Skeletal muscle strain unloading during injury, illness or hospitalization occurs relatively frequently in athletes and the elderly, which has serious consequences for muscle mass loss and musculoskeletal health.

For example, 5-7 days of bed rest has been shown to induce muscle atrophy and a state of anabolic endurance in older individuals (Drummond et al., 2012), however, what is not clear is whether there is a decrease in cardiorespiratory fitness as this recent Meta-analysis shows.

How to avoid losing muscle mass during injury, disuse or immobilization
Some supplements such as HMB, are proposed as activators of protein synthesis, proliferation of satellite cells, but above all, where HMB looks stronger is as an inhibitor of protein degradation, so in situations where protein catabolism and muscle atrophy prevail or are increased, such as immobilization due to injury or illness, HMB can help delay or even reverse this loss of muscle mass, as this study shows.

I am not talking about strategies for recovery from the injury itself, but about the loss of muscle mass that accompanies the injury due to immobilization and/or reduced activity, which in middle-aged people can be up to 1 kg of muscle mass loss in just 10-15 days of immobilization and even in older people can be up to 1 kg of muscle mass loss in 3 days of hospitalization, although of course it depends not only on age but also on the metabolic and pathological context of the subject.

I have already written several times about HMB and I have emphasized the reasons why this supplement works especially in subjects where there is great muscle damage or muscle degradation, which leads to muscle atrophy.

And although in trained subjects, in general terms, HMB does not seem to produce substantial improvements, it does seem that in such conditions of injury, immobilization, bed rest, illness or in elderly subjects where situations of muscular catabolism prevail, HMB could provide some help for the preservation of muscle mass.

However, and I want to emphasize that this is a personal opinion not based on evidence, but on what I know about the subject, as we know, in only 5-7 days approximately of immobilization there is what we know as anabolic resistance, decreasing muscle protein synthesis (MPS), but we have to know, that contrary to what it may seem and what many people think, catabolism or protein degradation (MPB) in conditions of bed rest and/or immobilization is not the main cause of this atrophy and loss of muscle mass, since according to numerous studies, MPB is only increased in the early phase of immobilization and after approximately 3-4 days it returns to its basal level. What I mean is that in injuries or immobilizations, what really leads to muscle degradation and atrophy is not so much an increase in MPB, but a drastic decrease in MPS, since to exercise a positive net balance in terms of MPS-MPB, who really “rules” is the MPS (Baehr et al., 2016).

And why do I say this? Because although as I said, HMB can stimulate MPS, where it takes center stage above all is in a decrease in MPB, but I have already commented that it is not so much an increase in MPB, but a decrease in MPS, so although it is clear that HMB can help, sometimes I notice that sometimes it seems to recommend such a supplement in certain injuries, hospitalizations or immobilizations, but no doubt, what would really help us (among other interventions) is to ensure adequate protein intake, both in quantity and quality, with an adequate supply of leucine for optimal signaling of the MPS, (although this is secondary to the quantity and even with high amounts of vegetable protein high levels of leucine is achieved and this would give for another post) and secondly a correct distribution throughout the day. Even, and due to disease-induced anorexia which makes us decrease our appetite in injuries and diseases, we can opt for supplementation with some type of protein such as Whey Protein, which in my opinion will help much more than HMB or glutamine alone to prevent the loss of muscle mass, not only for its leucine content, but for containing the rest of essential amino acids.

*Even so, glutamine, in these conditions, can improve from other perspectives, since it should be known that glutamine helps leucine absorption, to decrease protein degradation because it is an important source as an energy substrate of the activated immune system and could also improve the intestinal function of the enterocyte, but this would give for another post that I will write later in the Premium Zone, as it would have to be nuanced and analyzed in detail.

This study on HMB, concludes that in 10 days of hospitalization in older adults, HMB helped preserve muscle mass, something we already know. It also concludes that HMB improved mitochondrial dynamics during disuse-induced atrophy, which obviously improves the outcome. Well, however, we have to know, that already in 1991 , Kondo et al. and many other authors such as Powers et al, years later proved that prolonged inactivity of skeletal muscle during immobilization, bed rest and so on, resulted in chronic increases in ROS production and this leads to oxidative damage in inactive muscle fibers, i.e., paradoxically, the mitochondria of muscle cells produce more ROS at rest than during physical exercise, which leads to an increase in oxidative stress in situations of injury, immobilization and so on, and this in turn by various mechanisms (I will not explain the mechanisms so as not to lengthen and hinder the understanding of the text) will lead to an increase in muscle degradation and a decrease in protein synthesis that will ultimately lead to muscle loss and atrophy. This is the main reason why supplementation with antioxidants is usually recommended when there are injuries in athletes, long-lasting immobilizations and so on, apart from other reasons such as vitamin C, which is not only antioxidant but also important for collagen synthesis, especially when there are tendon injuries, but both concepts are very long and nuanced, as well as individual.
Well, to form glutathione, a powerful endogenous antioxidant that limits the action of ROS, 3 amino acids are needed (cysteine, glutamate and glycine) and normally the limiting amino acid, i.e. the one that is usually missing is cysteine because it is less abundant in the diet. Whey Protein is rich in cysteine+glutamate, and this peptide is better absorbed. Therefore, whey protein can exert antioxidant actions and in situations where there is an increase in oxidative stress, such as in immobilization or bed rest as I have mentioned, it will help to reduce oxidative stress and therefore, among other things, to limit the loss and atrophy of muscle mass.

Increasing total protein should be a priority.
So, in my opinion, apart from first things first, and starting from an adequate general nutritional intervention based on real food (total calories, macronutrients and micronutrients, etc.), increasing total protein should be a priority, something that is rarely done in hospitals.

Moreover, this need is further increased in the elderly or in subjects with metabolic pathologies or diseases, as well as during long periods of hospitalization where muscle mass is compromised, with experts recommending between 1.4 and 2.2 g / kg body mass in these situations, depending on the severity of the disease and degree of malnutrition and the context/profile of the person. (Bauer et al., 2013) and if there is any supplement that should gain importance, especially due to possible disease-induced anorexia, it is Whey Protein, although others can also help but in the background.

In another post I will discuss whether using Omega 3 (DHA/EPA) supplementation in injury or immobilization is shown to be an effective aid or not and why this is the case and I will comment on the role of vitamin D and creatine among others also in all of this… I will also discuss how macros and total calories need to be adjusted when injured or immobilized to recover from injury efficiently and also not lose muscle mass.

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