Debunking the Lactic Acid Myth: Understanding DOMS and the Real Keys to Recovery

I recently saw a session upload on Strava, where a runner mentioned that were flushing out the lactic acid in an easy session, after having done a heavy track session the day before, and it got me wondering, how many runners still think that lactic acid causes sore legs and, if it doesn’t, what does?

So, first up, lactic acid does not cause the sore muscles which most know as ‘delayed onset muscles soreness’ or DOMS. Without getting overly technical, or should that be biological, lactic acid is a byproduct of anaerobic energy production. It accumulates in the muscles when we run hard and the body cannot meet the demands for oxygen that the muscles are creating. The muscles are constantly clearing lactate and it is actually utilised to create energy as well, but, when we are pushing really hard, the body can’t do this fast enough to prevent an accumulation. This then alters the PH in the muscles and we can feel that as a burning sensation in our legs.

That feeling disappears as soon as we slow and allow the body to catch up with its chores. Even so, our muscles can end a hard run full of lactic acid but, even after an extreme effort, that will be assimilated and cleared within an hour or so and the connection between lactic acid and post run muscle soreness has been pretty well disproven.

So, what does cause the DOMS? Muscles and connective tissue are damaged during a run. The harder we go, the more damage occurs and the less conditioned we are to the effort, again, the more damage results. This is not injury kind of damage though. These are micro tears that happen when we forcefully contract and relax the muscle fibres in our legs. The eccentric contraction, where we are ‘braking’ from the impact of our feet hitting the ground is more damaging and often why the DOMS are worse after a run with steep downhills and why we have to gingerly negotiate going down stairs a few days after one of these runs.

This damage is good, although it may not feel like it initially. The body reacts to this by firstly repairing the muscle damage but then, if we give it enough time, making it stronger in order to better withstand the same treatment. That, in a nutshell, is the training-effect. It is also the reason behind the adage, ‘there is no improvement without recovery’.

So, was the runner who’s Strava upload gave me the idea for this article doing the wrong thing by following his hard session with an easy one in order to help speed up his recovery? Not really. He was doing the right thing for the wrong reasons. The lactate was long gone from his muscles but the micro-damage was only just starting to be repaired. The theory behind a light session on sore legs is that repeating the exercise at a lower intensity will increase the blood circulation to the overworked muscles in the hopes that this will speed up the recovery process but without causing any more damage. The raw materials and nutrients required for the muscle recovery are transported to the muscles via the bloodstream.

A better method would be to do an easy session but using a form of exercise which is gentler on the muscles and connective tissue. Cycling is good because the muscles work but without the impact and jarring that running necessitates. This is where triathletes have an advantage over their single-discipline counterparts but there is nothing stopping a specialist runner from sitting on an exercise bike for a half an hour or so to spin out stiff and sore legs. Even walking is a good, in fact an excellent way for sore runners to try to improve recovery speed but it is not everyone who’s ego will allow them to go for a walk instead of a run.

Another good method is massage but again, we want the gentle, soothing type, not the over-enthusiastic massage therapist who likes to dig their elbows into knots and tight spots. That has its place for potential injury prevention but not for recovering from a hard session. Especially if we are planning to do another quality session in a few days’ time.

Stretching and yoga are also an effective recovery tool but, at the risk of sounding like a stuck record, this needs to be gentle, relaxed and non-competitive. We are not trying to see how low we can go. We are not looking to become gymnasts. We simply want to increase the circulation to the sore muscles and possibly work out some tightness in the joints that may have resulted from the body protecting itself from the hammering that we were giving it.

Nice, gentle ‘recovery sessions’ are just as important as the hard ones, even if they don’t garner as many kudos on Strava.