The inflammatory reaction: from acute to chronic stage

Article written by Antoine FRECHAUD and Nathan Touati, publishing directors at NeuroXtrain

Introduction

Skeletal muscle injuries, and particularly mechanical damage such as contusions, occur frequently in contact sports, as well as in sports of an accidental nature, such as BMX or horse riding. Wide variations in injury severity and affected muscle group, as well as non-specificity of reported symptoms, complicate research to find appropriate treatments. Therefore, in order to increase the chances of finding an effective treatment, it is important to understand the underlying mechanisms inherent to this type of skeletal muscle injury and the cellular processes involved in muscle healing following contusion.

Understanding inflammation

Perhaps the most important of these processes is inflammation, as it is a constant and long-lasting response. The inflammatory response depends on two factors, namely the extent of the actual physical damage and the degree of tissue vascularization at the time of injury. However, short- or long-term anti-inflammatory treatment is not necessarily effective in promoting healing, as indicated by various studies on treatment with non-steroidal anti-inflammatory drugs.

The early recovery phase is characterized by the overlap of inflammatory processes and the appearance of secondary damage. Although neutrophil infiltration has been cited as contributing to the latter phenomenon, no clear evidence exists to support this claim. Macrophages, although part of the inflammatory response, have been shown to play a role in healing rather than exacerbating secondary damage. Several probable roles of this cell type in the second phase of recovery, involving resolution processes, have been identified and include the following: (1) phagocytosis to remove cellular debris, (2) switching from a pro-phenotype to an anti-inflammatory phenotype in muscle regeneration, (3) preventing muscle cells from undergoing apoptosis, (4) releasing factors to promote activation and growth of muscle precursor cells, and (5) secretion of cytokines and growth factors to facilitate the repair of vascular and muscle fibers. These many different roles suggest that a single treatment with a specific target cell population, e.g. neutrophils, macrophages or satellite cells, may not be equally effective in all phases of the post-injury response.

Finding optimal but time-dependent targeted treatments requires further investigation. However, the techniques currently used to induce mechanical injury vary widely in terms of invasiveness, tools used to induce injury, muscle group selected for injury, and contractile state of the muscle, all of which influence the immune and/or cytokine responses. This makes interpretation of complex responses more difficult. 

Therefore, it may be premature to study highly targeted therapies, which may ultimately prove more effective in reducing athletes' recovery time than current therapies that are not phase specific or are not not administered in a phase-specific manner.

Inflammation management

Over the years, there has been a significant evolution in the approach to managing inflammation and injury, particularly in the first few days following a traumatic incident. Initially, the RICE protocol: Rest, Ice, Compression, Elevation, was the gold standard, aimed at minimizing inflammation and promoting healing. This method was then refined into the PRICE protocol: Protection, Rest, Ice, Compression, Elevation, emphasizing the importance of protecting the injured area and incorporating rest as a key element. Through research over the years and a deeper understanding of the body's response to injury, the approach has shifted to POLICE Protection, Optimal Loading, Ice, Compression, Elevation. This protocol highlights the role of optimal loading in the early stages of recovery replacing complete rest, with the body having adaptive responses to mechanical loading via mechanotransduction favoring regeneration more than rest. 

In the contemporary landscape, a paradigm shift has occurred with the introduction of the PEACE & LOVE protocol. This innovative approach prioritizes a different perspective: 

PEACE: Protect, Elevate, Avoid Anti-Inflammatory Modalities, Compress and Educate, focuses on minimizing further damage and creating an environment conducive to healing, while LOVE: Optimal Load, Optimism, Vascularization, Exercise, emphasizes the importance of controlled movements, a positive mindset, improved blood circulation and targeted exercises to aid recovery. 

By adopting PEACE & LOVE, the management of inflammation and injury on the first day after the incident has become more holistic, incorporating a balance between protection and activity, thereby optimizing the healing process and improving overall patient outcomes.

In the PEACE protocol we focus on this management of inflammation and a new paradigm is emphasized with “Avoid anti-inflammatory modalities”. As seen in the introduction to this article with the 5 points of the inflammatory response, we were able to see that it is a complex response created by the body which allows healing. It is not useless and just there to slow us down in healing, quite the opposite. 

This response is crucial for healing but when a trauma is too severe, this inflammatory response will be too strong in the acute setting, so we end up with excessive edema and hematoma, even incapacitating. We must therefore not cut off this inflammation completely but control it. 

How to control inflammation?

As seen in the PEACE & LOVE protocol, the acronym PEACE will direct us towards methods of Protection of the injured limb, Compression, methods of controlling inflammation without medication, elevation and education. 

The simplest method for controlling inflammation will be the application of cold locally. Coupling this cold application with compression will be the solution of choice. 

This is why Orthonov developed the kits Excell’ICE, an innovation which combines cryotherapy with adjustable static compression using an inflation pump. Its use is simple, involving recovery and rehabilitation sessions with sessions combining cold and compression, a practice often recommended in the days following an injury or after an operation. It is well established that external application of static compression associated with ice amplifies skin cooling.

Orthonov offers a wide selection of cryotherapy kits and sports recovery equipment, encompassing areas from feet to shoulders. Regardless of the musculoskeletal area affected, a specific solution is available to relieve athletes and help them regain their optimal performance. As a partner of national federations, clubs and many athletes, Orthonov attaches particular importance to the manufacturing of its products in France.

Then, elevating the injured limb and protecting it in the first few days is going to be a simple way to reduce this inflammation without completely cutting it off. 

Education will focus on the fact that therapists have a duty to educate patients about the benefits of an active approach to their recovery. Passive interventions such as electrotherapy, manual therapy or acupuncture, applied soon after an injury, have minimal impact on pain and function compared to an active approach. Moreover, they may even prove counterproductive in the long term. Indeed, maintaining a dependence on external control or the feeling of “needing to be fixed” can encourage therapy-dependent behavior. Better understanding of the condition and burden management can prevent overtreatment, reducing the risk of unnecessary interventions like injections or surgery. This contributes to lower health care costs.

Are there other solutions? 

The importance of dietetics in developing a personalized nutritional program cannot be underestimated, taking into account the individual needs and preferences of the athlete, and in accordance with the nutritional guidelines in force during the recovery phase.

Several strategies applied during rehabilitation integrate nutritional elements aimed at optimizing the physiological response and accelerating the return to sporting activity. These procedures can be particularly demanding, especially in the early stages of muscle disuse, where the extent of muscle loss significantly influences the duration of this phase. Thus, preserving muscle mass without fat accumulation becomes a major challenge for the injured athlete.

Adequate protein intake is of crucial importance, as it is linked to maintaining muscle mass and strength, while providing protection against fat accumulation. It is essential to adapt the dietary strategy to the specific needs of the athlete, taking into account the quantities, frequency, type and above all the quality of proteins. Similar approaches can be used in the injured athlete to stimulate muscle synthesis. However, recommendations for protein supplementation should be conservative, as part of an overall high-quality diet.

Fatty acids and fish oil are known for their antioxidant and anti-inflammatory properties. Prolonged intake of omega-3 fatty acids improves anabolic sensitivity to amino acids, providing benefits to the injured athlete. However, the consumption of fatty acids should be balanced as part of an overall diet including carbohydrates, proteins and other micronutrients, respecting appropriate doses and other considerations specific to the health status of the person. injured individual.

All content in this article is presented for informational purposes. It does not in any way replace the advice or visit of a health professional.

Sources:

• Di Battista AP, Churchill N, Rhind SG, Richards D, Hutchison MG. Evidence of a distinct peripheral inflammatory profile in sport-related concussion. J Neuroinflammation. 2019 Jan 26;16(1):17. doi:10.1186/s12974-019-1402-y. PMID: 30684956; PMCID: PMC6347801.

• Smith, C., Kruger, MJ, Smith, RM et al. The Inflammatory Response to Skeletal Muscle Injury. Sports Med 38, 947–969 (2008). https://doi.org/10.2165/00007256-200838110-00005
• Papadopoulou SK. Rehabilitation Nutrition for Injury Recovery of Athletes: The Role of Macronutrient Intake. Nutrients. 2020 Aug 14;12(8):2449. doi:10.3390/nu12082449. PMID: 32824034; PMCID: PMC7468744.