Exercise recovery: the role of protein in post-workout muscle soreness and damage

It is something that all regular and not-so-regular exercisers have experienced: muscle pain and soreness in the days following a particularly hard training session. It is the price paid for the benefits exercise, especially resistance training, can have on growing muscle mass and strength, stability, glucose tolerance and bone density. The list of ways that people deal with exercise-induced muscle soreness is long, but in this podcast, I’ll explore one aspect. And that’s how protein helps with the recovery process and how it can be doing you good even if the aches and pains don’t feel any less.

Links referred to in the podcast

• Meta-analysis on the effect of protein supplementation on exercise-induced muscle damage https://www.nature.com/articles/s41430-022-01250-y
• Review of protein timing https://jissn.biomedcentral.com/articles/10.1186/1550-2783-10-5

Episode transcript
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Transcript

It is something that all regular and not-so-regular exercisers have experienced: muscle pain and soreness in the days following a particularly hard training session. It is the price paid for the benefits exercise, especially resistance training, can have on growing muscle mass and strength, stability, glucose tolerance and bone density. The list of ways that people deal with exercise-induced muscle soreness is long, but in this podcast, I’ll explore one aspect. And that’s how protein helps with the recovery process and how it can be doing you good even if the aches and pains don’t feel any less.

A small amount of muscle pain and soreness after exercise (that isn’t related to an injury of course) is a good thing as it is a stimulus for the body to repair, adapt and grow stronger. And while that soreness means your body is giving you feedback that the last training session definitely was doing you some good, it can go too far if that pain persists for several days which may delay exercise recovery and limit future exercise quality.

Some estimates put acute muscle soreness and swelling as able to reduce muscle force-generating capacity by half, which can persist for several days. This is a more extreme case as regular training sees a reduction in this damage. Although it can be an arms race where a dedicated resistance training program would see progressive increases in exercise load, repetition range, or volume, thus imposing new exercise stimuli and susceptibility to muscle damage and soreness. And even mild symptoms of muscle soreness and weakness could diminish a person’s motivation to exercise and reduce the frequency and/or quality of exercise sessions.

So, what to do about it? And no, not getting off the couch in the first place isn’t the answer here. The strategies to help address muscle soreness and damage after training would keep me in business for months on end doing podcast after podcast on each of them, with most approaches lacking clear evidence that they will help.

Massage, stretching, foam rollers, compression garments, electrostimulation, ice water baths, and anti-inflammatory medications all feature. I’m even starting to see interest in flotation tanks to help with recovery. Then there are the nutritional ones that can have a food or supplement focus. Antioxidants, fish oil, curcumin, fluid, carbohydrate refuelling and the list goes on. And then of course there is the benefit of rest and a good night’s sleep in helping the body do what it needs to do – that one certainly will help with recovery at least.

But one that deserves a special focus is protein. It would have to be the number one nutrient at the forefront of the mind of athletes, especially those with a resistance and strength training focus. Without adequate protein, it will affect the gym gainz. So that’s why sportspeople have higher protein recommendations with numbers from 1.6 up to about 2 grams per kilogram body weight often quoted.

One important role of that extra protein is helping to repair damaged muscle. So could getting plenty of protein in the pre and post-exercise period help in reducing muscle damage and soreness? Despite extensive research, the evidence for peri-exercise protein supplementation (that is consuming protein in the pre, during and post-exercise period) in reducing exercise-induced muscle damage is quite mixed. The variety of exercise protocols, protein dosing and timing regimes, participant characteristics, dietary controls, and measurement tools employed all likely contribute to the diverse findings.

So, now we have an attempt to characterise this mixed bag of research into one study by way of a meta-analysis. This was a review of 40 clinical trials where supplemental protein was consumed before or after exercise. Whey protein was the most common protein source used, either alone or combined with carbohydrates. But other protein sources were also consumed and these included soy, egg, pea, casein, and collagen protein.

To measure how supplemental protein could aid recovery from exercise-induced muscle damage, the participants perform a maximal voluntary contraction under isokinetic (meaning constant speed) and isometric (meaning constant muscle length) conditions. Isometric testing involves measuring the force that a muscle can generate against an immovable object, such as a wall or a force plate. While isokinetic testing involves measuring the force that a muscle can generate while it moves at a constant velocity through a range of motion. Isometric and isokinetic tests of muscle function are considered the most valid and reliable tests for assessing exercise-induced muscle damage. These tests were performed 24, 48, 72, and 96 hours after resistance training.

The researchers also looked at the effect of supplemental protein on creatine kinase levels which is a blood marker related to exercise-induced muscle damage and where higher levels indicate more muscle damage. On top of all that, participants gave subjective ratings of their muscle soreness. And I’ll link to the study in the show notes. https://www.nature.com/articles/s41430-022-01250-y

So what did they find? Taking on additional protein before or after exercise saw less impact of the determinantal effect of exercise on maximal voluntary contraction under isometric conditions at 96 hours. And for isokinetic conditions, benefits were seen of the protein supplementation at 24, 48, and 72 hours after resistance training. So that’s good news for the functional effect of protein on reducing muscle damage in that the muscle can bounce back quickly to its pre-exercise potential. And to validate this, there was also less creatine kinase measured in the blood after 48 and 72 hours under conditions of protein supplementation. The effect size, which is a measure of the real-world effect of protein supplementation, was rated as moderate to large so we’re talking about meaningful results here.

Yet despite all this, supplemental protein did not improve people’s subjective ratings of muscle soreness after resistance exercise at any time point. So people were still feeling the burn for some days after exercise despite evidence their muscles had recovered well from the damage.

As with any review that combines a bunch of studies, there were issues. As with most of the exercise science literature, research is severely overly biased towards male participants with few women in the studies. And there is a clear difference between males and females with anything to do with muscle function which is further impacted by hormonal effects. And most of the studies used young people so it is unclear how the results may apply to older exercises.

Another limitation is that the control group in each of the studies were not always the same as some of the studies don’t replace the protein with a similar amount of energy from a non-protein source. Half of the studies were in trained individuals and the other half in untrained individuals, but the review didn’t discuss if there was a difference in outcomes between these groups.

So my take on all this is that firstly, there is already strong support for the role of additional protein in athletes and recreationally active individuals. And this research supports the benefits of that protein on muscle repair and recovery after exercise, and by extrapolation, longer-term muscle growth and adaptation. It’s just that the extra protein you’re taking on around the exercise period may not do much to help with your perception of muscle soreness which is the price of entry for those muscle gainz.

This all now leads me to the final part of the podcast and that’s to do with the timing and dose aspect of protein supplementation. Optimal muscle growth and recovery are more than just about meeting daily protein needs. And this is where the concept of protein timing around exercise has some credence. Each time protein is consumed there is a small spike in muscle synthesis with a ‘dose’ of just 20-25 g of high-quality protein sufficient to stimulate muscle protein synthesis following resistance exercise. Having these protein ‘doses’ spread throughout the day can help to maximise exercise-induced muscular growth and aid the repair of damaged tissue. Eating quantities of protein above this 20-25 g range in one sitting offers only a limited additional benefit with a very minor 10 percent further protein synthesis when the amount is doubled to 40 g.

However, despite the common recommendation to consume protein as soon as possible post-exercise, evidence-based support for this practice is currently lacking. That doesn’t mean that it shouldn’t be done, only that it shouldn’t be treated as Gospel despite what the bros at the gym may tell you.

How long the mythical ‘post-exercise muscle anabolism’ window remains open for is hotly debated, but it likely exists for several hours. So, fear not gym goers, your muscle gains aren’t going to shrivel away because you didn’t chug down your protein shake within five minutes of your last set of bench presses. There was a nice commentary paper on the topic of protein timing published in 2013 which I’ll link to in the show notes. https://jissn.biomedcentral.com/articles/10.1186/1550-2783-10-5

So, let’s wrap all this up. Combining all the protein timing research together leads to the conclusion that the body likely responds best to regular small ‘doses’ of protein throughout the day. I like to call this new muscle growth and recovery optimisation protocol “regular meals and snacks with a focus on higher-protein foods”. Others may just call it eating.

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.