3 with high pressures, 5 with low pressures), the meta-analysis favors lower pressures of 4.8–11.8 mmHg of which I assume that they can be achieved w/ less practical/design effort than the high(er) pressures of 18 to 18.3 mmHg. Unfortunately, the two studies I could find that did direct comparisons provide conflicting evidence with Ali (2011) showing optimal results with low pressure and Hill et al's (2017) more recent study showing benefits of higher pressure garments.

It doesn't help either that the garments that were used in the existing RCTs include stockings, pants, shirts and full body suits in form of commercially available products like "Venosan 4001" (Ali 2007) to funky prototypes with glue-on adhesive silicone stripes that were intended to mimic taping (Born 2014 | see illustration above). Studies comparing different products are missing and with the heterogeneous study designs it doesn't really help you if I tell you that the positive outlier, the study by Jakeman et al. (2010, see Figure 4) used commercially available lower limb (ankle to waist) compression tights (Skins, Sydney, Australia) made of 76% nylon tactel microfibre and 24% elastane; tights with an average compression of 17.3 mmHg at the calf and 14.9 mmHg at the thigh. If that's  better or worse than say Under Armor's Recharge® Suit that was used by Goto et al. (2014) in their resistance training study could be decided only based on a direct comparison... and again, this comparison has not been done or, at least, not published, yet | Comment!
  • Ali, A., Caine, M. P., & Snow, B. G. (2007). Graduated compression stockings: physiological and perceptual responses during and after exercise. Journal of sports sciences, 25(4), 413-419.
  • Ali, A., Creasy, R. H., & Edge, J. A. (2011). The effect of graduated compression stockings on running performance. The Journal of Strength & Conditioning Research, 25(5), 1385-1392.
  • Born, D. P., Holmberg, H. C., Goernert, F., & Sperlich, B. (2014). A novel compression garment with adhesive silicone stripes improves repeated sprint performance–a multi-experimental approach on the underlying mechanisms. BMC sports science, medicine and rehabilitation, 6(1), 21.
  • Brown, F., Gissane, C., Howatson, G., van Someren, K., Pedlar, C., & Hill, J. (2017). Compression Garments and Recovery from Exercise: A Meta-Analysis. Sports Medicine, 1-23.
  • Fournier, P. A., Bräu, L., Ferreira, L. B., Fairchild, T., Raja, G., James, A., & Palmer, T. N. (2002). Glycogen resynthesis in the absence of food ingestion during recovery from moderate or high intensity physical activity: novel insights from rat and human studies. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 133(3), 755-763.
  • Goto, K., & Morishima, T. (2014). Compression garment promotes muscular strength recovery after resistance exercise. Medicine & Science in Sports & Exercise, 46(12), 2265-2270.
  • Hill, J., Howatson, G., van Someren, K., Gaze, D., Legg, H., Lineham, J., & Pedlar, C. (2017). The effects of compression garment pressure on recovery from strenuous exercise. International journal of sports physiology and performance, 1-22.
  • Jakeman, J. R., Byrne, C., & Eston, R. G. (2010). Lower limb compression garment improves recovery from exercise-induced muscle damage in young, active females. European journal of applied physiology, 109(6), 1137-1144.
  • Kraemer, W. J., Flanagan, S. D., Comstock, B. A., Fragala, M. S., Earp, J. E., Dunn-Lewis, C., ... & Powell, M. D. (2010). Effects of a whole body compression garment on markers of recovery after a heavy resistance workout in men and women. The Journal of Strength & Conditioning Research, 24(3), 804-814.
  • Lixandrão, M. E., Ugrinowitsch, C., Berton, R., Vechin, F. C., Conceição, M. S., Damas, F., ... & Roschel, H. (2017). Magnitude of Muscle Strength and Mass Adaptations Between High-Load Resistance Training Versus Low-Load Resistance Training Associated with Blood-Flow Restriction: A Systematic Review and Meta-Analysis. Sports Medicine, 1-18.
  • Marqués-Jiménez, D., Calleja-González, J., Arratibel, I., Delextrat, A., & Terrados, N. (2016). Are compression garments effective for the recovery of exercise-induced muscle damage? A systematic review with meta-analysis. Physiology & behavior, 153, 133-148.