Athletes train hard. They train almost every day, often twice a day, in order to be elite..
Does this mean athletes are constantly in a state of delayed-onset muscle soreness (DOMS) or fighting off excessive inflammation to effectively adapt to training to achieve their goals? Maybe. What about an athlete’s training phase, does that play a role? For example, if an athlete is optimizing for competition versus adapting to get bigger, stronger, or faster?
What about recreational clients?
For many people, the sensation of mild to moderated delayed DOMS that creeps into your muscles 24-48 hours post-training is a sign of a good workout. You feel like you’ve trained and are making progress toward your goal. However, if it persists for more than 48 hours, if it limits your range of motion (ROM) or muscle function is it still helpful?
Exercise-induced muscle damage (EIMD) is a complex and nuanced topic.
A better question is when does exercise-induce muscle damage become so pronounced it requires specific nutrition strategies to mitigate the effects? I interviewed expert Dr. Daniel Owens PhD from Liverpool John Moore’s university to talk about his research in this area and what nutrition solutions you can turn to for evidence-based recovery support.
First, let’s define exercise-induced muscle damage.
What Is Exercise-Induced Muscle Damage?
Exercise-induced muscle damage (EIMD) is characterized by symptoms that come on directly after training and persist for 1-5 days afterwards (although potentially all the way up to 14 days post-training). That’s a pretty wide margin, what happens if you get your training plan or recovery process wrong?
For the athlete, the consequences of EIMD include is a direct effect on functional capacity (e.g. strength, range of motion, etc.), muscle soreness, muscle capacity and sense of force production and limb position.(1,2,3,4) How long and how intense these symptoms are for you depends on the intensity and duration of exercise and how your own individual susceptibility to the damaging stimulus of training.
For the athlete, loss of muscle function and increased muscle soreness likely have the greatest potential to negatively impact performance.
Can targeted nutrition strategies help to offset these effects? Could this allow you to train more frequently or more intensely, thereby increasing the likelihood of achieving your goals? Or could it actually interfere with the recovery process?
It’s a matter of balance; adequate training stress combined with sufficient recovery. Let’s take a deeper-dive into what causes exercise-induced muscle damage.
What Causes EMID?
Training of any type can cause exercise-induced muscle damage (EIMD), however there are a few types of training that may trigger greater muscle damage, such as; resistance training, prolonged or downhill running, and high-intensity interval training.(5,6,7,8)
Muscle damage is amplified during eccentric actions, particularly at longer muscle lengths, with greater forces, and faster angular velocities.(9,10,11) Interestingly, if you perform a training session with more eccentric loading, it may actually reduce the EMID in the subsequent sessions, a phenomenon known as the “rebound effect”.
What are the underlying mechanisms that cause EMID? Let’s review.
#1 Primary Muscle Damage
Experts aren’t exactly sure the principle reason why eccentric training is more damaging to the muscle, however the consensus seems to be the mechanical loading during exercise.(12) Eccentric contractions have a lower motor unit activation compared to isometric and concentric contractions (when force is equal), putting an increased mechanical stress on a smaller number of muscle fibers during eccentric movements, and thus more muscle damage.(13)
#2 Secondary Muscle Damage
After the initial primary damage of training, a secondary effect occurs when calcium moves into cells, as the mitochondria attempt to maintain homeostasis.(14) The resultant inflammatory response is a crucial and natural process that clears away damage tissue, triggers tissue repair, and ultimately adaptation.
#3 Satellite Cell Activation
Muscle fiber recovery and regeneration requires the activation of muscle stem cells called satellite cells. Satellite cells are activated post-training, specifically in response to eccentric compared to concentric contractions.(15) The research highlights that sustained activation of satellite cells provides the muscle with the capacity to adapt more effectively from training.
To sum up, impaired muscle function, increased muscle soreness, elevated inflammatory levels and activation of satellite cells all play a role in exercise-induced muscle damage.
What does all this mean for you the athlete?
Nutritional strategies to target these areas - when used in the right context – may improve recovery from exercise-induced muscle damage. Let’s review five evidence-based nutrition strategies.
Dietary Solutions for EIMD
Now you’ve understood the mechanisms underlying exercise-induced muscle damage (EIMD), you can better appreciate what nutritional interventions influence those mechanisms in order to exert a desired effect.
There is a lot of nuance when it comes to application.
You don’t want to limit or buffer the exercise-induced stress and subsequent beneficial adaptations to training. The nutritional strategies we’ll discuss impact inflammation and oxidative stress – known to be important stimuli for adaptation - so it’s important to consider why you’re using them (i.e. to cope with increased training volume and/or intensity) and when you’re using them (i.e. adaptation versus optimization phase).
The following are five potential evidence-based nutritional strategies.
Protein is crucial to muscle protein synthesis and adaptation to resistance and endurance exercise.(16) Experts can’t say for sure whether protein around intense or damaging exercise can limit EIMD, but recent evidence suggests it can improve markers of muscle damage and accelerate recovery of force.(17,18) Aim for a protein intake of 0.2-0.5g/kg/meal around exercise, with bigger athletes trending toward the upper end of the range.
#2 Tart Cherry Juice
Dietary polyphenols are most commonly found in the diet via fruit, vegetable, tea and coffee consumption. Polyphenols have shown to exert significant antioxidant and anti-inflammatory effects, possessing the ability to attenuate cyclo-oxygenase (COX) 1 and 2 output to a similar degree compared to common, over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs).(19,20)
In particular, tart cherry juice stands out from the pack when it comes to recovery.
Research in resistance training using heavy eccentric bicep curls combined with two servings of tart cherry juice per day found an accelerated rate of recovery and reduced muscles soreness.(21)
A key benefit to using a “food first” approach to performance nutrition is that it’s unlikely to interfere with the primary muscle damage response from exercise and thus not limit positive adaptation to training (compared to supra-physiological doses in supplements). Where functional foods like cherry juice can exert its effect is during the secondary phase, when inflammation and oxidative stress ramp up post-training.
Omega-3 polyunsaturated fats, specifically eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA), are important nutrients that exert anti-inflammatory effects. Omega-3 fats like EPA and DHA are found in highest abundance in cold, deep-water fatty fish (e.g. salmon, mackerel, anchovies, sardines, herring, etc.), seafood (e.g. oysters, mussels, etc.), grass-fed beef and nuts like macadamia and walnuts
Numerous studies have shown beneficial effects of omega-3 on inflammation, oxidative stress, and muscle function after intense exercise.(22,23,24,25)
Interestingly, there appears to be a “loading phase” of approximately two weeks to see changes in muscle omega-3 composition. A recent study found a highly effective loading protocol to be 5g/day dose of fish oil capsules (providing 3,500mg EPA and 900mg DHA), however this is much higher than the current recommendations.(26) Typically, a dose of 1,000-1,500mg (combined EPA/DHA) is suggested in athletes, however more research is needed in this area to confirm an ideal dose.
#4 Vitamin D
Vitamin D isn’t really a vitamin. In truth, it’s a seco-steroid hormone acquired by the body through exposure to the sun (e.g. ultraviolet B radiation or UVB). Sedentary lifestyles in the general population and athletes training indoors (or even outdoors in sun-shy athletes wearing skin covering apparel) has led to a large of number of athletes and active people being diagnose with deficient (< 30 nmol/L 25[OH]D) or insufficient levels of vitamin D.
In the last decade, new technology has allowed for discoveries of the important effects of vitamin D on muscle function and performance.
Vitamin D is a potent regulator of the immune system and has shown to exert potentially important effects on athletic recovery; anti-inflammatory response post-exercise was found to correlate with the individual’s vitamin D levels, runners with low vitamin D exhibited increase inflammatory responses post-exercise, and athletes performing eccentric-concentric jumps on a plyo-press displayed faster recovery at higher vitamin D status.(27,28)
Creatine is keystone supplement in many athlete’s nutritional arsenal. However, many are unaware of the impacts of creatine on recovery. Creatine has shown beneficial effects on satellite cell number and muscle function post-training.(29)
The Bottom Line
Exercise-induced muscle damage is an important and natural phenomenon that triggers the positive and beneficial adaptations to exercise. In the general population, training stimulus and volume is unlikely to require additional recovery support beyond the nutrition fundamentals of adequate protein, omega-3 and vitamin D intake are likely all you need to support your training goals.
In athletes, the stakes are much higher. Greater training volume and intensity, as well as two-a-day (sometimes three-a-day training in MMA athletes!) increases the need for the application of functional food strategies to support quicker recovery.
As always, think about the type, timing, and total amount of the supplement, functional food, or nutritional strategy you’re implementing with clients and athletes.
(Now get back to your training!)
Dr. Marc Bubbs ND, CISSN, CSCS
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