When you train intensely with weights, you’re incurring injury to your muscles. It sounds bad, but the body compensates by adding an extra layer of protection to muscles to minimize or prevent further injury—muscular hypertrophy, or growth.
Through a complex interplay involving increased muscle protein synthesis and a short-term immune response, individual muscle fibers thicken, which we recognize as growth. Even so, there is a specific process that occurs in muscle following training, and timing is an important part of it.
For example, while protein synthesis is increased up to 48 hours after intense training, the major impetus for that occurs within two hours after a workout due to heightened enzymatic and hormonal activity. Hence, the “anabolic window,” in which it’s suggested that you take in essential amino acids as soon as possible after training to fuel protein synthesis.
Before the protein-production process can go into full gear, however, the immune system must intercede. It does that via cells such as macrophages, which clear out debris left over in muscle by the imposed injury of exercise. In addition, the macrophages and other immune cells secrete cytokines, which are signaling factors that, among other functions, stimulate the activity of muscle-stem cells called satellite cells that are directly involved in the repair-and-growth process.
The immune infiltration of muscle after training produces an inflammatory effect that triggers a muscular response. A problem occurs if trainees take anti-inflammatory drugs, such as ibuprofen, too soon after training because it blocks the usual postworkout inflammation along with the growth response. In short, a temporary level of muscle inflammation following training is vital for muscle growth to occur. The key word here is temporary, since, if extended, the inflammation phase of muscle repair can, paradoxically, impede full recovery. The ideal scenario is a short period of muscle inflammation after training followed by an accelerated recovery and repair process.
Some interesting recent research shows that you can optimize the muscle-recovery process through nutrition. One way is to take in essential amino acids as soon as possible after training. Another is to eat certain foods and supplements. One study compared two sources of protein, peanuts and cod, for their ability to promote more efficient muscle repair after injury.1 Although the subjects were rats, the effects are applicable to humans.
The researchers noted that previous studies have found that the amino acid arginine seems to help heal injuries and accelerate muscle repair. The likely mechanism relates to the fact that arginine is the immediate precursor of nitric oxide synthesis in the body, and NO is an established stimulant of healing and tissue repair.
The rats were placed in groups, with one group eating the milk protein casein and peanut protein. Other rats got protein derived from cod fish. After 21 days the rats’ legs were injected with either a substance that causes muscle injury or a salt solution. The peanut protein was slightly more efficient at maintaining muscle mass than the casein, but it did not trigger any additional gains.
In contrast, the cod protein proved superior to casein in promoting muscle mass gains and healing injured muscle quickly. More important, the cod protein proved most efficient in curtailing excessive inflammation in the muscle by modifying the immune cells’ activity. That helped significantly boost muscle recovery in the rats better than the combined peanut and casein proteins.
The peanut protein didn’t trigger muscle growth because of its relative lack of essential amino acids, especially when compared to cod. Excess inflammation delays muscle healing because the immune cells release large amounts of free radicals. While that is normally efficient for killing invading bacteria, when excessively released in damaged muscle, free radicals increase the damage by attacking muscle cell membranes, leading to the death of the muscle cell. Cod intercedes by speeding the clearing out of immune cells, which lowers inflammation and allows full muscle recovery to proceed.
The cod also proved superior to casein by 11 percent in promoting muscle fiber size. That was thought to be due to the reduction of inflammatory cytokines discussed above. While recent studies show that fish oil can both reduce excess muscle breakdown and help promote muscle protein synthesis, fish oil didn’t play a role in this study, as the oil had all been removed from the cod used. So what does explain the beneficial effects of cod that it shows?
The authors suggest two possible mechanisms. The first involves an upgrade in the activity of insulinlike growth factor 1 in the rats’ muscle triggered by their eating cod. IGF-1 in muscle is a major factor in muscle repair and growth after injury and exercise. Other studies have shown that when rats are fed casein or soy but also allowed to eat high-fat diets, the IGF-1 repair system is impaired. The lack of fat in the cod may have served to maximize the IGF-1 activity.
The other mechanism suggested by the researchers was that cod is rich in the amino acids arginine, glycine and taurine, all of which are potent natural anti-inflammatory compounds. Arginine, by enhancing nitric oxide release, would speed healing of wounds and reduce inflammatory cell accumulation. Glycine also provides anti-inflammatory activity in muscle by reducing the inflammatory cytokines released by immune cells. Taurine helps by acting as an antioxidant in muscle, which reduces free radical–induced damage to muscle cells and prevents their premature destruction. Cod’s high content of essential amino acids also encourages more muscle protein synthesis along with less muscle breakdown.
Another study, also involving rats, tested the effects of grape-seed extract on muscle recovery.2 The rats’ gastrocnemius muscles were purposely injured, with only some of the rats getting grape-seed extract two weeks prior to being injured.
The results showed that rats given the grape-seed extract had less immune cell infiltration in the injured muscle plus a shorter release time of inflammatory cytokines. Muscle fiber regeneration began earlier in the grape-seed-extract rats and was completed more rapidly. The injured muscles healed more rapidly because the grape-seen extract, by decreasing the excess inflammation, boosted the activity of muscle satellite repair cells.
Finally, those who want to recover more rapidly from intense training should take the advice of their mothers: Eat more greens. The wisdom of those words was shown in a recent study in which 10 healthy men, average age 23, ate 85 grams of watercress, a leafy green vegetable, for eight weeks prior to engaging in intense treadmill exercise.3 As a control, the men also didn’t eat the watercress during a different eight-week period.
The results showed that the subjects who exercised intensely but didn’t eat the watercress had more DNA cell damage than those who got the watercress. Some of the men didn’t eat watercress for eight weeks but ate it only two hours prior to the exercise—and they showed the same level of protection against DNA damage. So the protective effect of eating watercress, which is likely the result of natural antioxidants found in it, isn’t accumulative but works immediately. —Jerry Brainum
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1 Dort, J., et al. (2012). Beneficial effects of cod protein on skeletal muscle repair following injury. Appl Physiol Nutr. 37:489-98.
2 Myburgh, K.H., et al. (2012). Accelerated skeletal muscle recovery after in vivo polyphenol administration. Nutr Biochem. 23(9):1072–1079.
3 Fogarty, M.C., et al. (2013). Acute and chronic watercress supplementation attenuates exercise-induced peripheral mononuclear cell DNA damage and lipid peroxidation. Br J Nut. 9(2):293-301.