Exercise-induced muscle damage: the what, why, and how not

Exercise induced muscle damage results in muscle soreness and a temporary loss of muscle function. Which nutritional interventions can accelerate recovery of muscle function and ameliorate soreness?

We've all been there. Soreness across the chest after the first heavy bench session in a while. Feeling it in the quads after a squat session.Exercise-induced Muscle damage (EIMD) is one of the reasons behind these symptoms, that can occur any time from immediately-post, up to ∼14 days after the initial exercise bout. The magnitude and time course of these symptoms and their subsequent impact on performance are variable and depend on the intensity and duration of the damaging exercise and the individual’s susceptibility to the damaging stimulus.

When we perform eccentric muscle actions, this typically produces greater structural muscular damage and DOMS, it can cause mild swelling of the trained limb, a decreased range of motion and impair how much muscle force we can produce (1). This can all occur during different types of training and exercise: resistance training , prolonged running, downhill running , and intermittent, high intensity exercise. As we adapt to training, we become protected to this damage from similar bouts of training in the near future.

Many nutrients and functional foods have been examined for their potential to ameliorate exercise-induced muscle damage but not all have been shown to be effective.

The EIMD associated losses in muscle function and increases in muscle soreness are not always welcome given their potential to impair performance. When we want to make sure we can train or compete at the highest level in the days following a damaging bout of exercise, we may want to limit EIMD. As such, we can look to sports nutrition strategies to maximize the recovery from exercise and prepare for the next exercise bout.

Nutrition to help exercise-induced muscle damage

Protein

Dietary protein intake is undoubtedly a crucial factor in regulating muscle protein turnover, particularly when we exercise. In fact, we get greater adaptations to both resistance and endurance-type exercise are enhanced when protein is fed around the exercise bout (2). Whether protein intake around intense/damaging exercise can reduce the symptoms muscle damage is less clear. While some evidence suggests protein or free amino acids fed around exercise can reduce markers of muscle damage and accelerate recovery of force (3), others have not found comparable effects (4).

However, difference in study design and the amount or type of protein used in studies may explain some of the differences seen. What we know is that protein is important for adaptation of skeletal muscle after any form of exercise, and should never be compromised in the diet. What is still unclear is whether supplementing with protein after EIMD accelerates recovery.

What we know is that protein is important for adaptation of skeletal muscle after any form of exercise, and should never be compromised in the diet.

Omega 3 fatty acids

Omega-3 polyunsaturated fatty acids, specifically  eicosapentaenoic acid (EPA) and docasahexaenoic acid (DHA) are a group of nutrients that possess anti-inflammatory properties. They occur in natural abundance in nuts and oily fish like salmon, mackerel and tuna. Studies have now began to examine the effects of omega-3 fatty acids on muscle function, inflammation and oxidative stress induced by damaging exercise. For the most part, these have shown a positive effect (5, 6) in reducing some of these symptoms or markers of EIMD.

What is important to take away from these studies is that they used a loading phase (from a few days all the way up to a month) not just a one off dose. Taken collectively these studies support the efficacy of n-3 PUFA as a promising intervention to manage EIMD.

Vitamin D

Data suggest vitamin D may be important in the repair process after muscle damage. In one of the first studies to lool at this effect, after 10 sets of 10 repetitive eccentric-concentric jumps, individuals with higher circulating 25[OH]D, the main marker of vitamin D status, demonstrated a faster recovery of maximal force in the recovery phase after exercise (7).

Supplementing 4,000 IU/day vitamin D has also shown to accelerate recovery of maximal force after eccentric exercise compared to a placebo control group (8). With regards to muscle soreness, pain receptors express the vitamin D receptor (VDR) making them a potential vitamin D target. Vitamin D deficiency may lead to possible pain receptor hypersensitivity and pain (9).

Functional foods

An emerging area of research is that of foods that have the potential to exert a positive physiological effect that is related to improved or preserved human health and disease prevention. For example, foods high in polyphenols (micronutrients that we get through certain plant-based foods) have begun to be put to the test in terms of exercise performance and recovery.

Polyphenol enriched foods such as tea, coffee, grapes, cocoa, nuts, blueberries, cherries, and pomegranates. For example, a recent review found that the majority of studies to date have found positive effects of Montmorency cherries on reductions in EIMD and faster recovery from intense exercise (10). From a mechanistic perspective, how polyphenols exert their effects is unclear. However, this is an area to keep an eye on.

Food for thought - can nutrition help reduce symptoms of exercise-induced muscle damage?

  • Dietary protein is important to help maximise our adaptation to exercise but it is unclear whether it helps with EIMD
  • Omega-3 fatty acids have been shown to reduce inflammation, oxidative stress, and soreness following damaging exercise
  • Vitamin D has been shown to accelerate recovery of muscle function following eccentric exercise
  • Functional foods, particularly those high in polyphenols are being investigated more and more for their role in exercise performance and recovery
weight training

More harm than good?

The long-term use of recovery strategies on adaptation to training and athletic development is an area of interest. But it is also one of concern. What has been seen in some instances is that interventions reducing the exercise-induced stress response can also reduce the adaptive potential. In trying to recover quicker, are we sometimes blunting adaptation? For example, vitamin C and vitamin E modulate oxidative stress which is known to be important in the adaptive response to an exercise stimulus. High dose supplements of both of these vitamins have been shown to worsen training outcomes following a period of intensive training (10).

What we need to consider is what the aim of our training and nutrition is. If we are looking to train or compete intensely, multiple times over a short period of time, we want to recover as quickly as possible. If we have enough time to recover between exercise bouts, we might think twice before throwing all modes of recovery at and into our body. With pragmatism in mind, a balanced diet that is rich in fruits and vegetables is always necessary. Similarly for adequate protein. We want to avoid deficiencies of key nutrients such as vitamin D. When we need it, there are then nutritional strategies that we can turn to when we want to recover as quickly as possible.

References

1 - Hyldahl, R. D., & Hubal, M. J. (2014). Lengthening our perspective: Morphological, cellular, and molecular responses to eccentric exerciseMuscle & Nerve49(2), 155170.

 2 - Phillips, S. M., & Van Loon, L. J. C. (2011). Dietary protein for athletes: From requirements to optimum adaptationJournal of Sports Sciences29(Suppl 1), S29S38.

3 - Cockburn, E.Stevenson, E.Hayes, P. R.Robson-Ansley, P., & Howatson, G. (2010). Effect of milk-based carbohydrate-protein supplement timing on the attenuation of exercise-induced muscle damageApplied Physiology, Nutrition, and Metabolism35(3), 270277

4 - Blacker, S. D.Williams, N. C.Fallowfield, J. L.Bilzon, J. L. J., & Willems, M. E. T. (2010). Carbohydrate vs protein supplementation for recovery of neuromuscular function following prolonged load carriageJournal of the International Society of Sports Nutrition72

5 - Jouris, K. B.McDaniel, J. L., & Weiss, E. P. (2011). The effect of omega-3 fatty acid supplementation on the inflammatory response to eccentric strength exerciseJournal of Sports Science & Medicine10(3), 432438.

6 - Marques, C. G.Santos, V. C.Levada-Pires, A. C.Jacintho, T. M.Gorjão, R.Pithon-Curi, T. C., & Cury-Boaventura, M. F. (2015). Effects of DHA-rich fish oil supplementation on the lipid profile, markers of muscle damage, and neutrophil function in wheelchair basketball athletes before and after acute exerciseApplied Physiology, Nutrition, and Metabolism40(6), 596604.

7 -Barker, T.Schneider, E. D.Dixon, B. M.Henriksen, V. T., & Weaver, L. K. (2013). Supplemental vitamin D enhances the recovery in peak isometric force shortly after intense exerciseNutrition and Metabolism10(1), 69.

8 - Owens, D. J.Sharples, A. P.Polydorou, I.Alwan, N.Donovan, T.Tang, J., … Close, G. L. (2015). A systems-based investigation into vitamin D and skeletal muscle repair, regeneration, and hypertrophyAmerican Journal of Physiology-Endocrinology and Metabolism309(12), E1019E1031.

9 - Tague, S. E.Clarke, G. L.Winter, M. K.McCarson, K. E.Wright, D. E., & Smith, P. G. (2011). Vitamin D deficiency promotes skeletal muscle hypersensitivity and sensory hyperinnervationJournal of Neuroscience31(39), 1372813738.