For weeks now many of you have been asking what the deal is with regard to compressions socks - you've all been wondering if they really do serve a purpose, or if in fact, they're just another hyped-up accessory item that does little more than enhance our running get-up. I decided to do some digging and see what I could find, and I came across an article written by running coach and exercise science expert, Steve Magness. Steve posted an excellent article on his website, http://scienceofrunning.com/, about guess what? Compression Socks! With his permission, I have copied his article below. If you are really interested in the science behind all of the compression sock hype, you'll find this article extremely informative and helpful.
Post Contributed By Steve Magness
If you’ve been at a road race recently or watched Pro’s like Chris Solinksy or Paula Radcliffe race, you might have noticed the extremely long compression socks that are seemingly popping up everywhere. While Radcliffe was probably the earliest adopter to the compression socks while racing trend, it seems like in the last year the idea of wearing compression socks when running or after running has taken off.
As I’ve mentioned before, “new” trends/ideas seem to go through a cycle of heavy emphasis or de-emphasis before settling into around their likely place. So, where do compression socks fall and more importantly do they work?
I’ve been wanting to do a post on compression socks for a while, because they seem like the new “fad”. Sigvaris(http://www.sigvarisusa.com/) sent me a nice pair of compression socks to test out, so that solved my problem of critiquing something I haven’t used. As I told Sigvaris, I’m going to give a critical review of the science behind it and then my practical experience. As you’ll see shortly, there is a lot of mixed research on compression socks that is likely due to the wide variety of types used and the types of people used in the studies. It’s likely that there is a large individual component to it.
To examine that let’s use what one of my physiology professors, Dr. Winchester, called the 3 stool test. We’ll look at the theory, the research, and the practical experience to see if compression socks actually work:
First, let’s look at the possible theories behind why compression socks might improve performance. We need to separate this out into improving performance during the race/run itself and improving recovery post run/race.
The Blood flow hypothesis basically says that the compression of the lower leg increases the blood flow. Partially due to gravity, blood can tend to pool in the lower legs. This can occur both during exercise or when at rest. As I’m sure you’re aware, compression socks became popular in clinical use to prevent such things as deep vein thrombosis. They were initially used for people who were bed ridden or had forced inactivity, and then latter branched out to being prescribed for people who had to sit for long periods of time, such as on airplane or long car rides.
In terms of improving performance during a race, the idea is that if increased venous blood flow can occur, more by-products that are transported by the blood can be flushed out and cleared better. If these products that can cause fatigue are gotten rid of quicker, then performance improves. In terms of recovery after a race, the idea is similar. If we can increase venous blood return, you’re going to get back to homeostasis much quicker.
The second main theory is somewhat less known among athletes. When we run, and strike the ground, those impact forces cause the muscle/tendon/lower leg to vibrate. It’s thought that this vibration could be one cause of the delayed muscle soreness that we’ve all experienced. If you look back at the article I wrote entitled ‘Why running shoes don’t work’ you’ll recall the concept of muscle tuning, which is a similar principle. If this theory is correct, an improvement in efficiency could occur while wearing compression socks.
Taking this idea a little further, long and triple jumpers can often be seen wearing compression socks. Obviously they are not doing this for blood flow reasons. Instead, some research as shown that compression socks may improve leg power (Kraemer et al., 1996, 1998). The theory put forth on why this might occur is the decreased in muscle vibration and an increase in proprioception.
On a practical level, the theories are at least sound, with some ideas seeming more plausible then others. The bottom line though is that in theory, it could make sense.
Now that we know the theories, let’s look at what the research says.
First, the idea that compression socks improve venous blood flow at rest has been substantiated (Byrne et al., 2001). Similarly, the idea that graduated compression is better than constant compression at rest has been demonstrated. In theory, this should mean better clearance of by products and enhanced recovery. How much so is up for debate.
The question that has not been answered is whether compression during a run improves blood flow. Additionally, the question remains if either at rest or during running, the blood flow increase is enough to improve performance or recovery. Let’s look at the research:
During exercise, the research is mixed. Ali et al. (2007) found that no performance or changes in physiological parameters occurred during or after a 10k run. However, they did find a reduction in muscle soreness, pointing to the muscle vibration and recovery aspects of socks. Contrasting these results, Kremmier et al. (2009) found improved performance and an improved lactate threshold when wearing compression socks while running. Similarly, two separate studies found improved 5k performance and improved running economy (Chatard et al., 1998 & Bringard et al., 2006). The study by Bringard et al. (2006) is particularly interesting. They found improved economy at 3 different speeds, but it was most substantial at the middle speed (12km/hr).
Lastly, let’s look and see if compression socks can improve lactate clearance. In a study by Berry et al. (1987) they found that blood lactate clearance was improved after a maximal treadmill test. This effect has been further substantiated by other studies (Creasy, 2008). The problem according to Creasy, is in understanding why the lactate changes occur. Remember that we are measuring blood lactate, not muscle lactate. Early authors proposed that the decrease in blood lactate might be due to the compression decreasing the flow of lactate from the muscle out to the blood stream. The other option is that an increase in blood flow caused by the compression socks increases the flow of the lactate to other muscles that can take up and use the lactate. In essence, it would enhance the lactate shuttle. What exactly happens is hard to determine at this point.
On the damage and recovery side of things, a study using full lower body graduated compression tights only after the exercise showed improvements in muscle soreness and recovery following plyometrics (Byrne & Easton, 2010). As mentioned above, Ali (2007) found enhanced recovery which they speculated was due to the compression alleviating swelling and inflammation. The exact mechanisms for why compression garments may decrease muscle soreness is unknown. But that is partially due to the fact that the exact cause of delayed onset muscle soreness is also unknown. There are a couple different theories based on mechanical or metabolic damage, some more accepted than others, but if we don’t know exactly what causes soreness, it’s pretty hard to figure out why compression socks decrease it.
So what does this all mean?
The problem with the contrasting running performance studies is there wide range of different socks used and the wide range of experience of runners, from recreational to well trained. At rest in certain populations, compression socks definitely increase venous blood flow. The question is does this happen during exercise and if so does it improve performance? I’m afraid that testing that idea during intense running is a bit too hard to do at the present moment.
There seems to be a bit more consistent effect demonstrated on decreasing muscle soreness and thus enhancing recovery in a wide variety of groups. The results for performance enhancement while running due to blood flow increases and/or product removal is mixed. Although neither is well studied at this point in time.
Why the differences?
One concept that I’ve briefly mentioned that may explain the mixture of results is the idea of the degree of compression needed. In testing compression socks in a clinical setting, Byrne et al. found that there seemed to be an optimal amount of compression. First, they found that a graduated compression was better, meaning more compression at the bottom near the ankle and less as it goes up towards the knee. Secondly, the amount of compression mattered. In their study, they found 20mmHg at the ankle improved blood flow, while 30mmHg restricted blood flow at rest (Byrne et al. 2001). What this and other studies demonstrate is that there seems to be a sweet spot in compression. At rest, this sweet spot has at least been researched and found to be in that 20 +/- 5mmHg level, but during exercise the exact compression level needed is unknown. Additionally, there is likely an individual component to the level of compression needed.
It’s likely that the mixture of socks and graduated vs. non-graduated compression explains why the results are mixed. So, while we don't quiet know what optimal compression is, from sedentary studies it looks like graduated socks are a must.
Although elite athletes do a lot of stuff that is useless or doesn’t work, looking at what they are doing provides some clues for what might work. In general, if one or two athletes are using it, they are either far ahead of the curve or it’s not worthwhile. It’s when you get a significant amount of athletes having success with a product or training method that you start to take notice. As mentioned in the beginning with the success of Paula Radcliffe, numerous elites have taken to wearing compression socks like Chris Solinsky, Jo Pavey, and Benitta Johnson. Are they on to something?
Just my opinion, but for most distance runners I’d think the most likely benefit would be the decrease in soreness or muscle damage, more so than the blood flow improvements. For the marathon and longer events on the track, muscle damage could interfere with muscle contraction or the amount of recruitable fibers, thus limiting performance. Additionally, with the calves in particular, muscle damage could limit the use of elastic energy and the stretch shortening cycle. We’ve all felt the effects of running a 10k in spikes and what that does to our calves. If this damage could be limited during the run or even post workout, performance or at least our rebounding from a race or workout could be improved.
In the compression socks that I got to test out, I tried them during a long run, post workout, and while traveling. The idea was to use them during my most damaging workout, the long run. When you’re running for close to 2 hours a ton of damage happens and my next day run is always slow because of the residual pain/fatigue. In particular, my calves are extremely tight almost all the time, so long runs or long workouts in flats/spikes always leave me with some residual soreness in that area.
While it’s impossible to tell, following a long run and a longer threshold workout in flats, my calves definitely felt better the next day then they normally do. I can’t say that anything else felt noticeably different, but the calf/Achilles complex on both sides seemed to see benefits. I can’t say whether it was wearing the socks during or after the runs that made the difference. For the post workout recovery test, I tested blood lactate clearance with and without the socks. On separate days, with workouts that produced similar levels of max lactate, I then lied on the ground for 15min either with socks on or without, then took another lactate sample. For what it’s worth, the time I wore socks cleared 1.1mmol/L more lactate during the timed segment.
For what it's worth, I found the socks to be pretty comfortable both during and after the run. I'm used to wearing high socks when running, so to me it didn't feel weird. I'm not sure how they'd work on long runs in the heat and humidity of a Texas long run. I haven't tried that out yet. I was told by Sigvaris' reps that they have an athletic performance sock coming out that is made for combatting such a situation, though I haven't tried it out.
Lastly, I wore compression socks on and off during my travel day to the Peachtree road race. For those who don’t know, when you run at a relatively high level, a lot of racing encompasses long travel days and then lots of sitting around at a hotel. I must say out of all of the uses for compression socks this is where I saw the most benefit. My legs felt better during the long travel and then also during the whole sitting around watching too many movies period of the day. I think this is the area for the most benefit of recovery compression socks. Similar to the athlete who takes an ice bath a day or two before the big race, I can see compression socks being useful in the days leading up to a big race.
There is a place for compression socks I think. Are they the cure all, guaranteed to improve performance? Doubtful. But there is no magic cure all, so you shouldn’t be looking for one. But they might be able to help increase recovery/decrease soreness. I’d look at them as a tool to use that is similar to ice baths. They don’t need to be used every day, but pull them out when you need them after that killer workout, or before that important race. Remember that while reducing muscle damage is generally a good thing, sometimes we need that damage to be the trigger for adaptation. It’s only when we break down stuff that it gets built up.
As mentioned earlier, with my chronically tight calves, they seem to at least do something for me. I can see myself using them on occasional long tempos in flats and then during travel and as a recovery aid in the days preceding big races.
As a review, overall I'd recommend the socks I used for the purposes mentioned above.
So the takeaway message is this: Compression socks are a tool, like an ice bath or a recovery shake that can be used. Is it a magic pill? Nope, but could it help? Possibly.