Each time we run, as well as building endurance, we cause damage to our muscles. This may sound shocking but it's part of the process of how our muscles adapt to become better at running. As tempting as it is to continue to push your body harder and further to support more adaptations, rest and recovery is paramount. Onetrack speaks to Dr John Fernandes, lecturer and researcher in Exercise Physiology at Cardiff Metropolitan University, to learn more about muscle damage and the importance of recovery for runners.
Can we define muscle damage and how it occurs?
There is no set definition for muscle damage, and some would even suggest that the term ‘damage’ is inappropriate (because damage has negative connotations and the damage response from exercise isn’t negative). However, muscle damaged is described by aberrations to the muscle ultrastructure e.g. micro-tears, z-line streaming, and popping sarcomeres, and known in terms of its symptomatology i.e. muscle soreness, prolonged reductions in strength, swelling, among other things.
Muscle damage differs to fatigue in that it is more long-lasting. That is, fatigue will be typically be recovered in the minutes and hours after exercise, whereas muscle damage takes days and sometimes weeks to recover from.
Primary muscle damage occurs when exercise is of high volume or there are eccentrically biased muscle actions (think of the quads when running downhill). Sometimes there is a secondary and more long-lasting damage, and this occurs when the initial exercise bout induces a severe inflammatory responses.
How long does it take to recover from a large dose of damage?
The longest cases documented within the literature are 2 weeks (!). However, the length of recovery is mostly dependent on the exercise bout and the physical condition of the person (i.e. how much of that exercise you have done previously). If you’re well adapted its extremely unlikely that it will take you 2 weeks to recover. Most cases would suggest that even with high doses recovery will be complete within 2-4 days for those who are athletic. From lower doses, recovery will likely take 1-3 days.
Does this change with age?
The literature does not support the notion that ageing is associated with a prolonged recovery from exercise. In fact, most of the studies indicate that recovery is comparable between younger and older age groups. Most anecdotes would refute this though. But I think what needs to be distinguished here is whether exercise is perceived to be harder, or recovery is different? From my experience, older people blur the two. Also, much of the perception of recovery is based on soreness and changes in in range of motion (feeling stiff), which are poor indicators of the magnitude of damage and time course of recovery.
Unfortunately, there are only 3 studies looking at recovery between age groups in females (there are 20 in males). So we really don’t know if recovery is altered with age in females.
With running, what is different in the amount of damage done on a run between those who haven’t run much before and those who have run consistently for years?
The repeated bout effect is a phenomenon which describes a protect effect against future bouts of exercise. Essentially, if you do two bouts of running, your muscle damage will be less on the second, and you’ll recover quicker. That’s because the body undergoes a number of cellular, mechanical and neural adaptations to protect the muscle in subsequent bouts. So, those who have run more will damage less. In my opinion, the repeated bout effect is the best thing someone can do to help their recovery (over ice baths, supplements etc!).
What are the signs of damage (and should we run with DOMS)?
Associated symptoms include delayed onset muscle soreness, increases in specific intramuscular proteins (e.g. muscle-specific creatine kinase (CK), myoglobin), swelling of the affected limb, decreased range of motion and impaired muscle function. In my opinion, alterations in muscle function (e.g. strength, jump performance) provides the best marker, especially practically. It’s quite hard to measure this in practice, but new mobile technologies (e.g. MyJump) have helped.
If the muscle is damaged then its likely that you won’t be able to run as fast or for sustained efforts (e.g. high intensity intervals). It would then follow that the quality of the training stimulus would be reduced. If possible doing harder sessions when sore should be avoided. Ideally, you wouldn’t train when the muscle is damaged, but it’s almost impossible to avoid this (runners love running!). So, it’s best to opt for recovery/low-intensity runs.
How do we know if we’re recovered enough to go for another run?
If possible, recovery would be based on a combination of muscle function (e.g. strength, jump performance) and soreness. In this case here you’d take a baseline (e.g. you can jump 30cm or your muscles aren’t sore at all) and then wait till you can do this again. If you’re jumping only 25cm or your muscles are sore on movement, then you might want to opt for a low-intensity run or do some form of other training that won’t cause more damage. When you’re back to jumping 30cm or your muscles aren’t sore, then that would indicate that you’re recovered.
How do you build up your volume of running safely?
From a recovery perspective, I’d wait until the running session that are being done don’t cause excessive damage (it’s likely that running will always cause some minor damage) or your recovery is noticeably quicker. This might take 1-3 weeks, then you can increase your running volume. Another way to do this is to slowly increase running volume over the course of 4-6 weeks then include a recovery week. Acutely you need to make sure that ample time (typically 48-72 hours) is afford between harder sessions.
At the elite level some runners are covering 100 miles a week. Are they recovering quicker than the general public and/or causing less damage to themselves?
Both. To get that volume of running in they needed to be training most days/several times a day. So inevitably, they’ll need to have quick within and between day recovery. That said, to run that about of volume you’ve got to be well adapted. So certainly, they won’t be damaging as much.
Is there any evidence that recovery can be enhanced through products or supplements?
Considering muscle function and soreness as the main marker of recovery, then a lot of recovery methods don’t work. I’d argue that most of them are a marketing ploy! But some do show promising results e.g. compression garments, omega 3 fatty acids, vitamin D. But there are two important things to consider. 1) certain recovery methods blunt the inflammatory response, which can be helpful for recovery, but likely blunts adaptation. So, they could be used during competition time, but should probably be avoided out of season. 2) does your recovery really need to be enhanced? Or is planning and supporting your recovery enough (i.e. taking time between sessions, eating enough proteins and calories).
If you could give advice to runners on how to avoid injury what would it be?
Get strong would be the first one. If you develop the capacity within your tissues then they’re less likely to tear/damage and will be able to deal with the demands of running (repetitive, unilateral loading). The second is more simple; don’t over do it. Overuse injuries are such a common occurrence in running. If you build volume up slow, and strength train then you can reduce this.
To ensure you're getting enough recovery and managing your training load effectively to suit your training goals, speak to a Onetrack coach about bespoke coaching plans.
About Dr John Fernandes
Dr John Fernandes, who joined Cardiff Metropolitan University in November 2021 as a lecturer and researcher in Exercise Physiology. Prior to this, Fernandes lectured Hartpury University, and at the University of Chester whilst completing his PhD (acute strength and power responses to resistance exercise in trained middle-aged males). John’s research has focused on fatigue, muscle damage and recovery from exercise, as well as velocity-based training. During the course of his education he gained experience as strength and conditioning coach and sports scientist in a number of settings (e.g. Warrington Wolves RLFC, Welsh RU, GB rowing, Chester Hockey Club).
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